Optimization of Microwave-Assisted Extraction from Peppermint (Mentha piperita L.) Using Ethanol and β-Cyclodextrin as Green Solvents

This study explores the use of microwave-assisted extraction of bioactive compounds from peppermint (Mentha piperita L.) using aqueous ethanolic and β-cyclodextrin solvents. The experiments were performed according to Response Surface Methodology, and the central composite design was employed, with the independent variables being treatment time, microwave power and solvent concentration. During the research, the total polyphenol content (TPC, expressed as gallic acid equivalents, GAE), total flavonoid content (TFC, expressed as quercetin equivalents, QUE), antioxidant capacity (AC) using the FRAP (Ferric Reducing Antioxidant Power, expressed as ascorbic acid equivalents, ASE) and DPPH (2,2-diphenyl-1-picrylhydrazyl) methods, and total menthol content (TMC, expressed as menthol equivalents, MEE) were examined. For the ethanolic extraction, the optimum conditions were 571 W, 7.3 min, and 10% v/v. The following results were obtained for these parameters: TPC, 1025 µg GAE/mL; TFC, 66.69 µg QUE/mL; FRAP, 3786.24 µg ASE/mL; DPPH, 80.24%; and TMC, 62.63 µg MEE/mL. In the case of β-cyclodextrin, the optimum conditions are 800 W, 11.81 min, and 1.70 mM. In this case, the results are as follows: TPC, 949.29 µg GAE/mL; TFC, 90.75 µg QUE/mL; FRAP, 4275.54 µg ASE/mL; DPPH, 89.81%; and TMC, 84.99 µg MEE/mL. β-cyclodextrin increased the flavonoid, antioxidant and menthol content, although there were no significant differences between the concentrations. The use of ethanol had a greater effect on the polyphenol content. β-cyclodextrin proved to be an effective green alternative solvent for peppermint.