title: Tyrosinase inhibitors isolated from the edible brown alga Ecklonia stolonifera.
abstract: Extracts from seventeen seaweeds were determined for tyrosinase inhibitory activity using mushroom tyrosinase with L-tyrosine as a substrate. Only one of them, Ecklonia stolonifera OKAMURA (Laminariaceae) belonging to brown algae, showed high tyrosinase inhibitory activity. Bioassay-guided fractionation of the active ethyl acetate (EtOAc) soluble fraction from the methanolic extract of E. stolonifera, led us to the isolation of phloroglucinol derivatives [phloroglucinol (1), eckstolonol (2), eckol (3), phlorofucofuroeckol A (4), and dieckol (5)]. Compounds 1 approximately 5 were found to inhibit the oxidation of L-tyrosine catalyzed by mushroom tyrosinase with IC50 values of 92.8, 126, 33.2, 177, and 2.16 microg/mL, respectively. It was compared with those of kojic acid and arbutin, well-known tyrosinase inhibitors, with IC50 values of 6.32 and 112 microg/ mL, respectively. The inhibitory kinetics analyzed from Lineweaver-Burk plots, showed compounds 1 and 2 to be competitive inhibitors with Ki of 2.3x10(-4) and 3.1x10(-4) M, and compounds 3 approximately 5 to be noncompetitive inhibitors with Ki of 1.9x10(-5), 1.4x10(-3) and 1.5x10(-5) M, respectively. This work showed that phloroglucinol derivatives, natural compounds found in brown algae, could be involved in the control of pigmentation in plants and other organisms through inhibition of tyrosinase activity using L-tyrosine as a substrate.
authors.affiliation: Faculty of Food Science and Biotechnology, Pukyong National University, Busan 608-737, Korea.
authors.forename: Hye Sook
authors.initials: HS
authors.lastname: Kang
authors.forename: Hyung Rak
authors.initials: HR
authors.lastname: Kim
authors.forename: Dae Seok
authors.initials: DS
authors.lastname: Byun
authors.forename: Byeng Wha
authors.initials: BW
authors.lastname: Son
authors.forename: Taek Jeong
authors.initials: TJ
authors.lastname: Nam
authors.forename: Jae Sue
authors.initials: JS
authors.lastname: Choi
mesh_terms: D004791:Enzyme Inhibitors / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D007795:Laminaria / Q000302:isolation & purification*; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000459:Phaeophyceae / Q000302:isolation & purification
chemical_list: D004791:Enzyme Inhibitors; D014442:Monophenol Monooxygenase