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

What if the sweetener in your tea could be extracted with a solvent that's green, recyclable, and powered by microwaves? Scientists just found a way to do exactly that.

Rubusoside, the sweet compound in Rubus chingii leaves, is a natural sweetener with low calories and high safety. But extracting it efficiently without harming the environment has been a challenge. Now, researchers have developed a microwave-assisted method using a ternary deep eutectic solvent (DES) — a mixture of choline chloride, 1,2-propylene glycol, and 1,3-butanediol — that outperforms traditional water extraction.

By optimizing conditions with response surface methodology, they achieved a rubusoside yield of 7.89 ± 0.25% under 33% moisture, a liquid-solid ratio of 21 mL/g, 6 minutes, and 320 W. The team used advanced analyses like FTIR and electrostatic potential to reveal that the DES forms strong non-covalent interactions with rubusoside, particularly through hydrogen bonds and van der Waals forces.

Microscopy showed that the DES and microwaves work together to break down plant tissues, boosting mass transfer. The process is not just green — it's also recyclable. After separating rubusoside with LX-28 resin, the DES remained stable for five reuse cycles, offering a sustainable path for natural sweetener production.

Key Points

• Ternary DES outperforms water extraction for rubusoside.
• Optimal yield: 7.89% under 6 min microwave.
• DES recyclable over five reuse cycles.