Chemical composition and in vitro antimicrobial, insecticidal and antioxidant activities of the essential oils of Mentha pulegium L. and Mentha rotundifolia (L.) Huds growing in Algeria

Abstract

The essential oils of Mentha pulegium L. (MPE) and Mentha rotundifolia (L.) Huds (MRE) which are growing in Algeria were prepared by hydrodistillation and their chemical compositions investigated by GC/MS. The oils were tested for their antimicrobial activity using disc-diffusion and spot assays, antioxidant activity using 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic) acid (ABTS) test and Kit Radicaux Libres® (KRL) biological assay. Also, contact toxicity, fumigant toxicity and repellency tests of these essential oils were evaluated against adults of Rhyzopertha dominica (F.) (the principal pest of wheat). The major components found in MPE are pulegone (70.4%), neo-menthol (13.4%), neo-menthol acetate (3.5%) and menthone (2.7%). On the other hand, MRE provided trans-piperitone epoxide (30.2%), piperitone oxide (8.7%), thymol (4.5%), germacrene D (3.5%) and terpinen-4-ol (2.7%) as major ingredients. MRE exhibited stronger antimicrobial effect and antioxidant activity in the KRL test than MPE. In the contact assay, DL50 values of MRE and MPE were 3.3 and 6.9μL/mL, respectively. Fumigant toxicity assay of MPE and MRE showed mortality ratio of 39.2 and 44.3%, respectively at the dose of 2μL/mL. Moreover, at this dose and after 30min exposure time, the repellent effect showed death rates of 46.03% and 47.54% for MPE and MRE, respectively. As conclusion, MPE and MRE are potential alternatives to chemical additives in food and pharmaceutical industries.