Antioxidant properties of date palm (Phoenix dactylifera L.) cultivars

The fruit and pits of date palm (Phoenix dactylifera L.) cultivars from the United States (US) and Saudi Arabia (SA) were analyzed for their total phenolic contents and antioxidant activity for two years. The amount of total phenolic compounds and antioxidant activity in all date fruit and pit cultivars tested in this study, at the Tamar stage, were significantly different. Total phenolic contents of fruit ranged from 507.03 (Gur SA) to 225.02 (Medjool US) mg Gallic Acid Equivalents (GAE)/100g FW and antioxidant activities ranged from 1400.14 to 228.06 mumole TEAC/100g of fresh weight (ABTS) in Deglet Noor US and Khalasa US respectively. DPPH of fruit ranged from 117.75 to 165.42 mumole TEAC/100g of fresh weight in Deglet Noor (US) and Khalasa (US) respectively. The pit, which is about 12% of date fruit weight, ranged from 66.68 (Hilali US) to 14.51 (Amir Hajj US) mg GAE/g DW total phenolics. ABTS ranged from 679.01 to 45.83 micromole TEAC/1g of dry weight in Hilali US and Hayany (US) respectively. DPPH ranged from 15.94 to 3.92 mumole TEAC/g of dry weight in Sukari (SA) and Khalasa (SA) respectively. A significant association between the total phenolic content and antioxidant activities was found in both years with ABTS and DPPH. Moreover, there was a strong relationship between measurement of antioxidant capacity by ABTS and DPPH in both years in fruit and pits. Fruit of one cultivar, Khalasa, was available both years from the (US) and (SA). Phenolic content, ABTS and DPPH radical scavenging capacity of fruit and pits differed in their antioxidant activity due to different location and other environmental factors. Fruit or pit (SA) cultivar was significantly higher than the (US) cultivar over all treatments. Deglet Noor (US) fruit which makes up about 90% of California's date crop was found to be the best over all cultivars of those tested in this study. Hilali (US) was the best antioxidant source of date pit cultivars in (US), whereas, Sukari (SA) was the best antioxidant source of pits in (SA). Thus, this research demonstrates the potential of date fruit and pits as antioxidant functional food ingredients.