Fragmentation pattern of certain isatin–indole antiproliferative conjugates with application to identify their in vitro metabolic profiles in rat liver microsomes by liquid chromatography tandem mass spectrometry

The fragmentation pattern of certain isatin-based compounds was carried out using collision-induced dissociation inside the triple quadrupole mass analyzer. These data were used as a clue for the identification of metabolites of the recently reported isatin-based antiproliferative agent, namely, N′-[5-bromo-1-methyl-2-oxo-1,2-dihydro-3H-indol-3-ylidene]-5-methoxy-1H-indole-2-carbohydrazide (1) in rat liver microsomes (RLMs) using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Prediction of the vulnerable sites for metabolic pathways in compound 1 was performed by WhichP450 module of StarDrop software. In vitro metabolites for compound 1 were identified with the aid of rat liver microsomes. The in silico data were utilized as a guide for the practical work. Compound 1 was metabolized into three (hydroxylated, reduced and O-demethylated) metabolites in RLMs in the presence of NADPH. The chemical structures of those metabolites were elucidated, and the metabolic pathways were proposed by comparing the fragmentation pattern of the isatin–indole conjugates 1–7. The data presented in this paper provided useful information on the effect of different substituents on the ionization/fragmentation processes and can be used in the characterization of isatin derivatives. In silico toxicity assessments for the title compounds 1–7 and for the metabolites of compound 1 were conducted utilizing the deductive estimation of risk from existing knowledge (DEREK) module of StarDrop software.