Inhibition of TNF-alpha promoter activity and synthesis by A11-99-1, a new cyclopentenone from the ascomycete Mollisia melaleuca.

In a search for inhibitors of the inducible tumor necrosis factor-a (TNF-a) promoter activity and synthesis, a new chlorinated cyclopentenone was isolated from fermentations of the ascomycete Mollisia melaleuca. The structure was determined by a combination of spectroscopic techniques The compound blocked the inducible human TNF-alpha promoter activity and synthesis with IC50-values of 2.5-5 microg/ml (8.1-16.1 microM). Studies on the mode of action of the compound revealed that the inhibition of TNF-a promoter activity is caused by an inhibition of the phosphorylation of the IkappaB protein which prevents the activation of the transcription factor NF-xB. No cytotoxic, antibacterial and antifungal activities could be observed up to 100 microg/ml (323 microM) of the compound.