Abstract
BackgroundEndophyte bestows beneficial aspects to its inhabiting host, along with a contribution to diverse structural attributes with biological potential. In this regard, antimicrobial profiling of fungal endophytes from medicinal plant Adiantum philippense revealed bioactive Nigrospora sphaerica from the leaf segment. Chemical and biological profiling through TLC–bioautography and hyphenated spectroscopic techniques confirmed the presence of phomalactone as an antimicrobial metabolite. ResultsThe chemical investigation of the broth extract by bioassay-guided fractionation confirmed phomalactone as a bioactive antimicrobial secondary metabolite. The antimicrobial activity of phomalactone was found to be highest against Escherichia coli by disc diffusion assay. The MIC was found to be significant against both Escherichia coli and Xanthomonas campestris in the case of bacteria and dermatophyte Candida albicans at 150 μg/ml, respectively. ConclusionsOverall, the results highlighted the antimicrobial potential of phomalactone from the endophyte Nigrospora sphaerica exhibiting a broad spectrum of antimicrobial activity against human and phytopathogenic bacteria and fungi. This work is the first report regarding the antibacterial activity of phomalactone.
Highlights
ResultsThe chemical investigation of the broth extract by bioassay-guided fractionation confirmed phomalactone as a bioactive antimicrobial secondary metabolite
Endophyte bestows beneficial aspects to its inhabiting host, along with a contribution to diverse structural attributes with biological potential
The developed Thin layer chromatography (TLC) sheets were placed onto sterile Petri plates and overlaid with Mueller-Hinton agar amended with tetrazolium chloride (TTC) (1 mg/ml) for bacteria and Sabouraud Dextrose agar for fungi previously seeded with 1% standardized (McFarland standard) microbial inoculum and incubated
Summary
Isolation and identification of endophytic fungi Nigrospora sphaerica In the present study, bioactive mycoendophyte isolated from the surface-sterilized leaves of A. philippense was subjected to morphological, microscopic (Fig. 1), and molecular identification. The antimicrobial activity was found to be highest against E. coli with a 24.33 mm diameter followed S. typhi (22.67 mm), B. cereus (21.67 mm), S. aureus (19 mm), K. pneumonia (18.67 mm), B. subtilis (17.67 mm), X. campestris (17.67 mm), V. parahaemolyticus (16.67 mm), and S. epidermidis (12.67 mm) at 30 μgdisc-1 concentration. The zone of inhibition was observed at a Rf = 4.5 indicating the purified bioactive metabolite from the ethyl acetate extract of N. sphaerica (Fig. 4). The compound obtained was in the form of a yellow amorphous semi-solid with a molecular mass of 155.07 in ESI-positive mode. The secondary metabolites of N. sphaerica, extracted with ethyl acetate showed a significant antimicrobial activity against bacteria and fungus viz., S. aureus, B. subtilis, S. epidermidis, E. coli, K. pneumonia, P. aeruginosa, S. typhi, S. flexneri, X. campestris, Fig. 3 Antimicrobial activity of phomalactone isolated from N. sphaerica.
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