PARTICIPATION OF ASCORBIC ACID IN THE FORMATION OF TYROSINE MELANIN

Abstract

As preliminary studies on the clinical application for the treatment of pigmented dermatosis with a massive doses of ascorbic acid (1〜2g), participations of ascorbic acid in the formation of melanin as well as absorption and excretion of the vitamin in man and experimental animal were investigated. Ascorbic acid inhibited melanin formation in tyrosine-tyrosinase system by its reducing property, and the reaction did not proceed untill all ascorbic acid in the reaction system was oxidized to dehydroascorbic acid. The minimum amount of complete inhibition of melanin formation was 0.5μM. The amounts of ascorbic acid in the skin after intramuscular injection of 300 mg to guinea pig or rabbit were 3.0μM. There was no marked difference in amount between pigmented and nonpigmented skin. The level of ascorbic acid did not precede than 2.4〜2.6mg%, whenever massive amount was given orally. Urinary excretion of ascorbic acid was 20% of the amount administered after daily oral administration of 2g for one month.