Sustainable extraction and bioconversion of tea stems using NADES: Dual benefits in polyphenolic recovery and carbohydrates enzymatic hydrolysis.

This study presents a novel and sustainable strategy for valorizing tea stems, an abundant agricultural by-product, using natural deep eutectic solvents (NADESs) composed of choline chloride as the hydrogen bond acceptor and levulinic acid, acetic acid, glycerol, lactic acid, or urea as hydrogen bond donors. The NADES system enabled efficient extraction of polyphenolic and flavonoid compounds, with total flavonoid content (83.49 ± 0.40 mg/g) significantly exceeding that obtained using ethanol (61.65 mg/g). The extracts exhibited enhanced stability under thermal and light stress and demonstrated strong antioxidant activity and inhibitory effects against α-amylase and pancreatic lipase. Importantly, the solid residues remaining after extraction were further enzymatically hydrolyzed to release monosaccharides, supporting complete biomass utilization. This dual-phase NADES-based approach not only maximizes recovery and stability of bioactive compounds but also enables integrated valorization of tea stem residues, highlighting both scientific novelty and practical applicability in functional foods, nutraceuticals, and renewable energy.