Insecticidal Peptide from Mungbean:  A Resistant Factor against Infestation with Azuki Bean Weevil

A resistant factor from a strain (TC1966) of wild mungbean (Vigna radiata var. sublobata) active against the azuki bean weevil (Callosobruchus chinensis) was genetically transferred into a susceptible cultivar. The resulting strain (BC20F4) tolerated an infestation by C. chinensis. The ethanol extract of BC20F4 inhibited larval growth. Vignatic acid A (1) was isolated and evaluated as one of the inhibitors present in BC20F4. Structure 1 was determined to be a cyclopeptide alkaloid composed of l-tyrosine, 3(S)-hydroxyl-l-leucine, l-phenylalanine, and 2-hydroxyisocaproic acid by FAB-HRMS, DQF-FGCOSY, FG-HMQC, FG-HMBC, and NOE-DF. This compound is the first example of an insecticidal cyclopeptide alkaloid base of plant origin. Keywords: Mungbean; Vigna radiata; azuki bean weevil; Callosobruchus chinensis; azuki bean; Vigna angularis; vignatic acid; cyclopeptide alkaloid