Myrtus Communis Leaf Extract - A Source of Secondary Metabolites Exhibiting Anticancer and Antimycobacterial Activities

Background: Plant-derived products or extracts are widely used in folk/traditional medicine to treat several, infections, ailments, or disorders. A notable therapeutic herb Myrtus communis, worldwide utilized in the traditional medication for centuries, is an evergreen aromatic and medicinal plant of the Mediterranean region. Materials and methods: The SulphoRhodamine-B assay and DNA flow cytometry were used to investigate the proliferation and subsequent distribution of cells among different phases of the cell cycle. Annexin V-FITC/PI staining coupled with flow cytometry was used to analyze apoptosis and necrosis of the cancer cells. Western blotting detected the expression of pro- and anti-apoptotic proteins. Zone of inhibition and MIC were determined by well diffusion method and microplate alamar blue assay, respectively. Biofilm formation was studied by crystal violet method. For statistical analysis, a two-tailed Student’s t-test of GraphPad Prism 6.0 was used.Results: In this study, the secondary metabolites of M. communis leaves extracted in ethanol showed the highest cytotoxicity and thus the greatest anticancer effects against diverse cancer cell lines of the breast (MCF-7), liver (HepG2), cervix (HeLa), and colon (HCT116) (IC50; ranging from 33 to 83 mg/ml). The cancer cells arrested in the G1 phase of the cell cycle undergo apoptosis. The induction of the latter is mediated by activation of the intrinsic mitochondrial pathway. Furthermore, the extract showed a strong growth inhibitory effect (zone of inhibition; 20.3±1.1 - 26.3±2.5 mm, MIC; 4.88 - 312.5 µg/ml, and MBC; 39.07 - 1250 μg/ml) against several rapid and slow-growing mycobacterial strains that cause tuberculosis and several other mycobacterial infections. The biofilm formation in BSL2 microorganisms, M. smegmatis and S. aureus, is strongly inhibited by the extract. Conclusion: These results suggest that M. communis leaf extract is a potential source of secondary metabolites, which could be developed further as potential anti-cancer and anti-mycobacterial agents to treat diverse types of cancers and mycobacterial infections.