School of Pharmaceutical Sciences, Sun Yat-Sen University, Guangzhou, 510006, Guangdong Province, China.
China Resources Sanjiu Medical & Pharmaceutical Co.,Ltd., Shenzhen, 518110, Guangdong Province, China.
J Ethnopharmacol. 2020 May 10;253:112652. doi: 10.1016/j.jep.2020.112652. Epub 2020 Feb 6.
Cinnamomum camphora (Linn.) Presl (C. camphora) is one of the oldest herbal medicines used as a traditional medicine, owning a wide range of biological functions including anti-bacterial, anti-oxidative, anti-fungal, anti-inflammatory, insecticidal and repellent activities.
The aim of this study was to investigate the antibacterial activity and mechanism of action of the essential oil (EO) from C. camphora.
The EO was isolated from the leaves of C. camphora by hydrodistillation, and the chemical compositions of the EO were analyzed by gas chromatography-mass spectrometry (GC-MS). The minimum inhibitory concentration (MIC) and the minimal bactericidal concentration (MBC) values of the EO were estimated by the microbroth dilution method. Growth curve was investigated by turbidimetry. Apoptosis was measured by flow cytometry. Morphological change of bacteria was observed by field emission scanning electron microscopy and transmission electron microscopy. The integrity of cell membrane was evaluated by NanoDrop and BCA Protein Assay Kit. The methicillin-resistant Staphylococcus aureus (MRSA) metabolic profile in the presence of the EO was explored by GC-MS-based metabolomics. Isocitrate dehydrogenase (ICDH), α-ketoglutarate dehydrogenase (α-KGDH), succinic dehydrogenase (SDH) and malic dehydrogenase (MDH) activities were detected by commercial kits.
The main components of the EO from the leaves of C. camphora were identified to be linalool (26.6%), eucalyptol (16.8%), α-terpineol (8.7%), isoborneol (8.1%), β-phellandrene (5.1%), and camphor (5.0%). The EO had good activity against MRSA, Staphylococcus aureus, Enterococcus faecalis, Bacillus subtilis, Salmonella gallinarum and Escherichia coli. MRSA was selected as the model bacterium to illustrate antibacterial mechanism of action of the EO, and the MIC and MBC values was 0.8 and 1.6 mg/mL, respectively. Apoptosis rate of MRSA increased in a concentration-dependent manner after the addition of EO. The cell morphology was damaged by the EO. There were 74 significantly different metabolites, including 29 upregulated and 45 downregulated metabolites in the result of metabolomics evaluation. Seven pathways were enriched by shared differential metabolites. The EO enhanced the activity of ICDH by 47.35%, while weaken MDH, SDH and α-KGDH by 72.63%, 31.52% and 63.29%, respectively.
The EO from C. camphora showed anti-MRSA activity via damaging cell membranes and disturbing the amino metabolism.
樟科植物樟（C. camphora）是一种历史悠久的草药，具有广泛的生物学功能，包括抗菌、抗氧化、抗真菌、抗炎、杀虫和驱避作用，被用作传统药物。
本研究旨在探讨樟树叶精油的抗菌活性和作用机制。
采用水蒸馏法从樟树叶中提取精油，用气相色谱-质谱联用仪（GC-MS）分析精油的化学成分。采用微量肉汤稀释法测定精油的最小抑菌浓度（MIC）和最小杀菌浓度（MBC）。用比浊法研究生长曲线。用流式细胞术测量细胞凋亡。用场发射扫描电子显微镜和透射电子显微镜观察细菌形态变化。用 NanoDrop 和 BCA 蛋白分析试剂盒评估细胞膜完整性。采用基于 GC-MS 的代谢组学方法研究精油存在下耐甲氧西林金黄色葡萄球菌（MRSA）的代谢谱。用商业试剂盒检测异柠檬酸脱氢酶（ICDH）、α-酮戊二酸脱氢酶（α-KGDH）、琥珀酸脱氢酶（SDH）和苹果酸脱氢酶（MDH）的活性。
从樟树叶精油中鉴定出的主要成分是芳樟醇（26.6%）、桉油醇（16.8%）、α-松油醇（8.7%）、异龙脑（8.1%）、β-水芹烯（5.1%）和樟脑（5.0%）。该精油对 MRSA、金黄色葡萄球菌、粪肠球菌、枯草芽孢杆菌、鸡白痢沙门氏菌和大肠杆菌具有良好的活性。选择 MRSA 作为模型菌，以阐明精油的抗菌作用机制，其 MIC 和 MBC 值分别为 0.8 和 1.6 mg/mL。MRSA 的细胞凋亡率在加入精油后呈浓度依赖性增加。细胞形态被精油破坏。代谢组学评价结果有 74 种差异显著的代谢物，其中上调 29 种，下调 45 种。通过共享差异代谢物，共富集 7 条通路。该精油使 ICDH 的活性增强了 47.35%，同时使 MDH、SDH 和 α-KGDH 的活性分别减弱了 72.63%、31.52%和 63.29%。
樟树叶精油通过破坏细胞膜和干扰氨基酸代谢来抑制耐甲氧西林金黄色葡萄球菌。
