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

Ratnaweera PB, de Silva ED, Williams DE, Andersen RJ - BMC Complement Altern Med (2015)

Bottom Line: The most bioactive fungus was identified as Fusarium sp. and the second most active as Aspergillus niger.O. dillenii, harbors several endophytic fungi capable of producing antimicrobial substances with selective antibacterial properties.Further investigations on the secondary metabolites produced by these endophytes may provide additional drug leads.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of Colombo, Colombo 03, Sri Lanka. pamoda.b@gmail.com.

ABSTRACT

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(-1) against Bacillus subtilis, 16 μg mL(-1) against 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.

No MeSH data available.


Related in: MedlinePlus

600 MHz 1H and 13C NMR spectra of equisetin in DMSO-d6
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Fig3: 600 MHz 1H and 13C NMR spectra of equisetin in DMSO-d6

Mentions: Large scale extraction of the Fusarium sp. with ethyl acetate gave 1 g of crude extract. Bioassay guided isolation of 400 mg of the crude extract resulted in the isolation of 2 mg of the active compound. The active component gave a [M + H]+ ion with m/z 374 in the low-resolution electrospray ionization mass spectrum. Analysis of 1H and 13C NMR data along with 2D NMR (COSY, HSQC, HMBC, ROESY) data revealed that the structure of the active compound matches that of the known tetramic acid derivative, equisetin (Fig. 2) [25] with a molecular formula of C22H31NO4 which was consistent with a molecular weight of 373 daltons as seen in the ESIMS. A comparison of 13C NMR values obtained in the present study for equisetin with those reported in the literature is shown in Table 2. The 1H and 13C NMR spectra of equisetin are illustrated in Fig. 3.Fig. 2


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

Ratnaweera PB, de Silva ED, Williams DE, Andersen RJ - BMC Complement Altern Med (2015)

600 MHz 1H and 13C NMR spectra of equisetin in DMSO-d6
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4496918&req=5

Fig3: 600 MHz 1H and 13C NMR spectra of equisetin in DMSO-d6
Mentions: Large scale extraction of the Fusarium sp. with ethyl acetate gave 1 g of crude extract. Bioassay guided isolation of 400 mg of the crude extract resulted in the isolation of 2 mg of the active compound. The active component gave a [M + H]+ ion with m/z 374 in the low-resolution electrospray ionization mass spectrum. Analysis of 1H and 13C NMR data along with 2D NMR (COSY, HSQC, HMBC, ROESY) data revealed that the structure of the active compound matches that of the known tetramic acid derivative, equisetin (Fig. 2) [25] with a molecular formula of C22H31NO4 which was consistent with a molecular weight of 373 daltons as seen in the ESIMS. A comparison of 13C NMR values obtained in the present study for equisetin with those reported in the literature is shown in Table 2. The 1H and 13C NMR spectra of equisetin are illustrated in Fig. 3.Fig. 2

Bottom Line: The most bioactive fungus was identified as Fusarium sp. and the second most active as Aspergillus niger.O. dillenii, harbors several endophytic fungi capable of producing antimicrobial substances with selective antibacterial properties.Further investigations on the secondary metabolites produced by these endophytes may provide additional drug leads.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of Colombo, Colombo 03, Sri Lanka. pamoda.b@gmail.com.

ABSTRACT

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(-1) against Bacillus subtilis, 16 μg mL(-1) against 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.

No MeSH data available.


Related in: MedlinePlus