Process-driven Valorization of Sonchus oleraceus Leaves: Optimization of Microwave-assisted Aqueous Extraction of Antioxidant Phytochemicals

This study developed a green strategy to valorize Sonchus oleraceus leaves by optimizing microwave-assisted aqueous extraction of antioxidant phytochemicals. A three-factor Box–Behnken design quantified the individual and interactive effects of microwave power, extraction time, and particle size on total phenolic content (TPC), total flavonoid content (TFC), total tannin content (TTC), and antioxidant capacity assessed by DPPH and ABTS. Extraction was performed in water at a solid-to-liquid ratio of 1:20 (w/v) using a pulsed microwave regime (5 s on, 15 s off) to limit boiling, followed by centrifugation and filtration. Quadratic models were retained for all responses, showing improvement over simpler structures and acceptable predictability across the design space. Experimental responses covered wide ranges, confirming strong process sensitivity. Numerical desirability optimization predicted an operating optimum at 378.39 W, 18.81 min, and 174 µm, with high predicted phytochemical yields and antioxidant activities. Validation at practical setpoints of 360 W, 20 min, and 180 µm produced TPC 99.82 ± 0.06 mg GAE/g ds, TFC 59.78 ± 0.09 mg RE/g ds, TTC 18.73 ± 0.04 mg TAE/g ds, DPPH 4.40 ± 0.04 mM TE/g ds, and ABTS 4.70 ± 0.05 mM TE/g ds. Taken together, these conditions represent a balanced operating window that supports efficient mass transfer while preserving redox-active phytochemicals under food-grade constraints.