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'-CH2OH-7-NH2 derivative) and 31 (2'-CONH2-7-NHCOC3H7-n derivative) with reduction rates of 263 +/- 30 and 0.1 +/- 0.1 micromol/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.

A 1H69 crystal structure-based in silico model of the NAD(P)H:quinone oxidoreductase 1 (NQO1) active site has been developed to facilitate NQO1-directed lavendamycin antitumor agent development. Lavendamycin analogues were designed as NQO1 substrates utilizing structure-based design criteria. Computational docking studies were performed using the model to predict NQO1 substrate specificity. Designed N-acyllavendamycin esters and amides were synthesized by Pictet-Spengler condensation. Metabolism and cytotoxicity studies were performed on the analogues with recombinant human NQO1 and human colon adenocarcinoma cells (NQO1-deficient BE and NQO1-rich BE-NQ). Docking and biological data were found to be correlated where analogues 12, 13, 14, 15, and 16 were categorized as good, poor, poor, poor, and good NQO1 substrates, respectively. Our results demonstrated that the ligand design criteria were valid, resulting in the discovery of two good NQO1 substrates. The observed consistency between the docking and biological data suggests that the model possesses practical predictive power.

A series of benzimidazole- and benzothiazole-quinones has been synthesized. The ability of these heterocyclic quinones to act as substrates for recombinant human NAD(P)H:quinone oxidoreductase (NQO1), a two-electron reductase upregulated in tumour cells, was determined. Overall, the quinones were excellent substrates for NQO1.