RESUMO
The inhibitor of tyrosinase activity in black rice bran was investigated. The methanol extract from black rice bran was re-extracted with hexane, chloroform, ethyl acetate, or water. The ethyl acetate extract had the most potent inhibition against tyrosinase activity by 80.5% at a concentration of 0.4 mg/mL. Inhibitory compound in the ethyl acetate fraction was isolated by silica gel column chromatography, and identified as protocatechuic acid methyl ester (compound 1) by GC, GC-MS, IR, and 1H and 13C NMR spectroscopy. Compound 1 inhibited 75.4% of tyrosinase activity at a concentration of 0.50 micromol/mL. ID(50) (50% inhibition dose) value of compound 1 was 0.28 micromol/mL. To study the structure-activity relationship, protocatechuic acid (2), vanillic acid (3), vanillic acid methyl ester (4), isovanillic acid (5), isovanillic acid methyl ester (6), veratric acid (7), and veratric acid methyl ester (8) were also assayed.
Assuntos
Inibidores Enzimáticos/isolamento & purificação , Monofenol Mono-Oxigenase/antagonistas & inibidores , Oryza/química , Acetatos , Cromatografia Gasosa , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , Hidroxibenzoatos/análise , Hidroxibenzoatos/química , Hidroxibenzoatos/farmacologia , Metanol , Extratos Vegetais/química , Relação Estrutura-AtividadeRESUMO
The components of the volatile oils from the straws of Oryza sativa L. (Onshinomai, Asamurasaki, Hinohikari) were analyzed by capillary GC/GC-MS. The quantification of volatile compounds in the oils was made by the internal standard method, using palmitic acid as reference substance. Palmitic acid was the most abundant component in these samples, followed by hexahydrofarnesyl acetone and phytol.