title: Inhibitory effects on mushroom tyrosinase by flavones from the stem  barks of Morus lhou (S.) Koidz.
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 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).
authors.affiliation: Division of Applied Life Science (BK21 program), EB-NCRC, Institute of Agriculture & Life Science, Gyeongsang National University, Jinju 660-701, Korea.
authors.forename: Y B
authors.initials: YB
authors.lastname: Ryu
authors.forename: T J
authors.initials: TJ
authors.lastname: Ha
authors.forename: M J
authors.initials: MJ
authors.lastname: Curtis-Long
authors.forename: H W
authors.initials: HW
authors.lastname: Ryu
authors.forename: S W
authors.initials: SW
authors.lastname: Gal
authors.forename: K H
authors.initials: KH
authors.lastname: Park
mesh_terms: 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
chemical_list: D047309:Flavones; D014442:Monophenol Monooxygenase