Antioxidant Capacities of Phlorotannins Extracted from the Brown Algae Fucus vesiculosus

• Published in: Journal of agricultural and food chemistry 2012-06, Vol.60 (23), p.5874-5883
• Main Authors: Wang, Tao, Jónsdóttir, Rósa, Liu, Haiyan, Gu, Liwei, Kristinsson, Hordur G, Raghavan, Sivakumar, Ólafsdóttir, Gudrún
• Format: Article
• Language: English
• Subjects: acetates; alpha-tocopherol; alpha-Tocopherol - analysis; antioxidant activity; Antioxidants - analysis; ascorbic acid; bioassays; Biological and medical sciences; butylated hydroxytoluene; Chemical Fractionation; chromatography; Chromatography, High Pressure Liquid; Dextrans - chemistry; Food industries; fractionation; Fucus vesiculosus; Fundamental and applied biological sciences. Psychology; Mass Spectrometry; Molecular Weight; Phaeophyceae - chemistry; polymerization; polymers; polyphenols; reactive oxygen species; Reactive Oxygen Species - metabolism; Seaweed - chemistry; Tannins - chemistry; ultrafiltration
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf3003653

A process for the effective extraction and fractionation of phlorotannins from Fucus vesiculosus with high antioxidant potentials was investigated. The antioxidant activity of F. vesiculosus extract/fractions was assessed by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, reducing power, and ferrous ion-chelating assays. Among the crude extract and different polarity fractions, the phlorotannin-enriched ethyl acetate fraction possessed the highest DPPH scavenging activity and reducing power. This fraction was further fractionated by Sephadex LH-20 column chromatography or ultrafiltration. The antioxidant properties were evaluated by both the above chemical antioxidant tests and a mononuclear cell-based bioassay. Sephadex subfractions LH-2 and LH-3 with high total phlorotannin content exhibited strong DPPH quenching activity, comparable to those of ascorbic acid and butylated hydroxytoluene and significantly higher than that of α-tocopherol. Polyphenols in F. vesiculosus were found to consist mainly of high molecular weight phlorotannin polymers. There were no clear relationships between the degree of polymerization, molecular size, and antioxidant activity. All the subfractions separated by Sephadex LH-20 column chromatography and ultrafiltration showed a high ability to scavenge reactive oxygen species generated by mononuclear cells. Further characterization of the phlorotannin compounds was performed on six Sephadex subfractions. Several phlorotannin oligomers were tentatively identified on the basis of HPLC–ESI-MS n analyses.