Essential oil of Lippia alba impedes the growth of Propionibacterium acnes by modulating membrane potential and ROS level

Introduction: Propionibacterium acnes (P. acnes) is a rod-shaped, anaerobic, Gram-positive, opportunistic bacterium, that causes infectious and inflammatory diseases, such as acne vulgaris synovitis-acnes-pustulosis-hyperostosis-osteitis syndrome, sarcoidosis, and prostate cancer. Earlier evidence suggests that essential oils have been used to treat skin diseases and disorders since ancient times. Thus, the present study investigated the antimicrobial activity of 28 essential oils from nine families, including Lamiaceae, Poaceae, Geraniaceae, Myrtaceae, Zingiberaceae, Verbenaceae, Cupressaceae, Asteraceae, and Cyperaceae against P. acnes.Methods: The anti-bacterial susceptibility and efficacy of the essential oils were examined using paper disc diffusion, broth micro-dilution, time-kill kinetics and ROS assays. P. acnes was cultured under anaerobic conditions. The kinetic process evaluated the time and dose-dependent effects of essential oils. The alteration in membrane potential and ROS production were measured in terms of mean fluorescence intensity. Consequently, the chemical composition of essential oil was analyzed by GC and GC/MS analysis. Results: Eighteen essential oils inhibited the growth of P. acnes with a clear zone of 5 - 20.33 mm. Eucalyptus, Mentha, Palmarosa, Lemongrass, Citronella, Geranium, Patchouli, Ocimum, and Clarysage possess better antibacterial activity (ZGI: 10.33 & PLUSMN; 2.31 mm - 20.33 & PLUSMN; 4.72 mm). Lippia alba oil showed the minimum inhibitory concentration (MIC) of 0.125% v/v, and the MIC of Mentha, Ocimum, and Patchouli oils ranged from 0.25% to 0.50% v/v. Further, the concentration and time-kill kinetic study indicated that L. alba and O. sanctum oils suppress the growth at MIC till 12 h and at 2 x MIC until 72 h. Moreover, the oils induced ROS production with one fold change at 2 x MIC. In addition, O. sanctum oil altered the membrane integrity with a fold change of 1.0 and 2.0 at MIC and 2 x MIC, respectively, while L. alba oil modified a fold change of 1.0. Discussion/conclusion: The essential oils suppressed bacterial growth by inducing ROS and modulating membrane integrity. Therefore, L. alba and O. sanctum essential oils could be used as an alternative to chemicals/ drugs for treating microbe-associated acne problems.