Visual Estimation and Spectrophotometric Determination of Tannin Content and Antioxidant Activity of Three Common Vegetable

Antioxidant activities of different vegetables Bitter gourd, Tomato and Spinach (Momordica charantia, Lycopersicon esculentum, Spinacia oleracea) were determined. In addition, rapid visual estimation of tannin content, total phenolic, tested for their free radical scavenging activity (FRSA) in the DPPH (1, 1-dephenyl2-picrylhydrazil radical) of those samples were assessed. A new technique was used to quickly distinguish between intermediate, moderately high and high tannin content by the development of shades of purple, light blue and deep blue colors (Bitter gourd, Tomato and Spinach) respectively. The total phenolics in methanol solution for all the samples were analyzed with slightly higher value for spinach paste. The % of condensed tannin of all the three vegetables were low as determined by the VanillinHCl method respectively. The antioxidant activity with DPPHmethod expressed as per percent inhibition of oxidation ranged from a high of 88% in bitter gourd extract to near about 70% in tomato and spinach respectively. The studies can be further extended to exploit their possible application for the preservation of food products as well as health supplements and neutraceuticals.