Antimicrobial Activity of Phomopsis sp. ED2 Residing in Medicinal Plant Orthosiphon stamineus Benth

Aims: To investigate the antimicrobial activity of Phomopsis sp. ED2, endophytic fungus isolated from Orthosiphon stamineus Benth against various pathogenic microorganisms. Study Design: Place and Duration of Study: Industrial Biotechnology Research Laboratory, Universiti Sains Malaysia, Penang, Malaysia, between Dec 2011 to August 2013. Methodology: The endophytic fungus Phomopsis sp. ED2 was cultivated in the culture medium supplemented with the host plant extract. Then the antimicrobial activities of the crude extracts were screened via disc diffusion assay. The minimal inhibitory concentration and minimal lethality concentration of the extract against selected test microorganisms by using broth microdilution assay. The bioactive constituents of the extract were analyzed by using gas chromatography-mass spectroscopy analysis. Results: The ethyl acetate extract of this fungus showed broad spectrum inhibitory activity on both Gram positive and Gram negative bacteria with the minimal inhibitory concentrations ranged from 31.25 to 250 μg/mL. The gas chromatography-mass spectroscopy analysis of the extract showed that the bioactive constituents present in the extract were benzoic acid, lomustine and penicillic acid. Conclusion: The endophytic fungus residing in Orthosiphon stamineus Benth, Phomopsis Original Research Article Annual Research & Review in Biology, 4(9): 1490-1501, 2014 1491 sp. ED2 exhibited significant antibacterial activity of the test microorganisms. It is a potential source of antibacterial compounds.