New antifungal compounds from Aspergillus terreus isolated from desert soil

Two new butyrolactone I derivatives: 3-[3-hydroxy-4-(3-methyl-but-2-enyl)-phenyl]-5-(-4-hydroxybenzyl)-4-methyl-dihydrofuran-2(3H)-one (1) and (Z)-3-[3-hydroxy-4-(3-methyl-but-2-enyl)-phenyl]-5-(-4-hydroxybenzylidene)-4-methyl-dihydrofuran-2(3H)-one (2), in addition to the previously described (S)-methyl-4-hydroxy-2-[4-hydroxy-3-(3-methyl-but-2-enyl)-benzyl]-3-(4-hydroxy-phenyl)-5-oxo-2,5-dihydro-furan-2-carboxylic acid methyl ester (3), were identified from a strain of Aspergillus terreus Thom (Trichocomaceae) isolated from desert soil. The antifungal activities of both intra- and extracellular metabolites of A. terreus grown on yeast extract sucrose and malt extract media were determined. Only the secondary metabolites of A. terreus grown on yeast extract sucrose medium were active against Aspergillus fumigatus RCMB 002008. The antifungal activity of A. terreus was attributed to the presence of the compounds (1) and (2), whose minimum inhibitory concentrations (MIC) against A. fumigatus were found to be 32.00 and 16.00 µg/mL respectively. Structure elucidation was carried out using UV spectrometry, electrospray ionization mass spectrometry (ESIMS), high resolution electron impact (HREIMS) spectrometry, (1)H- and (13) C-NMR, proton-proton correlation spectroscopy ((1)H-(1)H Cosy), distortionless enhancement by polarization transfer (DEPT), heteronuclear single quantum coherence (HSQC) and heteronuclear multiple bond correlations (HMBC) spectroscopy.