New antibiotic metabolites from the fungal endophyte Stemphylium globuliferum isolated from Mentha pulegium
During our ongoing search for new bioactive metabolites from endophytic fungi with focus on the discovery of new antimicrobial compounds, we investigated the fungal strain Stemphylium globuliferum isolated from the medicinal plant Mentha pulegium (Lamiaceae). The EtOAc extract of the poorly investigated S. globuliferum fungal strain afforded six new bisanthraquinones, together with four known related compounds. All compounds were tested for their antimicrobial activity (including antibacterial, antifungal and antiviral activities). All dimers were found to be highly active at minimal inhibitory concentrations (MIC) of 7–125 µg/mL. Of specific interest is the fact that the alterporriol-type dimers, alterporriol E and its atropisomer D, exhibited different activity patterns against similar pathogenic microorganisms.