Inhibitory effect of red koji extracts on mushroom tyrosinase.
Red koji has been recognized as a cholesterol-lowering diet supplement because of it contains fungi metabolites, monacolins, which reduce cholesterol synthesis by inhibiting HMG-CoA reductase. In this study, water extracts of red koji were loaded onto a C(18) cartridge, and the acetonitrile eluate was collected as test fraction. Red koji water extracts and its C(18) cartridge acetonitrile eluent had total phenols concentrations of 5.57 and 1.89 mg/g of red koji and condensed tannins concentrations of 2.71 and 1.20 mg/g of red koji, respectively. Both exhibited an antioxidant activity and an inhibitory activity to mushroom tyrosinase. The higher antioxidant activity of the red koji acetonitrile eluent was due to the existence of a high percentage of condensed tannins. The results from the kinetic study for inhibition of mushroom tyrosinase by red koji extracts showed that the compounds in the extracts competitively inhibited the oxidation of tyrosine catalyzed by mushroom tyrosinase with an ID(50) of 5.57 mg/mL.
Wu
Li-Chen
LC
Department of Applied Chemistry, National Chi-Nan University, Puli, Nantou 545, Taiwan. lw25@ncnu.edu.tw
Chen
Yun-Chen
YC
Ho
Ja-An Annie
JA
Yang
Chung-Shi
CS
D000363:Agaricales / Q000201:enzymology*; D000975:Antioxidants / Q000032:analysis; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005285:Fermentation; D032741:Monascus / Q000378:metabolism*; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors*; D012275:Oryza / Q000737:chemistry* / Q000382:microbiology*; D010636:Phenols / Q000032:analysis; D010936:Plant Extracts / Q000494:pharmacology*
D000975:Antioxidants; D004791:Enzyme Inhibitors; D010636:Phenols; D010936:Plant Extracts; D014442:Monophenol Monooxygenase