Green and integrated recovery of luteolin from peanut shells using ionic liquid-microwave extraction and macroporous resin purification.

Peanut shells, an abundant agricultural by-product, represent a promising source of the bioactive flavonoid luteolin. This study developed a green and efficient strategy for luteolin recovery by integrating ionic liquid-based microwave-assisted extraction (IL-MAE) with macroporous resin purification. The IL-MAE process was optimized using response surface methodology (RSM), achieving a maximum yield of 3.36 mg/g under optimal conditions: [BMIM][BF₄] concentration of 2 mol/L, liquid-to-solid ratio of 27 mL/g, microwave power of 800 W, and irradiation time of 120 s. Molecular dynamics simulations revealed that hydrogen bonding between luteolin and the ionic liquid governs the extraction mechanism. The crude extract was further purified using NKA-9 macroporous resin, which exhibited high adsorption capacity (2.10 mg/g) and desorption efficiency (93.57%). Dynamic adsorption studies established optimal conditions: sample pH 3.0, loading volume of 1.95 bed volumes (BV), flow rate of 2 BV/h, and temperature of 25 °C. Efficient desorption was achieved by sequential elution with water, 50% ethanol, and 70% ethanol (5 BV each), yielding a final luteolin purity of 84.1%. Notably, the ionic liquid was successfully recycled with over 90% of its initial extraction efficiency retained after multiple cycles. This integrated approach offers a sustainable and scalable pathway for valorizing agricultural waste into high-value bioactive compounds within a circular bioeconomy framework.