Antibacterial cyclopentenones from the coprophilous fungus Clonostachys pseudochroleuca

The chemical study of the ethyl acetate soluble fraction from the ethyl acetate:methanol (1:1) extract of the culture of Clonostachys pseudochroleuca led to the isolation of a new cyclopentenone, (4S,5R) 4-benzoyl-3,4,5-trihydroxy-2-(4-hydroxyphenyl)cyclopent-2-en-1-one (2), along with the known phaseocyclopentenone A (1). Their structures were assigned on the basis of 1D and 2D NMR spectroscopy and HRESIMS data. The absolute configuration of the chiral centres was determined by Electronic Circular Dichroism (ECD) analysis. In the microdilution assay, the crude extract exhibited weak activity against Escherichia coli AG100 and Klebsiella pneumoniae 55 with MIC values of 256 µg/mL and 512 µg/mL, respectively. Compound 1 showed moderate activity against E. coli AG100 with an MIC of 64 µg/mL, while the new metabolite 2 exhibited moderate activity against Klebsiella pneumoniae ATCC11 with an MIC of 64 µg/mL.