Vitamin B1 (thiamin) is water-soluble and a natural ingredient of cereal and yeast extracts (faex extract).
In aqueous solutions it is deactivated by heat. The decomposition products partly generate the meaty flavour which is characteristic for cooked food. As a co-enzyme component the vitamin plays an important part in the carbohydrate metabolism. In cosmetic applications it is used as a salt (hydrochloride) and frequently combined with other B-vitamins (vitamin B complex) for the treatment of compromised skin.
Vitamin B2 (riboflavin): Sources of riboflavin are yeast, milk, liver and other innards. The vitamin is involved in the formation of numerous oxidoreductases. It is used as a yellow colouring agent (E 101) in food and cosmetic products.
Vitamin B3 (niacin) occurs either as nicotinic acid or nicotinamide (INCI: Niacinamide). As a component of the coenzymes NAD and NADP, hence dehydrogenases, it is found in non-processed food (meats, cereals) and involved in the biochemical redox reactions. The vitamin is reabsorbed as nicotinic acid in the intestinal tract. In cosmetic products, the amide is used for skin recovering purposes due to its better water-solubility. Niacinamide is anti-inflammatory for blemished skin.
Vitamin B5 (pantothenic acid): As a component of coenzyme A it is contained in milk, liver and vegetables. In the cosmetic field sometimes the calcium salt (INCI: Calcium Pantothenate) is used, however frequently the easily penetrating provitamin (D-Panthenol) is preferred which is oxidized in the skin into pantothenic acid.
Fields of application are:
- enhanced skin hydration
- treatment of inflammatory processes
- cell formation and epithelisation after skin lesions
- suppression of itching
- hair cures
Vitamin B7 (biotin) has an interesting double ring structure that contains a urea group, among others. The former term “vitamin H” indicates its significance for the skin. In low concentrations it is ubiquitous in food. The highest concentration occurs in yeast. The vitamin is a key component in the enzymes of the amino acid and fatty acid metabolism. Deficiencies lead to growth disturbances of the hair, nails and the skin. Consequences are loss of hair and dermatitis.
Vitamin B9 (folic acid): The yellow compound is rich in nitrogen and occurs in vegetables, liver and cereals. It plays a significant role in the C1 metabolism, i.e. in the transfer of methyl-, methylene or formyl groups, where it is effective in the form of tetrahydrofolic acid. Folic acid participates in the DNA synthesis.
Vitamin B12 (cobalamin) is a macro molecule that contains cobalt and can only be synthesized by micro-organisms living in the intestinal tract of animals or on the surface of soiled food. Hence, it can only be assimilated with animal food where it occurs in concentrated form in liver and kidneys; an exception though is the algae spirulina maxima. Deficiencies can occur in vegetarians or vegans however also pathological conditions of the intestinal micro flora inhibit the resorption of the vitamin. The vitamin as such is inactive and can only be activated by its conversion into coenzyme B12. Coenzyme B12 catalyzes specific rearrange- ment reactions in the body. Its use in skin care products is controversially discussed as it is assumed that the molecule is able to bind nitrogen oxide. However, this function can also be assumed by the amino acids of the NMF.
The water-soluble vitamin C (ascorbic acid) is sufficiently supplied with fruit and vegetables. It participates in the biosynthesis and the crosslinking of collagen but also is involved in many other metabolic activities in the field of steroids, amino acids and catecholamines.
Main functions in cosmetics are:
- product protection (antioxidant)
- deactivation of free radicals
- keratolytic effects of free, concentrated ascorbic acid at a low pH level analogous to the AHA acids
- prevention of hyper pigmentation
- stimulation of the collagen formation
Hence it is essential to use derivatives and carrier substances:
- Ascorbyl Phosphate is applied in the form of sodium or magnesium salts. It is the water-soluble ester of vitamin C with phosphoric acid and enzymatically hydrolyzed after having passed the skin barrier. The carrier substance is phosphatidylcholine in the form of liposomes.
- Ascorbyl Palmitate and ascorbyl stearate as well as their respective multiple esters are the fat-soluble variants that are appropriately encapsulated in nanodispersions where the phosphatidylcholine also has penetration enhancing effects. Analogously, the esters are enzymatically hydrolyzed into ascorbic acid, palmitic acid and stearic acid. Phosphatidylcholine is produced naturally in the body and hence com- patible with all barrier and cell structures of the body. Here, phosphatidylcholine is also reinforcing penetration.
% are sufficient to achieve this effect.
The most significant sources of vitamin D (calcitriol) are the provitamin D2 (ergosterol) that occurs in mushrooms and wheat germ oil among others, and provitamin D3 (7-dehydrocholesterol) that is found in egg yolk, liver and fish oils. Vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol) are formed from provitamin D2 resp. provitamin D3 under the influence of sunlight. They are transported into the liver and there transformed into 25-hydroxycholecalciferol (calcidiol). After the transport into the kidneys via blood stream, it is transformed into the active form of vitamin D (1,25-Dihydroxy- cholecalciferol = calcitriol). From there the blood stream again transports it into the target organs where it is bound to proteins. Calcitriol controls the calcium and phosphate metabolism in the small intestine, the bones and the kidney.
The European Cosmetics Directive explicitly bans the use of vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). However this does not apply to the provitamins that also in the US are licensed for the use in skin care products.
A whole series of interesting effects in the skin are described in the context of vitamin D:
- Calcitriol influences the differentiation and the growth process of keratinocytes. This function plays an important role in the psoriasis treatment.
- Calcitriol participates in the proper maintenance of the calcium gradients in the skin.
- Calcitriol stimulates the formation of antimicrobially effective peptides such as defensins and cathelicidins. The effect of these peptides is particularly interesting in the context of inflammatory processes in neurodermatitis cases.
- Calcitriol prolongs the self-protection of the skin during the exposure to UVB radiation. It stimulates the heat shock proteins.
- Several studies even describe a re- pigmentation in vitiligo cases after the application of calcitriol or vitamin D analogous products.
Vitamin E (d-D-tocopherol) is equipped with a terpene side chain that is bound to a chromane ring and belongs to the group of fat-soluble vitamins just as the vitamins A, D and K. As a natural antioxidant, vitamin E occurs in all unsaturated vegetable oils. Wheat germ oil is on top position in this regard. Outstanding physiological function of this vitamin is the protection of oxygen sensitive cellular components such as omega-3 and omega-6 fatty acids. In the cosmetic field, the free vitamin and its derivatives are used. The derivatives are the esters of organic acids. As the esterification occurs on the phenolic hydroxyl group, they lack the antioxidative effects. Hence they do not have antioxidative functions in the products but are stable active agents that are hydrolyzed by esterases after having passed the skin barrier. The ester hydrolysis activates the antioxidative features. The following vitamin E derivatives are of significance:
- Tocopheryl Acetate is the ester of acetic acid.
- Tocopheryl Palmitate is the ester of palmitic acid.
Tocopheryl Linoleate (ester of linoleic acid) shows a combination of antioxidative effects with the effects of an essential omega-6 acid.
- Tocopheryl Nicotinate (ester with nicotinic acid) is a combination of vitamin E with vitamin B3. The ester supports the microcirculation in the skin without the features that are typical for short-chained nicotinic acid esters such as generating heat or erythema.
- Antioxidative effects and radical scavenger features – in this context it is important to select the appropriate concentration as high concentrations will trigger the pro-oxidative features of vitamin E.
- Protection of vitamin A and derivatives in combination with vitamin C.
- The radical scavenger features also naturally involve a reduction of the stress caused by UV radiation. The same applies to inflammatory processes.
- Stimulation of cell formation (epithelisation)
The moisture retention capacity of the skin is improved.
Vitamin K belongs to the fat-soluble vitamins and occurs in two natural forms, vitamin K1 (phyllochinone; 2-methyl-3-phytyl-naphthochinone) and vitamin K2 (menachinone, 2-methyl- 3-difarnesyl-1.4-vitamin. The phytyl side chain of vitamin K1 is equivalent to a monoterpene with 20 C-atoms. In contrast to vitamin K1, vitamin K2 can have differently sized terpene side chains. Vitamin K1 is mainly assimilated with vegetable food, while vitamin K2 is formed by intestinal bacteria such as escherichia coli. Hence, vitamin K deficiencies will appear, if an antibiotics treatment has affected the intestinal flora or it has not yet been formed as e.g. in newborns.
Vitamin K is a blood coagulation factor and, among others, supports the steady flow characteristics of the blood. Vitamin K deficiencies slow down the blood coagulation and can be responsible for increased bleedings after injuries. Also the disposition to form hematomas, purpura (efflorescence-like skin bleedings), nose bleeding as well as gastrointestinal or mucous tissue bleedings can be caused by vitamin K deficiency.
Topically applied, the vitamin stabilizes the superficial capillary system and firms the skin. That is why vitamin K can also be used to treat rosacea and couperosis. Despite of the 2009 imposed ban of vitamin K, the epoxide of the vitamin, a pre-stage, still is licensed although its sensitization potential is incomparably higher due to its reaction with protein components on the skin surface. The vitamin K content in vegetable sources such as wheat germ, Brussels sprouts, spinach and tomatoes is too insignificant to use it for skin care purposes.
From a present-day perspective, skin conditions caused by hypovitaminoses such as pellagra e.g. can practically be excluded as today’s nutrition is multi-faceted and rich in vitamins. The vitamins B12 and D constitute an exception though and should be kept in mind when following a vegetarian or vegan diet. Vitamin D deficiencies then become all the more serious, if the daily skin care routine involves creams with UV filters.
Apart from the daily minimum requirement, some of the vitamins also show effects that make them valuable components of products for the daily skin care, for the treatment of skin disorders and the prevention of premature skin aging. Aside from that, they meet the criteria for natural and physiological cosmetics.
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