Antioxidant activity and phenolic content of lentils (Lens culinaris), chickpeas (Cicer arietinum L.), peas (Pisum sativum L.) and soybeans (Glycine max), and their quantitative changes during processing

Total phenolic content (PC) was similar to 12 mg g(-1) in lentils, 2.2 mg g(-1) in chickpeas, 2.3 mg g(-1) in soybeans, 2.5 mg g(-1) in yellow peas and 1.2 mg g(-1) in green peas. Total antioxidant activity (AA) determined by ABTS (2,2'-azinobis-3-ethyl-benzthiazoline-6-sulfonic acid) assay was highest in lentils at around 14 mu mol Trolox equivalent antioxidant capacity (TEAC) g(-1) and lowest in green peas at 1.9 mu mol TEAC g(-1). Bound phytochemicals contributed to 82-85% total AA in lentils. Free phytochemicals contributed more to total AA in chickpeas, yellow peas, green peas and soybeans than bound phytochemicals. AA and PC was reduced by similar to 80% in lentils and < 30% in yellow peas by decortication, by 16-41% in lentils, chickpeas and peas by cooking, and by 22-42% in lentils by soaking. Total AA was significantly correlated with total PC. Soybeans had the greatest ability to scavenge free radicals, inhibit lipid peroxidation and chelate metals among the legumes tested. Different legumes exhibited different AA mechanisms.