ABSTRACT
In the field of dermatology, antioxidants are widely used and are innovative ingredients in topical applications. This chapter is intended to provide an overview of the current state of research on the use of antioxidants in cosmeceutical applications. The most important antioxidants, vitamin E, vitamin C, thiols, and flavonoids, will be introduced, and their intriguing cooperation as well as their role in signal transduction events will be discussed. The body is continuously exposed to oxidants. Endogenous sources arise as a consequence of normal metabolic pathways. For example, mitochondrial respiration produces superoxide and hydrogen peroxide, whilst enzymes such as lipoxygenases, xanthine oxidase, and NADPH oxidase produce hydroperoxides and superoxide, respectively. Exogenous oxidants arise from environmental pollutants such as smoke, smog, UV radiation, and diet. In response to these oxidants, a number of systemic antioxidants are available whose functions are to scavenge reactive oxygen species preventing damage to macromolecules such as lipids, DNA, and proteins. Antioxidant protection arises from molecules synthesized as part of metabolism, e.g., glutathione (GSH) and uric acid; essential vitamins which must be taken in from the diet, e.g., vitamins E and C; enzymes which decompose reactive oxygen species, e.g., superoxide dismutases, catalase, and the glutathione peroxidases. These systems provide protection in various intra-and intercellular compartments. Usually there is a tight balance between oxidants produced and antioxidant scavenging, however, under certain conditions the balance can be tipped in favor of the oxidants, a condition called oxidative stress. Potentially oxidative stress can be caused either by an increase in the number of oxidants, for example, as a result of cigarette smoking or UV irradiation, or by a deficiency in antioxidants. This is of major concern because oxidative stress has been implicated in a number of conditions including atherosclerosis, skin cancer, and photoaging.
