Antioxidant Activity of The Extracts From Freshwater Macroalgae ( Cladophora glomerata ) Grown in Northern Thailand and Its Preventive Effect Against Lipid Oxidation of Refrigerated Eastern Little Tuna Slice

摘要

Characteristic and antioxidant activity of the extracts from freshwater macroalgae (C. glomerata) as influenced by extraction media, i.e., water or ethanol (20-100%, v/v) were studied. The highest yield (28.0%) was obtained when water was used. Ethanolic extracts had significantly lower yields (2.98-15.5%) (P0.05). However, total phenolic and chlorophyll contents were lower in water extract. Among all extracts, the 60% ethanolic extract (E60) had the highest antioxidant activities, including DPPH and ABTS radical scavenging activities, ferric reducing antioxidant power and metal chelating activity. Based on LC/MS of E60, quercetin, isoquercetin and hydroquinin were the major phenolic compounds. When E60 at different levels (100, 200 and 400 mg/kg) were added to eastern little tuna (Euthynnus affinis) slices, the reduction in lipid oxidation was dose-dependent (P0.05) as shown by smaller increases in peroxide and thiobarbituric acid-reactive substances (TBARS) values, compared to the control. Therefore, C. glomerata could be a source of alternative natural antioxidant in lipid based muscle food.