Novel lavendamycin analogues as antitumor agents: Synthesis, in vitro cytotoxicity, structure-metabolism, and computational molecular modeling studies with NAD(P)H:quinone oxidoreductase 1

Novel lavendamycin analogues with various substituents were synthesized and evaluated as potential NAD(P)H:quinone oxidoreductase (NQO1)-directed antitumor agents. Pictet-Spengler condensation of quinoline- or quninoline-5,8-dione aldehydes with tryptamine or tryptophans yielded the lavendamycins. Metabolism studies with recombinant human NQO1 revealed that addition of NH₂ and CH₂OH groups at the quinolinedione-7-position and indolopyridine-2′-position had the greatest positive impact on substrate specificity. The best and poorest substrates were 37 (2′-CH ₂OH-7-NH₂ derivative) and 31 (2′-CONH ₂-7-NHCOC₃H₇-n derivative) with reduction rates of 263 ± 30 and 0.1 ± 0.1 μmol/min/mg NQO1, respectively. Cytotoxicity toward human colon adenocarcinoma cells was determined for the lavendamycins. The best substrates for NQO1 were also the most selectively toxic to the NQO1-rich BE-NQ cells compared to NQO1-deficient BE-WT cells with 37 as the most selective. Molecular docking supported a model in which the best substrates were capable of efficient hydrogen-bonding interactions with key residues of the active site along with hydride ion reception.