Evaluation of (S)‐ and (R)‐Misonidazole as GPX Inhibitors: Synthesis, Characterization Including Circular Dichroism and In Vitro Testing on Bovine GPx‐1

Abstract

Racemic misonidazole, a radiosensitizer formally used in radiation therapy of cancer and to date still applied, was once reported to exhibit strong inhibitory effects on mouse glutathione peroxidases (GPX). This appeared to qualify misonidazole as a lead structure for the development of novel GPX inhibitors to cause oxidative stress in chemotherapy-resistant tumors. A unique feature of misonidazole as an inhibitor of GPX is the absence of a thiol functionality. Therefore, it was expected to selectively target inhibition devoid of promiscuous interactions with cations and sulfhydryl groups. We synthesized the isomers of misonidazole and analyzed the ability of chiroptical high-performance liquid chromatography (HPLC) to identify the particular enantiomers. Due to the chiral pool synthesis, the assignment of the correct configuration could be verified. Finally, we evaluated both isomers for their inhibitory activities on bovine erythrocyte GPx-1, which is 87% homologous to the human enzyme. Despite the previously reported inhibition of racemic misonidazole on the less homologous mouse GPx-1, we did not find any significant inhibitory activity on the bovine enzyme for either isomer. Though misonidazole appears unlikely to be an inhibitor of human GPx-1 activity, we still spotlight misonidazole as a promising fragment-like lead structure in general.

Near-Infrared Fluorescence Probe for in Situ Detection of Superoxide Anion and Hydrogen Polysulfides in Mitochondrial Oxidative Stress

“…As expected, remarkable increase in the fluorescence intensity was obtained. However, once inhibited the GPx activity by racemic misonidazole, 49 the increase in fluorescence emission were suppressed (Figure 2e). These results demonstrated that our probe was suitable for the detection of endogenous O 2…”

“…As expected, remarkable increase in the fluorescence intensity was obtained. However, once inhibited the GPx activity by racemic misonidazole, 49 the increase in fluorescence emission were suppressed (Figure 2e 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59demonstrated that our probe was suitable for the detection of endogenous O 2…”

Comprehensive Evaluation of Biological Effects of Pentathiepins on Various Human Cancer Cell Lines and Insights into Their Mode of Action

“…It is based on the catalytic cycle of the enzyme coupled to an NADPH detection reaction. Here, a bovine erythrocyte GPx1 with a sequence similarity of 87% to the human homolog [ 50 ] was used for reasons of affordability. The GPx1 was treated with either vehicle (solvent DMF) or the respective pentathiepin, and the reaction started by addition of tert -butylhydroperoxide ( t -BHP).…”

Functionalized Nitroimidazole Scaffold Construction and Their Pharmaceutical Applications: A 1950–2021 Comprehensive Overview

“…In 2011, Phukan et al also developed a solvent-free process for its synthesis from 2-nitroimidazole 1 , where potter’s clay and sodium nitrite under microwave conditions were used (route D) [ 41 ]. Wilde et al, in 2014, also developed a method where the 2-aminoimidazole ring was first constructed using amino acetaldehyde dimethyl acetal and O -methylisourea sulfate as starting materials, which then underwent diazotization, nitration, and finally furnished Azomycin 1 (route E) [ 42 ].…”

“…Jin et al in 2004 synthesized both ( R )- and ( S )-Misonidazole 3 by treating 2-nitroimidazole with ( R )- and ( S )-epichlorohydrins, respectively ( Scheme 4 , route B) [ 61 ]. In 2014, Wilde et al synthesized optically pure Misonidazole 3 , wherein the reaction of 2-aminoacetaldehyde dimethylacetal with O -methylisourea sulfate led to the formation of the 2-aminoimidazole hemisulfate, which on cyclization and diazotization followed by nitration, produced 2-nitroimidazole [ 42 ]. Then, 2-nitroimidazole further underwent a nucleophilic opening reaction with R and S -2-(methoxy methyl)oxirane and finally led to the optically pure Misonidazole 3 ( Scheme 4 , route C).…”