Pyrrole-Hemoglobin Adducts, A More Feasible Potential Biomarker of Pyrrolizidine Alkaloid Exposure

Pyrrolizidine alkaloids (PAs) are naturally occurring phytotoxins widely distributed in about 3% of flowering plants. The formation of PA-derived pyrrole-protein adducts is considered as a primary trigger initiating PA-induced hepatotoxicity. The present study aimed to (i) further validate our previous established derivatization method using acidified ethanolic AgNO3 for the analysis of pyrrole-protein adducts; and (ii) apply this method to characterize the binding tendency, dose-response, and elimination kinetics of pyrrole-protein adducts in the blood samples. Two pyrrole-amino acid conjugates, (±)-6,7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine (DHP)-cysteine (7-cysteine-DHP) and 9-histidine-DHP, were synthesized and used to demonstrate that acidified ethanolic AgNO3 derivatization can cleave both S-linkage and N-linkage of pyrrole-protein adducts. Subsequently, using pre-column AgNO3 derivatization followed by UHPLC-MS analysis we quantified pyrrole-protein adducts in monocrotaline-treated rat bl...