Anti-Inflammatory Property of the Essential Oil from Cinnamomum camphora (Linn.) Presl Leaves and the Evaluation of Its Underlying Mechanism by Using Metabolomics Analysis.

Cinnamomum camphora (Linn.) Presl has been widely used in traditional Chinese medicine for a variety of purposes. Our previous study indicated the antibacterial mechanism of the essential oil (EO) from C. camphora leaves; however, its anti-inflammatory activity and the underlying mechanism have not been clearly demonstrated. Thus, the present study investigated its anti-inflammatory property. Our data revealed that EO significantly decreased the release of nitric oxide (NO) and the mRNA expression of inducible NO synthase (iNOS) in lipopolysaccharide (LPS)-induced BV2 microglial cells. EO also attenuated LPS-induced increase in the mRNA expression and secretion of inflammatory cytokines including interleukin-6 (IL-6), IL-18, IL-1ß and tumor necrosis factor-α (TNF-α). Furthermore, the metabolic profiles of LPS-induced BV2 microglial cells treated with or without EO were explored. Thirty-nine metabolites were identified with significantly different contents, including 21 upregulated and 18 downregulated ones. Five pathways were enriched by shared differential metabolites. Compared with the control cells, the glucose level was decreased, while the lactate level was increased, in the culture supernatant from LPS-stimulated cells, which were reversed by EO treatment. Moreover, compared to the LPS-treated group, the activities of phosphofructokinase (PFK) and pyruvate kinase (PK) in EO group were decreased. In summary, the current study demonstrated that EO from C. camphora leaves acts as an anti-inflammatory agent, which might be mediated through attenuating the glycolysis capacity of microglial cells.

Metabolomics analysis to evaluate the antibacterial activity of the essential oil from the leaves of Cinnamomum camphora (Linn.) Presl.

ETHNOPHARMACOLOGY RELEVANCE: 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. OBJECTIVE: The aim of this study was to investigate the antibacterial activity and mechanism of action of the essential oil (EO) from C. camphora. MATERIALS AND METHODS: 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. RESULTS: 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%), ß-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. CONCLUSIONS: The EO from C. camphora showed anti-MRSA activity via damaging cell membranes and disturbing the amino metabolism.