Antioxidant Activity and Total Phenolic Content of Date Palm (Phoenix dactylifera L.) Fruits from Taif Governorate, Saudi Arabia

Date palm (Phoenix dactylifera L.) fruit is well known for its nutritional and health benefits in Middle East countries. The present study has been carried out to evaluate antioxidant activity and total phenolic content of three date varieties known as Sefri, Sari and Ruzeiz, from Taif Governorate, Saudi Arabia. The samples, at their tamr stage of ripening, were extracted separately with five solvents of decreasing polarity; 20% and 50% aqueous ethanol, absolute ethanol, acetone and ethyl acetate using incubator orbital shaker. Their antioxidant activity was evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay. The results were expressed as efficient concentration (EC50) and ascorbic acid equivalent antioxidant capacity (AEAC). The total phenols were quantified by Folin-Ciocalteu assay as tannic acid equivalent (TAE). The highest antioxidant activity was shown by Sari 50% aqueous ethanolic extract with EC50 9.23 +/- 0.09 mg/mL and AEAC 61.38 +/- 2.05 mg AE/100 g fresh weight of dates. Highest phenolic content was shown by the aqueous alcoholic extracts in the range 1744.90 +/- 37.82-1165.49 +/- 120.02 mg TAE/100 g fresh weight of dates. Statistical analyses revealed strong positive, significant correlation r=0.89, P<0.0014) between antioxidant activity and total phenolic content of alcoholic extracts. Strong negative, significant correlation (r=-0.87, P<0.0022) had been found between EC50 and AEAC.