Three antimicrobial metabolites from Aspergillus caespitosus.

Aspergillus caespitosus NRRL 5769 growing in broth containing small amounts of sitosterol produced substance(s) with greater inhibitory activity against Candida albicans ATCC 10231 than in broth without sitosterol. Subsequent isolation, purification, and structural elucidation yielded 5,6-dihydro-5(S)-acetoxy-6(S)-1,2-trans-epoxypropyl)-2H-pyran-2-one (asperline (1), compound I) and two new metabolites. These were 5,6-dihydro-5(S)-acetoxy-6(S)-(1,2-trans propenyl)-2H-pyran-2-one (compound II) and 5,6-dihydro-5(R)-acetoxy-6(S)-(1,2-trans-epoxy-propyl)-H-pyran-2-one (compound III). These three metabolites showed anti-microbial activity against C. albicans and against specific bacteria, fungi, and a trichomonad.