Anti-tyrosinase activity of purple glutinous rice Thailand local genotypes

Abstract

Purple glutinous rice (Oryza sativa L.) is widely cultivated in the north and northeast of Thailand. Its purplishblack pericarp layers is rich in anthocyanin. Purple glutinous rice is a good source of fiber, minerals, and severalimportant amino acids; furthermore, the high content of γ-oryzanol and the anthocyanin which were identified ascyanidin 3-glucoside and peonidin 3-glucoside. The aim of this study was to examine anti-tyrosinase compoundin difference local genotypes of purple glutinous rice. Among 36 genotypes of purple glutinous rice were collected,K-Entry 9 showed the highest anti-tyrosinase activity (IC₅₀ = 369.5 μg/ml). By means of column chromatographyand high performance liquid chromatography, the ethyl acetate extract yielded purified compound which inhibitedtyrosinase enzyme activity with IC₅₀ = 64.2 ± 1.04 μg/ml. The structure was elucidated by spectroscopic methodas protocatechuic acid. This valuable data would be useful for standardization of purple glutinous rice products usedin anti-aging and whitening cosmetics. Also, this was an alternative process for value added to purple glutinousrice Thailand local genotypes.

Key words: Oryfa sativa L., tyrosinase