Comparison of chemical composition of essential oils obtained by hydro -distillation and microwave-assisted extraction of Japanese mint (Mentha arvensis L.) grown in Vietnam

Japanese mint (Mentha arvensis L.) is known as a culinary and medicinal herb widely cultivated in several countries. The mint essential oil is considered as one main source of menthol. In this study, the Japanese mint collected from the Central Highlands of Lam Dong Province (Vietnam) was extracted the essential oil by hydro-distillation (HD) and microwave-assisted extraction (MAE). Different extraction parameters were investigated, involving mint leaf drying periods (30, 60, and 90 mins) at 50 degrees C, material to water ratios (1:4, 1:6, 1:8, and 1:10 for HD and 1:1, 1:1.5, 1:2, and 1:2.5 for MAE), extraction durations (60-180 for HD and 10-25 mins for MAE), and microwave energy (230, 380, 540, and 700 W) in order to discover the conditions with the highest yields for both HD and MAE. The GC-MS was used to determine the oil chemical constituents. For dried mint leaves (nearly 40 % moisture), the highest oil yield of 0.0832 mL g(-1) (dried weight) was recorded, and the content of menthol was up to 70.60 % extracted by MAE whilst 0.0510 mL g(-1) of yield (dried weight) and lower menthol (62.80 %) were obtained from HD. Besides, menthol, trans- and cis-menthone were found at relatively high concentrations for both HD and MAE (20.19-16.30 and 4.62-5.01 %, respectively). Compared to HD, MAE exhibited higher oil yields and menthol contents, but lower distillation time, resulting in more effective extraction performance of MAE.