Development of a sensitive HPLC method to measure in vitro permeability of E- and Z-isomeric forms of thiosemicarbazones in Caco-2 monolayers

► We developed a sensitive HPLC method for assessment of BpT-E/Z isomers. ► We demonstrated effective iron chelation of BpT-iron chelators that inhibit HIV-1. ► We estimated the permeability profile of BpT-E/Z isomers in Caco2 monolayers. ► We anticipate that BpT chelators could hold promise as orally effective agents. In the current study, we developed a HPLC method to quantitatively measure the permeability of the BpT-based chelators, 2-benzoylpyridine 4-ethyl-3-thiosemicarbazone (Bp4eT) and 2-benzoylpyridine 4-allyl-3-thiosemicarbazone (Bp4aT), across human colorectal adenocarcinoma (Caco-2) monolayers as a model of gut absorption. In aqueous solution, Bp4eT and Bp4aT formed inter-convertible Z and E isomers that were resolved by HPLC. Peak area was linear with respect to chelator concentration. Acceptable within-day and between-day precision (