Utilization of accelerated solvent extraction and deep eutectic solvents as synergistic green extraction technique for the recovery of bioactive compounds from date palm (Phoenix dactylifera L.) seeds

This study aimed to valorize date seeds, a by-product of date fruits, through the recovery of bioactive compounds using a sustainable green approach. The date seed was extracted using one of the most efficient automated green extraction techniques, accelerated solvent extraction (ASE), which is coupled with deep eutectic solvents (DES). Six different DES were initially used for the extraction of date seed bioactive compounds (DSBCs), and the most efficient DES (lactic acid: ethylene glycol) with high efficiency for the recovery of DSBCs was further optimized using a single-factor optimization process. The optimized parameters used were the solid-to-solvent ratio (1:1:50, 1.5:2:50, 2:2:50, 3:2:50, and 5:2:50 g/g/mL), number of static cycles (1, 2, and 4 cycles), static time (5, 10, and 15 min), temperature (60, 80, and 100 °C), and particle size of date seeds (250 µm and 500 µm). The results revealed that among the six DES and two conventional solvents (70 % ethanol and methanol), DES (lactic acid: ethylene glycol) showed the highest recovery of the DSBCs. The optimized conditions for the efficient recovery of DSBCs were a solid-to-solvent ratio of 2.0:2:50 g/g/mL, static cycle of 2 cycles, and a static time of 10 min at 100 °C. The efficiency of date seed bioactive compounds extraction using ASE was evaluated and compared with other green extraction methods, including microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE). MAE was the most effective in recovering DSBCs, followed by ASE and UAE. This study revealed that for DES to be utilized as an extraction solvent in an ASE system, it should have a low viscosity for easier movement of the DES into the extraction cell. This study provides valuable insights into the use of green and sustainable extraction technologies to convert agro-waste into value-added products.