Inhibitory effects on mushroom tyrosinase by flavones from the stem  barks of Morus lhou (S.) Koidz.
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 microM, 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), K(app)(i) = 1.354 microM).
Ryu
Y B
YB
Division of Applied Life Science (BK21 program), EB-NCRC, Institute of Agriculture & Life Science, Gyeongsang National University, Jinju 660-701, Korea.
Ha
T J
TJ
Curtis-Long
M J
MJ
Ryu
H W
HW
Gal
S W
SW
Park
K H
KH
D000363:Agaricales / Q000187:drug effects* / Q000201:enzymology*; D055162:Biocatalysis; D047309:Flavones / Q000737:chemistry / Q000494:pharmacology*; D015394:Molecular Structure; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D031625:Morus / Q000737:chemistry*; D024301:Plant Bark / Q000737:chemistry*; D018547:Plant Stems / Q000737:chemistry*; D013329:Structure-Activity Relationship
D047309:Flavones; D014442:Monophenol Monooxygenase