Green approach to phenolic compound extraction from date fruit (Phoenix dactylifera L.)

In recent times, green and efficient natural deep eutectic solvents (NADESs) that can replace harmful traditional ones have attracted considerable attention. The objective of the present study was to investigate a sustainable method for enhancing the extraction of phytochemicals from date palm fruit (Tazizaout cultivar), a valuable source of bioactive compounds. In this study, lactic acid/sucrose-based NADESs were employed as an alternative to conventional chemical solvents, in conjunction with the ultrasound-assisted extraction (UAE) method. Subsequently, the extracts were subjected to analysis in order to determine their bioactive compound contents, phenolic composition, antioxidant activity, and enzyme inhibitory potential. The results demonstrated that the Tazizaout extract contained considerable contents of total phenolics (570.8 mg GAE/100 g), total flavonoids (40.3 mg QE/100 g), proanthocyanidins (38.8 mg CE/100 g), and total triterpenoids (9.72 mg OAE/100 g). The cultivar displayed high antioxidant capacity against the ABTS^•+ cation radical (214 mg TE/100 g) and ferric-reducing antioxidant potential (136 mg AAE/100 g). The extract exhibited moderate antioxidant activity when tested using the DPPH^•, phosphomolybdenum, NO^•, and linoleic acid lipid peroxidation assays. Furthermore, the extract exhibited notable inhibitory effects on α-amylase and acetylcholinesterase enzymes in vitro, with inhibition rates of 33% and 34%, respectively. High-performance liquid chromatography with diode array detection and mass spectrometry (HPLC-DAD-MS) identified a total of five compounds (three phenolic acids and two flavonoids) as the main phenolics present in the extract, with the predominant compound being gallic acid. The results indicated that the combination of UAE and NADESs represents a novel and useful alternative to chemical solvents for sustainable and green extraction. This approach could have implications for industries seeking eco-friendly alternatives for the extraction of phytochemicals, with potential applications in foods, pharmaceuticals, and other related sectors.