Catalyst-free synthesis of highly biologically active 5-arylidene rhodanine and 2,4-thiazolidinedione derivatives using aldonitrones in polyethylene glycol

Harnessing ROS-Induced Oxidative Stress for Halting Colorectal Cancer via Thiazolidinedione-Based SOD Inhibitors

Based on the "canonical" view of reactive oxygen species' (ROS) contribution to carcinogenesis, ROS induce oxidative stress and promote various tumor progression events. However, tumor cells also need to defend themselves against oxidative damage. This "heresy" was supported by several recent studies underlining the role of cellular antioxidant capacity in promoting metastasis and resistance to chemotherapy. Accordingly, harnessing the ROS-induced oxidative stress via selective suppression of the cancer antioxidant defense machinery has been launched as an innovative anticancer strategy. Within this approach, pharmacological inhibition of superoxide dismutases (SODs), the first-line defense antioxidant enzymes for cancer cells, selectively kills tumor cells and circumvents their acquired resistance. Various SOD inhibitors have been introduced, of which some were tolerated in clinical trials. However, the hit SOD inhibitors belong to diverse chemical classes and lack comprehensive structure-activity relationships (SAR). Herein, we probe the potential of newly synthesized benzylidene thiazolidinedione derivatives to inhibit SOD in colorectal cancer with special emphasis on their effects on correlated antioxidant enzymes aldehyde dehydrogenase 1 (ALDH1) and glutathione peroxidase (GPx). This may possibly bring a new dawn for utilizing thiazolidinediones (TZDs) in cancer therapy through SOD inhibition mechanisms. The preliminary 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that all of the evaluated TZDs exhibited excellent safety profiles on normal human cells, recording an EC100 of up to 47.5-folds higher than that of doxorubicin. Compounds 3c, 6a, and 6e (IC50 = 4.4-4.7 μM) were superior to doxorubicin and other derivatives against Caco-2 colorectal cancer cells within their safe doses. The hit anticancer agents inhibited SOD (IC50 = 97.2-228.8 μM). Then, they were selected for further in-depth evaluation on the cellular level. The anticancer IC50 doses of 3c, 6a, and 6e diminished the antioxidant activities of SOD (by 29.7, 70.1, and 33.3%, respectively), ALDH1A (by 85.92, 95.84, and 86.48%, respectively), and GPX (by 50.17, 87.03, and 53.28%, respectively) in the treated Caco-2 cells, elevating the Caco-2 cellular content of ROS by 21.42, 7.863, and 8.986-folds, respectively. Docking simulations were conducted to display their possible binding modes and essential structural features. Also, their physicochemical parameters and pharmacokinetic profiles formulating drug-likeness were computed.

Environmentally Friendly Approach to Knoevenagel Condensation of Rhodanine in Choline Chloride: Urea Deep Eutectic Solvent and QSAR Studies on Their Antioxidant Activity

A series of rhodanine derivatives was synthesized in the Knoevenagel condensation of rhodanine and different aldehydes using choline chloride:urea (1:2) deep eutectic solvent. This environmentally friendly and catalyst free approach was very effective in the condensation of rhodanine with commercially available aldehydes, as well as the ones synthesized in our laboratory. All rhodanine derivatives were subjected to 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) scavenging activity investigation and quantitative structure-activity relationship (QSAR) studies were performed to elucidate their structure-activity relationship. The best multiple linear QSAR model demonstrate a stability in the internal validation and Y-randomization (R² = 0.81; F = 24.225; Q²loo = 0.72; R²Yscr = 0.148). Sphericity of the molecule, ratio of symmetric atoms enhanced atomic mass along the principle axes in regard to total number of atoms in molecule, and 3D distribution of the atoms higher electronegativity (O, N, and S) in molecules are important characteristic for antioxidant ability of rhodanine derivatives. Molecular docking studies were carried out in order to explain in silico antioxidant studies, a specific protein tyrosine kinase (2HCK). The binding interactions of the most active compound have shown strong hydrogen bonding and van der Waals interactions with the target protein.