Prevention of the photodamage in the hairless mouse dorsal skin by kojic acid as an iron chelator.

Kojic acid, a fungal metabolic product, has been used as a skin-depigmenting agent in skin care products marketed in Japan. Iron in the skin is known to be involved in wrinkling as a result of chronic photodamage. Kojic acid was expected to have anti-wrinkling activity, since it possesses iron-chelating activity. We now evaluated the anti-wrinkling activity of kojic acid by using hairless mice exposed to chronic solar-simulating ultraviolet (UV) irradiation as model animal. At the end of a 20-week irradiation period, topical application of kojic acid before UV irradiation was observed to dramatically prevent: (1) the wrinkling, (2) hyperplasia of the epidermis, (3) fibrosis of the lower dermis, and (4) the increase of extracellular matrix components in the upper dermis. These findings indicate that kojic acid is a typical agent preventing wrinkling of the skin due to chronic photodamage.