Abstract
The valorization of agricultural by-products through sustainable extraction strategies represents a pivotal milestone in green chemistry. In this study, deep eutectic solvents (DESs) were tailored and evaluated as eco-friendly alternative extraction media for the selective recovery of antioxidant phenolic compounds from Opuntia ficus-indica (prickly pear) cladodes. A series of choline chloride-based DESs paired with diverse hydrogen bond donors (lactic acid, glycerol, ethylene glycol, and urea) were screened, among which choline chloride:lactic acid (ChCl:LA, molar ratio 1:2) exhibited superior extraction efficiency. Using a Box-Behnken response surface design, the extraction parameters were systematically optimized under ultrasound-assisted conditions. The optimal operational conditions were determined to be a water content of 25% (v/v), an extraction temperature of 55 °C, an ultrasonic power of 240 W, and an extraction duration of 35 min. Under these conditions, the total phenolic content reached 42.68 ± 1.15 mg gallic acid equivalents per gram of dry weight (mg GAE/g DW), outperforming conventional 80% aqueous methanol (27.34 ± 0.82 mg GAE/g DW) and aqueous ethanol (29.12 ± 0.94 mg GAE/g DW). Chromatographic profiling via HPLC-DAD revealed elevated yields of piscidic acid, isorhamnetin-3-O-rutinoside, and rutin. Furthermore, the extracts displayed pronounced free radical scavenging activity against DPPH (IC50 = 38.42 ± 1.10 µg/mL) and robust ferric reducing antioxidant power (FRAP = 312.45 ± 8.70 µmol Fe2+/g DW). These findings substantiate the efficacy of tailored acidic DESs as biocompatible, low-toxicity media for maximizing the recovery of bioactive phytochemicals from O. ficus-indica cladodes for food and pharmaceutical applications.
