title: Determination of the total antioxidant activity of fruits and vegetables by a liposome assay.
abstract: The effects of mixtures of antioxidants on the oxidation of phospholipids have been investigated in large unilamellar liposomes following initiation by 2,2'-azobis(2-aminopropane) dihydrochloride. The lag phase increased linearly with antioxidant concentration. The lag phases of mixtures containing alpha-tocopherol with ascorbic acid showed synergy between the antioxidants, but mixtures of beta-carotene with alpha-tocopherol or ascorbic acid were not synergistic. The liposome system was used to investigate the total antioxidant activity of lipid- and water-soluble extracts from 16 samples of fruits, vegetables, and related food products. The water-soluble extracts caused greater increases in lag phase than the lipid-soluble extracts. The lag phase of liposomes containing the water-soluble extracts from fruits and vegetables increased linearly with the total phenolic concentration, with the continental salad extract having the longest lag phase. The lipid-soluble extract from apples caused the largest increase in lag phase of the lipid-soluble extracts. The lag phases of the lipid-soluble and water-soluble extracts of all fruits and vegetables studied were additive, but no synergy was detected. The lag phase of the liposomes containing both the water-soluble and lipid-soluble extracts varied from 611.5 min for the continental salad extracts to 47.5 min for the cauliflower extracts.
authors.affiliation: Hugh Sinclair Unit of Human Nutrition, School of Food Biosciences, The University of Reading, PO Box 226, Whiteknights, UK.
authors.forename: William G
authors.initials: WG
authors.lastname: Roberts
authors.forename: Michael H
authors.initials: MH
authors.lastname: Gordon
mesh_terms: D000975:Antioxidants / Q000032:analysis* / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000032:analysis / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D004357:Drug Synergism; D005638:Fruit / Q000737:chemistry*; D008055:Lipids; D008081:Liposomes; D010084:Oxidation-Reduction; D010636:Phenols / Q000032:analysis / Q000494:pharmacology; D010743:Phospholipids / Q000737:chemistry; D012995:Solubility; D014675:Vegetables / Q000737:chemistry*; D014867:Water; D024502:alpha-Tocopherol / Q000032:analysis / Q000494:pharmacology; D019207:beta Carotene / Q000032:analysis / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D008055:Lipids; D008081:Liposomes; D010636:Phenols; D010743:Phospholipids; D019207:beta Carotene; D014867:Water; D024502:alpha-Tocopherol; D001205:Ascorbic Acid