Generation and characterization of monoclonal antibodies against the pyrrolizidine alkaloid retrorsine

Monoclonal antibodies against retrorsine were established using a retrorsine-hemisuccinate::bovine-thyroglobuline conjugate as antigen for immunization. In competitive enzyme-linked immunoassays the specificity of the obtained antibodies was tested with 20 different pyrrolizidine alkaloids. Among these the alkaloids acetylgynuramine, gynuramine, integerrimine, neoplatyphylline, platyphylline, rosmarinine, senecionine, and seneciphylline were able to bind the antibody. There was no cross-reactivity with the alkaloids senkirkine, angeloylheliotridine, heliotridine, axillarine, anacrotine, monocrotaline, madurensine, otosenine, retronecine, tussilagine, triangularine, and jacoline as well as with seneciphylline N-oxide. From this antigen spectrum it can be concluded that besides the necic structure itself the dominant and discriminative epitope consists of the exocyclic ethylidene group of the various diesters.