Microwave-Assisted Extraction of Rubusoside from Rubus chingii var. suavissimus Leaves Using a Recyclable Ternary...

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.