Antimicrobial activities of endophytic fungi obtained from the arid zone invasive plant Opuntia dillenii and the isolation of equisetin, from endophytic Fusarium sp.

BMC Complementary and Alternative Medicine

Raymond J. Andersen²  David E. Williams²  E. Dilip de Silva³  Pamoda B. Ratnaweera¹ 

[1] Department of Science and Technology, Uva Wellassa University, Badulla, Sri Lanka;Department of Chemistry and Earth, Ocean and Atmospheric Science, University of British Columbia, Vancouver, Canada;Department of Chemistry, University of Colombo, Colombo 03, Sri Lanka

关键词: Fusarium sp.;    Arid ecosystem;    Equisetin;    Opuntia dillenii;    Invasive plants;    Endophytic fungi;   

Others  :  1220067
DOI  :  10.1186/s12906-015-0722-4

 received in 2014-12-22, accepted in 2015-06-12,  发布年份 2015

【 摘 要 】

Background

Opuntia dillenii is an invasive plant well established in the harsh South-Eastern arid zone of Sri Lanka. Evidence suggests it is likely that the endophytic fungal populations of O. dillenii assist the host in overcoming biotic and abiotic stress by producing biologically active metabolites. With this in mind there is potential to discover novel natural products with useful biological activities from this hitherto poorly investigated source. Consequently, an investigation of the antimicrobial activities of the endophytes of O. dillenii, that occupies a unique ecological niche, may well provide useful leads in the discovery of new pharmaceuticals.

Methods

Endophytic fungi were isolated from the surface sterilized cladodes and flowers of O. dillenii using several nutrient media and the antimicrobial activities were evaluated against three Gram-positive and two Gram-negative bacteria and Candida albicans. The two most bioactive fungi were identified by colony morphology and DNA sequencing. The secondary metabolite of the endophyte Fusarium sp. exhibiting the best activity was isolated via bioassay guided chromatography. The chemical structure was elucidated from the ESIMS and NMR spectroscopic data obtained for the active metabolite. The minimum inhibitory concentrations (MICs) of the active compound were determined.

Results

Eight endophytic fungi were isolated from O. dillenii and all except one showed antibacterial activities against at least one of the test bacteria. All extracts were inactive against C. albicans. The most bioactive fungus was identified as Fusarium sp. and the second most active as Aspergillus niger. The structure of the major antibacterial compound of the Fusarium sp. was shown to be the tetramic acid derivative, equisetin. The MIC’s for equisetin were 8 μg mL ⁻¹against Bacillus subtilis, 16 μg mL ⁻¹against Staphylococcus aureus and Methicillin Resistant Staphylococcus aureus (MRSA).

Conclusions

O. dillenii, harbors several endophytic fungi capable of producing antimicrobial substances with selective antibacterial properties. By producing biologically active secondary metabolites, such as equisetin isolated from the endophytic Fusarium sp., the endophytic fungal population may be assisting the host to successfully withstand stressful environmental conditions. Further investigations on the secondary metabolites produced by these endophytes may provide additional drug leads.

【 授权许可】

   
2015 Ratanweera et al.

【 图 表 】

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