Evaluation of phenyl hydrazide-based compounds as myeloperoxidase inhibitors

Myeloperoxidase (MPO) has been associated with a broad range of chronic inflammatory diseases since activated MPO catalyzes the production of HOCl, triggering both oxidative stress and inflammation. Since benzohydrazides are known as MPO inhibitors, a series of six N'-phenylbenzohydrazides and one quinazolin-4(3H)-one analogue was evaluated through in vitro assays to measure inhibition of MPO, superoxide dismutase (SOD), and catalase (CAT) activities, as well as DPPH and superoxide-scavenging effects. Pharmacokinetic parameters of the compounds were evaluated in silico, and molecular docking studies were performed to predict their binding modes with the catalytic site of MPO. All phenylbenzohydrazides exhibited potent inhibitory effect on MPO activity, with four of them presenting IC₅₀ values below 0.5 μM. Bromine substitution, as in 2b, 2e, and 2f, enhanced the binding affinity to the active site of MPO, resulting in high inhibitory potency. In concentrations as high as 50 μM, compounds did not inhibit SOD activity but showed some inhibitory activity over CAT. Except for compound 2c, the phenylbenzohydrazides can scavenge DPPH radical, while only 2e can sequester superoxide anion. Quinazolin-4(3H)-one analogue 3, obtained from phenylbenzohydrazide 2a showed a more selective profile towards MPO compared to CAT but antioxidant activity was not observed. Phenylbenzohydrazide 2e is a potent MPO inhibitor with antioxidant properties, demonstrated through DPPH and superoxide anion scavenging, with high predicted gastrointestinal absorption. The results obtained in this study with N'-phenylbenzohydrazides highlight the importance of structural modifications to improve the pharmacological profile of phenylhydrazides, contributing to the development of new anti-inflammatory drugs.