Antioxidant activity of various Mauritanian date palm (Phoenix dactylifera L.) fruits at two edible ripening stages

The increasing interest in plant phenolics and flavonoids outlined the necessity of determining their contents and biological activity in Mauritanian date palm fruits. Methanolic extracts of fruit of six date palm cultivars commonly grown in Mauritania were screened for their antioxidant activity, total phenolics, and flavonoid content at two edible ripening stages. Polyphenols and flavonoids were higher in the Blah stage, corresponding to Khalal in the standard Iraqi Arabic nomenclature, compared to the fully mature Tamr stage regardless the cultivar. The average of total phenolics at Blah and Tamr stages were 728.5 and 558.9 mg gallic acid equivalents (GAE) per 100 g dry matter (DM), whereas the average flavonoid content was 119.6 and 67.3 mg quercetin equivalents (QE) per 100 g DM, respectively. The Blah stage also exhibited the highest total antioxidant activity with a Trolox equivalents antioxidant capacity (TEAC) value of 129.3 μmol/100 g DM founded in Bou seker's Blah date, followed by Tijib cultivar with TEAC value of 114.3 μmol/100 g DM and an average TEAC value of 107.5 μmol/100 g DM. Furthermore, a high positive correlation was found between total phenolics in Tamr (r = 0.92) and Blah (r = 0.87) stages and TEAC of fruit methanolic extracts compared to the flavonoids, suggesting that phenolics were the major contributor to the antioxidant activity.