Chemical Composition and Antioxidant Activity of Date Seeds from Different Tunisian Date Palm Cultivars

Chemical composition, polyphenolic and flavonoid contents, and antioxidant activity were determined in date seeds derived from four Tunisian date palm (Phoenix dactylifera) cultivars namely: Goundi, Chekena, Mnekher and Remtha. Sodium and potassium contents in date seeds were determined by flame photometry, phenolic compounds by the Folin-Ciocalteu method, flavonoids by colorimetric quantification, and the antioxidant activity by the DPPH free radical scavenging method. Crude protein content varied widely (p < 0.001) between date seed varieties and ranged from 3.95 (Goundi) to 7.51 % DM (Chekena). No significant differences (p > 0.001) were detected between seed varieties for their dry matter (DM) and ash contents. However, sodium, potassium and phosphorus varied widely (p < 0.001) between varieties. The highest phenolic content (p < 0.001) was observed in Goundi (39.4 mg gallic acid equivalent (GAE)/g DM) and Remtha (36.6 mg GAE/g DM) seed varieties. Likewise, Goundi had the highest (p < 0.001) flavonoid content (16.4 mg quercetin equivalent (QE)/g DM) and antioxidant activity (1,807 μM Trolox equivalent antioxidant capacity (TEAC)/g DM); however the lowest values (p < 0.001) of phenolic (19.2 mg GAE/g DM), flavonoid (8.8 mg QE/g DM) and antioxidant activity (682 μM TEAC/g DM) were observed for Chekena seeds. Further studies are needed to verify the potential of date seeds as alternative for animal nutrition.