Leafy vegetable extracts—antioxidant activity and effect on storage stability of heated oils B.N. Shyamala, Sheetal Gupta, A. Jyothi Lakshmi, Jamuna Prakash T Department of Studies in Food Science and Nutrition, University of Mysore, Manasagangotri, Mysore-570 006, India Received 14 August 2004; received in revised form 23 December 2004; accepted 23 December 2004 Abstract The investigation was undertaken with an objective of analyzing the antioxidant 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 antioxidant 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—spinachbcabbagebcoriander leavesbhongone 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. D 2005 Elsevier Ltd. All rights reserved. Keywords: Leafy vegetables; Polyphenol; Reducing power; Free radical; Hydroxyl radical; Refined oils Industrial relevance: This paper presents an interesting approach using leafy vegetable extract with antioxidative properties to prevent oxidative damage during storage of heated oils. The temperature stability of antioxidants from leavy vegetables would allow to produce highly useful antioxidantive extracts from vegetable processing wastes. 1. Introduction Virtually all cellular components appear to be sensitive to oxidative damage. Lipids, proteins, nucleic acids, and carbohydrates are all known to undergo oxidative modifi- cation. The process of lipid peroxidation is initiated by the abstraction of a hydrogen atom in an unsaturated fatty acyl chain and propagated as a chain reaction. Therefore, inhibition of lipid peroxidation is of great importance in the disease processes involving free radicals (Vayalil, 2002). Antioxidants are known to scavenge free radicals and singlet oxygen. They are known to reduce hyroperoxides and prevent rancidity or off-flavors in edible oils. Butylated Hydroxy Anisole (BHA), Butylated Hydroxy Toluene (BHT), and propyl gallate (PG) are widely used in the food industry, but the associated ill effects have limited their use. Elimination of synthetic antioxidants in food applications has given more impetus to exploring natural sources of antioxidants. In this context a large number of vegetables such as kale, spinach, brussels sprout, broccoli, onion, eggplant, and cucumber are known to be rich sources of antioxidants (Gazzani, Papetti, Massolini, & Daglia, 1998; Velioglu, Mazza, Gao, & Oomah, 1998; Vinson, Hao, Su, & Zubik, 1998). Leafy vegetables apart from being a good source of minerals also contain antioxidant vitamins and pigments. Leafy vegetables are also known for their therapeutic value. This investigation attempts to study the antioxidant potential of leafy vegetables and their efficacy in preventing the oxidative changes on storage of heated oils. 1466-8564/$ - see front matter D 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.ifset.2004.12.002 T Corresponding author. Tel.: +91 821 2510054; fax: +91 821 2516308. E-mail address: jampr55@hotmail.com (J. Prakash). Innovative Food Science and Emerging Technologies 6 (2005) 239– 245 www.elsevier.com/locate/ifset