Antimicrobial activity of essential oils from Lippia alba, Lippia sidoides, Cymbopogon citrates, Plectranthus amboinicus, and Cinnamomum zeylanicum against Mycobacterium tuberculosis

ABSTRACT: The rise in cases of antibiotic-resistant Mycobacterium tuberculosis has become a major obstacle to the effective control of tuberculosis (TB) worldwide. Essential oils (EO) are complex mixtures that may contain between 20 and 60 components, with two or three major compounds at relatively high concentrations (20-70%) that are responsible for their pharmacological properties. The objective of this study was to assess the antimicrobial activity of the EOs, bushy lippia (Lippia alba), rosemary pepper (Lippia sidoides), lemon grass (Cymbopogon citratus), Mexican mint or Indian borage (Plectranthus amboinicus), and true cinnamon (Cinnamomum zeylanicum), against Mycobacterium tuberculosis H37Rv. Chemical characterization of the EOs was performed by gas chromatography coupled to mass spectrometry. The minimum inhibitory concentration (MIC) was determined by the microdilution-based resazurin microtiter assay. Four EOs were able to inhibit the growth of M. tuberculosis, with MICs of 286.5±130.2μg/mL (C. zeylanicum), 299.5±117.2μg/mL (L. sidoides), 351.6±39.06μg/mL (P. amboinicus), and 1,250μg/mL (C. citratus). Only the EO of L. alba showed no antimycobacterial activity at the tested concentrations, with an MIC greater than 1,250µg/mL. Results of this study suggested that C. zeylanicum, L. sidoides, and P. amboinicus could be important sources of bactericidal compounds against M. tuberculosis and require further investigation. The activity against M. tuberculosis of these three EOs has not been reported previously. The results show the high potential of the tested antimycobacterial EOs, making them a promising alternative for TB treatment. This data also confirms the importance of bioprospecting studies for active substances with antimycobacterial activity, which are still scarce.