Vitamin E as a bioactive agent in cosmetics Wolfgang Pittermann

Henkel KGaA, D-40191 Düsseldorf

Introduction

There has been a major change in the development of cosmetic products in the recent years. Vitamins and other bioactive substances are increasingly being used alongside conventional ingredients.

The immediate cause is increasing knowledge of the 'stress environment' to which the skin, as the human body's largest organ, is exposed. Stress factors include environmental influences such as ultraviolet radiation and the possibly inadequate intake of certain vitamins as a result of modern lifestyles, etc. The present interest in the common roots of health, nutrition and body care is also changing consumer expectations with regard to the performance characteristics of cosmetic products. This development has temporarily pushed the significance of decorative cosmetics into the background. The focus is now on protection and preventive measures against harmful environmental influences and biological aging processes, as well as the possible repair or regeneration of unwelcome changes in the skin.

Oxidative stress in the skin

The present use of vitamins is an example of the response to these new requirements. One target area is oxidative stress, i.e. the consequences of the creation of reactive forms of oxygen in the skin. The reactive forms that usually undergo physiological metabolization may, under abnormal stress conditions and in the absence of adequate protection by enzymatic and non-enzymatic mechanisms, cause pathophysiological dysfunctions within the skin. Vitamins C and E belong to the non-enzymatic components of the body's own protective system. While vitamin C is the most important water-soluble antioxidant, vitamin E is one of a group of lipid-soluble radical interceptors, localized in the cell membrane (Mayer et al., 1993).

Smoothness and moisture content

As well as providing protection against UV-radiation, topical application of vitamin E has a positive effect on the skin's smoothness and moisture content. Both of these parameters are closely linked to the functionality of the skin barrier. The objective of all long-term skin care must be to maintain, strengthen or regenerate this.

Vitamin E´s natural distribution in the skin

According to a paper recently published (Thiele et al., 1999) the sebaceous gland secretion is a major physiologic route of vitamin E delivery to skin. In order to characterize the frequently used in vitro model of the isolated bovine udder (BUS-model), the vitamin E content of three different levels (epidermo-dermal = level 1; sebaceous glands = level 2; hair follicle = level 3) of the skin was evaluated (figure 1). Approx. 70 % of the total vitamin E content of the skin was found within the level 2 containing the sebaceous glands. The epidermo-dermal level shows about the double amount (approx. 20 %) of vitamin E than the level 3 (hair follicle).
This demonstrates that sebaceous gland secretion may be involved in the vitamin E delivery to skin of the bovine udder similar to the situation in the human skin.

Vitamin E´s release from the body care products

For vitamin E to be able to take effect, it has to be released from the body care product. To prove the release in-vitro studies using the viable skin of the isolated perfused bovine udder (BUS)-model) were performed in various study designs.
Complex emulsions are preferable to simple oil-based products, even when the initial application concentrations are the same, due to the universal solubility conditions and the higher effective concentration in the oil phase (Förster et al., 1997). Under leave-on conditions vitamin E penetrates in larger amounts and at a faster rate from w/o than from o/w emulsions. Vitamin E is also absorbed at the surface of the horny layer from surfactant products such as shower preparations under rinse-off conditions (Förster et al 1999).
The penetration of vitamin E into the horny layer is modified in emulsions containing chitosan (Pittermann et al., 1997) and can be accelerated significantly by liposomal techniques (Blume et al., 2000).

Market products containing vitamin E

Topical application in cosmetics that contain vitamin E initially strengthens the inwardly aligned effective protective mantle of the skin. For this reason an overview (selection of current German and European market products, in the case as they contain vitamin E and offer relevant product claims) is also given in the presentation.

Literature

1) Blume G., Pittermann W., Waldmann-Laue M., Kietzmann M., Verma D.D. and C. Johann; Liposomes and Vitamins; IN-COSMETICS 2000 - Conference Proceedings, pp 131-134 (2000)
2) Förster Th., Jackwerth B., Pittermann W., van Rybinski W. and M. Schmitt; Properties of Emulsions: Structure and skin penetration; Cosmetics & Toiletries 112, 73-82 (12/1997)
3) Förster Th., Pittermann W., Schmitt M. and M. Kietzmann; Skin penetration properties of cosmetic formulations using a perfused bovine udder model; J. Cosmet. Sci. 50, 147-157 (1999)
4) Mayer P. Pittermann W. and S. Wallat; The effects of Vitamin E on the Skin; Cosmetics & Toiletries 108, 99-109 (1993)
5) Pittermann W., Hörner V. and R. Wachter; Efficiency of high molecular weight chitosan in skin care applications. Chitin Handbook, R.A.A. Muzzarelli and M.G. Peter, eds., European Chitin Society. 1997. ISBN 88-86889-01-1
6) Thiele J.J., Weber S. and L. Packer; Sebaceous Gland Secretion is a major Physiologic Route of Vitamin E delivery to Skin; J Invest. Derm. 113, 1006-1010 (1999)