Switchable temperature-responsive deep eutectic solvents: A sustainable strategy for polyphenol extraction from sorghum bran

Innovative TRDES-UAE for green polyphenol extraction from sorghum bran • Higher phenolic yields than conventional solvents & control DES • Enhanced bioactivity linked to SEM/molecular docking findings • Excellent recyclability (>85% efficiency over multiple cycles) This study developed a green extraction method using a switchable temperature-responsive deep eutectic solvent (TRDES) combined with ultrasound-assisted extraction (UAE) for polyphenol recovery from sorghum bran. TRDES formation was confirmed by FT-IR. Under optimized conditions, TRDES-UAE significantly enhanced the total polyphenol yields (22.14 mg/g DW), total flavonoid yields (24.71 mg/g DW), and total proanthocyanidins yields (29.47 mg/g DW), representing 1.15- to 6.02-fold higher yields than conventional solvents and a conventional DES. SEM revealed pronounced plant matrix disruption by TRDES, and molecular docking confirmed strong binding affinities between TRDES and target polyphenols. The TRDES extract exhibited potent antioxidant activity—DPPH IC 50 : 90.39 μg/mL; ABTS + IC 50 : 101.55 μg/mL; superoxide anion IC 50 : 117.30 μg/mL; hydroxyl radical IC 50 : 124.24 μg/mL; FRAP value: 1081.29 μmol Fe 2+ /L—as well as strong antibacterial activity, with MIC values of 0.15 mg/mL against Staphylococcus aureus and Escherichia coli , and 0.10 mg/mL against Salmonella enterica . Six greenness metrics validated the environmental benefits, and TRDES maintained >85% extraction efficiency over five consecutive reuse cycles. This work establishes TRDES-UAE as a sustainable strategy for sorghum bran upcycling with potential for functional food applications.