title: Tyrosinase inhibitor isolated from the leaves of Zanthoxylum piperitum.
abstract: Two flavonols, quercetin (1) and quercitrin (2), were isolated from the leaves of Zanthoxylum piperitum. Their structures were established by UV, one- and two-dimensional NMR, and mass spectroscopic methods. Quercetin showed significant inhibition against mushroom tyrosinase with an IC50 value of 3.8 microg/ml, and appeared to inhibit the polyphenol oxidase activity of tyrosinase in a competitive manner (Ki = 10 +/- 0.20 microM) when L-tyrosine was used as a substrate, although it did not inhibit the melanin production of Streptomyces bikiniensis.
authors.affiliation: Division of Applied Life Science, Graduate School and Institute of Agricultural Life Sciences, Gyeongsang National University, JinJu, Korea.
authors.forename: Chang Ho
authors.initials: CH
authors.lastname: Jeong
authors.forename: Ki Hwan
authors.initials: KH
authors.lastname: Shim
mesh_terms: D000363:Agaricales / Q000201:enzymology; D004156:Catechol Oxidase / Q000037:antagonists & inhibitors; D004791:Enzyme Inhibitors / Q000302:isolation & purification* / Q000494:pharmacology; D044948:Flavonols / Q000302:isolation & purification / Q000494:pharmacology; D005656:Fungal Proteins; D020128:Inhibitory Concentration 50; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008543:Melanins / Q000096:biosynthesis; D015394:Molecular Structure; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors*; D018515:Plant Leaves / Q000201:enzymology; D011794:Quercetin / Q000031:analogs & derivatives* / Q000302:isolation & purification / Q000494:pharmacology; D032106:Zanthoxylum / Q000201:enzymology*
chemical_list: D004791:Enzyme Inhibitors; D044948:Flavonols; D005656:Fungal Proteins; D008543:Melanins; C012526:quercitrin; D011794:Quercetin; D004156:Catechol Oxidase; D014442:Monophenol Monooxygenase