Bioprospecting Calotropis procera-Associated Endophytic Fungi for Antifungal Bioactive Compounds

Abstract

Endophytic fungi associated with Medicinal Plants represent a promising source of biologically active Secondary Metabolites with potential applications in antimicrobial drug discovery. The present study aimed to isolate and evaluate Endophytic fungi associated with the roots of Calotropis procera for their phytochemical constituents and antifungal potential. Root tissues of C. procera were processed for the isolation of culturable Endophytic Fungi, resulting in the recovery of Six isolates designated EFM01, EFM02, EFM03, EFM04, EFM05, and EFM06. The isolates were cultured under in vitro conditions, and crude secondary metabolites were obtained by Methanolic extraction. Qualitative phytochemical screening revealed the presence of alkaloids, phenols, tannins, and steroids in all six fungal extracts. Anthraquinones were detected in EFM02, EFM04, and EFM06, whereas terpenoids were detected in EFM01, EFM04, and EFM05. Flavonoids and saponins were not detected in any of the tested extracts. The antifungal activity of the crude extracts was evaluated by the Agar well diffusion method against three fungal pathogens, namely Candida albicans, Fusarium oxysporum, and Alternaria sp., at different concentrations. At 100 µg, all six extracts exhibited measurable antifungal activity, although the magnitude of inhibition varied among isolates and test fungi. Against C. albicans, EFM06 produced the highest inhibition zone (22 mm), followed by EFM04 (21 mm), while EFM06 showed 16.8 mm inhibition against F. oxysporum. Against Alternaria sp., EFM06 and EFM04 produced inhibition zones of 19.1 and 18.9 mm, respectively. EFM06 exhibited comparatively strong and broad-spectrum antifungal activity, while EFM04 also showed considerable activity against the tested fungi. These findings demonstrate that root-associated endophytic fungi of C. procera are a potential source of chemically diverse secondary metabolites with antifungal properties.