Inhibitory effects on mushroom tyrosinase by flavones from the stem barks of Morus lhou (S.) Koidz |
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| Authors: | Y B Ryu T J Ha M J Curtis-Long H W Ryu S W Gal |
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| Institution: | 1. Division of Applied Life Science (BK21 program), EB-NCRC, Institute of Agriculture &2. Life Science, Gyeongsang National University, Jinju 660-701, Korea,;3. Yeongnam Agricultural Research Institute, National Institute of Crop Science, RDA, Miryang 627-803, Korea,;4. , Woodview, 12 New Road, Nafferton, East Yorkshire, YO25 4JP, UK, and;5. Department of Microbiological Engineering, Jinju National University, Jinju 660-758, Korea |
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| Abstract: | Five flavones displaying tyrosinase inhibitory activity were isolated from the stem barks of Morus lhou (S.) Koidz., a cultivated edible plant. The isolated compounds were identified as mormin (1), cyclomorusin (2), morusin (3), kuwanon C (4), and norartocarpetin (5). Mormin (1) was characterized as a new flavone possesing a 3-hydroxymethyl-2-butenyl at C-3. The inhibitory potencies of these flavonoids toward monophenolase activity of mushroom tyrosinase were investigated. The IC50 values of compounds 1–5 for monophenolase activity were determined to be 0.088, 0.092, 0.250, 0.135 mM, and 1.2 μM, respectively. Mormin (1), cyclomorusin (2), kuwanon C (4) and norartocarpetin (5) exhibited competitive inhibition characteristics. Interestingly norartocarpetin (5) showed a time–dependent inhibition against oxidation of l–tyrosine: it also operated under the enzyme isomerization model (k5 = 0.8424 min? 1, k6 = 0.0576 min? 1,  | |
| Keywords: | Morus lhou (S ) Koidz stem barks tyrosinase norartocarpetin time-dependent inhibition |
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