Antimicrobial metabolites from the plant endophytic fungus Penicillium sp.

Five rare dichloro aromatic polyketides (1-5) were obtained from an endophytic fungus Penicillium sp., along with five known metabolites (6-10). Their structures were elucidated by extensive spectroscopic analysis, Mosher methods, as well as [Rh2(OCOCF3)4]-induced electronic circular dichroism (ECD) experiments. Compounds 2-4 and 6 structurally involved acyclic 1.3-diols, the uneasy configuration determinations of which were well carried out by double-derivation NMR methods. Compounds 1-10 were evaluated for their antibacterial and antifungal activities against five strains of human pathogenic microorganisms. Helvolic acid (7) showed potent inhibitory effects against Staphylococcus aureus and Pseudomonas aeruginosa with MIC (minimum inhibitory concentration) values of 5.8 and 4.6μg/mL, respectively.