Comparative evaluation of total phenols, flavonoids content and antioxidant potential of leaf and fruit extracts of Omani Ziziphus jujuba L

The present study was designed to prepare different extracts from the leaves and fruit of Omani Ziziphus jujuba (Z. jujube) and to determine their total phenols and flavonoids content, including antioxidant activity, by applying modified established methods. Different extracts were prepared by Soxhlet extraction with methanol of powdered samples of either leaves or fruit. Both extracts were separately suspended in water and fractionated using solvents of different polarities, namely, hexane, chloroform, ethyl acetate, butanol, methanol and water, in an increasing polarity pattern. The different parameters mentioned above were determined using Folin-Ciocalteu reagent (FCR), aluminium chloride (AlCl₃) and 1, 1-diphenyl-2-picrylhydrazyl (DPPH) methods, as applied to each assay. The maximum content of total phenols in leaves was detected in the ethyl acetate extract, and the lowest was in the water extract. A similar result was also obtained from fruit extracts of Ziziphus jujube. However, the maximum content of flavonoids was detected in chloroform extract, and the minimum content was observed in hexane extract, with a similar trend being observed for total flavonoids content in the case of fruit extracts. Both the leaf and fruit extracts exhibited significant antioxidant activity, with the maximum percentage of inhibition being obtained in chloroform and hexane extracts and the lowest inhibition in the ethyl acetate extract. The present study demonstrates that all polar extracts of Omani Z. jujuba have significant antioxidant effects. This report is the first in Oman describing total phenols and flavonoids content, including assessment of antioxidant activity, of the extracts of Omani Z. jujube. Therefore, the active polar extracts of Omani Z. jujuba could be candidates for use as antibiotics.