In vitro analysis of antioxidant capacity of Indian yellow raspberry (Rubus

We examined for first time the ripened fruits of Indian yellow raspberry (Rubus ellipticus Smith) (RE), an under exploited fruit from the Nilgiris, India, for its polyphenolic compounds and in vitro antioxidant/radical scavenging ability. The fruit yielded phenolic content (TPh) of 6100 ± 0.082 mg gallic acid equivalents (GAE)/100g of fresh material (FM) and total flavonoid content (TFl) of 320 ±0.120 mg quercetin equivalents (QE)/100g of fresh material (FM). The RE extract displayed excellent scavenging capacity towards 1, 1 – diphenyl – 2picryl hydrazyl (DPPH∙) (EC50 9.85 ±1.33 μg mL -1), superoxide anion (O2·ˉ) (EC50 64.65 ±0.82 μg mL-1), hydroxyl ion radicals ( ̇OH) (EC50 79.98 ±1.02 μg mL -1) and nitric oxide (NO) (EC50 75.21 ±1.32 μg mL-1). The RE also showed strong reducing capacity (OD at 700 nm -1.435), strong Fe2+ chelation (EC50 45.24 ±1.42 μg mL -1) and exhibited remarkable reduction of lipid peroxidation (EC50 71.1 ±0.22 μg ml -1). The antioxidant capacities of the extract were comparable butyl hydroxytoluene (BHT), ethylene diamine tetraacetic acid disodium salt (EDTA-Na2) and catechin. Significant and positive correlations were observed between polyphenolic contents and the antioxidant capacities, indicating that the phenolics were major contributors of the antioxidant property. Further, the separation of ethyl acetate (EtOAc) soluble fraction on a silica gel column afforded ellagic acid and quercetin. The results strongly point that Indian yellow raspberry may be a promising source of natural antioxidant agents.