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Abstract

Cajanus cajan L. (Pigeonpea) is an important pulse crop of India. The aim of this study was to determine and compare the antioxidant activity and bioactive compounds of seed coat and cotyledon of C. cajan. The antioxidant properties of pet ether, chloroform, ethanol and aqueous extracts of the seed coat and cotyledon of C. cajan were examined by a ferric thiocynate (FTC) assay, DPPH radical scavenging assay, hydroxyl radical scavenging assay and ferric reducing power were analyzed separately for its inhibition percentage at different concentration (20 µg, 40 µg, 60 µg, 80 µg and 100 µg/ml). Both the samples possessed antioxidant activity however the seed coat ethanolic extract possessed prominent activity by FTC (68.2 ± 0.07%), DPPH (90.1 ± 0.17%) and hydroxyl radical scavenging assay (75.2 ± 0.05%) at 100 µg/ml compared to other extracts. It was interesting to note that ferric reducing power of ethanolic extract of seed coat (1.590 ± 0.002%) was significantly (P<0.5) higher than that of standard BHA (1.575 ± 0.015%) at 100 µg/ml. The cotyledon extracts showed very minimal antioxidant activity compared to seed coat. Total contents of phenols (45.35±0.045 mg/g gallic acid equivalent), flavonoids (32.38 ± 0.021 mg/g catechin equivalent) and tannins (2.38 ± 0.021 mg/g tannic acid equivalent) were superior in ethanolic extract of seed coat compared to cotyledon. These experimental findings suggest that the ethanolic extract of seed coat as a potential extract for the natural antioxidant present in C. cajan. INRODUCTION: Leguminous seeds are an important source of nutrient compounds such as protein, starch, dietary fibre and minerals 1 , particularly in third-world countries. Incorporation of leguminous seeds into the human diet in developing countries offer protective effects against chronic diseases 2. Legumes contain a number of bioactive substances including phenolics that can diminish protein digestibility and mineral bioavailability 3, 4 .