New unsymmetrical bisacridines (UAs) demonstrated high activity not only against a set of tumor cell lines but also against human tumor xenografts in nude mice. Representative UA compounds, named C-2028, C-2045 and C-2053, were characterized in respect to their physicochemical properties and the following studies aimed to elucidate the role of metabolic transformations in UAs action. We demonstrated with phase I and phase II enzymes in vitro and in tumors cells that: (i) metabolic products generated by cytochrome P450 (P450), flavin monooxygenase (FMO) and UDP-glucuronosyltransferase (UGT) isoenzymes in noncellular systems retained the compound’s dimeric structures, (ii) the main transformation pathway is the nitro group reduction with P450 isoenzymes and the metabolism to N-oxide derivative with FMO1, (iii), the selected UGT1 isoenzymes participated in the glucuronidation of one compound, C-2045, the hydroxy derivative. Metabolism in tumor cells, HCT-116 and HT-29, of normal and higher UGT1A10 expression, respectively, also resulted in the glucuronidation of only C-2045 and the specific distribution of all compounds between the cell medium and cell extract was demonstrated. Moreover, P4503A4 activity was inhibited by C-2045 and C-2053, whereas C-2028 affected UGT1A and UGT2B action. The above conclusions indicate the optimal strategy for the balance among antitumor therapeutic efficacy and drug resistance in the future antitumor therapy.

Referring to our previous laboratory results related to the tyrosinase and urease inhibition by pyrazolo[4,3-e][1,2,4]triazine sulfonamides, we examined here in silico the mechanism of action at the molecular level of the investigated pyrazolotriazine sulfonamides by the molecular docking method. The studied compounds being evaluated for their cytotoxic effect against cancer cell lines (MCF-7, K-562) and for recombinant Abl and CDK2/E kinase inhibitory potency turned out to be inactive in these tests. The pyrazolotriazines were also investigated with respect to their lipophilicity and plasma protein binding using HPLC chromatography in isocratic conditions. The observed small affinity for plasma proteins could be advantageous in the potential in vivo studies. Moreover, the compounds were sensitive to metabolic transformations with phase I enzymes, which led to the hydroxylation and dealkylation products, whereas phase II transformations did not occur.

The present studies were carried out to evaluate the simultaneous one-pot metabolism of opipramol (IS-opi) and analog (IS-noh) by phase I and phase II enzymes present in rat liver microsomes (RLM) as an alternative to separate testing with recombinant enzymes. This approach allows for more time-saving and cost-effective screening of the metabolism of newly discovered drugs. We also considered that the lack of results for phase II, including UGT, often creates problems in correct selection of valuable compounds. Moreover, microsomes data set is richer in the contest and provides medical scientist to determine also the susceptibility of drugs to undergo phase I and then phase II. In the present work, we have shown that IS-noh was metabolized in vitro by phase I enzymes to the oxidation product, which was next transformed with UGTs to glucuronide. The results showed also that the previously known oxidation product of opipramol was changed to previously no reported glucuronidation product by UDP-glucuronosyltransferases. In addition, unlike IS-noh, opipramol did not prove to be the substrate for UGTs. Therefore, tricyclic antidepressants depending on the structure can trigger a different response after contact with UGT enzymes. Some will metabolize directly with UGTs, others only after activation by phase I enzymes.