Anti-inflammatory activities of some Mentha essential oils in lipopolysaccharide-activated macrophages

Abstract Essential oils from some species belonging to Mentha genus have been reported to have anti-inflammatory actions. However, little has been known about their relative anti-inflammatory potency, especially with species cultivated and collected in Vietnam. In this study, we aimed to compare the anti-inflammatory effects of eight essential oil samples extracted from different varieties of three Mentha species, including M. arvensis, M. piperita, and M. longifolia, using two cell models of lipopolysaccharide (LPS) induced inflammation: Raw 264.7 and mouse primary peritoneal macrophages. We found that these essential oil samples exhibited anti-inflammatory effects with different levels, in which essential oils from M. longifolia and M. piperita possessed the most potent inhibitory activity against nitric oxide (NO) production in both Raw and peritoneal macrophages. Further insights into the inflammatory modulation by M. longifolia essential oils (MLO) revealed that MLO suppressed the release of NO from Raw 264.7 and peritoneal macrophages upon LPS stimulation with the fifty-percent inhibitory concentrations (IC50) of 0.899 and 0.635 µg/mL, respectively. The production of pro-inflammatory mediators other than NO, including IL-6 and TNFα, was also significantly inhibited by MLO in LPS-activated Raw 264.7 macrophages. Moreover, the quantitative reverse transcription polymerase chain reaction (RT-qPCR) analyses indicated that MLO decreased the expression of pro-inflammatory genes such as Ptgs2, Il1b, Il6, nos2, and Tnf. Taken together, this study suggests Mentha essential oils as promising anti-inflammatory agents and further studies should focus on exploring potential therapeutic applications of these essential oils against inflammatory disorders. Keywords: Anti-inflammatory, essential oils, Mentha arvensis, Mentha longifolia, Mentha piperita.