Leafy vegetable extracts - antioxidant activity and effect on storage stability of heated oils

The investigation was undertaken with an objective of analyzing the antioxiclant capacity of leafy vegetables (LV) and testing their efficacy on storage of heated oils. Four leafy vegetables viz., cabbage (Brassica oleracea var. capitata), coriander leaves (Coriandrum sativum), hongone (Alternanthera sessilis), and spinach (Spinacia oleracea) were analyzed for antioxiclant activity by standard methods. The ethanol extracts of LV were added to refined sunflower and groundnut oils heated to frying temperature and stored for 4 weeks, analyzed for peroxide value that indicates the oxidative state of oils. The polyphenol content ranged from 5 mg in cabbage to 69.5 mg in spinach. Reducing power of the leafy vegetables indicative of electron donating property for termination of free radical chain reactions followed the order-spinach < cabbage < coriander leaves < hongone leaves. LV exhibited good hydroxyl radical and DPPH scavenging activities. LV extracts conferred a protective effect on peroxide formation on storage of heated oils. LV are excellent antioxidants that are stable at high temperatures and can serve as substitutes for synthetic antioxidants. (c) 2005 Elsevier Ltd. All rights reserved.