Comprehensive evaluation of in vitro antioxidant activity, total phenols and chemical profiles of two commercially important strawberry varieties

Strawberry is one of the most popular fruits globally because of its color, texture, and aroma. Previous studies have shown that the fruits are rich in antioxidant compounds like flavonoids, anthocyanins and proanthocyanins. We, for the first time, comprehensively evaluated the total phenol content, and antioxidant activity (based on 1,1-diphenyl-2-picrylhydrazyl (DPPH) free-radical scavenging, anti-lipid peroxidation and ferric reduction potential (FRP) assay) of two popular strawberry cultivars namely, Sweet Charlie and Camarosa, at four different fruit developmental stages. A significant decrease in phenol content (nearly 89%) was observed in ripened fruits as compared to green fruits. The antioxidant potential, as evidenced by DPPH and FRP assays, increased gradually during fruit maturation with dose-dependent increase in activity. The EC50 values for DPPH and FRP assays ranged from 23.71±6.40% to 296.85±3.50% and 120.06±4.9μg to 219.50±1.0μg, respectively. The anti-lipid peroxidation assay also revealed a steady increase in activity from green to red fruit. The HPLC-DAD profiling of fruits revealed stage-specific chemical patterns during the four stages of fruit development. We studied the changes in concentrations of Chlorogenic acid, Catechin, Rutin and Quercetin during fruit developmental stages. It was clearly demonstrated that the antioxidant activity varied during fruit maturation stages. Maximum antioxidants were found to accumulate during the fruit ripening stage. To the best of our knowledge, this is the first report of such a comprehensive analysis of antioxidant potential of strawberry fruits from commercial varieties in India