Brown seaweed polyphenols as novel antioxidants for better health and food quality

In the Far East and Pacific, there is a long tradition of consuming seaweeds as sea vegetables, while in western countries the principal use of seaweeds is as source of phycocolloids (eg. thickening and gelling agents for agro-food industry). In Asia, recent epidemiological studies have demonstrated that regular consumption of seaweeds might be related to a reduction of prostate, colorectal and breast cancer risk. Researches carried out on natural products from seaweeds lead to the identification of a variety of antioxidant compounds, among which polyphenolic compounds. Brown seaweeds are particularly rich in polyphenols: from 5 to 15 % of the dry weight. These compounds are made from phloroglucinol units, connected by aryl/aryl bonds (fucols), by aryl ether bonds (phlorethols) or both (fucophlorethols). Some of them contain one additional hydroxyl group at each second ring and a regular sequence of para- and ortho- positioned ether links (fuhalols and pseudofuhalols). In comparison with terrestrial plants, little is known about the antioxidant activity of seaweed polyphenols. The main objectives of the SEAHEALTH project carried out with financial support from the Commission of the European Communities (“Quality of Life and Management of Living Resources” RTD programme) is to demonstrate benefits of seaweeds antioxidant substances on human health (prevention of atherosclerosis and cancer) and food quality. This paper presents the results obtained during the first half of the SEAHEALTH project. In a first step, extraction/purification process of seaweed antioxidants was optimised. For comparative reasons and to establish a superior method for polyhenols determination, two quantitative methods were evaluated: Folin Ciocalteu’s and DMBA (2,4-dimethoxybenzaldehyde). Qualitative analysis were performed by 1H NMR and HPLC-MS. Size exclusion chromatography (SEC) was evaluated as a method to separate polyhenols according to their molecular weight. An important antioxidant and scavenging activity of some of the extracts was observed in vitro (DPPH and ORAC tests). The capacity of seaweed extracts to scavenge superoxide anion radical generated during the oxidation of xanthine to uric acid in the presence of xanthine oxidase was measured. The influence of the extracts on carcinogen metabolism was assessed by measuring inhibition of phase I enzyme (cytochrome P450 Cp1A) activity. The anti-inflammatory and the anti-hormonal effects of the extracts were evaluated by measuring inhibition of cyclooxygenase and aromatase activity, respectively. Acute toxicological studies were performed on mice and rats by oral and intraperitoneal routes with two different oral doses of seaweed extracts. Finally, some food products (fruit juices and yoghourts) were formulated from seaweed extracts. Results showed that antioxidant activity was still detectable in formulated products.