Antioxidant and anti-atherogenic properties of phenolic acid and flavonol fractions of fruits of ‘Amari’ and ‘Hallawi’ date (Phoenix dactylifera L.) varieties.

Date (Phoenix dactylifera L.) fruit phenolic-acid or flavonol fractions were examined in vitro for antioxidant and anti-atherogenic properties. Two fractions of each subgroup were prepared from two date varieties, 'Amari' and 'Hallawi', by solid phase extraction on C18. The fractions were analyzed for phenolics' composition by RP-HPLC, and tested for ferric-reducing antioxidant power, free radical scavenging capacity, inhibition of Cu(2+)-induced LDL-oxidation and enhancement of HDL-mediated cholesterol efflux from macrophages. All four fractions exhibited variable capacities to reduce ferric ions, scavenge radicals and inhibit LDL-oxidation. Flavonol fractions were considerably better inhibitors of LDL-oxidation compared to phenolic-acid fractions, with IC50 of 9-31 nmol GAE mL(-1) compared to 85-116 nmol GAE mL(-1), respectively. Only the flavonol fractions stimulated cholesterol removal from macrophages. Within each subgroup, the levels of all the activities varied with fraction composition. The results demonstrated strong structure-activity relationships for date phenolics, and identified date flavonols as potential anti-atherogenic bioactives.