ABSTRACT
Introduction 413
Melatonin and UV Protection 414
Melatonin: A “Hair Growth Inducer” 416
Melatonin: A Natural Product in Edible Plants 416
Melatonin: A Food Supplement 417
Conclusion 417
References 418
INTRODUCTION
Melatonin (N-acetyl-5-methoxytryptamine) is a phylogenetically very old
molecule, which is produced by the pineal gland of mammals including the human
being and primarily defined as a hormone. In this function, melatonin is active
via three receptors, Mel 1, Mel 2, and Mel 3 (1,2). Melatonin regulates the day
and night rhythm dependent on light perception of the retina, seasonal rhythm
concerning reproduction and hair growth in animals, aging, and immunoregula-
tion (3,4). Apart from the receptor-mediated hormonal function, melatonin is a
strong antioxidative substance acting pharmacologically by directly scavenging
free radicals as a nonreceptor dependent substance. It also stimulates antioxida-
tive enzymes such as superoxiddismutase. In 1993, Reiter and Tan discovered the
antioxidative potential of melatonin describing its strong affinity to the hydroxyl
radical, one of the most damaging radicals involved in photoinduced oxidative
stress (5). In different organ systems, numerous effects ascribed to the antioxida-
tive capacities of melatonin have been reported and investigated: melatonin
protects the stomach by inhibition of the gastral peroxidase and stimulation of
the mitochondrial superoxiddismutase (6). Melatonin is used to protect the
heart against oxidative damage induced by chemotherapeutics and is able to
reduce the overall toxicity of chemotherapeutic agents in the body (7,8). Melato-
nin reduces the oxidative damage in the skin in disturbances of heme metabolism
in porphyria. UVA light-induced toxic free radicals in the skin lead to oxidation
of guanin-bases and lipid peroxidation which is suppressed by melatonin (9).
Concerning the skin, melatonin is able to increase cell viability in fibroblasts
challenged by UVB irradiation and ionizing irradiation (10,11). In this chapter,
we review the results of in vitro and in vivo studies on melatonin, as well as
its current therapeutic and possible future applications.
