title: Phenols displaying tyrosinase inhibition from Humulus lupulus.
abstract: Tyrosinase is the rate-limiting enzyme for the production of melanin and other pigments via the oxidation of l-tyrosine. The methanol extract from Humulus lupulus showed potent inhibition against mushroom tyrosinase. The bioactivity-guided fractionation of this methanol extract resulted in the isolation of seven flavonoids (1-7), identified as xanthohumol (1), 4'-O-methylxanthohumol (2), xanthohumol C (3), flavokawain C (4), xanthoumol B (5), 6-prenylnaringenin (6) and isoxanthohumol (7). All isolated flavonoids (1-7) effectively inhibited the monophenolase (IC50s = 15.4-58.4 µM) and diphenolase (IC50s = 27.1-117.4 µM) activities of tyrosinase. Kinetic studies using Lineweaver-Burk and Dixon-plots revealed that chalcones (1-5) were competitive inhibitors, whereas flavanones (6 and 7) exhibited both mixed and non-competitive inhibitory characteristics. In conclusion, this study is the first to demonstrate that the phenolic phytochemicals of H. lupulus display potent inhibitory activities against tyrosinase.
authors.affiliation: a Korea Institute of Oriental Medicine, KM Convergence Research Division , Daejeon , Republic of Korea and.
authors.forename: Dae Wook
authors.initials: DW
authors.lastname: Kim
authors.affiliation: b Division of Applied Life Science , Gyeongsang National University , Jinju , Republic of Korea.
authors.forename: Hyun Sim
authors.initials: HS
authors.lastname: Woo
authors.affiliation: b Division of Applied Life Science , Gyeongsang National University , Jinju , Republic of Korea.
authors.forename: Jeong Yoon
authors.initials: JY
authors.lastname: Kim
authors.affiliation: a Korea Institute of Oriental Medicine, KM Convergence Research Division , Daejeon , Republic of Korea and.
authors.forename: Jin Ah
authors.initials: JA
authors.lastname: Ryuk
authors.affiliation: b Division of Applied Life Science , Gyeongsang National University , Jinju , Republic of Korea.
authors.forename: Ki Hun
authors.initials: KH
authors.lastname: Park
authors.affiliation: a Korea Institute of Oriental Medicine, KM Convergence Research Division , Daejeon , Republic of Korea and.
authors.forename: Byoung Seob
authors.initials: BS
authors.lastname: Ko
mesh_terms: D001681:Biological Assay; D050150:Chalones / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D005419:Flavonoids / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D027582:Humulus / Q000737:chemistry*; D020128:Inhibitory Concentration 50; D000432:Methanol / Q000737:chemistry; D015394:Molecular Structure; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D010636:Phenols / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*
chemical_list: D050150:Chalones; D004791:Enzyme Inhibitors; D005419:Flavonoids; D010636:Phenols; D014442:Monophenol Monooxygenase; D000432:Methanol
keywords: Competitive inhibition; Hulumuls lupulus; diphenolase; monophenolase; tyrosinase inhibitor