Novel insights into conjugation of antitumor-active unsymmetrical bisacridine C-2028 with glutathione:Characteristics of non-enzymatic and glutathione S-transferase-mediated reactions / 药物分析学报

Unsymmetrical bisacridines (UAs) are a novel potent class of antitumor-active therapeutics.A significant route of phase II drug metabolism is conjugation with glutathione (GSH),which can be non-enzymatic and/or catalyzed by GSH-dependent enzymes.The aim of this work was to investigate the GSH-mediated metabolic pathway of a representative UA,C-2028.GSH-supplemented incubations of C-2028 with rat,but not with human,liver cytosol led to the formation of a single GSH-related metabolite.Interestingly,it was also revealed with rat liver microsomes.Its formation was NADPH-independent and was not inhibited by co-incubation with the cytochrome P450 (CYP450) inhibitor 1-aminobenzotriazole.Therefore,the direct conjugation pathway occurred without the prior CYP450-catalyzed bioactivation of the substrate.In turn,incubations of C-2028 and GSH with human recombinant glutathione S-transferase(GST) P1-1 or with heat-/ethacrynic acid-inactivated liver cytosolic enzymes resulted in the presence or lack of GSH conjugated form,respectively.These findings proved the necessary participation of GST in the initial activation of the GSH thiol group to enable a nucleophilic attack on the substrate molecule.Another C-2028-GSH S-conjugate was also formed during non-enzymatic reaction.Both GSH S-conju-gates were characterized by combined liquid chromatography/tandem mass spectrometry.Mechanisms for their formation were proposed.The ability of C-2028 to GST-mediated and/or direct GSH conjugation is suspected to be clinically important.This may affect the patient's drug clearance due to GST activity,loss of GSH,or the interactions with GSH-conjugated drugs.Moreover,GST-mediated depletion of cellular GSH may increase tumor cell exposure to reactive products of UA metabolic transformations.

Electrochemical and in silico approaches for liver metabolic oxidation of antitumor-active triazoloacridinone C-1305 / 药物分析学报

5-Dimethylaminopropylamino-8-hydroxytriazoloacridinone (C-1305) is a promising antitumor com-pound developed in our laboratory. A better understanding of its metabolic transformations is still needed to explain the multidirectional mechanism of pharmacological action of triazoloacridinone de-rivatives at all. Thus, the aim of the current work was to predict oxidative pathways of C-1305 that would reflect its phase Ⅰ metabolism. The multi-tool analysis of C-1305 metabolism included electrochemical conversion and in silico sites of metabolism predictions in relation to liver microsomal model. In the framework of the first approach, an electrochemical cell was coupled on-line to an electrospray ioni-zation mass spectrometer. The effluent of the electrochemical cell was also injected onto a liquid chromatography column for the separation of different products formed prior to mass spectrometry analysis. In silico studies were performed using MetaSite software. Standard microsomal incubation was employed as a reference procedure. We found that C-1305 underwent electrochemical oxidation pri-marily on the dialkylaminoalkylamino moiety. An unknown N-dealkylated and hydroxylated C-1305 products have been identified. The electrochemical system was also able to simulate oxygenation re-actions. Similar pattern of C-1305 metabolism has been predicted using in silico approach. Both proposed strategies showed high agreement in relation to the generated metabolic products of C-1305. Thus, we conclude that they can be considered as simple alternatives to enzymatic assays, affording time and cost efficiency.