Antioxidant and free radical scavenging activities of some fruits

Abstract

Phenols, a major group of antioxidant phytochemicals, have profound importance due to their biological and free radical scavenging activities. To identify their potential sources extracts of some fruits and their different parts were studied for total phenolic contents (TPC), antioxidant (AOA) and free radical scavenging activities (FRSA). The amount of TPC varied from 10.5 (Carissa carandus, fruit peel) to 343.2 mg/g (Caesalpinia Mexicana, fruits) and AOA from 20.3% (Musa paradisiacal, fruits) to 96.7% (Caesalpinia Mexicana, fruits). Fruits of Caesalpinia Mexicana, Acacia auriculiformis, fruit pericarp green fibres of Cocus nucifera, and fruits of Emblica officinalis were found to have high TPC (73.1-343.2 mg/g) and high AOA (68.5-96.7%). Promising fruits were studied for their FRSA and reducing power (RP) measured by DPPH assay where the fruits of Caesalpinia mexicana, fruit pericarp fibres of Cocus nucifera, fruits of Emblica officinalis showed very low IC50 ranging from 0.009 to 0.016 mg/ml, EC50 from 0.39 to 0.70 mg/mg DPPH and reasonably high values (142.1-256.3) of anti radical power (ARP), indicating their strong FRSA and reducing power (RP) as evident by their low ASE/ml values (0.42-1.08). They also showed better inhibition of lipid peroxidation measured by using ferric thiocyanate assay and by using egg yolk compared to the reference standard quercetin. The ferrous and ferric ion chelating capacity of the promising fruits and their underutilized parts in terms of IC50 varied from 0.12 (Emblica officinalis, fruits) to 2.44 mg/ml (Mangifera indica, Seed kernel) and 0.22 (Caesalpinia Mexicana, fruits) to 2.59 mg/ml (Litchi chinensis, fruit peel) respectively. Fruit pulp, peel and seeds of Litchi chinensis with reasonable amount of phenols (48.3, 43.9, 50.1 mg/ml) showed low ARP (23.5, 38.3, 33.8) and ASE/ml (3.13, 2.18, 2.62) respectively in contrast to Aegle marmelos with comparatively lower phenols (35.1 mg/g) exhibited good ARP (57.4) and RP (1.67 ASE/ml). Extracts (20 μg/ml) of fruits of Acacia auriculiformis, Caesalpinia Mexicana, Emblica officinalis, fruit pericarp fibres of Cocus nucifera, were found effective in protecting plasmid DNA nicking induced by Fenton’s reagent generated hydroxyl radicals. They were further assayed for their specific phenolic composition through HPLC and MS/MS where the amount of caffeic acid varied from 48.5 to 2231 μg/g, chlorogenic acid 63.8 to 912.1 μg/g, ellagic acid 46.4 to 1429.1 μg/g, ferulic acid 36.7 to 762.9 μg/g, gallic acid 181.6 to 2831.6 μg/g, protocatechuic acid 41.7 to 322.8 μg/g, and quercetin 44.6 to 367.6 μg/g.