Pyrimidine Based Inhibitors Targeting Glutathione S-Transferase in Phase II Detoxification: Antioxidant, ADMET,...

The present study has been conducted to investigate the inhibitory effects and antioxidant capacities of two pyrimidine derivatives, 4,6-Dichloro-2-(methylthio) pyrimidine-5-carbonyl chloride (p1) and 4,6-Dichloro-2-(methylthio) pyrimidine-5-carboxyamide (p2), against the glutathione S-transferase (GST) enzyme for exploring their potential as therapeutic agents in conditions related to oxidative stress and drug resistance mediated through GST. The data are compared with that of ethacrynic acid (EA), a well-documented GST inhibitor. The IC₅₀ values for molecules p1, p2, and EA were computed to be 38.5 nM, 46.2 nM, and 5.82 nM, respectively. During the second part of the inhibition study, Ki values calculated from IC₅₀ plots became 57.61 nM for molecule p1, 43.75 nM for molecule p2, and 4.43 nM for EA. Molecules p1 and p2 depicted non-competitive mechanisms, while EA followed competitive inhibition. Moreover, antioxidant capacities of molecules were tested by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay method. Using the DPPH method scavenging activity in both p1 and p2 was comparable to that of the reference standard, ascorbic acid (AA). Other than this, biological activities of GST enzyme complexes were further validated using molecular docking, molecular dynamics, and ADMET (Absorption, Distribution, Metabolism, Excretion, and Toxicity) analyses. These complementary studies gave further insight into binding affinities, dynamic stability, and pharmacokinetic properties, reinforcing the impact of p1 and p2 complexation on GST structural and functional characteristics.