Recovery of Cembratrien-Diols from Waste Tobacco ( Nicotiana tabacum L.) Flowers by Microwave-Assisted Deep Eutectic Solvent Extraction: Optimization, Separation, and In Vitro Bioactivity.

Deep eutectic solvents (DESs) are novel solvents with physicochemical properties similar to those of ionic liquids, and they have attracted extensive attention for the extraction of bioactive compounds from different plant materials in the context of green chemistry and sustainable development. In this study, seven DESs with different polarities were explored as green extraction solvents for cembratrien-diols (CBT-diols) from waste tobacco flowers. The best solvent, DES-3 (choline chloride: lactic acid (1:3)), which outperformed conventional solvents (methanol, ethanol, and ethyl acetate), was selected and further optimized for microwave-assisted DES extraction using the response surface methodology. The maximum yield of CBT-diols (6.23 ± 0.15 mg/g) was achieved using a microwave power of 425 W, microwave time of 32 min, solid/liquid ratio of 20 mg/mL, and microwave temperature of 40 °C. Additionally, the isolated CBT-diols exhibited strong antimicrobial activity against Salmonella , Staphylococcus aureus , Escherichia coli , Bacillus subtilis , and Pseudomonas aeruginosa and antitumor activity in the human liver cancer HepG2 and SMMC-7721 cell lines. This study highlights the feasibility of recovering CBT-diols from tobacco flower waste using DESs and provides opportunities for potential waste management using green technologies.