It has been previously theorized that free-radical reactions led to the first life on Earth and their ability to randomly cause mutations may have subsequently led to the evolution of life. One of the most efficient free-radical quenchers is ascorbate, which most animals manufacture endogenously. It is generally believed that, approximately 25 million years ago, an ancestor of the Anthropoidea primate suborder, which includes Homo sapiens, lost the ability to produce its own ascorbate, and all descending species inherited this genetic defect. The first of three hypotheses presented here proposes that a genetic defect, caused by either free radicals or a virus, deleted the gene needed by Anthropoidea to manufacture endogenous ascorbate. The second hypothesis proposes that this evolutionary accident permitted large numbers of free radicals to remain metabolically unquenched. The third hypothesis proposes that the presence of these excessive free radicals increased the likelihood of free-radical-induced genetic mutations, and these mutations propelled the evolution of Anthropoidea, leading to Homo sapiens.i
Antioxidants and ageing
The ageing process in skin is intimately related to the acute and chronic control of free radical formation.
The first Line of Defense
The body has many antioxidant defenses, many of which you know. They are classified in many ways.
I prefer to separate them into two major groups. The Protein & enzyme group:
Protein – transferring, ferritin and ceruloplasmin. These are proteins that bind metals in the blood stream.
Enzymes – superoxide dismutase, catalase, glutathione peroxide, glutathione transferase, thio- specific peroxidases and others.
And the vitamin & metabolite group:
Vitamin – ascorbic acid, tocopherol and retinol – Vit C, E and A respectively. Metabolites – bilirubin, uric acid, glutathione, nicotinamide, dinucleotide, phosphate complex, magnesium, manganese, zinc and lipoic acid.
Recent findings indicate the first molecular line of defense against free-radical lipid peroxidation damage in the body involves water-soluble vitamin L-ascorbate (i.e., in salt form at physiological pH values).
Even in the presence of high levels of Vitamin E, in vitro experiments indicate L-ascorbate is consumed first because it reduces atocopheroxyl radical back to atocopherol.
This can also be accomplished to a lesser extent by cysteine and glutathione. Antioxidant activity after sun exposure
Among the non-enzymic antioxidants two different dose-response patterns were seen. Ascorbate was rapidly depleted at doses between 0 and 5 J/cm2 but was less affected between 5 and 25 J/cm2. In contrast, glutathione, ubiquinol/one, and alpha-tocopherol levels remained approximately equal to control levels between 0 and 5 J/cm2, then decreased to varying degrees from 5 to 25 J/cm2; ubiquinol was almost completely depleted, whereas alpha-tocopherol dropped only 30%.
Catalase activity decreased dramatically at does above 5 J (to 11.8% of initial activity in epidermis and 27.7% in dermis at 25 J). The dramatic loss of catalase is almost entirely accounted for by direct destruction by the simulated solar light, but superoxide dismutase was unaffected by direct exposure; hence its destruction must be due to indirect effects, either mediated by free radicals or other harmful species formed upon irradiation. At low does of UV light many components of the cutaneous antioxidant system were damaged, whereas at high does all components were damaged and some were almost completely destroyed.ii
Impairment of cutaneous catalase and glutathione reductase activity was observed. Superoxide dismutase and glutathione peroxidase were not significantly influence. Inhibition of catalase may render skin more susceptible to the damaging effects of hydrogen peroxide and its reaction products such as the hydroxyl radical.
This partial impairment of the cutaneous antioxidant defense system by near ultraviolet/visible light, showing that the most susceptible component in skin is catalase, suggests possible pharmacological interventions.iii
Ultraviolet radiation of murine skin causes a large degree of destruction of enzymic and non- enzymic antioxidants immediately after irradiation. The pattern of recovery was different for each enzyme and for epidermis and dermis. The activities of superoxide dismutase and catalase decreased remarkably and recovered slowly. Super oxide dismutase in the dermis recovered full activity by 120 h and in the epidermis by 12 h. Catalase activity in both epidermis and dermis had returned to only 50% of control activity at 120 h, although the epidermis showed a temporary increase (to 93%) at 24 h. Glutathione peroxidase and glutathione reductase were slightly decreased immediately after irradiation, recovered to 100% at 3 h and then increased to
200-250% in both the epidermis and dermis at various times; values had returned to 100% in epidermis by 120 h but remained elevated in dermis.iv
Iron can act as a catalyst for free radical oxidative reactions; chronic exposure of skin to UV radiation causes increased iron deposition. Using our spin trapping system, we have shown that topical application of the iron-chelator, Desferal, to a section of skin reduces the UV light- induced POBN adduct radical signal.v
Ultraviolet radiation damage to the skin is due, in part, to the generation of reactive oxygen species. Vitamin C (L-ascorbic acid) functions as a biological co-factor and antioxidant due to its reducing properties. Topical application of vitamin C has been shown to elevate significantly cutaneous levels of this vitamin in pigs, and this correlates with protection of the skin from UVB damage as measured by erythema and sunburn cell formation. This protection is biological and due to the reducing properties of the molecule. Further, we provide evidence that the vitamin c levels of the skin can be severely depleted after UV irradiation, which would lover this organs’ innate protective mechanism as well as leaving it at risk of impaired healing after photo induced damage, In addition, vitamin C protects porcine skin form UVA-mediated phototoxic reactions (PUVA) and therefore shows promise as a broad-spectrum photo-protectant.vi
From the well-characterized enzymatic reactions involving ascorbic acid, it seems that the major function of ascorbate is to protect tissues from harmful oxidative products and to keep certain enzymes in their required reduced forms. However, it remains unclear how the deficiency of ascorbate leads to the pathological symptoms found in scurvy.vii
If Vit C is not in the daily diet, then within about six weeks we develop the signs of deficiency of Vit C, beginning with bruising, slowness to heal, bleeding gums and in its most serious form the skin condition called scurvy.
Vit C is a water-soluble vitamin and we do not have large stores of Vit C in our body. We cannot manufacture Vit C and are entirely dependent of dietary sources. Vit C helps the absorption of iron. However, supplemental iron in baby food may carry potential risk of increasing free radical damage.viii Vit C plays an essential part in the incorporation of the amino acid proline into collagen and is involved in the formation of elastin. Vit C is also necessary for the formation of cartilage, dentine in the teeth and bone, and it maintains the integrity of our capillaries, and prevents them from bruising.
Recommended Daily Dietary Allowances (RDA) FOR ADULTS IS 45 MG. (HIGHER DOSES RECOMMENDED DURING PREGNANCY AND LACTATION and persons on prescription medication for schizophrenia or mood disorders). Ascorbic acid is the acidic form of vitamin C, and even when encapsulated can cause gastric upset or diarrhea for some people. This can often be alleviated by consuming it with meals.
Especially if you have a stomach ulcer, use of an antacid buffering agent, or a buffered form of vitamin C is suggested. Unbuffered ascorbic acid in the mouth may be harmful to tooth enamel.
It is well known that UVR causes a great influx of free radicals, even the energy produced by the conversion of ADP in ATP creates free radicals. In fact just staying alive creates free radicals.
All vitamin C products should be stored away from heat, light, and moisture although this is most important for pure ascorbic acid and ascorbyl palmitate powders.
How much vitamin C? When the daily dose is increased from 200 to 2500 mg (from 1.1 to 14.2 mmol) the mean steady state of plasma concentration increases only from approximately 12 to 15 mg/L (from 68.1 to 85.2 mumol/L).
The analysis indicates that both saturable gastrointestinal absorption and nonlinear renal clearance act additively to produce the ceiling effect in plasma concentrations. As a consequence of their ceiling effect, there is no pharmacokinetic justification for the use of mega does of ascorbic acid.ix However, the consensus is that adverse effects do not occur in healthy subjects ingesting large amounts of vitamin C.x
Oral supplementation of 500 mg of ascorbic acid daily for two months alone without any other antioxidant does not appear to have protective effect on either in vitro lipoprotein oxidation resistance or in vitro lipid peroxidation in smoking men, but might even promote the formation of MDA (Malonaldehyde).xi
In general, at low ascorbate concentration, ascorbate is prone to be a pro-oxidant, and at high concentration, it will tend to be an antioxidant. Hence there is a crossover effect. We propose that the “position” of this crossover effect is a function of the catalytic metal concentration.xii
Vitamin C also protects Vit A against oxidation, improves the benefits of B12 and compensates for deficiencies of pantothenic acid, another B vitamin. As we age, we show poor absorption and retention of many nutrients like Vit C and other water-soluble vitamins. Topical delivery of Vit C is much more efficient than massive does or oral supplements. Experiments have proven that Vit C once absorbed into the skin, cannot be rubbed, washed or perspired off for three days. Vit C is destroyed by ULTRA VIOLET RADIATION. It is denatured in the skin by exposure to UVR and as with Vitamin A will probably develop an chronic deficiency of Vit C in all the areas of skin that are exposed to sunlight. The Vit C concentration in sun-exposed skin has been found to be considerably lower than that in unexposed skin. Experiments also show that the skin gets considerably less damage if significant amounts of Vit C are applied topically before sun exposure.
What destroys Vit C. Smoking: Smokers and older persons have a greater need for Vit C (each cigarette destroys 25 mg) 2 cigarettes will destroy the daily RDA of 45 mg
UVR: All forms of ultra violet radiation will destroy Vit C, but it is particularly susceptible of UVA (sun beds).
Stress: We use up more Vit C when under physical and emotional stress. Oxygen destroys ascorbic acid. It is metabolized to dehydroascorbic acid generally and that is about 1/6th as effective as ascorbic acid.
Skin conditions Vit C is best for: All forms of Environmental Defense Collagen Loss
Thin skin density (fragile) Diffused redness
Vitamin C as an antioxidant.
Vitamin C (Ascorbic acid) is an extremely powerful antioxidant but also has significant metabolic functions that make it particularly important for the normal action of skin.
Our skin certainly needs lots of vitamin C to counteract the dangers of free radicals. Because it is water-soluble, vitamin C cannot be stored for a significant period in the cell, and should be replaced daily. Since the body consists mainly of water, vitamin C is an important antioxidant for the cytoplasm of the cell (that is the liquid/gel that forms the main filler of the cell and in which the various structures like the mitochondria, Golgi apparatus, nucleus etc. are cushioned). The paradox is that vitamin C seems to have an extremely important role in the protection of lipid membranes and the prevention of peroxidation of lipids. We now understand that ascorbic acid works in tandem with vitamin E neutralizes a lipid based free radical. This free radical form of vitamin E that occurs when vitamin E neutralizes a lipid based free radical. This free radical form of vitamin E is inactive and vitamin C can convert it into the antioxidant form of vitamin E, while itself being changed into a weak free radical. This weak free radical can itself be re- activated by either glutathione, which is a common amino acid found in cells, or by dihydroplipoic acid (alpha lipoic acid). Co-enzyme Q10 is also used in this mutual reactivation between these five special antioxidants that are normally found in the skin.
Nevertheless, we need good doses of vitamin C to protect the skin constantly so as to minimize photo damage. Research has shown us that when we supply adequate doses of vitamin C topically, we not only increase the antioxidant protection of the skin and reduce the dangers of developing sun burn cell, but we also stimulate the fibroblast to make more collagen and elastin, and persuade the sideline effect is that the vitamin A in the skin is better protected and less liable to being destroyed by free radicals.
Vitamin C and a healthy stratum corneum:
Vitamin C plays an important part in the formation of stratum corneum barrier lipids. With the extensive production of lamellar bodies, their complete extrusion at the stratus granulosum/stratum corneum interface, and the formation of multiple broad lipid lamellar structures in the intercorneocyte space. Ascorbic acid ensures.xiii
Vitamin C and the production of collagen:
Ascorbic acid is essential to incorporate praline into collagen. Without this, defective collagen would be made. Vitamin C also has effects on the DNA of fibroblasts to promote the formation of collagen and elastin and the GAGs (glycoseaminoglycans).
Vitamin C and melanin formation:
Ascorbic acid is the most powerful natural controller of melanin formation. First of all, melanin formation has to occur in an oxidizing atmosphere because the enzymes that produce melanin can only work in under oxidizing conditions. Because ascorbic acid is such a powerful antioxidant in the mitochondria, it creates a reducing (anti-oxidizing) atmosphere and makes it almost impossible to make any melanin.
In addition, ascorbic acid inhibits melanin formation by specifically inhibiting the transformation of the melanin pre-cursor, tyrosine, into melanin by blocking the action of the enzyme tyrosinase.
Significant increase of melanin concentrations in skin were found after 4, 5, 6 and 8 weeks of dietary antioxidant intake in both groups (p<0.05). These results are discussed with regard to the redox control theory of melanocytes, which regulates the tyrosinase activity.xiv
VC-PMG suppressed melanin formation by tyrosinase and melanoma cells. In situ experiments demonstrated that VC-PMG cream was absorbed into the epidermis and that 1.6% remained 48 hours after application. The lightening effect was significant in 19 of 34 patients with chloasma or senile freckles and in 3 or 25 patients with normal skin. CONCLUSION: VC-PMG is effective in reducing skin hyperpigmentation in some patients.xv
As you can see there is great value in applying vitamin C topically but here is the crunch: vitamin C is a water-soluble molecule and we have to get it through the lipid based horny layer of the epidermis in order to get its benefits. The horny layer is a virtually solid lipid membrane that acts as an extremely effective barrier. The story becomes interesting as we learn about how scientists have managed to get around this obstacle. There is a lot of hype about vitamin C and if you read some advertisements then you would think that certain companies only have the magic formula to get vitamin C into the skin cell itself. Lets examine the chemistry of vitamin C.
Ascorbic acid is inexpensive and easy to obtain but unfortunately, it is unstable and does not last long. On the other hand, scientists have managed to stabilize Vitamin C by combining it with certain other chemicals but stable versions of Vitamin C are expensive and are usually trashed by companies selling ascorbic acid precuts. They say that you have to use natural ascorbic acid and nothing else will work the same.
First of all let’s deal with the myths about natural ascorbic acid. Ascorbic acid is one of the most important vitamins in our lives. The exact chemical configuration of natural vitamin C is described as I-ascorbic acid. That means that if polarized light is passed through ascorbic acid crystals, then the light is twisted to the left. When we synthesize vitamin C then d-ascorbic acid is created and as you have probably guessed, it is labeled “d”-because it twists light to the right. In fact synthetic ascorbic acid comprises both d- and l- forms and they can be separated – of course this adds some expense, but not much. It just so happens that virtually all “natural” ascorbic acid that is used in the manufacture of cosmetics is synthesized, but it has been “purified” and made natural by excluding the d-ascorbic acid. Although this ascorbic acid is synthesized, it is true “natural” vitamin C.
Ascorbic acid is commercially available as a dry powder (technically called dehydro-ascorbic acid), which is relatively stable and is white in color. When ascorbic acid powder is exposed to light and air, it slowly decomposes to oxidized ascorbic acid, which is yellowish-brown in color. When ascorbic acid crystals are mixed in water, the solution, as its name implies, has an acidic pH. Under natural conditions the pH can easily be 2 or lower, depending on the concentration. Obviously the greater the saturation, the lower the pH. And the lower the pH, the more stable the ascorbic acid solution. Of course, the lower the pH the more irritant the solution is to the skin. A solution of vitamin C is much less stable than dry powdered ascorbic acid and rapidly decomposes to its oxidized form. I have found that under the best laboratory conditions, ascorbic acid gels even with so-called “stabilizers”, only last at its intended concentration for a maximum of three weeks. Therefore, a solution of ascorbic acid, even in a gel, has a limited shelf life and once the solution has been made up, it should be used within three weeks to get the optimum levels of vitamin C. It is easy to see when ascorbic acid gel has become oxidized: it becomes a yellowish brown in color. When the solution starts too turn a pale yellow, then one already has less than the original concentration of vitamin C. Many manufacturers claim to have 10% ascorbic acid in their product and because ascorbic acid is so unstable they must “overage” the product and add about 25% more, which means that they have 12.5% ascorbic acid in the final product immediately after manufacture. A light yellow color develops within a few days and by then the concentration may have dropped to 10%. By four weeks, it is likely that the concentration that was intended.
By three months, you can forget about achieving any enhanced vitamin C effects. So in other words, check the date of expiry on your ascorbic acid products. Also check the list of ingredients. I cannot understand why any manufacturer of ascorbic acid products would want to include a yellow brown colorant or any other color into their product. There is no aesthetic reason, neither is there a functional, physiological reason. I leave you to decide what the motives could be. Therefore, check with your supplier and find out if the ascorbic acid product they sell you has any color in it. If it does, then ask why and make sure that you get a detailed answer.
You need the freshest product that you can get, and it has to be the freshest possible by the time your client uses it. Under ideal conditions, the client should use up the ascorbic acid product before three weeks have passed after its manufacture. That sounds impossible but some very clever and ethical companies have arranged that the ascorbic acid products are sold unmixed to their clients. Sometimes separate sachets preserve the ascorbic acid crystals from exposure to light and air. The crystals are kept stable by packing them with nitrogen instead of air. Other companies have made special bottles that separate the fluid from the ascorbic acid crystals.
When the client presses a plunger, the powder falls into the solution and after shaking, the final solution is made which ensures the freshest possible vitamin c. However, it does not ensure that the concentration is as strong as it should be. You really need a concentration of ascorbic acid at a minimum of 10% or more, to get the real benefits of ascorbic acid. I don’t think that you have to worry about the pH because the manufacturer is bound to make sure that the pH will be about
- At this pH of 2, it will ensure the best penetration of the ascorbic acid through the horny layer into the skin and unfortunately, it will also sting! The pH is naturally low because ascorbic acid acts like an AHA (alpha hydroxyl acid) and softens the glue between the cells of the horny layer and increases the penetration of vitamin C into the deeper layers of the skin. That, however, does not ensure the bet penetration into the cell. Vitamin C passes with difficulty from the
intercellular fluid into the cell wall because it is a water-soluble molecule. When it is oxidized, it can be taken into the cell itself masquerading as glucose, and can be converted into active vitamin C by glutathione and alpha lipoic acid. That, of course, uses up essential components of the antioxidant brigade and can weaken the total antioxidant protection mechanism.
So, in summary, vitamin C as ascorbic acid has a difficult task to get through into the skin and if it does than it cannot easily get into the cell itself where it has to work!
Although vitamin C is critical to human physiology, it is not clear how it is taken up into cells. The kinetics of cell and tissue accumulation of ascorbic acid in vitro indicate that the process is mediated by specific transporters to the cell membrane. Some experimental observations have linked the transport of ascorbic acid with hexose transport systems in mammalian cells, although no clear information is available regarding the specific role(s) of these transporters, if any, in this process.
These observations indicate that mammalian facilitative hexose transporters are a physiologically significant pathway for the uptake and accumulation of vitamin C by cells, and suggest a mechanism for the accumulation of ascorbic acid against a concentration gradient.xvi
The significance of the functional linkage between vitamin C and adrenal glucocorticoid, which has been confirmed both in both the humans and rats in our laboratory, was discussed in the light of the historical development of vitamino-endocrinology.xvii
Topical vitamin C
Topical L-ascorbic acid, when used in an appropriate vehicle and when initiated at an appropriate postoperative period, may decrease the degree and duration of erythema after cutaneous CO2 laser resurfacing. It is presumed that the anti-inflammatory effect of vitamin C is responsible for the clinical changes observed in this study.xviii
Absorption of ascorbic acid
The data clearly show that ascorbic acid uptake is inhibited instantly by glucose in a concentration dependent fashion. The results support the contention that local ascorbic acid deficiency in tissues could be a natural consequence of hyperglycaemia of whatever cause. The rate of ascorbic acid uptake under various conditions suggests that additional supplements of ascorbic acid might be helpful to individuals in averting deleterious effects of hyperglycaemia on tissue ascorbic acid supply.xix
- Ascorbic acid was absorbed across the mucosa of the human of the human
- Omission of sodium ions from the medium decreased the absorption of ascorbic
- The pressure of D-glucose, or 3-O-methyl-D-glucose, increased the absorption of ascorbic acid but D-fructose had little effect and D-mannitol had no
- Calcium ions also increased ascorbic acid absorption probably by a secondary effect on “Na+ fluxes.
- Buccal mucosa was also permeable to dehydroascorbic acid and D-isoascorbic xx
Many cell types transport vitamin C solely in its oxidized form, dehydroascorbic acid, through facilitative glucose transporters. These cells accumulate large intracellular concentrations of vitamin C by reducing dehydroascorbic acid to ascorbate, a form that is trapped intracellularly. Certain specialized cells can transport vitamin C in its reduced form, ascorbate, through a sodium-dependent co-transporter. We found that normal human melanocytes and human malignant melanoma cells are able to transport vitamin C using both mechanisms.xxi
The conditions used for glycation reactions in vitro rapidly oxidized ASA, but not glucose. The UVA-dependent generation of oxygen free radicals also oxidized ASA at a 10(3) faster rate that glucose. Superoxide anion and singlet oxygen were identified as the principal oxidants as ASA in this process. ASA may be the primary glycating agent in aging normal lenses.xxii
The degree to which antioxidant loss occurs in human skin after UV irradiation is unknown, as is the cascade of events that might occur. Human skin equivalents, a tissue culture model, were irradiated using a full solar UV spectrum (UVA and UVB, 280-400 nm) (0 to 16.8 J/cm2, 0-12) minimal erythemal does, (MED), then incubated from 1 to 24h. Ubiquinol was the most UV- light sensitive antioxidant and was depleted by 2.1 J/cm2 (1.5 MED, p<.004); ubiquinone decreased with 4.2 J/cm2 (3 MED, p<.0007). A linear decrease in alpha-tocopherol occurred— approximately 1.7 pmol tocopherol/cm2 surfaces were destroyed per J/cm2 UV-light. Urate was depleted by irradiation with 8.4 J/cm2 (6 MED), while ascorbate was depleted by 16.8 J/cm2 (12 MED). In conclusion, human skin equivalents respond to suberythemal levels of UV- irradiation by increasing production of respond to suberythemal levels of UV-irradiation by increasing production of PGE2; higher levels of UV-irradiation (at least 1 MED) were needed to deplete cellular antioxidants and induce immediately detectable oxidative damage.xxiii
The rate of ascorbate oxidation in the presence of vitamin E homologues was enhanced by a photosensitizer (riboflavin) but was not influenced by reactive oxygen radical quenchers, superoxide dismutase or 5,5 dimethyl-1-pyrroline-N-oxide. These experimental results suggest that the UV irradiation-induced ascorbate oxidation in murine skin homogenates is caused by photoactivated reactions rather than reactive oxygen radical reactions.xxiv
50 days after supplementation alpha-Toc keratinocyte levels were increased in groups (1) and (3), Asc concentrations were elevated in groups (2) and (3), and the a/gamma-Toc ratio increased in groups (1) and (3). The dose response curve of UVR induced erythema showed a significant flattening and the MED increased from 103 +/- 29 mJ/cm2 (before supplementation) to 183 +/- 35 mJ/cm2 (after supplementation) in group (3), while there were no significant changes in groups (1) and (2) after vitamin supplementation.
Conclusion: Alpha-Toc and Asc act synergistically in suppression of the sunburn reaction.xxv
L-Ascorbic acid was able to down regulate 1L-1alpha mRNA expression in both UVA-irradiated and non-irradiated cells; however, 1L-6 mRNA expression remained unaffected. The secretion of these cytokines was reduced to nearly normal in the presence of L-ascorbic acid. These finding indicate a major cell-protective effect of L-ascorbic acid on UVA-irradiated human keratinocytes.xxvi
The skin processes an elaborate antioxidant defense system to deal with UV-induced oxidative stress. However, excessive exposure to UV can overwhelm the cutaneous antioxidant capacity, leading to oxidative damage and ultimately to skin cancer, immunosuppression and premature skin aging. Therefore, an interesting strategy for photoprotection is the support of the endogenous antioxidant system. This can be accomplished by induction or transdermal delivery of the various antioxidant enzymes, such as glutathione peroxidase, catalase, or superoxide dismutase. Supplementation of non-enzymatic antioxidants such as glutathione, alpha- tocopherol, ascorbate and beta-carotene was also found to be very effective in photo protection. Although treatments with single components of the antioxidant system were successful against a wide variety of photo damage, the balance between the different antioxidants in the skin is very important. In some studies, it was found that too much of a single component could even have deleterious effects. The most promising results were obtained in studies combining several compounds, often resulting in synergism of the protective cells.xxvii
A critical step in the escape from the carcinogenic potential of UV radiation is mediated by the protein p53. P53 activates growth arrest, allowing for DNA repair, and apoptosis, which removes damaged cells.
Here I show that p53 in cultured human skin fibroblasts is elevated after treatment with hydrogen peroxide, an oxidant produced in cells during exposure to solar UV radiation. Simulated solar UV radiation increased p53 and agents that scavenge active oxygen species, N- acetyl cysteine, ascorbate and alpha-tocopherol, inhibited the increase. The generation of DNA single strand breaks has been proposed to be an important step in the pathway leading to the increase p53 initiated by a variety of cytotoxic agents.xxviii
Pre-clinical studies amply illustrate the photo protective properties of supplemental antioxidants, particularly RRR-alpha-tocopherol, L-ascorbate and beta-carotene. However, clinical evidence that these antioxidants prevent, retard or slow down solar skin damage is not yet convincing.
Topical application of combinations of both vitamins, or of melatonin with vitamins, enhanced the photo protective response. Better protection was obtained by sing the combination of melatonin with both vitamins.xxx
Combined vitamins C and E reduce the sunburn reaction, which might indicate a consequent reduced risk for later sequelae of UV-induced skin damage. The increase of sunburn reactivity in the placebo group could be related to “priming” by the previous UV exposure.
Photo protective effect of AA-2G on cytotoxicity of UVB in SCC cells was dose dependent (0.125-1 mM) and more effective than that of ascorbic acid (AsA) at 1mM. This protection was completely abolished in the presence of an alpha-glucosidase inhibitor, castanospermine, indicating that release of AsA from this derivative was essential for reduction of the actinic injury. AA-2G significantly suppressed cytotoxicities of hydrogen peroxide and superoxide anion produced by xanthine and xanthine oxidase. In addition, AA-2G reduced UVB-promoted formation of lipid peroxide and accumulation of lipofuscin, which is known to be a complex of cellular proteins and metabolites of lipid peroxide. These data suggest that AA-2G prevents the
acute inflammation induced by UVB irradiation partly through scavenging reactive oxygen species and potentiating antioxidative activity of alpha-tocopherol.xxxii
Melatonin (N-acetyl-5-methoxytryptamine), vitamin E (alpha-tocopherol) and vitamin C (ascorbic acid) were topically administered alone or in combination following UVR exposure as single applications (immediately or 30 minutes after irradiation, respectively) or as multiple applications (three times: 30 min, 1 h and 2 h after irradiation). The erythemal reaction was evaluated visually and noninvasively with bioengineering methods (skin color and skin blood flow). RESULTS: No significant protective effect of melatonin or the vitamins when applied alone or in combination were obtained when antioxidants were applied after UVR exposure. No improved photo-protective effect was obtained when multiple applications were done.
UVR-induced skin damage is a rapid event, and antioxidants possibly prevent such damage only when present in relevant concentrations at the site of action beginning and during oxidative stress.xxxiii
The effects of reactive oxygen species (ROS) on elastin molecules (tropoelastin) were studies in vitro.
ROS generated by ultraviolet A and hematoporphyrin rapidly degraded tropoelastin within 5 min. Their degradative activity was inhibited by the addition of NaN3. Treatment of tropoelastin with copper sulfate/ascorbic acid resulted in degradation of tropoelastin producing fragments of molecular weight 45, 30 and 10kDa within 30 min.
ROS generated by copper-ascorbate seems to be unique in that it cleaves relatively specific sites of the tropoelastin molecule. Thus ROS may play a degradative role in elastin metabolism, which may cause the elastolytic changes or the deposition of fragmented elastic fibers in photoaged skin or age-related elastolytic disorders.xxxiv
Ascorbate and collagen formation
Ascorbic acid specifically increased type 1 and type 111 procollagen messenger RNA levels in human fibroblasts.xxxv
L-ascorbic acid is an essential cofactor for lysyl hydroxylase and prolyl hydroxylase, enzymes essential for collagen biosynthesis. In addition, L-ascorbic acid preferentially stimulates collagen synthesis in a manner, which appears unrelated to the effect of L-ascorbic acid on hydroxylation reactions. This reaction is stereospecific and unrelated to intracellular degradation of collagen. The effect apparently occurs at a transcriptional or translational level, since L- ascorbic acid preferentially stimulates collagen-specific mRNA. In addition, it stimulates lysyl hydroxylase activity but inhibits prolyl hydroxylase activity in human skin fibroblasts in culture.xxxvi
L-ascorbic acid stimulates procollagen synthesis in cultured human skin fibroblasts without appreciably altering noncollagen protein synthesis. The effect is unrelated to intracellular
degradation of newly synthesized procollagen. Levels of mRNA for pro alpha 1(l), pro alpha 2(l), and pro alpha 1(lll), measured by hybridization with the corresponding cDNA probes, are elevated in the presence of ascorbic acid, whereas the level of mRNA for fibronectin is unchanged. Levels of functional mRNA for procollagen, measured in a cell-free translation assay, and are specifically increased in the presence of ascorbic acid. Thus, ascorbic acid appears to control the expression of three different procollagen genes, each of which is located on a separate chromosome. It is proposed that intracellularly accumulated procollagen in ascorbate deficiency may lead to a translational repression of procollagen synthesis. Ascorbic acid may relieve this block by promoting hydroxyproline formation and, consequently, secretion of procollagen from the cell. The increased level of procollagen mRNA under the influence of ascorbic acid may be secondary to increased synthesis of procollagen polypeptides; the control point may be gene transcription of mRNA degradation.xxxvii
Ascorbate is required for hydroxylation of praline residues in procollagen and hydroxyproline stabilizes the collagen triple helical structure. Proteoglycan synthesis, which does not require ascorbate, also is decreased and both effects are correlated with the extent of weight loss during scurvy. The inhibitor appears to consist of two IGF-binding proteins induced during vitamin C deficiency and may relieve this block by promoting hydroxyproline formation and, consequently, secretion of procollagen from the cell. The increased level of procollagen mRNA under the influence of ascorbic acid may be secondary to increased synthesis of procollagen polypeptides; the control point may be gene transcription of mRNA degradation.xli
These studies indicate that the ascorbic-induced increase in type 1 procollagen synthesis is due to increased levels of type l procollagen mRNA and is interdependent of the level of hydroxylation of the procollagen.xlii
Transforming growth factor-beta (TGF-beta) is a prototype of a family of polypeptides that regulates cellular growth and phenotypic differentiation. TGF-beta injection induces angiogenesis and fibrosis locally and stimulates the synthesis of extracellular matrix proteins, fibronectin, collagens, and proteogylcans in vitro in many cell types. Ascorbate is also known to induce collagen synthesis and to promote would healing. We report that in cultured human skin fibroblasts, ascorbate and TGF-beta synergistically enhance the biosynthesis of type l and type lll collagens and their steady-state mRNAs. TGF-beta alone has no enhancing effect on type lll collagen synthesis. The cooperation between ascorbate and TGF-beta may be a significance in would healing and in disorders of fibrosis.xliii
Ascorbate contributes to several metabolic processes including efficient hydroxylation of hydroxyproline in elastin, collagen, and proteins with collagenous domains, yet hydroxyproline in elastin accumulation in vitro and to alter morphology of elastic tissues in vivo. Ascorbate doses that maximally stimulated collagen production (10-200 microM) antagonized elastin biosynthesis in vascular smooth muscles cells and skin fibroblasts, depending on a combination of dose and exposure time. Diminished elastin production paralleled reduced elastin mRNA levels, while collagen l and lll mRNAs levels increased. We compared the stability of mRNAs for elastin and collagen l with a constitutive gene after ascorbate supplementation or withdrawal. Ascorbate decreased elastin mRNA stability, while collagen l mRNA was stabilized to a much greater extent. Ascorbate withdrawal decreased collagen l mRNA stability markedly (4.9-fold),
while elastin mRNA became more stable. Transcription of elastin was reduced 72% by ascorbate exposure. Differential effects of ascorbic acid on collagen l and elastin mRNA abundance result from the combined, marked stabilization of collagen mRNA, the lesser stability of elastin mRNA, and the significant repression of elastin gene transcription.xliv
Ascorbic acid (vitamin C) is a cofactor required for the function of several hydroxylases and monooxygenases. Its absence is responsible for scurvy, a condition related in its initial phases to defective synthesis of collagen by the starving and may be responsible for in vivo inhibition of collagen and proteoglycans.xxxviii
Procollagen biosynthesis and matrix deposition were studied in long-term human skin fibroblast cultures exposed to ascorbic acid. Ascorbic acid specifically stimulated types l and lll collagen synthesis, reaching a maximum at day 2 and maintaining a specific high rate of production until day 10 of ascorbate exposure, after which collagen production declined. The increased level of collagen synthesis after different exposure times could also be achieved by only brief treatment (10h) of parallel scorbutic (ascorbic-acid-deficient) cultures with ascorbic acid. This brief exposure did not result in increased collagen synthesis at all stages of ascorbic acid exposure was due to post-transcriptional mechanisms, most likely rapid increase in type l collagen mRNA translation efficiency. This mechanism, rather than the transcriptional activation, was primary response and is adequate to explain the ascorbate-induced increase in collagen synthesis.
These data also demonstrate that the presence of a collagenous extracellular matrix was not involved in this collagen biosynthetic regulation. During long-term exposure (18 days) to ascorbic acid, a substantial cross-linked collagenous matrix formed, following an approximately sigmoidal time course. The most rapid matrix deposition occurred during the later days of exposure when the rate of collagen synthesis was decreasing, suggesting that the presence of a preexisting matrix is important for further collagen accumulation. Procollagen was also efficiently processed to collagen during this phase, demonstrating that efficient procollagen processing is an important regulatory event in collagen matrix deposition.xxxix
Ascorbate has been shown to stimulate collagen synthesis in cultured human dermal fibroblasts by increasing transcription of the collagen genes. In the present studies, ascorbate stimulates lipid peroxidation at concentrations similar to those necessary to affect collagen synthesis.
Molecules, which inhibit lipid peroxidation, such as propyl gallate, cobalt chloride, and alpha- naphthol, also inhibit collagen synthesis, suggesting a correlation between the two phenomena. Retinoic acid and some synthetic retinoids have previously been shown to inhibit different retinoids, at similar concentrations, inhibit both ascorbate-stimulated lipid peroxidation and collagen synthesis. Since high concentrations of retinoids were required, the ability of retinoids to inhibit the oxidant effect of ascorbate, and not their receptor-mediated activity, may be responsible for their effect on collagen synthesis.xl
Thus, ascorbic acid appears to control the expression of three different procollagen genes, each of which is located on a separate chromosome. It is proposed that intracellularly accumulated procollagen in ascorbate deficiency may lead to a translational repression of procollagen synthesis. Ascorbic acid reduced function of prolylhydroxylase and production of collagen polypeptides lacking hydroxyproline, therefore, they are unable to assemble into stable triple-
helical collagen molecules. In fibroblast cultures, vitamin C also stimulates collagen production by increasing the steady-state level of mRNA of collagen types l and lll through enhanced transcription and prolonged half-life of the transcripts. The mRNA of collagen type l and lll were increased to a similar extent by vitamin C and that of three post-translational enzymes, the carboxy-and amino-procollagen proteinases and lysyloxidase similarly increased. The mRNA of decorin was also stimulated, but elastin, and fibrillin 1, 2, and 9 was not significantly changed, but an increased level of tissue inhibitor of matrix metalloproteinase 1 mRNA was observed without modification of tissue inhibitor of matrix metalloproteinase 2 mRNA. The stimulating activity of topical vitamin C was most conspicuous in the women with the lowest dietary intake of the vitamin and unrelated to the level of actinic damage. The results indicate that the functional activity of the dermal cells in not maximal in postmenopausal women and can be increased.xlv
The study of nitroxide radical interactions with tissue antioxidants and oxidants is of growing interest. Skin is a target organ of the EPR methodology and is frequently exposed to oxidative stress. We investigated the piperidine-type nitroxide 2,2,5,5-tetramenthyl-4-piperidin-1-oxyl (TEMPO) because it is skin permeable and readily accepts electrons in biological systems.
Quantitative considerations indicate that the major reduction site of TEMPO in skin and skin cells is the cytosol ascorbate/glutathione redox cycle. We suggest that analysis of TEMPO radical scavenging by the EPR technique is a convenient method for measuring skin ascorbate and thiol-dependent antioxidant activity in vitro and in vivo.xlvi
The benefit of AA and PA supplementation could be due to the variations of the trace elements, as they are correlated to mechanical properties of the scars.xlvii
To make healthy collagen, lsyl hydroxylase, a vitamin C-dependent enzyme, is essential to convert lysyl residues to hydroxylysine on procollagen peptides.xlviii
Ascorbate stimulated the deposition of glycosaminolglycans into the insoluble matrix of normal fibroblasts.xlix
These results suggest that collage peptide synthesis, posttranslational hydroxylations, and activities of the two hydroxylases are independently regulated by ascorbate.l
A similar increase in prolyl hydroxylase activity occurred when cells were incubated with ascorbate. Lysyl hydroxylase activity remained unaltered under these conditions.li
Old scars break open in scorbutic patients because (1) the rate of collagen degradation is greater in an old scar than it is in normal skin, and (2) the rate of collagen synthesis is diminished throughout the body in ascorbate deficiency.lii
Our results suggest that there are differences in collagen synthesis between photoaged and aged cells, depending on culture conditions. Responsiveness to ascorbic acid, TGF-beta and IFN- gamma related to collagen synthesis in photoaged and aged fibroblasts, even though basal levels of collagen synthesis are downregulated a photoaging- or aging –dependent manner.liii
L-ascorbic (vitamin C) stimulated growth and collagen synthesis, as well as synthesis of non- collagenous proteins, with no significant effect on hyaluronic acid synthesis. Co-presence of epidermal growth factor and ascorbate gave additive effects on growth-promoting factors, epidermal growth factor and L-ascorbate, modulate metabolism of extracellular matrix components as well as cell growth in a quite different manner in human skin fibroblasts.liv
For a fructose concentration of 25 mM, we observed that in the absence of glucose, intracellular total proteins increased 1.5-fold and peroxidase specific activity, 1.8-fold. For ascorbate, a broad optimum concentration was found (range 0.01 – 0.50 mM). Addition to cultures of 0.1 mM ascorbate increased total proteins 1.4-fold, and doubled peroxidase activity. This investigation was prompted by our previous results [j. Metab. Dis. 1983, 6, 27-31], confirmed here, and suggesting that increased prolidase activity at confluency was due to a rise in cell density.lv
Ascorbate and nitroxides
The most convincing evidence for the involvement of vitamin C in cancer prevention is the ability of ascorbic acid to prevent formation of nitrosamine and of other N-nitroso compounds.lvi
UV radiation (300 nm) increases the ascorbate free radical (Asc.-) electron paramagnetic resonance (EPR) signal inhuman facial skin biopsies (340%). Visible light (lambda>400 nm;
0.23 mW/cm2 UVA) also increased the Asc.- signal in human skin samples (45%) indicating that human skin is more susceptible to free radical formation and that a chromophore for visible light may be present. These results provide the first direct evidence for UV radiation-induced free radical formation at near physiological temperatures in human skin and suggest that iron chelators may be useful as photo protective agents.lvii
B-Carotene, a precursor of vitamin A, and tocopherol (vitamin E) are the main lipid-soluble non- enzymatic antioxidants and are mainly confined to cell membranes and low-density lipoprotein. Among water-soluble antioxidants, ascorbate is the most efficient antioxidant. Table 4 summarizes the most important characteristics of these systems.
Experimentally, the topical application of antioxidants has shown promising results in preventing damage and the photo induced inflammatory response (63-66).lvii lix lx lxi lxii
Magnesium ascorbyl phosphate
We found, in an in vitro experiment, that MAP was converted to AS as it crossed the epidermis, but that AS-Na did not pass through the epidermis. Furthermore, MAP was also converted to AS in serum. These results suggest that the protective effect of MAP on UVB-induced cutaneous damage is due to conversion of MAP to AS.lxiii
L-Ascorbic acid 2-phosphate (Asc 2-P), a long-acting vitamin C derivative, stimulated transcription of genes for pro alpha 1(l) and pro alpha 2(l) collagen in normal human skin fibroblasts after 8 h or treatment in the absence or in the presence of cycloheximide, indicating
Asc 2-P stimulates transcription of type l collagen genes in the absence of protein synthesis. The transcription rate in these cells reached the maximum value after 40 h of treatment, and at that time it was three to four times higher than that of the control cells cultured in the absence of Asc 2-P. Steady-state levels of mRNAs for pro alpha 1(l) and pro alpha 2(l) chains were also increased to be three to four times higher than the control levels by treatment of the cells with Asc 2-P for 72 h.lxiv
The interaction between vitamin C and E and other antioxidants
Ascorbate regenerates vitamin E by a nonenzymic mechanism, whereas glutathione regenerates vitamin E enzymatically. These studies suggest that significant interaction occurs between water- and lipid-soluble molecules at the membrane-cytosol interface and that vitamin c may function in vivo to repair the membrane-bound oxidized vitamin E.lxv
Vit C. produced a clear cytoprotective effect on aged cells over the entire range of doses applied. The protection provided by Vit E, was less pronounced.lxvi
The results showed a modest protective effect of the vitamins when applied alone and a dose- dependent photo protective effect of melatonin. Topical application of combinations of both vitamins, or of melatonin with vitamins, enhanced the photo protective response. Better protection was obtained by using the combination of melatonin with both vitamins. The role of reactive oxygen species and oxygen-derived free radicals, as well as potential sun screening properties of the employed antioxidants, are discussed in view of possible mechanisms to explain this elevated photo proactive effect.lxvii
The literature associates low vitamin C levels in the blood to an increased relative risk of gastrointestinal cancer, including cancer of the esophagus, mouth, stomach, and pancreases (Gey, 1993). The reason for its effect on cancer in the gastrointestinal tract is thought to be due to the pH of the stomach and vitamin C’s nitrate trapping property. Below pH 6, as in the stomach, vitamin c may have an increased trapping ability for nitrates that are produced in the stomach and esophagus and thus an increased protective effect at those sites. Vitamin E has a very similar mechanism of prevention to that of vitamin C, but is different in that vitamin E.
Vitamins E and C as well as many other antioxidants are very effective inhibitors of skin tumor promotion.lxviii
Ascorbic acid, while by itself not cytoprotective synergized with quercetin, lowered the quercetin EC50 and prolonged the window for cytoprotection. The related flavonoids rutin and dihydroquercetin also decreased BSO-induced injury to dermal fibroblasts, albeit less efficaciously so than quercetin. The cytoprotective effect of rutin, but not that of dihydroquercetin, was enhanced in the presence of ascorbic acid. Further, quercetin rescued sensory ganglion neurons from death provoked by GSH depletion. Direct oxidative injury to this last cell type has not been previously demonstrated. The results show that flavonoids are broadly protective for cutaneous tissue-type cell populations subjected to a chronic intracellular form of oxidative stress. Quercetin in particular, paired with ascorbic acid, may be of therapeutic benefit in protecting neurovascularture structures in skin from oxidative damage.lxix
Vitamin C Fact File
There is an enormous amount of literature on vitamin C intake and health in animals, cell cultures, and humans. Beyond its function in collagen formation, ascorbic acid is known to increase absorption of inorganic iron, to have essential roles in the metabolism of folic acid and of some amino acids and hormones, and to act as an antioxidant.lxx
Because ascorbic acid is water-soluble and the cell membranes are lipid structures, we have to find ways of persuading the cells to take up increased doses of vitamin C through the lipid membranes. There is another way to get the ascorbic acid into the cell itself: combine it with another molecule that is selectively taken into the cell. An example of this form of vitamin C is magnesium (or sodium) ascorbyl phosphate, which is also water-soluble but is taken into cells much more effectively because the cells select the minerals, which they need for their normal metabolism. Unfortunately this is an expensive ingredient to work with. Can this be one reason why some manufacturers of the less expensive form of ascorbic acid tend to trash the more effective ascorbyl phosphate salts? Inside the cells, the vitamin C compound is easily converted to ascorbic acid and phosphate and magnesium (or sodium). The advantage of using these solutions are that they are also more stable than conventional ascorbic acid and can last up to 200 days before there is any appreciable loss of activity. Lower concentrations (compared to ascorbic acid) are required to get the same amount of ascorbic acid into the cell itself. I have used both ascorbic acid and these stabilized salts of vitamin C. They are both useful and depending on dose and means of administration, have similar results, but have a different client profile. People with sensitive skins cannot use ascorbic acid and so I use magnesium ascorbyl phosphate products for them. People with pigmentation problems should avoid any product that peels the skin significantly. Ascorbic acid has an exfoliant property so I generally recommend that clients with melasma or other pigmentation problems should rather use the more neutral ascorbyl phosphate salt. Both ascorbic acid and its salts are suitable for iontophoresis and sonophoresis and generally they can both be used for salon treatments for pigmentation. Your client will tell you if the ascorbic acid stings too much and in that case use magnesium ascorbyl phosphate.
I am pleased to tell you that wonderful strides have been made in vitamin C variants for cosmetics. The latest, which I believe will set the standards for vitamin C treatments, is ascorbyl tetra-isopalmitate, which is fat soluble and extremely stable. That means that there are four molecules of palmitic acid attached to the ascorbic acid molecule. The palmitic acid molecule is about the same weight as the ascorbic acid molecule so you can see that vitamin C forms only about a quarter of this large molecule. However, with only a tiny amount of vitamin C, this fat soluble form passes easily through the horny layer and enters the cell was with great ease and you can get up to ten times more active vitamin C into the cell itself. As a result, there is more effective control of melanin formation, greater collagen deposition and more efficient antioxidant protection.
My experience with this wonderful molecule makes me believe that we have entered a new era in vitamin C treatments for the skin. However, bear in mind that this vitamin C is fat-soluble so it cannot be used for iontophoresis or sonophoresis.
Ascorbyl-tetra-isopalmitate, combined with vitamin A, produces rapid smoothening, without any irritation, and significant lightening of the skin (provided it is adequately protected from light).
Of course if it is also combined with a wide antioxidant brigade and effective UV-A protection, then pigmented marks seem to melt away. Very few companies have used this new ingredient. Don’t confuse this molecule for the less effective ascorbyl palmitate, or ascorbyl di-palmitate, which are less effective at getting through the skin and into the cell itself. These ingredients have been used for many years. The fact remains that not nearly as much vitamin C gets inside the cell as with the tetra-isopalmitate. However, don’t avoid ascorbyl palmitate. It’s good, but just not as good as the current start ascorbyl tetra-isopalmitate.
In summary, we would like to show you briefly how I use the various forms of vitamin C:
Ascorbic acid – I use it as fresh as possible and discard anything that is older than a month after production. I sue this on people with tough, rough and wrinkled skin. I avoid using this on people prone to acne because the exfoliation can aggravate the acne. I have also used this for home vitamin c peels with great success.
Magnesium (or sodium) ascorbyl phosphate-I prefer to use this as fresh as possible and discard anything that is older than six to seven months after production. I sue this on normal, sensitive, or pigmented skin. Can be used on acne but may initially aggravate the acne.
Ascorbyl palmitate (ascorbyl di-palmitate) –Good stability so you don’t have to specially check the production date. Can be used on delicate skins and acne. I have never seen good changes and I cannot make a really active rejuvenating compound with it.
Ascorbyl tetra-isopalmitate (VCIP) – excellent stability but for the best results the product should not be older than 18 months after production. Gives the best levels of vitamin C inside the cells and can be used on delicate skins at high doses. I use it in preference to any other forms for pigmentation, wrinkles and even acne.
Types of Vit C found in cosmetic formulations. It is important to remember that the various types of vitamin C have been chosen for their greater stability than l-ascorbic acid. Whatever type of vitamin C is used, it eventually gets converted into ascorbic acid and that is how it expresses its effects. So ultimately, the amount of ascorbic acid inside the cell is what determines the effectiveness.
- L Ascorbic Acid
l-Ascorbic Acid: Natural vitamin C: A water-soluble antioxidant which interacts with Vit E and other fat-soluble antioxidants, which are in the lipid rich areas of the cell. (Cell membrane) Together they bind to free radicals before they have a chance to damage the tissue. However, the paradox is that ascorbic acid is water- soluble and has great difficulty penetrating through the epidermis and through cell walls.
The second difficulty is that vitamin C is very unstable and solutions rapidly turn brown and are inactive. If you do buy a serum that does not change color at all over the months, it probably has very little Vit C in it in the first place.
Despite claims of superior stabilization, all Vitamin C will lose strength after six months, (even if kept cool and away from direct sunlight). Some companies incorporate a calcium ion, to protect the ascorbic acid and keep it more stable.
- Ascorbyl Palmitate
This is l-ascorbic acid with an added palmitate group to make the vitamin C more soluble in the lipid phase and allow better penetration through the skin and cell walls. The palmitate section is selectively absorbed into the cell and then esterase enzymes cleave off the palmitate moiety and l-ascorbic acid is set free inside the cell.
- Ascorbyl di-palmitate
Similar to ascorbyl palmitate but more soluble in the lipid phase and gets into cell walls easier than ascorbyl palmitate. Once again esterase enzymes have to separate the palmitic acid from the l-ascorbic acid before it can start being effective.
- Magnesium ascorbyl phosphate (MAP or VCPMg)
This is water soluble Vit C that is not acidic and is more easily absorbed into the skin cell than ascorbic acid. This type of Vit C is converted by the metabolism into ascorbic acid plus the other important components such as magnesium and phosphorus. (Very important micronutrients).
The magnesium salt of ascorbyl-2phosphate was found to be equivalent to ascorbic acid in stimulating collagen synthesis in these assays, while the sodium salt required at least a tenfold greater concentration to produce the same effect as ascorbic acid. These data support the use of magnesium ascorbyl-2-phosphate in experiments where stability of ascorbic acid is a concern,
e.g. in long-term cultures or in in- vivo studies.lxxi
- Sodium ascorbyl phosphate
This is even more stable in water than VCPMg but research shows that the vitamin C is not as easily released inside the cell as compared to VCPMg.
Supplementation of the medium with Asc 2-P also accelerated procollagen processing to collagen and deposition of collagen in the cell layer. Among the acidic glycosaminoglycans (GAG), another major component of extracellular matrix (ECM), deposition of sulfated forms was increased by the additive.lxxii
- Ascorbyl tetra-isopalmitate
The most effective form of vitamin C today for topical application. As its name implies, it has four palmitic acid ions attached to the l-ascorbic acid molecule. That makes it lipophilic and so it easily penetrates through the stratum corneum and is rapidly absorbed into the cell where the palmitic acid is separated from the ascorbic acid.
Topical vitamin C has been used as a PHOTOPROTECTANT as an additive to sunscreens (Thomas, 1991). The amount of vitamin C in the preparation was not specified.
Cathcart reported that topical ascorbic acid or sodium ascorbate has been effective in treating HERPES SIMPLEX and KAPOSI’S SARCOMA in AIDS patients.lxxiii The vitamin C was applied as a paste made by using ascorbic acid powder or sodium ascorbate powder and water. It was applied as a solution of 20% ascorbic acid or sodium ascorbate in water used as a soak for 15 to 30 minutes 4 times daily.lxxiv
Slaga TJ & Bracken WM: The effects of antioxidants on skin tumor initiation and aryl hydrocarbon hydroxylase. Cancer Res 1977; 37:1631-1635.
Attempted use of vitamin C through iontophoresis in the treatment of circumscribed hyperpigmentations of the skin. Preliminary communication] Original Title Proby zastosowania jontoforezy z witzminy C w leczeniu ograniczonych przebarwien skory. (Doniesienie tymczasowe)
Author Ciecierski L
Source Przegl Dermatol, 54: 4, 1967 Jul-Aug, 473-4 Language of Publication Polish
Unique Identifier 68010245
Minocycline, a member of the tetracycline family of antibiotics, is widely used in the treatment of acne. It use has been associated with intrinsic staining of adult human teeth, bones, and soft tissues. It causes blackening of the thyroid glands in both animals and humans. It has been determined that the pigment is the product of an oxidation reaction. Laboratory studies have shown that the pigment formation can be induced by exposure to ultraviolet light in the presence of air, and that an antioxidant, such as ascorbic acid (vitamin C), can block its formation Microscopic examination revealed extensive deposits of black pigment throughout the follicles of the minocycline group, whereas the group receiving both minocycline and vitamin C showed no sign of pigmentation and were indistinguishable from controls. It is suggested that patients on long-term minocycline medication be monitored for thyroid function.lxxv
Further, we observed that for AA-2G, even on the 8th day of the culture, the amount of AA in the fibroblasts was virtually unchanged from the beginning of the experiment, whereas, in the case of adding AA and AA-2P, virtually no AA was detectable in the culture medium on the fifth day. These findings suggest that AA-2G is decomposed to AA by alpha-glucosidase in the cells. This AA promotes collagen synthesis, which is prolonged through AA-2G’s sustained decomposition.lxxvi
Robert L. Goldemberg Free radicals: Efforts to Reduce skin aging Process by fighting free radicals. “Drug & Cosmetic Industry” Nov 19933 v153 n5 p48(3)
Free radicals often activate chain reactions known as cascades, sometimes polymerizing into larger molecules, sometimes degrading longer ones into short pieces. The latter effect, especially when it involves free radicals containing oxygen (such as the hydroxyl radical) is the most damaging physiologically, leading to destruction of fatty membranes, cell collapse, or DNA mutation, which occasionally leads to cancer.
Absorbing in the UVB portion of the solar spectrum, Vitamin E is transformed in the process, itself forming a free radical (tocopheroxyl), which can regenerate back to tocopherol via reaction with the skin’s ascorbic acid content (water soluble Vitamin C). Packer’s hypothesis is that as UV dosage is gradually increased, these two antioxidant defenses of the skin are overwhelmed. The free radicals, which then form in the skin, cause various types of cell damage, including lipid peroxidation and oxidative modification of dermal protein and its DNA. Packer has succeeded in measuring the depletion of cutaneous lipid soluble antioxidants (such as Vitamin E) after UVAB skin irradiation; he also showed the protective effect of sunscreens in this respect.
Dr. Martin Rieger has discussed the chemistry of oxidation and peroxidation processes in various publications, pointing out that melanin is also a free radical scavenger, and therefore somewhat “photo-protective” in a sense which is unrelated to its light-scattering ability. Rieger has also noted that PABA may play a role in DNA-dimer formation.
Petrolatum, of which Dr. Albert Kligman recently observed, “Although not a sunscreen, we found it surprisingly effective in suppressing ultraviolet-induced tumors in hairless mice.
Moreover, its daily sue enabled their skins to avoid most of the structural changes which accompany old age.”
It may interest some of you to learn that – via a process known as photophoresis – the blood of skin cancer patients can be temporarily by-passed out of the body and irradiated with UV light before being returned. This process reduces symptoms of skin cancer called mycosis fungoides; it increases overall survival rates and does not produce the side effects commonly associated with chemotherapy. Once again here, we see the ambivalent role of UV radiation in human physiology.
At the University of Texas (Austin) a group led by Adam Heller is producing titanium dioxide coated glass “bubbles” 50-80 microns in diameter, which are then made water repellent so that they float on oceanic oil spills. These “bubbles” then bind to floating hydrocarbons and act as photocatalysts, destroying the oil via a sunlight-driven reaction with the seawater. A cascade of such reactions results in converting the oil to carbon dioxide and water. The effect is supposed to be quite spectacular, as the titanox-coated beadlets apparently “bleach” the oil, taking on their own weight in oil each hour, the reaction being most efficient in turbulent seas, just when other methods of oil spill control fail. It has been suggested that fly ash form burning’ coal – produced in the USA at the rate of 58 million tons/year, requiring costly land fills – could be coated with titanjura dioxide this way, providing a cheaper source of these photocatalytic “bubbles”.
The hyperglycaemia-activated aldose reductase was inhibited by alpha-lipoic (thioctic) acid, O- phenanthroline and aldose reductase inhibitors (ARIs) including Zeopolastat (ZPLS), Sorbinil (SBN) and AL-1576. This study also examined ARIs for the ability to chelate metal ions. We found that ARIs suppress copper-dependent ascorbate oxidation, lipid peroxidation and hydrogen peroxide production in erythrocytes.lxxvii
These results suggest that UVA might impair the function of LC by suppressing a co-stimulatory molecule, ICAM-1, expression via an oxidation pathway, and this suppression is mitigated by antioxidants.lxxviii
Genistein, a tyrosine kinase inhibitor, suppressed the effect of UVB irradiation and hydrogen peroxide on cyclooxygenase-2 induction in HaCat keratinocytes. Kirsi Isoherranen, Kari Punnonen, Christer Jansen, Pekka Uotila ULTRAVIOLET IRRADIATION INDUCES CYCLOOXYGENASE-2 EXPRESSION IN HACAT KERATINOCYTES AND IN HUMAN
SKIN. Department of Clinical Chemistry and Dermatology, University of Turku, Turku, Finland.
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ivShindo Y; Witt E; Han D; Tzeng B; Aziz T; Nguyen L; Packer L Recovery of antioxidants and reduction in lipid hydroperoxides in murine epidermis and dermis after acute ultraviolet radiation exposure. Photodermatol Photoimmunol Photomed, 10: 5, 1994 Oct, 183-91
vJurkiewicz BA, Buettner GR Ultraviolet light-induced free radical formation in skin: an electron paramagnetic resonance study.
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viDarr D; Combs S; Dunston S; Manning T; Pinnell S Topical vitamin C protects porcine skin from ultraviolet radiation-induced damage. Br J Dermatol, 127: 3, 1992 Sep, 247-53
viiPadh H Cellular functions of ascorbic acid. Biochem Cell Biol, 1990 Oct, 68:10, 1166-73
viiiAlmaas R; Rootwelt T; Oyasaeter S; Saugstad OD Supplemental ascorbic acid causes hydroxyl radical formation in iron- fortified infant nutrients in vitro. Ascorbic acid enhances hydroxyl radical formation in iron-fortified infant cereals and infant formulas. Eur J Pediatr, 1997 Jun, 156;6, 488-92
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xvKameyama K; Sakai C; Kondoh S; Yonemoto K; Nishiyama S; Tagawa M; Murata T; Ohnuma T; Quigley J; Dorsky A; Bucks D; Blanock; K Inhibitory effect of magnesium L-ascorbyl-2-phosphate (VC-PMG) on melanogenesis in vitro and in vivo. J Am Acad Dermatol, 34: 1, 1996 Jan, 29-33
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xviiKodama M; Inoue F; Kodama T; Kodama M Intraperitoneal administration of ascorbic acid delays the turnover of 3H-labeled cortisol in the plasma of an ODS rat, but not in the Wistar rat. Evidence in support of the cardinal role of vitamin C in the progression of glucocorticoid synthesis. In Vivo, 1996 Jan, 10:1, 97-102
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