Antioxidant activity of Bahraini date palm (Phoenix dactylifera L.) fruit of various cultivars

Fruits of sixteen cultivars of date palm (Phoenix dactylifera L.) commonly grown in Bahrain were evaluated for their antioxidant activity, total phenolics and ascorbic acid contents at different ripening stages using the ferric reducing antioxidant power (FRAP) assay. The highest total antioxidant activity was found at biser (unripe) stage, with a mean FRAP value of 5.71 +/- 4.31 mmol/100 g fresh weight (FW), followed by rutab (soft and ripped) with FRAP values of 1.2 mmol per 100 g FW and tamer (dried fruit) 0.94 +/- 0.21 mmol per 100 g FW. Total antioxidant activities of locally collected and imported tamer were similar. There was about twelve and six fold difference between cultivars possessing the highest and lowest antioxidant values at biser and rutab stages, respectively. A sharp decrease in antioxidant activity was found to be associated with the fruit ripening. The average of phenolics at biser and rutab stage were 196.8 +/- 72.1 and 116.7 +/- 44.1 mg per 100 g fresh weight, whereas the average of ascorbic acid was 6.6 +/- 2.4 and 3.3 +/- 1.3 mg per 100 g fresh weight, respectively. Significant correlation was found between the antioxidant activity and total phenolic content (r = 0.595) and ascorbic acid (r = 0.385) at biser stage, but not at rutab stage. It was concluded that the phenolics were the major contributor for the antioxidant activity.