Scavenging effect of Indian grape polyphenols on 2,2'-diphenyl-1-picrylhydrazyl(DPPH) radical by electron spin resonance spectrometry

Antioxidant potency of Indian grape cultivars varying in their skin color, seed and polyphenol content (Bangalore blue, Pandhari sahebi, Sharad seedless and Thompson seedless) and their components (whole grapes, pulp with skin and seeds) was examined as 2,2'-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity using electron spin resonance spectrometry. The total polyphenols in Indian grapes ranged between 3-51%. Extracted polyphenols caused a concentration dependent and significant loss in DPPH radical signal, similar to known antioxidants-Vitamin C, catechin and procyanidin B3 used as references. Among seedless cultivars, polyphenols from Sharad was more potent as antioxidant than Thompson, showing IC50 values of 1250 +/- 30 and 2650 +/- 125 microg/ml, respectively. The inhibitory effect of polyphenols from seedless grape cultivars was as effective as that of seeded variety. The results indicate that polyphenols extracted from Indian grapes/ components (with /without seeds) exhibited free radical scavenging activity and their chemopreventive properties need to be exploited by in vivo model system.