Five Tetramic Acid Derivatives Isolated from the Iranian Fungus Colpoma quercinum CCTU A372

Submerged mycelial cultures of the ascomycete Colpoma quercinum CCTU A372 were found to produce five previously undescribed tetramic acids, for which we propose the trivial names colposetins A-C (1-3) and colpomenoic acids A and B (4 and 5), along with the known compounds penicillide (6) and monodictyphenone (7). The planar structures of 1-5 were determined by high-resolution electrospray ionization mass spectrometry (HR-ESIMS) and extensive 1D and 2D nuclear magnetic resonance (NMR) spectroscopy. Their absolute configurations were determined by the combination of electronic circular dischroism (ECD) analysis, J-based configurational analysis, and a rotating-frame Overhauser effect spectroscopy (ROESY) experiment. Colposetin B displayed weak antimicrobial activity against Bacillus subtilis and Mucor hiemalis (MIC 67 mu g/mL).

Automated summary

In this study, it was discovered that submerged mycelial cultures of the ascomycete Colpoma quercinum CCTU A372 produced five previously undescribed tetramic acids, along with two known compounds. The planar structures of the compounds were determined using HR-ESIMS and NMR spectroscopy, while the absolute configurations were confirmed through various analyses. One of the compounds, Colposetin B, showed weak antimicrobial activity against Bacillus subtilis and Mucor hiemalis.