Comparative evaluation of the radical-scavenging activities of fucoxanthin and its stereoisomers

Abstract

Fucoxanthin (Fuco) is a characteristic carotenoid of brown seaweeds. In the present study, Fuco and its stereoisomers 9′Z-Fuco, 13Z- and 13′Z-Fuco were extracted from Laminaria japonica Aresch. They were isolated and purified by silica gel column chromatography, Sephadex LH-20, and reversed-phase HPLC. The radical-scavenging activities of the three stereoisomers were evaluated toward 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, 2-2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical, hydroxyl radical, and superoxide radical. The order of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity was 13Z- and 13′Z-Fuco > (all-E)-Fuco > 9′Z-Fuco. The order of 2-2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and hydroxyl radical-scavenging activities were 9′Z-Fuco > (all-E)-Fuco > 13Z-and 13′Z-Fuco. The order of superoxide radical-scavenging activity was 13Z- and 13′Z-Fuco > (all-E)-Fuco > 9′Z-Fuco. The scavenging activities of Fuco and its stereoisomers toward the four radical types were all dose-dependent. The ABTS, DPPH, and superoxide radical-scavenging activities were all weaker than that of tocopherol (VE), while their hydroxyl radical-scavenging activities were stronger than that of VE. The results confirmed that Fuco and its stereoisomers have potent antioxidant activities. © 2014 by the authors; licensee MDPI, Basel, Switzerland.