Tyrosinase inhibitors isolated from the edible brown alga Ecklonia stolonifera.
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.
Kang
Hye Sook
HS
Faculty of Food Science and Biotechnology, Pukyong National University, Busan 608-737, Korea.
Kim
Hyung Rak
HR
Byun
Dae Seok
DS
Son
Byeng Wha
BW
Nam
Taek Jeong
TJ
Choi
Jae Sue
JS
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
D004791:Enzyme Inhibitors; D014442:Monophenol Monooxygenase