Systematic evaluation of antioxidant capacities of the ethanolic extract of different tissues of jujube (Ziziphus jujuba Mill.) from China

Jujube (Ziziphus jujuba Mill.) has long been used for human consumption and medicinal purposes in China. It is recommended for some diseases in which radical species are produced as a result of oxidative stress. However, the systematic study on the antioxidant capacities of various tissues of jujube is still lacking. In order to address this, various tissues of three jujube varieties were characterized with respect to their antioxidant capacities and antioxidant compounds such as flavonoid, ascorbic acid, anthocyanin and phenolic. Antioxidant capacity was measured using the DPPH (2,2-diphenyl-1-picrylhydrazyl) and FRAP (ferric-reducing antioxidant power) assays. The phenolic acids were analyzed by high-performance liquid chromatography (HPLC). The results show that the peel of all cultivars has the highest antioxidant capacities, reflecting the highest content of total phenolics, flavonoids, and anthocyanins found in this part. In addition, the predominant phenolic acid in jujube was found to be protocatechuic acid, followed by gallic acid, chlorogenic acid and caffeic acid. The results obtained in this study clearly indicate that Chinese jujube has a significant potential to use as a natural antioxidant agent.