In our ongoing search for new bioactive metabolites from microbial resources, Aspergillus terreus (HKI0499) was examined by chemical metabolite profiling. Together with the known butyrolactone I ( 3), the unusual sulfate derivatives butyrolactone I 3-sulfate ( 1) and butyrolactone I 4''-sulfate ( 2) were discovered. The chemical structures were determined by NMR and MS data analyses. All compounds were tested on CDK1/cyclin B, CDK5/p25, DYRK1A, CK1, and GSK-3alpha/beta kinases; compounds 2 and 3 were also evaluated for their cytotoxic and antiproliferative activities. Butyrolactone I 3-sulfate ( 1) exhibited specific inhibitory activity against CDK1/cyclin B and CDK5/p25, yet 15-30-fold less than butyrolactone I ( 3). Likewise, butyrolactone I 3-sulfate ( 1) exhibited moderate cytotoxicity solely against HeLa cells (CC 50 = 80.7 microM).