Introduction: Recently, several endophytes have been shown to possess the potentials to synthesize novel bioactive compounds that have found use for drug discovery. We isolated endophytic fungi associated with Catharanthus roseus collected from the river banks of Amassoma in Southern Nigeria, and identified some of their bioactive secondary metabolites.
Methods: The fungi were subjected to solid-state fermentation on rice medium and the metabolites were extracted using ethyl acetate. The fungal crude extracts were screened for antimicrobial activity and were also subjected to high-performance liquid chromatography-diode-array detection (HPLC-DAD) analysis for the identification of the bioactive compounds.
Results: The fungal extracts showed both antibacterial and antifungal activities with minimum inhibitory concentrations ranging from 0.0625 to 1 mg/mL. The HPLC-DAD analysis of the extracts suggested the presence of citreoisocoumarin, citreoisocoumarinol, questinol, hydroxyemodin, acropyrone, methyl 2-(4-hydroxyphenyl) acetate, nigricinol, and cladosporin.
Conclusion: The results of this study suggest that endophytic fungi associated with C. roseus could be a promising source of novel bioactive compounds with pharmaceutical and industrial importance.
Three quercetin‐3‐O‐glycosides (1–3) were obtained from the endophytic fungus Nigrospora oryzae isolated from leaves of the Nigerian mistletoe Loranthus micranthus. The compounds were unequivocally identified based on their one and two dimensional NMR spectra and on their mass spectra. A fourth flavonoid glycoside (4) was tentatively identified as a luteolin monoglycoside. Comparative HPLC analyses of extracts of the endophyte and of the host plant indicated that compounds (1–3) were present as minor constituents in the extract of the host plant Loranthus micranthus whereas the latter was dominated by different gallic acid and by catechin derivatives that were missing in the endophyte extract. The presence of flavonoid glycosides in a fungal endophyte is remarkable and is unequivocally confirmed here for the first time. So far, compounds (1–3) were only known as commonly occurring plant secondary metabolites. This study adds further evidence to the remarkable plasticity of fungal secondary metabolism which has repeatedly been shown to produce the same compounds as present in plants.
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