Antioxidant Activity of Leaves’ Extracts of Citrus Sinensis: Determination of Radical Scavenging Capacity, Antiradical Power, Total Polyphenols and Flavonoids Content

Citrus sinensis has intensively been used for its nutritional and therapeutic values, usually attributed to their antioxidant properties. Several studies have earlier focused on its fruits, seeds, oils, juice and flowers. This study focuses on leaves and aimed at determining radical scavenging capacity (RSC), antiradical power(ARP), total polyphenols (TPC) and flavonoids (TFC) content of the aqueous (AE), hydroethanolic (HEE) and ethanolic (EE) extracts and their activities on free radicals DPPH•, ABTS+ and NO. Phenolic compounds of all the extracts were measured by Folin-Ciocalteu assays. RSC of 1,1-diphenyl-2-picrylhydrazyl (DPPH•), 2,2’-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS+) and nitric oxide (NO•) radicals were measured. Also, the reducing power of extracts on phosphomolybdenum was evaluated by total antioxidant capacity (TAC) assay, antiradical power and EC50 were determined. All the extracts possessed high TPC ranging from 306.67 ± 43.72 to 353.33 ± 30.55 µg of Eq Catechin /mg respectively for EA and EE.  EE, EA, EC showed their ability to scavenge all the radicals and an important reducing power. Aqueous extracts presented the lower EC50 (mg/ml) 4.60, 4.27, and 4.01x10-4 with DPPH•, ABTS+, NO• respectively and the highest ARP. Many correlations observed between TAC and ABTS+-RSC (r = 0.958, p