Simultaneous synergistic microwave-ultrasonic extraction and hydrolysis for preparation of trans-resveratrol in tree peony seed oil-extracted residues using imidazolium-based ionic liquid

•Tree peony seed oil-extracted residues were used as raw materials.•A basic imidazolium-based ionic liquid was selected and used.•Microwave-ultrasonic synergistic apparatus was successfully applied in this study.•Simultaneous extraction and hydrolysis of glycosides to trans-resveratrol.•The proposed technique performed better than that without microwave or ultrasound.

Imidazolium-based ionic liquid-based microwave-ultrasonic synergistic simultaneous extraction and hydrolysis (IMUSEH) method was developed to obtain trans-resveratrol from tree peony (Paeonia rockii (S.G. Haw & Lauener) T. Hong & J.J. Li) seed oil-extracted residues, in which the basic ionic liquid aqueous solution was used for extraction and transformation of trans-resveratrol glycosides to free trans-resveratrol. Through comparison, 1-butyl-3-methylimidazolium imidazolide ([C4C1im]Im) was selected as a dual solvent-catalyst, which showed an excellent solvent effect and catalytic activity. After optimization by a factorial design and response surface methodology, a higher yield of trans-resveratrol (3.06 ± 0.12 μmol/g) was obtained under optimal conditions (0.5 M [C4C1im]Im, 24 mL/g liquid-solid ratio, 25 min time, and 396 W microwave irradiation power). The developed technique was compared with ionic liquid-based microwave-assisted extraction and ionic liquid-based ultrasonic-assisted extraction based on first-order kinetic model and scanning electron microscopy, which highlighted the mechanism of the microwave-ultrasonic synergistic apparatus. Method validation studies showed that the proposed method can be used to prepare trans-resveratrol. The developed method showed promise in transforming glucoside to aglycone in plant materials.