Screening of antioxidant activity and phenolic compounds of various date palm (Phoenix dactylifera) fruits from Algeria

Abstract

The phenolic contents of methanolic extracts from five varieties of date palm (Phoenix dactylifera) fruits from Algeria, Deglet Nour (DN), Degla Baidha (DB), Ghars (Gh), Tamjhourt (Tam), and Tafezauine (Taf) were measured in this work. The antioxidant activities of these extracts were also evaluated. Total phenolic content ranged from 41.80 to 84.73 mg gallic acid equivalents (GAE)/ 100 g and the total flavonoid content varied from 7.52 to 14.10 mg rutin equivalents (RE)/100 g. The antioxidant activities of methanolic extracts were evaluated in vitro using scavenging assays of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) radical ion (ABTS⁺) and potassium ferricyanide complex as reducing power assay. Effective scavenging concentration (IC₅₀) on DPPH radical ranged from 10.83 to 21.27 mg/l, the IC₅₀ values decreased in the order DN > Gh > Tam > DB > Taf. ABTS radical cation scavenging activity (trolox equivalent 1.66–3.35 mM), the trolox equivalent antioxidant capacity values decreased in the order of DN > Gh > DB > Tam > Taf. In the potassium ferricyanide complex assay, the antioxidant capacity of the extracts ranged between 2.06 and 4.21 mM ascorbic acid equivalents and the ascorbic acid equivalents antioxidant capacity values of the extracts decreased in the order Gh > Tam > DB > DN > Taf. These results suggest that all date varieties constitute a good source of natural antioxidants and could potentially be considered as a functional food.