Chemical composition and antibacterial activity of essential oils from the medicinal plant Mentha cervina L. grown in Portugal

Mentha cervina is a medicinal plant traditionally used in Portugal in folk medicine, in different gastric disorders and inflammations of the respiratory tract. In order to validate those traditional uses, M. cervina essential oils (EOs) were characterized by GC and GC–MS and their antimicrobial activity was tested against 23 bacterial strains (including multiresistant strains). The EOs were dominated by the monoterpenes pulegone (52–75%), isomenthone (8–24%), limonene (4–6%), and menthone (1–2%). The antibacterial activity of these EOs was compared to that of the main components standards. The most effective antibacterial activity was expressed by the EOs against the Gram-negative bacteria, Escherichia coli and Acinetobacter baumanni, with MIC values of 1 mg/ml. The EOs complex mixtures were more active than the individual aromatic components supporting the hypothesis that the EOs antibacterial activity is a function of the synergistic effect of their different aromatic components. These results show the potential role of M. cervina EOs as antibacterial agents and validate the traditional use of this plant

Antibacterial and antioxidative characterisation of essential oils from Mentha piperita and Mentha spicata grown in Iran

The present work evaluated the antioxidant and antimicrobial activities of the essential oils of Mentha piperita and Mentha spicata . Survival and growth of Bacillus cereus, E. coli and S. aureus were studied. Twenty-six and fifteen compounds were identified in the essential oils of Mentha piperita and Mentha spicata , respectively. Mentha piperita contained major compounds of α-terpinene (19.7%), isomenthone (10.3%), trans carveol (14.5%), pipertitinone oxide (19.3%) and β-caryophyllene (7.6%). The major compounds of Mentha spicata were limonene (48%), menthol (4.7%), piperitone (20.27%) and caryophyllene (7.9%). The essential oils have good or excellent antimicrobial activities against all microorganisms tested. Complete death time on exposure to Mentha piperita L. and Mentha spicata L. oils were (90, 15 and 10 min) and (45, 30 and 15 min) for B. cereus, E. coli and S. aureus , respectively. Two-gram positive microorganisms, B. cereus and S. aureus , showed the same pattern of zone/oil concentration ratios, while E. coli responded differently. The essential oils notably reduced the concentration of DPPH free radical and bleached β-carotene. The performance of the M. piperita oil was better than that of Mentha spicata . Application of these oils in food industries is recommended