Here we report a cyclopeptide alkaloid, vignatic acid A, as one of the inhibitory factors conferring the bruchid resistance. This compound is the first example among the cyclopeptide alkaloids in plant that has insecticidal activity. A resistant gene (R) of the wild mungbean strain TC1966 was hybridized into a susceptible cultivar (Osaka-ryokuto) to give a BC20F4 resistant isogenic line (IL) by the selection for bruchid resistance against azuki bean weevil (Callosobruchus chinensis). The lipid contents in the seed flour were removed by acetone, and then the residue was extracted with 80% ethanol. After centrifugation and removal of the pellet, the supernatant was evaporated followed by extraction with 1-butanol. Two peaks denoted vignatic acid A (1) and B (2) were recognized to be the characteristic chemical differences between resistant and susceptible seed extracts by comparing their HPLC chromatograms. In bioassays using an artificial bean method, the larvae of C. chinensis died as first instars just after digging into the artificial beans containing 0.5-1% of vignatic acid A (1) in the seed flour of the susceptible variety. This compound is the first example of an insecticidal cyclopeptide alkaloid base of plant origin.