Identification and quantification of bioactive compounds from locally Isolated <i>Candolleomyces candolleanus</i> basidio fungus using High-Performance Liquid Chromatography (HPLC)  and evaluation of their antimicrobial activity

The continuous growth in antimicrobial resistance demands the identification of new antimicrobial substances, particularly those of natural origin, such as those derived from fungi. The Basidiomycetes are a significant source of bioactive secondary metabolites with high therapeutic potential. The study aimed to investigate the chemical composition and antimicrobial activity of Candolleomyces candolleanus, a basidiomycete fungus isolated from natural sources in Mosul, Iraq. Gas Chromatography-Mass Spectrometry (GC-MS) analysis detected three prime bioactive compounds: Trihexadecyl Borate, Cyclohexyl Propyl Phosphonofluoridate, and Borane Diethyl(decyloxy). High-Performance Liquid Chromatography (HPLC) analysis verified which the fungal extract of C. candolleanus contained a very high content of bioactive compounds, specifically Cyclohexyl Propyl Phosphonofluoridate, Borane Diethyl(decyloxy), and Trihexadecyl Borate. The antimicrobial efficacy of like compounds was determined using a microplate assay against a variety of clinically important pathogens: Bacillus cereus (ATCC 11778), Pseudomonas fluorescens(ATCC 13525) , Escherichia coli(ATCC 25922) , Staphylococcus aureus(ATCC 29213) ,and fungal strains, Candida albicans( ATCC 10231) , and Aspergillus niger ( ATCC 6275). Cyclohexyl Propyl Phosphonofluoridate showed the highest potency among distinct metabolites, with considerable microbial growth inhibition for both bacterial and fungal test species. The broad-spectrum activity means high drug-like potential. Whereas Borane Diethyl(decyloxy) and Trihexadecyl Borate had moderate antimicrobial activity, with observable but less intense inhibition, compared to Cyclohexyl Propyl Phosphonofluoridate. Their effectiveness against different pathogens varied, but was consistent across them, indicating that they may act as supporting or synergistic antimicrobial agents. The combination of biochemical characterization and antimicrobial screening provides a sound basis for ongoing research to explore new medicines with activity against drug-resistant microbes.