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.

摘要：耐药结核分枝杆菌（Mycobacterium tuberculosis）感染病例的增多已成为全球结核病（TB）有效防控的主要障碍。精油（Essential Oils, EO）是一类复杂混合物，通常包含20至60种组分，其中2~3种主要化合物浓度相对较高（20%~70%），是其药理活性的核心来源。本研究旨在评估五种精油对结核分枝杆菌H37Rv的抗菌活性，这五种精油分别为：白臭黄荆（Lippia alba）、迷迭香臭黄荆（Lippia sidoides）、香茅（Cymbopogon citratus）、墨西哥薄荷/印度牛至（Plectranthus amboinicus）以及锡兰肉桂（Cinnamomum zeylanicum）。采用气相色谱-质谱联用法对精油进行化学表征；最低抑菌浓度（Minimum Inhibitory Concentration, MIC）采用基于微量稀释法的刃天青微量滴定法测定。四种精油可抑制结核分枝杆菌生长，其最低抑菌浓度分别为：锡兰肉桂（286.5±130.2μg/mL）、迷迭香臭黄荆（299.5±117.2μg/mL）、印度牛至（351.6±39.06μg/mL）以及香茅（1250μg/mL）。仅白臭黄荆精油在测试浓度范围内未表现出抗分枝杆菌活性，其MIC大于1250μg/mL。本研究结果表明，锡兰肉桂、迷迭香臭黄荆及印度牛至精油可作为抗结核分枝杆菌杀菌化合物的重要潜在来源，有待开展进一步研究。目前尚未见关于这三种精油抗结核分枝杆菌活性的相关报道。本次研究结果证实，所测试的抗分枝杆菌精油具备极高应用潜力，有望成为结核病治疗的新型替代方案。本数据同时印证了抗分枝杆菌活性物质生物勘探研究的重要性，此类活性物质目前仍较为匮乏。