Diversity in eggplant (Solanum melongena) for superoxide scavenging activity, total phenolics, and ascorbic acid

Eggplant (Solanum melongena L.) extracts have demonstrated potency in scavenging reactive oxygen species that are implicated in many human diseases. We evaluated 33 S. melongena accessions and two S. aethiopicum accessions from the AVRDC Solanum collection for superoxide scavenging (SOS) activity with methanol (SOSm) and water (SOSw) extracts, and contents of total phenolics and ascorbic acid. Highly significant differences were detected among accessions for SOS activities with accession means ranging from 26% to 60% nitro blue tetrazolium (NBT) reduction inhibition for SOSm, and 40% to 81% NBT reduction inhibition for SOSw. The SOSm and SOSw produced similar results, evidenced by the highly significant linear correlation (0.79**) between the two assays. Environmental differences between the 2 years influenced expression of SOSm, but the ranking of accessions for SOSm activity was very consistent between years. There was no association between fruit colour and high SOS. Accessions S00062 (white with green stripes), S00022 (light purple and mottled fruit), and S00197 (orange-coloured S. aethiopicum accession) displayed high AOA. The SOSm and SOSw were positively correlated with dry matter content (r=0.65** and r=0.80**, respectively) and total phenolics content (r=0.44** and r=0.43**, respectively) and negatively correlated with fruit weight (r=−0.58** and r=−0.67**, respectively). There was no significant linear association between ascorbic acid content and SOSm (r=0.10) but we found a significant but low correlation (r=0.34*) between SOSw and ascorbic acid content. Accession means for total phenolics content averaged over years ranged from 0.74 to 1.43 g/100 g dry weight basis, although differences were not statistically significant due to a large accession–year interaction mean square. Sufficient genetic diversity exists in S. melongena for SOS and total phenolics to justify evaluation of a larger number of accessions. High AOA varieties will tend to be small-fruited.