Antioxidant Potential of Selected Underutilized Fruit Species Grown in Sri Lanka

Abstract

The aim of this study was to assess the potential of aqueous extracts of three underutilized fruit species namely Dialium guineense, Solanum nigrum and Carissa carandas grown in Sri Lanka. Aqueous extracts of fruits were obtained by extracting accurately measured and finely ground fresh fruit samples with distilled water for 90 min followed by centrifuging at 4500rpm. The supernatants were collected separately and the extraction was repeated twice with residues. The collected supernatants were combined and lyophilized. Total phenolic contents (TPC) were determined using a spectrophotometric technique, based on the FolinCiocalteau reagent, calculated as gallic acid equivalents GAE/g fresh weight. Antioxidant potential was determined using DPPH˙ and ABTS˙+ scavenging assays. The DPPH radical scavenging activity of the extracts was expressed as IC50 values that denote the concentration of the sample required to scavenge 50% of radicals. The radical scavenging activity (RSA) was calculated as percentage of ABTS˙+ discoloration over six minutes. The TPC varied among species from 1.16mg ± 0.049 GAE/g of fresh fruit of D. guineense to 3.12 mg ± 0.43 GAE/ g of fresh fruit of S. nigrum. The highest antioxidant potential was possessed S. nigrum as it showed about 66% ABTS˙+discoloration over six minutes and 12.23mg ± 0.11 of fresh fruit needed for IC50. Therefore these results suggested that wild fruit species could be exploited as an ingredient in developing a potential antioxidant supplement.