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：全球范围内，耐抗菌药物结核分枝杆菌（Mycobacterium tuberculosis）感染病例的增多，已成为结核病（Tuberculosis，简称TB）有效防控的一大主要障碍。精油（Essential oils，简称EO）是成分复杂的混合物，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，所测试的精油分别来自：灌木马鞭草（Lippia alba，别名bushy lippia）、迷迭香胡椒草（Lippia sidoides，别名rosemary pepper）、柠檬草（Cymbopogon citratus，别名lemon grass）、墨西哥薄荷/印度琉璃苣（Plectranthus amboinicus，别名Mexican mint或Indian borage）以及锡兰肉桂（Cinnamomum zeylanicum，别名true cinnamon）。本研究采用气相色谱-质谱联用法对五种精油进行了化学组分表征，并采用基于微量稀释法的刃天青微量滴定法测定了各精油的最低抑菌浓度（Minimum inhibitory concentration，简称MIC）。测试结果显示，四种精油可抑制结核分枝杆菌的生长，其MIC值分别为：锡兰肉桂（C. zeylanicum）：286.5±130.2μg/mL、迷迭香胡椒草（L. sidoides）：299.5±117.2μg/mL、印度琉璃苣（Plectranthus amboinicus）：351.6±39.06μg/mL，以及柠檬草（C. citratus）：1250μg/mL。仅灌木马鞭草（L. alba）在本次测试的浓度范围内未表现出抗分枝杆菌活性，其MIC值大于1250μg/mL。本研究结果表明，锡兰肉桂、迷迭香胡椒草及印度琉璃苣精油可作为抗结核分枝杆菌杀菌活性化合物的重要潜在来源，有待开展进一步的深入研究。这三种精油的抗结核分枝杆菌活性此前尚未见公开报道。本次研究结果证实，所测试的抗分枝杆菌精油具有较高的应用潜力，有望成为结核病治疗的新型替代方案。本数据集同时证实了针对抗分枝杆菌活性物质开展生物勘探研究的重要性——此类活性物质目前仍较为稀缺。