title: Barbarin as a new tyrosinase inhibitor from Barbarea orthocerus.
abstract: A tyrosinase inhibitor was isolated from the whole plant of Barbarea orthocerus Led. (Brassicaceae) by activity-guided fractionation, and identified as (R)-5-phenyl-2-oxazolidinethione (barbarin) by structural analysis followed by comparison with reported spectral data. The compound exhibited significant inhibitory effects on mushroom and murine tyrosinases at more than 1.6 x 10(-5) M. Barbarin exhibited IC50 values of 4.2 x 10(-5) M on mushroom tyrosinase and of 4.8 x 10(-5) M on murine tyrosinase. Kojic acid as a positive control exhibited IC50 values of 3.4 x 10(-5) M and 6.0 x 10(-5) M on mushroom and murine tyrosinases, respectively. Therefore, barbarin exhibited a similar level of inhibitory potency with kojic acid used as a positive control. In a kinetic study with various concentrations of L-dopa as the substrate, barbarin was identified as an uncompetitive inhibitor and kojic acid as a mixed inhibitor of both mushroom and murine tyrosinases. Barbarin exhibited KEIS values of 3.3 x 10(-5) M and 3.6 x 10(-5) M on mushroom and murine tyrosinases, respectively. Kojic acid exhibited KEIS and KEI values of 2.4 x 10(-5) M and 2.2 x 10(-5) M on mushroom tyrosinase and those of 8.9 x 10(-5) M and 7.2 x 10(-5) M on murine tyrosinase, respectively.
authors.affiliation: College of Pharmacy, Chungbuk National University, Cheongju, Korea.
authors.forename: B
authors.initials: B
authors.lastname: Seo
authors.forename: J
authors.initials: J
authors.lastname: Yun
authors.forename: S
authors.initials: S
authors.lastname: Lee
authors.forename: M
authors.initials: M
authors.lastname: Kim
authors.forename: K
authors.initials: K
authors.lastname: Hwang
authors.forename: J
authors.initials: J
authors.lastname: Kim
authors.forename: K R
authors.initials: KR
authors.lastname: Min
authors.forename: Y
authors.initials: Y
authors.lastname: Kim
authors.forename: D
authors.initials: D
authors.lastname: Moon
mesh_terms: D000818:Animals; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D051379:Mice; D015394:Molecular Structure; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors*; D010080:Oxazoles / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*
chemical_list: D004791:Enzyme Inhibitors; D010080:Oxazoles; C403584:barbarin; D014442:Monophenol Monooxygenase