Date (Phoenix dactylifera) seed is a potential source of natural antioxidants, and the use of innovative green and low temperature antioxidant recovery techniques (using CO2 as solvent) such as supercritical fluid (SFE) and subcritical (SubCO2) extractions can improve their yields and quality in the extracts. SFE, SubCO2 and Soxhlet techniques were employed to enrich antioxidants in extracts from Sukari (SKSE), Ambara (AMSE), Majdool (MJSE) and Sagai (SGSE) date seeds. Extract yields were evaluated and modelled for SFE extract using response surface methodology. Significantly higher (p < 0.05) phenolics (143.48−274.98 mg GAE/100 g), flavonoids (78.35−141.78 mg QE/100 g), anthocyanins (0.39−1.00 mg/100 g), and carotenoid (1.42−1.91 mg BCE/100 g) contents were detected in extracts obtained using SFE and SubCO2 methods. The evaluation of in vitro antioxidant properties showed that SFE and SubCO2 seed extracts demonstrated promising antioxidant (13.42−23.83 µg AAE/mL), antiradical (228.76−109.69 µg/mL DPPH IC50), ferric reducing antioxidant power (1.43−2.10 mmol TE/100 g) and ABTS cation scavenging (375.74-717.45 µmol TE/100 g) properties that were significantly higher than Soxhlet extracts. Both SFE and SubCO2 techniques can be effectively utilized as innovative and environmentally friendly alternatives to obtain high quality antioxidant rich extracts from date seed. These extracts may have potential functional and nutraceutical applications.
Keywords: Phoenix dactylifera; anthocyanins; antioxidant properties; carotenoids; date fruit seed; flavonoids; green extraction methods; phenolics; subcritical CO2; supercritical fluid.