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.

Investigation of Copaifera genus as a new source of antimycobaterial agents

“…According to Holetz et al [ 45 ], crude extracts with MIC values lower than 100 μg ml -1 , between 100 and 500 μg ml -1 , from above 500 to 1000 μg ml -1 and greater than 1000 μg ml -1 display good antimicrobial activity, moderate antibacterial activity, weak antibacterial activity and absence of antibacterial activity, respectively. Other authors have considered that MICs ≤200 μg ml -1 for extracts indicate good activity against M. tuberculosis [ 46 ].…”

Bioactivities of essential oils from different parts of Spiranthera odoratissima (Rutaceae)

“…MIC values of EOs from S. odoratissima against M. tuberculosis are quite promising, since some authors have considered that MICs ≤ 200 μg/ mL indicate good activity against M. tuberculosis (Mota et al 2018). In addition, according to Holetz et al (2002), natural products with MIC values below 100 µg/mL, between 100 and 500 µg/mL, from 500 to 1,000 µg/mL and above 1,000 µg/ mL exhibit good antimicrobial activity, moderate antibacterial activity, weak antibacterial activity and no antibacterial activity, respectively.…”

Antibacterial and cytotoxic activity assessment of Channa striatus (Haruan) extract

“…The concentration of the bacterial inoculum was 5×10 5 CFU/mL. Next, the authors completed the Resazurin Microtiter Assay method (REMA) according to Mota et al [22]. The authors performed the REMA microdilution method in sterile flat-bottom 96-well microplates.…”