Synthesis of novel carboxamide- and carbohydrazide-benzimidazoles as selective butyrylcholinesterase inhibitors.

Selectively inhibiting butyrylcholinesterase (BChE) is hypothesized to help in the management of Alzheimer's disease (AD). Several studies have determined a correlation between the increased activity of BChE and the onset of AD. An advantage of BChE over acetylcholinesterase inhibition is that absence of BChE activity does not lead to obvious physiological disturbance. However, currently no BChE inhibitors are available commercially as potential therapeutics for AD. In our continuous effort to find potent BChE inhibitors for Alzheimer's disease, a total of 22 novel benzimidazoles with diversified substitutions were synthesized and evaluated for their anticholinesterase activities in this study. Among the synthesized compounds, 2j and 3f were found to exhibit potent and selective BChE inhibition with IC50 values of 1.13 and 1.46 µM, respectively. Molecular docking studies were carried out to rationalize the observed inhibitory activities. The compounds were predicted to have high penetration across the blood-brain barrier. Moreover, cell proliferative studies were also performed to evaluate the toxicity profile of the interested compounds. Compound 3f was found to be a potent and selective butyrylcholinesterase inhibitor with an IC50 value of 1.46 µM.

Insight into Mechanism of Action of Anticancer Benzazoles.

BACKGROUND: Targeting the DNA topoisomerase II enzyme (topo II) is a promising anticancer treatment approach. TopoII controls and modifies the topological states of DNA and plays key roles in DNA replication, transcription, and chromosome segregation. The DNA binding and cleavage domain is one of the active sites of this enzyme. It is known that topoisomerase inhibitors, also known as topoisomerase poisons, bind to the transient enzyme-DNA complex and inhibit the religation of DNA, generating single- and double-stranded breaks that harm the integrity of the genome. This ultimately leads to the accumulation of DNA strand breaks and cell death. METHODS: Our previously synthesized benzazole derivatives were tested for their eukaryotic DNA topoisomerase II inhibitory activity in a cell-free system. Their interactions with the enzyme were studied by carrying out molecular docking studies using and comparing two different docking programs. RESULTS: The results of the docking studies clarified binding modes of these compounds to the topoisomerase II enzyme. CONCLUSION: This study also provides guidelines to design novel and more potent antitumor agents functioning as human topoisomerase II enzyme inhibitors.

Benzoxazines as new human topoisomerase I inhibitors and potential poisons.

BACKGROUND: The numbers of topoisomerase I targeted drugs on the market are very limited although they are used clinically for treatment of solid tumors. Hence, studies about finding new chemical structures which specifically target topoisomerase I are still remarkable. OBJECTIVES: In this present study, we tested previously synthesized 3,4-dihydro-2H-1,4-benzoxazin-3-one derivatives to reveal their human DNA topoisomerase I inhibitory potentials. METHODS: We investigated inhibitory activities of 3,4-dihydro-2H-1,4-benzoxazin-3-one derivatives on human topoisomerase I by relaxation assay to clarify inhibition mechanisms of effective derivatives with EMSA and T4 DNA ligase based intercalation assay. With SAR study, it was tried to find out effective groups in the ring system. RESULTS: While 10 compounds showed catalytic inhibitory activity, 8 compounds were found to be potential topoisomerase poisons. 4 of them also exhibited both activities. 2-hydroxy-3,4-dihydro-2H-1,4-benzoxazin-3-one (BONC-001) was the most effective catalytic inhibitor (IC50:8.34 mM) and ethyl 6-chloro-4-methyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazin-2-acetate (BONC-013) was the strongest potential poison (IC50:0.0006 mM). BONC-013 was much more poisonous than camptothecin (IC50:0.034 mM). Intercalation assay showed that BONC-013 was not an intercalator and BONC-001 most probably prevented enzyme-substrate binding in an unknown way. Another important result of this study was that OH group instead of ethoxycarbonylmethyl group at R position of benzoxazine ring was important for hTopo I catalytic inhibition while the attachment of a methyl group of R1 position at R2 position were play a role for increasing of its poisonous effect. CONCLUSION: As a result, we presented new DNA topoisomerase I inhibitors which might serve novel constructs for future anticancer agent designs. Graphical abstract.

The 12th AFMC International Medicinal Chemistry Symposium (AIMECS 2019) in Istanbul, Turkey.

AFMC-AIMECS meetings are internationally organized biannually by the Asian Federation for Medicinal Chemistry (AFMC) and are focused on recent studies in drug discovery and development both in academia and industry. Member organizations of the AFMC are the Pharmaceutical Society of Japan, the Chinese Pharmaceutical Association, the Royal Australian Chemical Institute, the Pharmaceutical Society of Korea, the Korean Chemical Society, the Chemical Society Located in Taipei, the Indonesian Society of Medicinal Chemistry, the Medicinal Chemistry Section of the Israel Chemical Society, and the Computer-Aided Drug Design & Development Society in Turkey. Each time, the symposium is organized within these member countries. The AIMECS 2019 symposium was held in Turkey this year, as Prof. Dr. Esin Aki-Yalcin is the current president of the AFMC (2018-2020); the next AIMECS meeting will be organized in 2021 in Tokyo, Japan. In this report, we discuss key topics at the 12th AFMC International Medicinal Chemistry Symposium - New Avenues for Design and Development of Translational Medicine (AIMECS 2019) held in Istanbul, September 8-11, 2019.

Homology modeling in drug discovery: Overview, current applications, and future perspectives.

Homology modeling is one of the computational structure prediction methods that are used to determine protein 3D structure from its amino acid sequence. It is considered to be the most accurate of the computational structure prediction methods. It consists of multiple steps that are straightforward and easy to apply. There are many tools and servers that are used for homology modeling. There is no single modeling program or server which is superior in every aspect to others. Since the functionality of the model depends on the quality of the generated protein 3D structure, maximizing the quality of homology modeling is crucial. Homology modeling has many applications in the drug discovery process. Since drugs interact with receptors that consist mainly of proteins, protein 3D structure determination, and thus homology modeling is important in drug discovery. Accordingly, there has been the clarification of protein interactions using 3D structures of proteins that are built with homology modeling. This contributes to the identification of novel drug candidates. Homology modeling plays an important role in making drug discovery faster, easier, cheaper, and more practical. As new modeling methods and combinations are introduced, the scope of its applications widens.

Biological evaluation and pharmacophore modeling of some benzoxazoles and their possible metabolites.

A series of benzoxazole derivatives and some possible primary metabolites were evaluated as anticancer agents. In vitro anti-proliferative activities of the compounds were tested using the SRB assay on cancerous (HeLa) and non-cancerous (L929) cell lines. It was found that 17 of 21 tested compounds had cytotoxic activity on HeLa cells and the cytotoxic activities of the compounds were 15-700 times higher than on L929 cells. We generated two distinct pharmacophore models for the cytotoxic activities of the compounds on HeLa and L929 cells. While active compounds such as camptothecin and X8 fitted the two models generated for both cell lines, selective cytotoxic compounds such as XT3B fitted only the model generated for HeLa cells. Evaluation of the genotoxic activities of the cytotoxic compounds with the alkaline comet assay revealed that compounds X17 and XT3 showed strong genotoxic effects against HeLa cells at low concentrations whereas they had no genotoxic effect on L929 cells. Due to the selective ability for inducing DNA strand breaks only on cancerous cells, the compounds were identified as effective derivatives for anticancer candidates.

Determination of the Apoptotic Effect and Molecular Docking of Benzamide Derivative XT5 in K562 Cells.

BACKGROUND: The tyrosine kinase inhibitor, imatinib, used as a first line treatment in Chronic Myeloid Leukemia (CML) patients, may lead to resistance and failure to therapy. Novel combinations of imatinib with other drugs is a strategy to improve treatment efficiency. OBJECTIVE: In this study, the antileukemic and apoptotic effects of a benzamide derivative XT5 and benzoxazole derivative XT2B and their combination with imatinib were investigated in imatinib-sensitive (K562S) and imatinib-resistant (K562R) CML cells. METHODS: In vitro cytotoxicity was determined by MTT assay. Then, apoptotic effect of XT5 on CML cell lines was tested by Annexin V flow cytometry, caspase activation and RT-PCR. Docking calculation was performed using AutoDock Vina in PyMOL environment using AutoDock/Vina plugin for PyMOL. RESULTS: According to our MTT assay data, XT5 indicated significant antiproliferative effect on cell lines, therefore we investigated apoptotic effects of XT5. Treatment of K562 cell lines with a combination of XT5 and imatinib-XT5 increased cytotoxicity, the Annexin V binding and caspase 3/7 activation. In addition to apoptosis assays, we observed an increase in the expression levels of the pro-apoptotic (BAX, BAD and BIM) genes in XT5 treated K562R and K562S cells. Molecular modelling experiments showed that XT5 showed hydrogenbonding interactions with important amino acids of BCR-ABL kinase receptor; however XT2B did not show any hydrogen bond interaction. CONCLUSION: Our results indicate that XT5 could be a potential candidate to be used as a new anticancer drug and XT5 combination with imatinib as an alternate treatment strategy for overcoming imatinib resistance.

Design and synthesis of 2-substituted-5-(4-trifluoromethylphenyl-sulphonamido)benzoxazole derivatives as human GST P1-1 inhibitors.

The glutathione transferases (GSTs) are a family of widely distributed Phase II detoxification enzymes. GST P1-1 is frequently overexpressed in rat and human tumours. It is suggested that overexpression of hGST P1-1 by human tumor cells may play a role in resistance to cancer chemotherapy. Hence, hGST P1-1 can be a promising target for cancer treatment. In this study, new hGST P1-1 inhibitors, 2-(4-substitutedphenyl/benzyl)-5-(4-trifluoromethylphenylsulphonamido) benzoxazole derivatives (Va-Vk) have been designed and synthesized. Surprisingly, in vitro hGST P1-1 enzyme inhibition studies demonstrated that all of the tested compounds except Vj had better activity than the reference drug EA and it is also correlated with the docking results. Additionally we compared the interactions with hGST P1-1 enzyme of newly synthesized compound Vh (bearing CF3 group) and previously synthesized compound 5f (bearing NO2 group). According to the docking results, compound Vh bound to the hGST P1-1 enzyme with a higher affinity compared to 5f. Therefore, we can consider that these data make a sense and can explain its higher activity. The compounds that obtained from this research could be used as scaffolds in design of new potent hGST P1-1 inhibitors useful in the treatment of the resistance of cancer chemotherapy.

Synthesis and biological evaluation of 2-substituted-5-(4-nitrophenylsulfonamido)benzoxazoles as human GST P1-1 inhibitors, and description of the binding site features.

Glutathione-S-transferases (GSTs) are enzymes involved in cellular detoxification by catalyzing the nucleophilic attack of glutathione (GSH) on the electrophilic center of numerous of toxic compounds and xenobiotics, including chemotherapeutic drugs. Human GST P1-1, which is known as the most prevalent isoform of the mammalian cytosolic GSTs, is overexpressed in many cancers and contributes to multidrug resistance by directly conjugating to chemotherapeutics. It is suggested that this resistance is related to the high expression of GST P1-1 in cancers, thereby contributing to resistance to chemotherapy. In addition, GSTs exhibit sulfonamidase activity, thereby catalyzing the GSH-mediated hydrolysis of sulfonamide bonds. Such reactions are of interest as potential tumor-directed prodrug activation strategies. Herein we report the design and synthesis of some novel sulfonamide-containing benzoxazoles, which are able to inhibit human GST P1-1. Among the tested compounds, 2-(4-chlorobenzyl)-5-(4-nitrophenylsulfonamido)benzoxazole (5 f) was found as the most active hGST P1-1 inhibitor, with an IC50 value of 10.2 µM, showing potency similar to that of the reference drug ethacrynic acid. Molecular docking studies performed with CDocker revealed that the newly synthesized 2-substituted-5-(4-nitrophenylsulfonamido)benzoxazoles act as catalytic inhibitors of hGST P1-1 by binding to the H-site and generating conjugates with GSH to form S-(4-nitrophenyl)GSH (GS-BN complex) via nucleophilic aromatic substitution reaction. The 4-nitrobenzenesulfonamido moiety at position 5 of the benzoxazole ring is essential for binding to the H-site and for the formation of the GST-mediated GSH conjugate.