Ripening Stage and Phenolic Composition Characterization of Fruit from Different Date (Phoenix dactylifera L.) Cultivars in Australia

Abstract

We analyzed the antioxidant potential and composition of phenolic compounds in six Australian date palm cultivars (Mejhoul, Barhee, Deglet nour, Thoory, Halawi, and Khadrawy) at three ripening stages: Kimri, Khalal, and Tamar. Total phenolic content in date fruits at the Kimri stage ranged from 19.7 to 117.5 mg GAE/g, significantly exceeding that of the Khalal (1.22–24.4 mg GAE/g) and the Tamar stages (0.47–8.72 mg GAE/g). Date fruits at the Kimri stage had higher antioxidant potential quantified in assays such as DPPH, FRAP, ABTS, RAP, FICA, and TAC compared to those at the Khalal and Tamar stages. The LC-ESI-QTOF-MS/MS analysis identified 28 phenolic compounds, categorized as 4 phenolic acids, 17 flavonoids, and 7 other phenolic compounds. Quantitative analysis using LC-DAD suggested cultivar-specific variations in the phenolic profile, with the Khadrawy cultivar having the highest quercetin content during the Kimri stage. At the Khalal ripening stage, Thoory and Mejhoul cultivars had higher quercetin and procyanidin A2 concentrations, respectively. At the Tamar stage, the Deglet nour cultivar had higher concentrations of procyanidin A2, gallic acid, and caffeic acid as compared to other date cultivars. Our findings indicate that the phenolic content decreases as date fruit matures from the Kimri to Tamar stage, with significant variations in phenolic composition and antioxidant capacity across different cultivars.