Comparative study on different extraction methods of oil extract from Mentha asiatica Boriss. and optimization of the extraction process by response surface methodology

In the current study, the lipophilic solvent (n-hexane) extraction, steam distillation (SD) and supercritical CO₂ fluid extraction (SC–CO₂) methods were used to extract the volatile components of Mentha asiatica Boriss. Comparisons were made between the extraction yield, chemical component and biological activity. Gas chromatography quadrupole-time-of-flight mass spectrometry (GC–QTOF–MS) and semi-quantitative analysis of chemical contents by flame ionization detector (GC–FID) were used to study the chemical ingredients in Mentha asiatica Boriss. aromatic extract. The oil extract obtained from lipophilic solvent (n-hexane) extraction (1.27 ± 0.03%, w/W) showed the highest yield, followed by supercritical CO₂ fluid extraction (1.15 ± 0.04%, w/W), the extraction rate of SD was (0.37 ± 0.01%，w/W). The oil extract of Mentha asiatica Boriss. contained a total of 70 components that were identified. In the following, the primary volatile compounds of the essential oil produced using the three extraction techniques: α-thujene, camphene, sabinene, β-pinene, β-cymene, limonene, β-terpinene, camphol, α-terpinene, carvenone, carvone, piperitone oxide, thymol, myrtenyl acetate, dihydrojasmone, caryophyllene, germacrene D and caryophyllene oxide. Findings from this study indicate that the three methods of essential oil extraction produced oils with varying antioxidant capacities against DPPH and ABTS free radicals. Against Staphylococcus aureus, Candida albicans, Bacillus subtilis and Escherichia coli, all of the essential oils simultaneously showed clear inhibitory actions. Response surface methodology (RSM) and the Box–Benhnken design with three factors and three levels were both utilized to optimize the distillation process of essential oils. The appropriate extraction parameters were a 3 h extraction period, a solid–liquid ratio of 1:10 and a 3 h soaking time. The highest yield of essential oil was 0.38%. The impact of extraction parameters on essential oil yield was examined using the SD method. The findings indicated that the main factors affecting the yield of volatile oil extracted by SD were soaking time > ratio of solid to liquid > extraction time.