Optimization of Extraction Process and Estimation of Flavonoids from Fenugreek Using Green Extracting Deep Eutectic Solvents Coupled with Ultrasonication

The extraction of flavonoids from fenugreek seeds was investigated using ultrasound-assisted deep eutectic solvents (DES). The selection of the most effective DES was based on the analysis of the bioactive profile, antioxidant potential, and antimicrobial properties of fenugreek extracts, taking into consideration the physicochemical properties of the DES. The results suggested that all six DES performed better than conventional solvent (methanol), and among DES, choline chloride-malic acid (CCMA), choline chloride-citric acid (CCCA), and choline chloride-1,4-butanediol (CCBU) performed better under set conditions and were further selected for optimization of processing conditions, including molar ratios, water required for dilution of DES, sonication power, sonication time, and sonication temperature. Identification and quantification of the flavonoids present in optimized-DES extracts were carried out using HPLC–DAD. The results revealed that prominent individual flavonoid compounds were kaempferol (10.65 ± 0.49), rutin (18.33 ± 0.84), and quercetin (10.82 ± 0.59) mg/gm d.w., with recovery percentages of 78.83%, 92.69%, and 87.18%, respectively. After analyzing the results of HPLC, we can conclude that CCMA (DES) is a safer, greener, and highly efficient extraction system for maximum and sustainable extraction of flavonoid compounds from fenugreek seeds.