Antioxidant activity and phenolic content of various date palm (Phoenix dactylifera) fruits from Iran

Edible parts of date palm (Phoenix dactylifera) fruits (DPF) from Iran were analyzed for their antioxidant activities (AA) using Trolox equivalent antioxidant capacity (TEAC) method, 2,2′-azinobis (3-ethylbenzothiazoline-6-sulphonic acid) radical cation (ABTS+) assays and the ferric reducing/antioxidant power method (FRAP assay). The total phenolic content (TPC) and total flavonoid content (TFC) of the DPF were measured using Folin–Ciocalteau and aluminum chloride colorimetric methods, respectively. The samples used included four types of soft dates (SD) namely Honey date, Bam date, Jiroft date and Kabkab date; three types of semi-dry dates (SDD) namely Sahroon date, Piarom date and Zahedi date and one type of dry date (DD) which was Kharak date. The AA (ABTS assay) of the DPF were 22.83–41.17, 47.6–54.61 and 500.33 μmol Trolox equivalents/100 g dry weights (dw) for SD, SDD and DD, respectively. The AA (FRAP assay) per 100 g dw sample were 11.65–20, 19.12–29.34 and 387.34 μmol FRAP for SD, SDD and DD, respectively. The TPC ranged from 2.89 to 4.82, 4.37 to 6.64 and 141.35 mg gallic acid equivalents (GAE)/100 g dw, while TFC ranged from 1.62 to 3.07, 1.65 to 4.71 and 81.79 mg catechin equivalents (CEQ)/100 g dw sample for SD, SDD and DD, respectively. Correlation analyses indicated that there was a linear relationship between AA and the TPC or TFC of DPF. This work demonstrates the potential of Iranian dates as antioxidant functional food ingredients.