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Inhibitory effects on mushroom tyrosinase by flavones from the stem barks of Morus lhou (S.) Koidz

2008; Taylor & Francis; Volume: 23; Issue: 6 Linguagem: Inglês

10.1080/14756360701810207

1475-6374

Young Bae Ryu, Tae Joung Ha, Marcus J. C. Long, Hyung Won Ryu, Sang Wan Gal, Ki Hun Park,

Biochemical Analysis and Sensing Techniques

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, = 1.354 μM).