Abstract

The fungal infections are growing global threat due the resistance to antifungal agents, so demands urgent attention. Soil actinomycetes are known to produce antifungal metabolites and Nepal’s soil has high potential to search antifungal actinomycetes. However, soil actinomycetes of Nepal have rarely been investigated for antifungal metabolites. In the present study, we aimed to detect antifungal compounds from selected Streptomyces species isolated from soil samples.  We selected three strains of Streptomyces (Streptomyces sp. 13104, Streptomyces sp. 13081, and Streptomyces sp. 12933), and fermentation was carried out using International Streptomyces Project (ISP) 2 medium. A rotary evaporator was used to isolate the crude extract and antifungal metabolites were detected using UPLC-MS/MS. The LC-MS data were processed using the T-ReX 3D algorithm in MetaboScape 2022b, and GNPS spectral library was used to annotate the features. Feature-Based Molecular Networking (FBMN) was used to create molecular networks and visualized using Cytoscape v. 3.8.2. Evaluation of LC-MS data of the different active extracts revealed several known compounds that can plausibly exhibit antifungal activity. The large linear polyenes linearmycins A and B were detected in the crude extract from Streptomyces sp. 13104. Several members of the antimycin and kitamycin family were produced by Streptomyces sp. 13081 and annotated by GNPS library comparison and NPAtlas. Similarly, amphotericin B produced by Streptomyces sp. 12933 was exclusively annotated by the GNPS spectral library. The various antifungal compounds identified in our study underscore the value of exploring actinomycetes from unique and extreme environments, which may be crucial in searching the novel antimicrobial compounds.