Antioxidant activity of commonly consumed plant foods of India: contribution of their phenolic content.

Antioxidants are important in protection against hypertension, diabetes, cardiovascular diseases and cancer. Polyphenols are potent antioxidants in plant foods, but their contribution to such protective effects is yet to be established. This study attempted to generate a database on the antioxidant activity (AOA) and phenolic content (PC) of some plant foods commonly consumed in India and to assess the contribution of the PC to their AOA. Plant foods belonging to different food groups such as cereals, legumes, oil seeds, oils, green leafy vegetables, other vegetables, spices, roots and tubers were analysed for AOA and PC. AOA was the highest in black pepper (0.43 mg food required for 50% inhibition of the coupled auto-oxidation of beta-carotene and linoleic acid in a mixture in vitro) and it had the highest PC (191 mg gallic acid equivalent/100 g food). The AOA (18.4 mg) as well as the PC (not detectable) were the lowest in sunflower oil. PC in oil seeds was higher than that in the oil, which could be due to the hydrophilic nature of phenolics and suggests the need for greater use of oil seeds than oils. A significant correlation was observed between the AOA and PC of the plant foods studied in general (r=-0.465), but the coefficient of correlation and determination were high only in spices (r=-0.86 and r2 =74%, respectively) and dehusked legumes (r=-0.65 and r2 = 42.2%, respectively). The results suggest that phenolics may contribute significantly to the AOA of some plant foods, such as spices and dehusked legumes.