By a screening program searching for new pesticides from fungal sources, an insecticidal compound was isolated from Penicillium citrinum F 1539 through solid-state fermentation (buckwheat medium, 12 days at 25°C), 1-butanol extraction, partitioning with ethyl acetate/water, repeated silica gel column chromatography, and recrystallization. The novel compound, named quinolactacide, had a molecular formula of C14H8O2N2 as determined by HR-EIMS. Its structure, elucidated via 1H/13C NMR, DEPT, COSY, HMQC, HMBC, IR, and EIMS linked scan, featured a quinolone skeleton conjugated to a bicyclic ring consisting of a γ-lactam ring and a pyrrole ring, with an unmethylated nitrogen atom at the 11 position (a key difference from related quinolactacins and quinocitrinines, whose corresponding nitrogen atoms are methylated). Quinolactacide showed 88% mortality against green peach aphids (Myzus persicae) at 250 ppm. Due to insufficient compound quantity, its activity against other pests was not investigated. Future studies will focus on synthesizing quinolactacide and its derivatives to clarify the insecticidal spectrum and structure-activity relationships.