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 alpha-terpinene (19.7%), isomenthone (10.3%), trans carveol (14.5%), pipertitinone oxide (19.3%) and beta-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 beta-carotene. The performance of the M. piperita oil was better than that of Mentha spicata. Application of these oils in food industries is recommended.