Design, synthesis, anti-inflammatory evaluation, and molecular docking studies of novel quinazoline-4(3H)-one-2-carbothioamide derivatives†

Abstract

In this paper, a series of novel quinazoline-4(3H)-one-2-carbothioamide derivatives (8a–p) were designed and synthesized via the Wilgerodt–Kindler reaction between 2-methylquinazoline-4-one 10 and amines using S₈/DMSO as the oxidizing system. Their characteristics were confirmed by IR, NMR, HRMS spectra, and their melting point. These novel derivatives (8a–p) were evaluated for their anti-inflammatory activity by inhibiting NO production in lipopolysaccharide (LPS)-activated RAW 264.7 macrophage cells. Compounds 8d (IC₅₀ = 2.99 μM), 8g (IC₅₀ = 3.27 μM), and 8k (IC₅₀ = 1.12 μM) exhibited potent inhibition of NO production compared to the standard drug dexamethasone (IC₅₀ = 14.20 μM). Compound 8a (IC₅₀ = 13.44 μM) exhibited NO inhibition comparable to dexamethasone. Structure–activity relationship (SAR) studies indicated that the presence of both the thioamide functional group (NH–CS) directly attached to the phenyl ring containing halogen substituents (4-Cl, 8d), (4-Br, 8g) and (4-CF₃, 8k), is responsible for the potent anti-inflammatory activity of these novel quinazolinone derivatives. Computational modeling studies revealed that compounds 8d, 8g, and 8k are potent inhibitors of TLR4 signaling through the formation of hydrophobic interactions and are stabilized by hydrogen bonds. Replacing the thioamide (8k) with an amide (8q) resulted in an 83-fold decrease in NO inhibitory potency. This highlights the important role of H-bonding involving the thioamide group. The structural shape difference results in favorable interactions of quinazolinones containing thioamide linkers compared to amide linkers to the target receptor. Furthermore, the ADMET profiles and physicochemical properties of these three lead compounds were predicted to meet the criteria for drug-like properties. Therefore, these compounds may be potential candidates for the treatment of many inflammatory diseases associated with immune disorders.