Paecilosetin Derivatives as Potent Antimicrobial Agents from Isaria farinosa.

Fifty-seven entomopathogenic microorganisms were screened against human pathogens and subjected to mass spectrometry molecular networking based dereplication. Isaria farinosa BSNB-1250, shown to produce potentially novel biologically active metabolites, was grown on a large scale on potato dextrose agar, and paecilosetin (1) and five new analogues (2-6) were subsequently isolated. The structures of the new compounds were elucidated using 1D and 2D NMR. The absolute configurations of compounds 1-6 were determined using Mosher ester derivatives (1, 3, 4), comparison of experimental and calculated ECD spectra (2-4 and 6), and single-crystal X-ray diffraction analysis (5). Compounds 1 and 5 exhibited strong antibacterial activity against MSSA and MRSA with MIC values of 1-2 µg/mL.

Ilicicolinic acids and ilicicolinal derivatives from the fungus Neonectria discophora SNB-CN63 isolated from the nest of the termite Nasutitermes corniger found in French Guiana show antimicrobial activity.

The fungus Neonectria discophora SNB-CN63 has been isolated from the nest of the termite Nasutitermes corniger found in French Guiana. From the ethyl acetate extract of fungal culture, bioassay guided fractionation led to the isolation of fourteen ilicicolinic acids and ilicicolinal derivatives. Their structures were elucidated by analyses of 1D and 2D NMR and MS spectroscopic data. All metabolites were tested against several microbial pathogens and six displayed antimicrobial activities with MIC <16 µg/mL on T. rubrum, Staphylococcus aureus and methicillin-resistant S. aureus. Based on their structural similarities, a common biosynthetic pathway is proposed for all isolated metabolites.