Prospection and antibacterial screening of metabolic extracts of endophytic fungi isolated from Tibouchina granulosa (Desr.) Cogn. (Melastomataceae)

The multidrug resistance of pathogenic microorganisms against widely used antimicrobials has grown in recent years. Among the different sources of bioactive compounds, endophytic fungi stand out for their ability to produce important classes of bioactive substances. The present study investigated the chromatographic profiles and antimicrobial activity against 10 pathogenic strains (four included in critical priority by WHO) of the extracts of 12 endophytic fungi isolated from Tibouchina granulosa (Melastomataceae). The activity of the metabolites was evaluated using broth microdilution to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Screening of partial chemical profiles was obtained using HPLC-DAD. Extracts of all fungi inhibited the proliferation of 4–10 pathogenic bacterial strains tested. At concentrations between 500 and 1,000 µg mL-1, Xylaria berteroi extract inhibited the growth of all strains tested, while Diaporthe oxe inhibited eight strains. Chemical analysis demonstrated diverse chromatographic profiles with the possibility of different classes of specialized metabolites, including polyketides, alkaloids, furanones, and terpenoids. Overall, endophytic fungi isolated from Tibouchina granulosa were found to synthesize different natural bioactive compounds, highlighting their potential for use in chemical prospecting and characterization.