Phenolic content and antioxidant activity ofZiziphus jujubaMill. fruit extracts

Abstract

The aim of this study is to evaluate the antioxidant activity of dried fruit extracts of Zizyphus jujubaMill. Polyphenols and flavonoids content determined in aqueous extract (aq), hydromethanolic (EM), hydroacetonic (EA) extracts, and their ethyl acetate (Acet) andn-butanol (n-but) fractions reveal variable rates; 42.84–94.70 mg gallic acid equivalent per g extract and 47.02–427.33 mg catechin equivalent per g extract. The antioxidant activity was evaluated by different assays using total antioxidant capacity, 2,2-Diphenyl-1-picrylhydrazyl (DPPH), β-carotene bleaching assay, and ferric reducing antioxidant power (FRAP). In DPPH assay, all extracts showed an interesting scavenging effect, an estimated reduction rate about 75.58–97.71% was determined with the IC50(the half maximal inhibitory concentration) values ranging from 12 to 503.6 μg/ml. In β-carotene bleaching assay, 500 μg/ml of each extract showed a large inhibition (51.14–85.01%) with IC50values ranging from 48 to 462 μg/ml compared to butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), and tannic acid 0.6, 2.00, and 461 μg/ml, respectively. The results of FRAP show that the crude extracts (aq ˃ EM ˃ EA) are less efficient than their fractions (Acet/aq˃ Acet/EA˃n-but/EA) which demonstrate an important activity. Concerning total antioxidant capacity essay (TAC), the highest capacity was noticed for Acet/aq (71.98 μg gallic acid equivalents [GAE]/mg extract) and Acet/EA extract (64.62 μg GAE/mg of extract). The antioxidant activity of dried fruit extracts ofZ. jujubais mainly related to its polyphenol content essentially on flavonoids, which qualifies this species as a source of natural antioxidant.