Green Extraction of Bioactive Phenolics From Withania somnifera Using Deep Eutectic Solvents: Efficiency, Antioxidant Potential, and Antibacterial Activity

Withania somnifera is a valuable source of bioactive phenolic compounds (PCs). To meet the growing demand for environmentally friendly extraction methods, deep eutectic solvents (DESs) have emerged as a promising alternative to traditional carbon-based solvents, offering advantages such as non-toxicity and biodegradability. In this study, six distinct DESs were evaluated for their efficiency in extracting PCs from dried W. somnifera biomass. The binary combination of choline chloride (ChCl) with acetic or lactic acids demonstrated the highest extraction efficiency, yielding 63.5 mg GAE/g WDB in total phenolic content (TPC) and 75.60 mg RE/g WDB. Notably, all tested DESs outperformed the control solvent (ethanol) in extraction efficiency. Moreover, the ferric reducing antioxidant power (FRAP) assay confirmed strong antioxidant activity, with DES-5, DES-2, and DES-1 showing the highest reducing power (130.3, 122.4, and 111.3 mg TE/g WDB, respectively). ChCl–acetic acid (DES-2) and ChCl–lactic acid (DES-5) showed the strongest antibacterial activity: DES-2 yielded inhibition zones of 38.5 mm against Streptococcus dysgalactiae and 35 mm against Pseudomonas putida, whereas DES-5 produced zones of 37.5 mm against P. putida and 34.5 mm against S. dysgalactiae. Both the synthesized DESs and the extracts from W. somnifera biomass demonstrated antibacterial efficacy across all tested bacteria. In conclusion, DESs offer a sustainable, non-toxic, and cost-effective alternative to organic solvents for extracting bioactive PCs from W. somnifera biomass. Their environmental friendliness and efficiency underscore their potential as a viable option for future applications in green extraction technologies.