Antibacterial metabolites from Paecilomyces niveus and their chemophenetic significance

The anthraquinone, 3-acetyl-2,8-dihydroxy-6-methoxyanthraquinone (1), alongside three naphtoquinones, 8-O-methylbostrycoidin (2), 5-O-methyljavanicin (3), 8-O-methylfusarubin (4), and one alcohol, 2-methylpropane-1,3-diol (5), were isolated from the ethyl acetate extract of the coprophilous fungus, Paecilomyces niveus. The complete NMR data of compound 1 are reported here for the first time, while bostrycoidin, javanicin, and fusarubin-related quinones are described for the first time within the genus Paecilomyces. Structures were elucidated by comprehensive spectroscopic analyses and high-resolution mass spectrometry, as well as by comparison with reported data. Antibacterial activity was assessed by microdilution assays, and the tested compounds exhibited weak activity with MIC values ranging from 781 to 5551 μM against Staphylococcus aureus, Shigella flexneri, Klebsiella pneumoniae, Salmonella typhimurium, and Escherichia coli. The chemophenetic relevance of the isolates is discussed.