Tyrosinase inhibitor from black rice bran.
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.
Miyazawa
Mitsuo
M
Department of Applied Chemistry, Faculty of Science and Engineering, Kinki University, Kowakae, Higashiosaka-shi, Osaka 577-8502, Japan. miyazawa@apch.kindai.ac.jp
Oshima
Teruo
T
Koshio
Katsuya
K
Itsuzaki
Yumi
Y
Anzai
Jun
J
D000085:Acetates; D002849:Chromatography, Gas; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D062385:Hydroxybenzoates / Q000032:analysis / Q000737:chemistry / Q000494:pharmacology; D000432:Methanol; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors*; D012275:Oryza / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry; D013329:Structure-Activity Relationship
D000085:Acetates; D004791:Enzyme Inhibitors; D062385:Hydroxybenzoates; D010936:Plant Extracts; C009091:protocatechuic acid; C007650:ethyl acetate; D014442:Monophenol Monooxygenase; D000432:Methanol