Stay-C® 50

Enhancing the performance of your products with stable vitamin C

Vitamins have long been known for their vital role in human health, in all parts of the body, including the skin. Some vitamins, such as vitamins A and E, or pantothenic acid in the form of panthenol, are not only ingested. They can be applied directly to the skin to protect its structure, or to prevent premature aging.
There has also been an interest for cosmetics containing vitamin C for many years, since consumers know the beneficial effects of this vitamin when ingested as citrus fruits or in vitamin supplements. But the many talents of vitamin C (ascorbic acid) in skin care have up to now been underused, because of its instability against oxidation and the resulting browning of products in which it was used. Thus cosmetic manufacturers were not able to make full use of its beneficial effects as an antioxidant, a collagen booster or a skin lightener. Stabilization has therefore been an important issue for many years.

One elegant way to overcome the stability problem is by temporarily blocking the active center of the ascorbic acid molecule. This is the principle of stable STAY-C 50.

With STAY-C 50, enhancing the performance of cosmetic products is no longer a dream.

STAY-C 50 is the sodium salt of the monophosphate ester of ascorbic acid.

STAY-C 50 is a white powder. It is easily soluble in water to concentrations up to 50%. In contrast to ascorbic acid, STAY-C 50 is stable in aqueous solutions
(Figures 2 and 3) at a pH above 6.5.

To prevent the decomposition of STAY-C 50 in cosmetics, the pH of the product must be kept at this level (Figure 4).

STAY-C 50 is a provitamin. To become biologically active ascorbic acid, the vitamin must first be freed by phosphatase. Such enzymes are normal constituents of the skin (1).

The high interest in vitamin C for use in cosmetic products is based on the many benefits for which it is known (2).

The topical application of vitamin C in skin-care products allows levels to be reached in skin which would not be possible by consuming it in food or as an oral supplement (3).

Prevention of oxidative damage

STAY-C 50 alleviates oxidative stress to the skin.

Lipid peroxidation induced by UV-A light entails the formation of peroxide radicals along the side chains of polyunsaturated fatty acids in lipids. A single initiating event can lead to many cycles of peroxidation, leading in turn to breakdown products that themselves damage DNA or protein (3). The irritating effect of lipoperoxides in connection with acne and dandruff is also under discussion (4).

A study conducted on 20 healthy volunteers shows that the application of a cream containing STAY-C 50 prevents the formation of UV-A-induced squalene hydroperoxide (Figure 5). This inhibition was even more pronounced when the STAY-C 50 was combined with tocopheryl acetate.

Stimulating collagen synthesis

Dermatologists have long observed that skin fibroblasts synthesize less collagen as they age. Vitamin C can counteract this decline in two ways (5, 6, 7). It is an essential cofactor in the hydroxylation of lysine and proline, which contribute to the stability of collagen. It also stimulates the synthesis of collagen, thus reaching a major target of skin care cosmetics: the delay of chronic aging (8).

Skin lightening

Ascorbic acid and its esters are also used in skin-care products as active ingredients to lighten the skin, and to prevent and attenuate age spots. There are several in vivo studies (1, 9) having demonstrated the suppression of pigmentation and in vitro studies (9, 10) showing how the vitamin acts at the level of melanogenesis.

Replenishing vitamin E

Ascorbic acid is the main water-soluble non-enzymatic antioxidant. As an ideal free-radical scavenger, it also plays an important role in the regeneration of vitamin E from the vitamin E radical. This recycling effect of ascorbic acid on oxidized vitamin E has been specifically shown in skin (3).

Moreover, when used in combination, vitamin C as the water-soluble and vitamin E as the oil-soluble vitamin form a very powerful antioxidant couple. The key is never to use one single antioxidant alone.

Recommended Applications

• Face-care products
• Body-care products
• Sun-care products
•  Oral-care products

Formulation Guidelines

• Recommended use levels for STAY-C 50 in daily care products:

0.5 to 1.0% as an antioxidant up to 10% in intensive and special products (e.g. lightening creams)

• Dissolve STAY-C 50 in water and add to the emulsion as a solution at 40 to 45°C
• Use always chelating agents (e.g. disodium EDTA) to avoid degradation of STAY-C 50 by metal ions.
• Maintain the formulation at a pH between 6.5 to 7.5.

Reference Formulas with Stay-C 50

Protective day cream

Oil/water emulsion with vitamins and UV-A/UV-B sunscreens

Moisturizing day cream, with UV-A and UV-B protection, rich in vitamins C and E and provitamin B5 to prevent premature skin aging, leaving the skin supple and smooth.

Transparent gel with vitamins and soft almond spheres

Gel with vitamin C and provitamin B5 cools and refreshes the skin immediately, and protects and improves the moisture content of the skin.

Oil/Water emulsion with vitamins and carotene

Light lotion with the antioxidant couple vitamin C and E, and panthenol to sooth and calm;

suitable also for after-sun treatment.

Oil/water emulsion with vitamins and UV-A/UV-B sunscreens

Lotion with UV-A and UV-B filters to shield the skin against harmful radiation, and vitamin C to protect against lipid peroxidation.

Suppliers

1) HOFFMANN-LA ROCHE LTD,
CH-4070 Basel / Switzerland

2) CRODA CHEMICALS LTD,
North Humberside
DN14 9AA / England

3 ) COGNIS DEUTSCHLAND GMBH,
D-40551 Düsseldorf / Germany

4) UNIQUEMA, 3078
Everberg/ Belgium

5) CONDEA CHEMIE GMBH,
D-58490 Witten / Germany

6) GOODRICH COMPANY,
Cleveland OH 44141-3247 / USA

7) GATTEFOSSE, 69804
Saint Priest / France

8) FLUKA CHEMIE AG,
CH-9471 Buchs / Switzerland

9) KOBO products, 31520
Ramonville / France

10) DOW CORNING CORP.,
Midland – Mi 48686-0994 / USA

11) GOLDSCHMIDT AG, D-4300
Essen 1 / Germany

References

1) Takashima H, Nomura H, Imai Y, Mima H. Ascorbic acid esters and skin pigmentation. Am. Perfum. Cosmet. 1971, 86: 29–36

2) Kretz A & Moser U. Vitamins. In: Handbook of Cosmetic Science and Technology, Marcel Dekker Inc., New York. In press

3) Colven RM & Pinnell SR. Topical vitamin C in aging. Clinics in Dermatology 1996, 14: 227–234

4) Erlemann GA. Vitamine in der Kosmetik. Seifen, Öle, Fette, Wachse 1984, 110: 181–186

5) Pinnell SR. Regulation of collagen biosynthesis by ascorbic acid: A review. The Yale Journal of Biology and Medecine 1985, 58: 553–559

6) Hata RI & Senoo H. L-ascorbic acid 2-phosphate stimulates collagen accumulation, cell proliferation, and formation of a three-dimensional tissuelike substance by skin fibroblasts. J. Cell. Physiol. 1989, 138: 8–16

7) Kurata SI, Senoo H, Hata RI. Transcriptional activation of type I collagen genes by ascorbic acid 2-phosphate in human skin fibroblasts and its failure in cells from a patient with a2(I)-chain-defective Ehlers-Danlos syndrom. Exp. Cell Res. 1993, 206: 63–71

8) Boyera N, Galey I, Bernard BA. Effect of vitamin C and its derivatives on collagen synthesis and cross-linking by normal human fibroblasts. Int. J. Cosm. Sci. 1998, 20: 151–158

9) Sakamoto T, Egawa M, Iwai I, Tanaka M, Akiba M, Akaiyama J, Yamamoto I. Development of the new types of skincare cosmetics containing the novel vitamin C derivative with prolonged effects. 19th IFSCC Congress Sydney 1996, 2: 5–17

10) Takenouchi K & Aso K. The relation between melanin formation and ascorbic acid. J. Vitaminol. 1964, 10: 123–134

The information given in this publication is based on current knowledge and experience, and may be used at your discretion and risk. It does not relieve you from carrying out your precautions and tests. We do not assume any liability in connection with your product or its use. You must comply with all applicable laws and regulations, and observe all third-party rights.