Microwave-Assisted Extraction of Rubusoside from Rubus chingii var. suavissimus Leaves Using a Recyclable Ternary Deep Eutectic Solvent: Process Optimization and Mechanistic Insights.

Rubusoside is the major sweet bioactive compound in Rubus chingii var. suavissimus (S.K.Lee) L.T.Lu, characterized by high sweetness, low caloric value, and favorable safety, with potential applications as a natural sweeteners and in functional foods. However, efficient green extraction technologies and their mechanisms remain insufficiently explored. Here, a microwave-assisted deep eutectic solvent (DES) system was developed for rubusoside recovery. The ternary DES composed of choline chloride, 1,2-propylene glycol, and 1,3-butanediol (1:2:2) showed the best performance and outperformed microwave-assisted water extraction. Response surface methodology identified optimal conditions of 33% moisture content, a liquid-solid ratio of 21 mL/g, 6 min, and 320 W, yielding 7.89 ± 0.25% rubusoside. Fourier-transform infrared spectroscopy, electrostatic potential, atoms-in-molecules theory, and independent gradient modelling based on Hirshfeld partition analyses revealed significant non-covalent interactions between the ternary DES and rubusoside. Scanning electron microscopy showed that DES and microwave treatment synergistically disrupted plant tissues and enhanced mass transfer. LX-28 macroporous resin enabled rubusoside separation, and the recovered DES retained stable performance after five reuse cycles. These results demonstrate a green, efficient, and recyclable strategy driven by cooperative hydrogen bonding and van der Waals interactions between the ternary DES and the rubusoside glycosyl moiety, together with DES-microwave-induced tissue disruption and mass-transfer enhancement.