title: Phenolic tyrosinase inhibitors from the stems of Cudrania cochinchinensis.
abstract: The phytochemcal profiles of Cudrania cochinchinensis leaf, twig, stem and root were compared by HPLC analysis. It was found that C. cochinchinensis stem extract contained some unknown natural products with potential tyrosinase inhibitory activities. Therefore, the chemical constitutes in extract (95% ethanol) of C. cochinchinensis stem were further investigated in this study. A new racemic mixture, (±)2,3-cis-dihydromorin, and fifteen known phenolic compounds, dihydrokaempferol 7-O-β-d-qlucopyranoside, skimmin, quercetin-7-O-β-d-glucoside, 2,3-dihydroquercetin 7-O-β-d-glucoside, kaempferol-7-O-β-glucopyranoside, quercetin-3,7-di-O-β-d-glucoside, morin-7-O-β-d-glucoside, 1,3,5,8-tetrahydroxyxanthen-9-one, 2,3-trans-dihydromorin, aromadendrin, oxyresveratrol, genistin, protocatechuic acid, kaempferol 3,7-di-O-β-glucopyranoside, and naringenin were isolated. Spectral techniques (MS, (1)H NMR and (13)C NMR) were utilized for their structural identification and their inhibitory activities on mushroom tyrosinase were also evaluated. The results showed that tyrosinase inhibitory activities of (±)2,3-cis-dihydromorin (IC(50) = 31.1 μM), 2,3-trans-dihydromorin (IC(50) = 21.1 μM), and oxyresveratrol (IC(50) = 2.33 μM), were more potent than that of kojic acid (IC(50) = 50.8 μM), a well-known tyrosinase inhibitor, indicating that Cudrania cochinchinensis stem will be a great potential agent for the development of effective natural tyrosinase inhibitors.
authors.affiliation: School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, People's Republic of China.
authors.forename: Zong-Ping
authors.initials: ZP
authors.lastname: Zheng
authors.forename: Qin
authors.initials: Q
authors.lastname: Zhu
authors.forename: Chun-Lin
authors.initials: CL
authors.lastname: Fan
authors.forename: Hui-Yuan
authors.initials: HY
authors.lastname: Tan
authors.forename: Mingfu
authors.initials: M
authors.lastname: Wang
mesh_terms: D000363:Agaricales / Q000201:enzymology; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005419:Flavonoids / Q000737:chemistry / Q000302:isolation & purification; D062385:Hydroxybenzoates / Q000737:chemistry / Q000302:isolation & purification; D007529:Isoflavones / Q000737:chemistry / Q000302:isolation & purification; D008279:Magnetic Resonance Imaging; D014442:Monophenol Monooxygenase / Q000378:metabolism*; D029586:Moraceae / Q000737:chemistry*; D010636:Phenols / Q000494:pharmacology*; D010936:Plant Extracts / Q000737:chemistry / Q000302:isolation & purification; D018517:Plant Roots / Q000737:chemistry*; D018547:Plant Stems / Q000737:chemistry*; D011794:Quercetin / Q000031:analogs & derivatives / Q000032:analysis / Q000378:metabolism; D013267:Stilbenes / Q000737:chemistry / Q000302:isolation & purification
chemical_list: D004791:Enzyme Inhibitors; D005419:Flavonoids; D062385:Hydroxybenzoates; D007529:Isoflavones; D010636:Phenols; D010936:Plant Extracts; D013267:Stilbenes; C040641:genistin; C009091:protocatechuic acid; C034912:puag-haad; C078277:quercetin-3-O-galactoside-7-O-glucoside; C080220:aromadedrin; D011794:Quercetin; D014442:Monophenol Monooxygenase