fucoxanthin and halocynthiaxanthin

Antioxidant activity of carotenoids is suggested to be one of the factors for their disease preventing effects. Marine carotenoids fucoxanthin and its two metabolites, fucoxanthinol and halocynthiaxanthin, have been shown to exhibit several biological effects. The antioxidant activities of these three carotenoids were assessed in vitro with respect to radical scavenging and singlet oxygen quenching abilities. The 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity of fucoxanthin and fucoxanthinol was higher than that of halocynthiaxanthin, with the effective concentration for 50% scavenging (EC 50) being 164.60, 153.78, and 826.39 microM, respectively. 2,2'-Azinobis-3-ethylbenzo thizoline-6-sulphonate radical scavenging activity of fucoxanthinol (EC 50, 2.49 microM) was stronger than that of fucoxanthin (EC 50, 8.94 microM). Hydroxyl radical scavenging activity as measured by the chemiluminescence technique showed that the scavenging activity of fucoxanthin was 7.9 times higher than that by fucoxanthinol, 16.3 times higher than that by halocynthiaxanthin, and 13.5 times higher than that by alpha-tocopherol. A similar trend was observed when the hydroxyl radical scavenging was assessed by the electron spin resonance (ESR) technique. ESR analysis of the superoxide radical scavenging activity also showed the superiority of fucoxanthin over the other two carotenoids tested. Singlet oxygen quenching ability of the three carotenoids was lower than that of beta-carotene, with quenching rate constants ( k Q, x10 (10) M (-1) s (-1)) being 1.19, 1.81, 0.80, and 12.78 for fucoxanthin, fucoxanthinol, halocynthiaxanthin, and beta-carotene, respectively. The higher radical scavenging activity of fucoxanthin and fucoxanthinol compared with halocynthiaxanthin is assumed to be due to presence of the allenic bond.

Topics: beta Carotene; Electron Spin Resonance Spectroscopy; Free Radical Scavengers; Hydroxyl Radical; Singlet Oxygen; Superoxides; Xanthophylls

We have reported that fucoxanthin, a natural carotenoid, inhibited the growth of human neuroblastoma GOTO cells. In the present study, we show that a metabolite of fucoxanthin, halocynthiaxanthin, which is isolated from sea squirt Halocynthia roretzi, has a more potent inhibitory effect. Halocynthiaxanthin (5 micrograms/ml) caused complete suppression of GOTO cell proliferation, whereas fucoxanthin reduced the growth rate by only 88.8% compared with the control, at day 2 after the drug treatment. Furthermore, halocynthiaxanthin also inhibited the growth of other human malignant tumor cells. Thus halocynthiaxanthin seems to be a promising anti-neoplastic agent.

Topics: Antineoplastic Agents; Carotenoids; Cell Division; Colonic Neoplasms; DNA, Neoplasm; Food; Gene Expression; Genes, myc; HeLa Cells; Humans; Kinetics; Neoplasm Proteins; Neuroblastoma; Pancreatic Neoplasms; RNA, Neoplasm; Stomach Neoplasms; Tumor Cells, Cultured; Xanthophylls