Comparison of antioxidant activity and total phenols of some date varieties

Background and the purpose of the study: Date palms (Phoenix dactylifera L., Arecaceae) are one of the oldest cultivated plants which are used in folk medicine for treatment of various diseases. Due to the presence of antioxidant compounds in this plant and the role of oxidative stress in pathogenesis of chronic diseases, the aim of this study was to determine the antioxidant activity and total phenolic contents of date palm fruits extracts with water, methanol 50%, DMSO, and mixture of water-methanol-acetone-formic acid (20:40:40:0.1). Methods: Antioxidant activity of extracts were measured by two tests: inhibition of 1,1- diphenyl-2-picrylhydrazyl (DPPH) radical and FRAP (Ferric Reducing Antioxidant Power). Results and major conclusion: Among 10 different varieties which were examined, the DMSO extract of Khenizi showed the highest antioxidant activity with the FRAP value of 3279.48 ìmol/100 g of the dry plant and DPPH inhibitory percentage of 56.61%. DPPH scavenging radical and FRAP values of some varieties including Khenrizi, Sayer, Shahabi and Maktub showed a significant increase and were comparable to á-tocopherol (10 mg/L) when extracted by DMSO. Formic acid extract of Shahabi variety with 276.85 mg GAE/100 g of the dry plant showed the highest total phenolic content compared to other varieties. There was no correlation between accumulation of total phenol and antioxidant activity of extracts, explaining existence of other antioxidant components in date.