Identification, Characterization, and Antibacterial Evaluation of Five Endophytic Fungi from Psychotria poeppigiana Müll. Arg., an Amazon Plant

Endophytic fungi, residing within plants without causing disease, are known for their ability to produce bioactive metabolites with diverse properties such as antibacterial, antioxidant, and antifungal activities, while also influencing plant defense mechanisms. In this study, five novel endophytic fungi species were isolated from the leaves of <i>Psychotria poeppigiana</i> Müll. Arg., a plant from the Rubiaceae family, collected in the tropical Amazon region of Bolivia. The endophytic fungi were identified as a <i>Neopestalotiopsis</i> sp., three <i>Penicillium</i> sp., and an <i>Aspergillus</i> sp. through 18S ribosomal RNA sequencing and NCBI-BLAST analysis. Chemical profiling revealed that their extracts obtained by ethyl acetate contained terpenes, flavonoids, and phenolic compounds. In a bioautography study, the terpenes showed high antimicrobial activity against <i>Escherichia coli</i>. Notably, extracts from the three <i>Penicillium</i> species exhibited potent antibacterial activity, with minimum inhibitory concentration (MIC) values ranging from 62.5 to 2000 µg/mL against all three pathogens: <i>Escherichia coli</i>, <i>Staphylococcus aureus</i>, and <i>Enterococcus faecalis</i> (both Gram-positive and Gram-negative bacteria). These findings highlight the potential of these endophytic fungi, especially <i>Penicillium</i> species as valuable sources of secondary metabolites with significant antibacterial activities, suggesting promising applications in medicine, pharmaceuticals, agriculture, and environmental technologies.