Abstract
Tyrosinase is well-known as a key enzyme responsible for the production of melanin in melanocytes. It is also known that inflammatory reactions such as active oxygen species and melanogenic factors in the skin are induced by UV irradiation. The keys to suppress melanin synthesis are considered to be not only the inhibition of tyrosinase activity but also that of inflammatory reactions. Raspberry ketone glucoside (RKG) in raspberry fruit (Rubus ideaeus) had the inhibitory effect on the melanin synthesis. As a result of an investigation with the glycosides that have similar structure of RKG at its glycoside moieties and alkyl chain, the structure of RKG was found to be suitable as an inhibitory factor on melanogenesis. RKG released raspberry ketone (RK) gradually after the reaction with both homogenated and desquamated cells of the stratum corneum. In addition to the inhibitory effect of melanin synthesis, RK also showed remarkable functions such as the scavenge of nitric oxide (NO) which was considered to induce pigmentation of human skin through activation of melanogenesis and the inhibition of the inflammation-related reactions such as production of superoxide anion and lipid peroxide. These data indicated that RKG had lasting effects for the inhibition of melanogenesis and various melanogenic factors after the degradation in the skin.
