Certain organic solvents in low concentrations have big impacts on metabolism of some microorganisms, including alterations in the production of secondary metabolites. Here we would like to report the formation, isolation, and characterization of a new secondary metabolite which was induced by dimethyl sulfoxide (DMSO) or acetone in the newly isolated Eupenicillium sp. fermentation system. The structure of this metabolite was confirmed to be the citreoisocoumarin derivative 1 (6, 8-dihydroxy-3-(4-hydroxy-2-oxopentyl)-1H-isochromen-1-one) by NMR and HR-ESI-MS, which has been reported as a component of the inseparable fermentation mixture. Here is the first report of this compound as a pure isolated product and by simple solvent-induction. The highly selective formation of compound 1 from Eupenicillium sp. make 1 as the only isolated product. This strategy might provide a valuable but neat way for the discovery of novel natural products.