Antioxidative and prooxidative effects in food lipids and synergism with α-tocopherol of acai seed extracts and grape rachis extracts

Extracts of acai seed and of grape rachis alone or in combination with a-tocopherol were evaluated as antioxidants in (i) bulk soybean oil, (ii) soybean oil liposomes and (iii) soybean-oil/water emulsions. The extracts made with 57% aqueous ethanol showed an antioxidant activity not dependent on concentration for grape rachis extracts and a concentration-dependent prooxidative activity for acai seed extracts in bulk soybean oil. Both the extracts, however, protected liposome suspensions and oil/water emulsions against lipid oxidation. Synergism was demonstrated when extracts were combined with a-tocopherol, effects explained by the solubility of extract components in the water-phase and of a-tocopherol in the lipid-phase. Phenolic profiling of the extracts by U-HPLC-ESI-LTQ-MS was used to identify active antioxidants. Acai seed and grape rachis extracts served as good sources of procyanidins and flavan-3-ols, imparted high antioxidant activity especially when combined with a-tocopherol and are suggested for protection of food oil/water emulsions. (C) 2016 Elsevier Ltd. All rights reserved.