Evaluation and discovery of novel benzothiazole derivatives as promising hits against Leishmania infantum

An early exploration of the benzothiazole class against two kinetoplastid parasites, Leishmania infantum and Trypanosoma cruzi, has been performed after the identification of a benzothiazole derivative as a suitable antileishmanial initial hit. The first series of derivatives focused on the acyl fragment of its class, evaluating diverse linear and cyclic, alkyl and aromatic substituents, and identified two other potent compounds, the phenyl and cyclohexyl derivatives. Subsequently, new compounds were designed to assess the impact of the presence of diverse substituents on the benzothiazole ring or the replacement of the endocyclic sulfur by other heteroatoms. All compounds showed relatively low cytotoxicity, resulting in decent selectivity indexes for the most active compounds. Ultimately, the in vitro ADME properties of these compounds were assessed, revealing a satisfying water solubility, gastrointestinal permeability, despite their low metabolic stability and high lipophilicity. Consequently, compounds 5 and 6 were identified as promising hits for further hit-to-lead exploration within this benzothiazole class against L. infantum, thus providing promising starting points for the development of antileishmanial candidates.

Unsymmetrical Pd(II) Pincer Complexes with Benzothiazole and Thiocarbamate Flanking Units: Expedient Solvent-Free Synthesis and Anticancer Potential

Driven by the growing threat of cancer, many research efforts are directed at developing new chemotherapeutic agents, where the central role is played by transition metal complexes. The proper ligand design serves as a key factor to unlock the anticancer potential of a particular metal center. Following a recent trend, we have prepared unsymmetrical pincer ligands that combine benzothiazole and thiocarbamate donor groups. These compounds are shown to readily undergo direct cyclopalladation, affording the target S,C,N-type Pd(II) pincer complexes both in solution and in the absence of a solvent. The solid-phase strategy provided the complexes in an efficient and ecologically friendly manner. The resulting palladacycles are fully characterized using nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy and, in one case, by single-crystal X-ray diffraction (XRD). The solvent-free reactions are additionally analyzed by powder XRD. The pincer complexes exhibit remarkable cytotoxicity against several solid and blood cancer cell lines, including human colorectal carcinoma (HCT116), breast cancer (MCF7), prostate adenocarcinoma (PC3), chronic myelogenous leukemia (K562), multiple plasmacytoma (AMO1), and acute lymphoblastic leukemia (H9), with the dimethylamino-substituted derivative being particularly effective. The latter also induced an appreciable level of apoptosis in both parental and doxorubicin-resistant cells K562 and K562/iS9, vindicating the high anticancer potential of this type of palladacycles.

Benzothiazole-Phthalimide Hybrids as Anti-Breast Cancer and Antimicrobial Agents

The benzothiazole nucleus is a major heterocyclic scaffold whose therapeutic potential has been thoroughly explored due to its structural simplicity and ease of synthesis. In fact, several benzothiazole derivatives have been synthesized over time, demonstrating numerous pharmacological properties such as anticancer, antimicrobial, anti-inflammatory, and antioxidant activities. Herein, we propose a new series of benzothiazole-phthalimide hybrids obtained by linking the phthalimide moiety to differently substituted benzothiazole nuclei through the N atom. These compounds have been screened for their anticancer properties against two human breast cancer cell lines. Furthermore, we delved into the mechanism of action of the most active hybrid, compound 3h, by assessing its capability to damage the nuclear DNA, trigger the apoptotic process in the high metastatic MDA-MB-231 cells, and prevent cellular migration. Moreover, in view of the documented antimicrobial activities of the two scaffolds involved, we explored the antibacterial and antifungal effects of the studied compounds by means of the broth microdilution method. Among the studied compounds, 3h showed the highest antimicrobial activity, both against gram-positive and gram-negative bacterial strains belonging to the ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) and against fungal strains of the Candida species with MICs values ranging from 16 to 32 µg/mL.

Design, synthesis, and unraveling the antibacterial and antibiofilm potential of 2-azidobenzothiazoles: insights from a comprehensive in vitro study

The present study reports the synthesis of 2-azidobenzothiazoles from substituted 2-aminobenzothiazoles using sodium nitrite and sodium azide under mild conditions. All the synthesized compounds were examined for their antibacterial activity against Gram (+) bacteria, Staphylococcus aureus (ATCC 25923), Enterococcus faecalis (ATCC 51299), Bacillus cereus (ATCC 10876) and Gram (-) bacteria, Escherichia coli (ATCC 10536), Pseudomonas aeruginosa (ATCC 10145), Klebsiella pneumonia (ATCC BAA-2146)and clinical isolates of Gram (+) Methicillin Resistant S. aureus (MRSA) and Multi Drug Resistant E. coli. The Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) values by broth dilution method revealed that compound 2d exhibited significant antibacterial potential against E. faecalis and S. aureus with MIC of 8 μg/mL, while other synthesized compounds had only moderate effects against all the tested species. The compound significantly inhibited the biofilm formation of the bacterial strains below its MIC. The selective cytotoxicity of Compound 2d towards bacterial cells was evidenced on extended exposure of Human Embryonic Kidney-293 cell line to higher concentrations of the compound. Hence, the present study confirmed that compound 2d can be a potential drug candidate for future development as an antibacterial drug.

Trace Cu(II)-Mediated Selective Oxidation of Benzothiazole: The Predominance of Sequential Cu(II)-Cu(I)-Cu(III) Valence Transition and Dissolved Oxygen

Trace Cu(II), which inherently exists in soil and some water/wastewater, can trigger persulfate oxidation of some pollutants, but the oxidation capability and mechanism are not well understood, especially toward refractory pollutants. We report in this research that benzothiazole (BTH), a universal refractory pollutant typically originating from tire leachates and various industrial wastewater, can be facilely and selectively removed by peroxydisulfate (PDS) with an equimolar BTH/PDS stoichiometry in the presence of environmental-relevant contents of Cu(II) (below several micromoles). Comprehensive scavenging tests, electron spin resonance analysis, spectroscopy characterization, and electrochemical analysis, revealed that PDS first reduces the BTH-coordinated Cu(II) to Cu(I) and then oxidizes Cu(I) to high-valent Cu(III), which accounts for the BTH degradation. Moreover, once the reaction is initiated, the superoxide radical is probably produced in the presence of dissolved oxygen, which subsequently dominates the reduction of Cu(II) to Cu(I). This facile oxidation process is also effective in removing a series of BTH derivatives (BTHs) that are of environmental concern, thus can be used for their source control. The results highlight the sequential Cu(II)-Cu(I)-Cu(III) transition during PDS activation and the crucial role of contaminant coordination with Cu(II) in oxidative transformation.

Novel hydroxy- and amidino-substituted benzimidazoles and benzothiazoles as antibacterial and antiproliferative agents

Aim: The aim was synthesis of novel benzazoles bearing amidino and 2-hydroxyphenyl substituents to explore their biological activity. Methods: Condensation of 5-substituted salicylaldehydes and intermediates gave new benzazoles by previously published and developed procedures, which were tested for antibacterial and antiproliferative activity in vitro. Results: The best antibacterial activity showed benzimidazole with 2-imidazolinyl group 27 and benzothiazole with an unsubstituted amidine 48 (minimum inhibitory concentration 8 μg/ml). Benzothiazole 53 proved most potent at inhibiting proliferation of all cancer cells (IC50: 1.2-2.0 μM). Conclusion: Most active compounds have been recognized as lead compounds for additional optimization to improve their biological activity. The type of amidine moiety markedly influenced the biological activity. Benzothiazoles showed improved antiproliferative activity in comparison to benzimidazoles.

Synthesis, Antiproliferative Evaluation and QSAR Analysis of Novel Halogen- and Amidino-Substituted Benzothiazoles and Benzimidazoles

Syntheses of 6-halogen-substituted benzothiazoles were performed by condensation of 4-hydroxybenzaldehydes and 2-aminotiophenoles and subsequent O-alkylation with appropriate halides, whereas 6-amidino-substituted benzothiazoles were synthesized by condensation of 5-amidino-2-aminothiophenoles and corresponding benzaldehydes. While most of the compounds from non-substituted and halogen-substituted benzothiazole series showed marginal antiproliferative activity on tested tumor cell lines, amidino benzazoles exhibited stronger inhibitory activity. Generally, imidazolyl benzothiazoles showed pronounced and nonselective activity, with the exception of 36c which had a strong inhibitory effect on HuT78 cells (IC50 = 1.6 µM) without adverse cytotoxicity on normal BJ cells (IC50 >100 µM). Compared to benzothiazoles, benzimidazole structural analogs 45a−45c and 46c containing the 1,2,3-triazole ring exhibited pronounced and selective antiproliferative activity against HuT78 cells with IC50 < 10 µM. Moreover, compounds 45c and 46c containing the methoxy group at the phenoxy unit were not toxic to normal BJ cells. Of all the tested compounds, benzimidazole 45a with the unsubstituted phenoxy central core showed the most pronounced cell growth inhibition on THP1 cells in the nanomolar range (IC50 = 0.8 µM; SI = 70). QSAR models of antiproliferative activity for benzazoles on T-cell lymphoma (HuT78) and non-tumor MDCK-1 cells elucidated the effects of the substituents at position 6 of benzazoles, demonstrating their dependence on the topological and spatial distribution of atomic mass, polarizability, and van der Waals volumes. A notable cell cycle perturbation with higher accumulation of cells in the G2/M phase, and a significant cell increase in subG0/G1 phase were found in HuT78 cells treated with 36c, 42c, 45a−45c and 46c. Apoptotic morphological changes, an externalization of phosphatidylserine, and changes in the mitochondrial membrane potential of treated cells were observed as well.

In Silico and In Vitro Studies of Benzothiazole-Isothioureas Derivatives as a Multitarget Compound for Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder. Inhibiting acetylcholinesterase (AChE), amyloid beta (Aβ1-42) aggregation and avoiding the oxidative stress could prevent the progression of AD. Benzothiazole groups have shown neuroprotective activity whereas isothioureas groups act as AChE inhibitors and antioxidants. Therefore, 22 benzothiazole-isothiourea derivatives (3a-v) were evaluated by docking simulations as inhibitors of AChE and Aβ1-42 aggregation. In silico studies showed that 3f, 3r and 3t had a delta G (ΔG) value better than curcumin and galantamine on Aβ1-42 and AChE, respectively. The physicochemical and pharmacokinetics predictions showed that only 3t does not violate Lipinski's rule of five, though it has moderated cytotoxicity activity. Then, 3f, 3r and 3t were synthetized and chemically characterized for their in vitro evaluation including their antioxidant activity and their cytotoxicity in PC12 cells. 3r was able to inhibit AChE, avoid Aβ1-42 aggregation and exhibit antioxidant activity; nevertheless, it showed cytotoxic against PC12 cells. Compound 3t showed the best anti-Aβ1-42 aggregation and inhibitory AChE activity and, despite that predictor, showed that it could be cytotoxic; in vitro with PC12 cell was negative. Therefore, 3t could be employed as a scaffold to develop new molecules with multitarget activity for AD and, due to physicochemical and pharmacokinetics predictions, it could be administered in vivo using liposomes due to is not able to cross the BBB.

Synthesis, Structure and Cytotoxic Properties of Copper(II) Complexes of 2-Iminocoumarins Bearing a 1,3,5-Triazine or Benzoxazole/Benzothiazole Moiety

A series of copper(II) complexes of 2-imino-2H-chromen-3-yl-1,3,5-triazines 2a-h, 3-(benzoxazol-2-yl)-2H-chromen-2-imines 4a-b, and 3-(benzothiazol-2-yl)-2H-chromen-2-imines 6a-c were obtained by reacting of appropriate 2-iminocoumarin ligands L1a-h, L3a-b, and L5a-c with 3-fold molar excess of copper(II) chloride. The structure of these compounds was confirmed by IR spectroscopy, elemental analysis, and single-crystal X-ray diffraction data (2f, 2g, 2h, and 6c). All the synthesized complexes were screened for their activity against five human cancer cell lines: DAN-G, A-427, LCLC-103H, SISO, and RT-4 by using a crystal violet microtiter plate assay and relationships between structure and in vitro cytotoxic activity are discussed. The coordination of 2-iminocoumarins with copper(II) ions resulted in complexes 2a-h, 4a-b, and 6a-c with significant inhibitory properties toward tested tumor cell lines with IC₅₀ values ranging from 0.04 μM to 15.66 μM. In comparison to the free ligands L1a-h, L3a-b, and L5a-c, the newly prepared Cu(II) complexes often displayed increased activity. In the series of copper(II) complexes of 2-imino-2H-chromen-3-yl-1,3,5-triazines 2a-h the most potent compound 2g contained a 4-phenylpiperazine moiety at position 6 of the 1,3,5-triazine ring and an electron-donating diethylamino group at position 7' of the 2-iminocoumarin scaffold. Among the Cu(II) complexes of 3-(benzoxazol-2-yl)-2H-chromen-2-imines 4a-b and 3-(benzothiazol-2-yl)-2H-chromen-2-imines 6a-c the most active was benzoxazole-2-iminocoumarin 4b that also possessed a diethylamino group at position 7' of the 2-iminocoumarin moiety. Moreover, compound 4b was found to be the most prominent agent and displayed the higher potency than cisplatin against tested cell lines.

Riluzole-Rasagiline Hybrids: Toward the Development of Multi-Target-Directed Ligands for Amyotrophic Lateral Sclerosis

Polypharmacology is a new trend in amyotrophic lateral sclerosis (ALS) therapy and an effective way of addressing a multifactorial etiology involving excitotoxicity, mitochondrial dysfunction, oxidative stress, and microglial activation. Inspired by a reported clinical trial, we converted a riluzole (1)–rasagiline (2) combination into single-molecule multi-target-directed ligands. By a ligand-based approach, the highly structurally integrated hybrids 3–8 were designed and synthesized. Through a target- and phenotypic-based screening pipeline, we identified hit compound 6. It showed monoamine oxidase A (MAO-A) inhibitory activity (IC₅₀ = 6.9 μM) rationalized by in silico studies as well as in vitro brain permeability. By using neuronal and non-neuronal cell models, including ALS-patient-derived cells, we disclosed for 6 a neuroprotective/neuroinflammatory profile similar to that of the parent compounds and their combination. Furthermore, the unexpected MAO inhibitory activity of 1 (IC₅₀ = 8.7 μM) might add a piece to the puzzle of its anti-ALS molecular profile.

Biological Activity of Newly Synthesized Benzimidazole and Benzothizole 2,5-Disubstituted Furane Derivatives

Newly designed and synthesized cyano, amidino and acrylonitrile 2,5-disubstituted furane derivatives with either benzimidazole/benzothiazole nuclei have been evaluated for antitumor and antimicrobial activity. For potential antitumor activity, the compounds were tested in 2D and 3D cell culture methods on three human lung cancer cell lines, A549, HCC827 and NCI-H358, with MTS cytotoxicity and BrdU proliferation assays in vitro. Compounds 5, 6, 8, 9 and 15 have been proven to be compounds with potential antitumor activity with high potential to stop the proliferation of cells. In general, benzothiazole derivatives were more active in comparison to benzimidazole derivatives. Antimicrobial activity was evaluated with Broth microdilution testing (according to CLSI (Clinical Laboratory Standards Institute) guidelines) on Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Additionally, Saccharomyces cerevisiae was included in testing as a eukaryotic model organism. Compounds 5, 6, 8, 9 and 15 showed the most promising antibacterial activity. In general, the compounds showed antitumor activity, higher in 2D assays in comparison with 3D assays, on all three cell lines in both assays. In natural conditions, compounds with such an activity profile (less toxic but still effective against tumor growth) could be promising new antitumor drugs. Some of the tested compounds showed antimicrobial activity. In contrast to ctDNA, the presence of nitro group or chlorine in selected furane-benzothiazole structures did not influence the binding mode with AT-DNA. All compounds dominantly bound inside the minor groove of AT-DNA either in form of monomers or dimer and higher-order aggregates.

Hybrid Materials Based on Magnetic Iron Oxides with Benzothiazole Derivatives: A Plausible Potential Spectroscopy Probe

Rare diseases affect a small part of the population, and the most affected are children. Because of the low availability of patients for testing, the pharmaceutical industry cannot develop drugs for the diagnosis of many of these orphan diseases. In this sense, the use of benzothiazole compounds that are highly selective and can act as spectroscopy probes, especially the compound 2-(4'-aminophenyl)benzothiazole (ABT), has been highlighted. This article reports the design of potential contrast agents based on ABT and iron to develop a new material with an efficient mechanism to raise the relaxation rate, facilitating diagnosis. The ABT/δ-FeOOH hybrid material was prepared by grafting (N-(4'-aminophenyl) benzothiazole-2-bromoacetamide) on the surface of the iron oxyhydroxide particles. FTIR spectra confirmed the material formations of the hybrid material ABT/δ-FeOOH. SEM analysis checked the covering of nanoflakes' surfaces in relation to the morphology of the samples. The theoretical calculations test a better binding mode of compound with iron oxyhydroxide. Theoretical findings show the radical capture mechanism in the stabilization of this new material. In this context, Fe³⁺ ions are an electron acceptor from the organic phase.

Importance of Fluorine in Benzazole Compounds

Fluorine-containing heterocycles continue to receive considerable attention due to their unique properties. In medicinal chemistry, the incorporation of fluorine in small molecules imparts a significant enhancement their biological activities compared to non-fluorinated molecules. In this short review, we will highlight the importance of incorporating fluorine as a basic appendage in benzothiazole and benzimidazole skeletons. The chemistry and pharmacological activities of heterocycles containing fluorine during the past years are compiled and discussed.

New Treatments in Renal Cancer: The AhR Ligands

Kidney cancer rapidly acquires resistance to antiangiogenic agents, such as sunitinib, developing an aggressive migratory phenotype (facilitated by c-Metsignal transduction). The Aryl hydrocarbon receptor (AhR) has recently been postulated as a molecular target for cancer treatment. Currently, there are two antitumor agent AhR ligands, with activity against renal cancer, that have been tested clinically: aminoflavone (AFP 464, NSC710464) and the benzothiazole (5F 203) prodrug Phortress. Our studies investigated the action of AFP 464, the aminoflavone pro-drug currently used in clinical trials, and 5F 203 on renal cancer cells, specifically examining their effects on cell cycle progression, apoptosis and cell migration. Both compounds caused cell cycle arrest and apoptosis but only 5F 203 potently inhibited the migration of TK-10, Caki-1 and SN12C cells as well as the migration signal transduction cascade, involving c-Met signaling, in TK-10 cells. Current investigations are focused on the development of nano-delivery vehicles, apoferritin-encapsulated benzothiazoles 5F 203 and GW610, for the treatment of renal cancer. These compounds have shown improved antitumor effects against TK-10 cells in vitro at lower concentrations compared with a naked agent.

Bar Adsorptive Microextraction Coated with Carbon-based Phase Mixtures for Performance-Enhancement to Monitor Selected Benzotriazoles, Benzothiazoles, and Benzenesulfonamides in Environmental Water Matrices

: In the present work we propose, for the first time, bar adsorptive microextraction coated with carbon-based phase mixtures, followed by microliquid desorption and high performance liquid chromatography-diode array detection (BAμE-μLD/HPLC-DAD) analysis, to enhance the performance of the determination of traces of benzotriazoles (BTRs), benzothiazoles (BTs), and benzenesulfonamide derivatives (BSDs) in environmental water matrices. Assessing six carbon-based sorbents (CA1, CN1, B test EUR, SX PLUS, SX 1, and R) with different selectivity properties allowed us to tailor the best phase mixture (R, 12.5%/CN1, 87.5%) that has convenient porosity, texture, and surface chemistry (pHPZC,mix ~6.5) for trace analysis of benzenesulfonamide, 1-hydroxybenzotriazole, 1H-benzotriazole, 5-methyl-1H-benzotriazole, benzothiazole, and 1,3-benzothiazol-2-ol chemicals in aqueous media. Optimized experimental conditions provided average recoveries ranging from 37.9% to 59.2%, appropriate linear dynamic ranges (5.0 to 120.0 µg L-1; r2 ≥ 0.9964), limits of detection between 1.0 and 1.4 μg L-1, and good precisions (relative standard deviation (RSD) ≤ 9.3%). The proposed methodology (BAμE(R, 12.5%/CN1, 87.5%)-μLD/HPLC-DAD) also proved to be a suitable sorption-based static microextraction alternative to monitor traces of BTRs, BTs, and BSDs in rain, waste, tap, and estuarine water samples. From the data obtained, the proposed approach showed that the BAμE technique with the addition of lab-made devices allows users to adapt the technique to use sorbents or mixtures of sorbents with the best selectivity characteristics whenever distinct classes of target analytes occur simultaneously in the same application.

Investigations on the Anticancer Potential of Benzothiazole-Based Metallacycles

A series of 2-phenylbenzothiazole derivatives and their corresponding organometallic ruthenium(II) and osmium(II) complexes were synthesized, designed to exploit both, the attributes of the half-sandwich transition metal scaffold and the bioactivity spectrum of the applied 2-phenylbenzothiazoles. All synthesized compounds were characterized via standard analytical methods. The obtained organometallics showed antiproliferative activity in the low μM range and are thus at least an order of magnitude more potent than the free ligands. ESI-MS measurements showed that the examined compounds were stable in aqueous solution over 48 h. Additionally, their binding preferences to small biomolecules, their cellular accumulation and capacity of inducing apoptosis/necrosis were investigated. Based on the fluorescence properties of the selected ligand and the corresponding ruthenium complex, their subcellular distribution was studied by fluorescence microscopy, revealing a high degree of colocalization with acidic organelles of cancer cells.

Recent Advances in Synthesis of Benzothiazole Compounds Related to Green Chemistry

Benzothiazoles have played an important role in the field of biochemistry and medicinal chemistry due to their highly pharmaceutical and biological activity. The development of synthetic processes is undoubtedly one of the most significant problems facing researchers. In this review paper, we provided recent advances in the synthesis of benzothiazole compounds related to green chemistry from condensation of 2-aminobenzenethiol with aldehydes/ketones/acids/acyl chlorides and the cyclization of thioamide or carbon dioxide (CO2) as raw materials, and the future development trend and prospect of the synthesis of benzothiazoles were anticipated.

Experimental and Computational Study of the Antioxidative Potential of Novel Nitro and Amino Substituted Benzimidazole/Benzothiazole-2-Carboxamides with Antiproliferative Activity

We present the synthesis of a range of benzimidazole/benzothiazole-2-carboxamides with a variable number of methoxy and hydroxy groups, substituted with nitro, amino, or amino protonated moieties, which were evaluated for their antiproliferative activity in vitro and the antioxidant capacity. Antiproliferative features were tested on three human cancer cells, while the antioxidative activity was measured using 1,1-diphenyl-picrylhydrazyl (DPPH) free radical scavenging and ferric reducing antioxidant power (FRAP) assays. Trimethoxy substituted benzimidazole-2-carboxamide 8 showed the most promising antiproliferative activity (IC₅₀ = 0.6–2.0 µM), while trihydroxy substituted benzothiazole-2-carboxamide 29 was identified as the most promising antioxidant, being significantly more potent than the reference butylated hydroxytoluene BHT in both assays. Moreover, the latter also displays antioxidative activity in tumor cells. The measured antioxidative capacities were rationalized through density functional theory (DFT) calculations, showing that 29 owes its activity to the formation of two [O•∙∙∙H–O] hydrogen bonds in the formed radical. Systems 8 and 29 were both chosen as lead compounds for further optimization of the benzazole-2-carboxamide scaffold in order to develop more efficient antioxidants and/or systems with the antiproliferative activity.

An overview of structurally diversified anticonvulsant agents

There are several limited approaches to treat epilepsy in hospitals, for example, using medicines, surgery, electrical stimulation and dietary interventions. Despite the availability of all these new and old approaches, seizure is particularly difficult to manage. The quest for new antiepileptic molecules with more specificity and less CNS toxicity continues for medicinal chemists until a new and ideal drug arrives. This review covers new antiseizure molecules of different chemical classes, the exact mode of action of which is still unidentified. Newer agents include sulfonamides, thiadiazoles, semi- and thiosemicarbazones, pyrrolidine-2,5-diones, imidazoles, benzothiazoles and amino acid deriva tives. These new chemical entities can be useful for the design and development of forthcoming antiseizure agents.

Preparation of Benzothiazolyl-Decorated Nanoliposomes

Amyloid β (Aβ) species are considered as potential targets for the development of diagnostics/therapeutics towards Alzheimer’s disease (AD). Nanoliposomes which are decorated with molecules having high affinity for Aβ species may be considered as potential carriers for AD theragnostics. Herein, benzothiazolyl (BTH) decorated nanoliposomes were prepared for the first time, after synthesis of a lipidic BTH derivative (lipid-BTH). The synthetic pathway included acylation of bis(2-aminophenyl) disulfide with palmitic acid or palmitoyl chloride and subsequent reduction of the oxidized dithiol derivative. The liberated thiols were able to cyclize to the corresponding benzothiazolyl derivatives only after acidification of the reaction mixture. Each step of the procedure was monitored by HPLC analysis in order to identify all the important parameters for the formation of the BTH-group. Finally, the optimal methodology was identified, and was applied for the synthesis of the lipid-BTH derivative. BTH-decorated nanoliposomes were then prepared and characterized for physicochemical properties (size distribution, surface charge, physical stability, and membrane integrity during incubation in presence of buffer and plasma proteins). Pegylated BTH-nanoliposomes were demonstrated to have high integrity in the presence of proteins (in comparison to non-peglated ones) justifying their further exploitation as potential theragnostic systems for AD.

Design of Aminobenzothiazole Inhibitors of Rho Kinases 1 and 2 by Using Protein Kinase A as a Structure Surrogate

We describe the design, synthesis, and structure-activity relationships (SARs) of a series of 2-aminobenzothiazole inhibitors of Rho kinases (ROCKs) 1 and 2, which were optimized to low nanomolar potencies by use of protein kinase A (PKA) as a structure surrogate to guide compound design. A subset of these molecules also showed robust activity in a cell-based myosin phosphatase assay and in a mechanical hyperalgesia in vivo pain model.

Discovery of Thiazole Based Bis Heterocyclic System for Anti- Inflammatory Potential

BACKGROUND

We have developed a new series of 36 substituted thiazole derivatives prepared via reaction of substituted benzothiazole-2-amine with substituted phenacyl bromide.

OBJECTIVE

This study was aimed to develop and successfully evaluate anti-inflammatory activity of substituted thiazole derivatives.

METHOD

A new series of 36 substituted thiazole derivatives was synthesized and derivatives were characterized by analytical and spectrometric methods like IR, MS, and 1H NMR. The molecular docking was performed for all the synthesized thiazole derivatives to assess their binding affinities to COX-2 isozyme. The best compounds from docking study were subjected for their anti-inflammatory activity by using rat hind paw edema method.

RESULTS

Results from carrageenan-induced hind paw edema showed that compounds 3h, 5a, 5e, 9d, and 9h possess significant anti-inflammatory activity. The result from vascular permeability indicating inhibition of vascular permeability with compounds 3h and 9h is significant and results from cotton pellet granuloma formation models show greater degree of inhibition with compounds 3h and 5a to contribute to their significant anti-inflammatory activity.

CONCLUSION

This study provides successful development of novel thiazole derivatives. Their binding affinities to COX-2 enzyme were also confirmed, indicating that developed molecules are comparable to diclofenac and hence could be promising anti-inflammatory agents.

Copper(II)- and gold(III)-mediated cyclization of a thiourea to a substituted 2-aminobenzothiazole

Benzothiazole derivatives are a class of privileged molecules due to their biological activity and pharmaceutical applications. One route to these molecules is via intramolecular cyclization of thioureas to form substituted 2-aminobenzothiazoles, but this often requires harsh conditions or employs expensive metal catalysts. Herein, the copper(II)- and gold(III)-mediated cyclizations of thioureas to substituted 2-aminobenzothiazoles are reported. The single-crystal X-ray structures of the thiourea N-(3-methoxyphenyl)-N'-(pyridin-2-yl)thiourea, C₁₃H₁₃N₃OS, and the intermediate metal complexes aquabis[5-methoxy-N-(pyridin-2-yl-κN)-1,3-benzothiazol-2-amine-κN³]copper(II) dinitrate, [Cu(C₁₃H₁₁N₃OS)₂(H₂O)](NO₃)₂, and bis{2-[(5-methoxy-1,3-benzothiazol-2-yl)amino]pyridin-1-ium} dichloridogold(I) chloride monohydrate, (C₁₃H₁₂N₃OS)₂[AuCl₂]Cl·H₂O, are reported. The copper complex exhibits a distorted trigonal-bipyramidal geometry, with direct metal-to-benzothiazole-ligand coordination, while the gold complex is a salt containing the protonated uncoordinated benzothiazole, and offers evidence that metal reduction (in this case, Au^III to Au^I) is required for the cyclization to proceed. As such, this study provides further mechanistic insight into the role of the metal cations in these transformations.

Synthesis, Molecular Properties Estimations, and Dual Dopamine D2 and D3 Receptor Activities of Benzothiazole-Based Ligands

Neurleptic drugs, e.g., aripiprazole, targeting the dopamine D_2S and D₃ receptors (D_2SR and D₃R) in the central nervous system are widely used in the treatment of several psychotic and neurodegenerative diseases. Therefore, a new series of benzothiazole-based ligands (3-20) was synthesized by applying the bioisosteric approach derived from the selective D₃Rs ligand BP-897 (1) and its structurally related benz[d]imidazole derivative (2). Herein, introduction of the benzothiazole moiety was well tolerated by D_2SR and D₃R binding sites leading to antagonist affinities in the low nanomolar concentration range at both receptor subtypes. However, all novel compounds showed lower antagonist affinity to D₃R when compared to that of 1. Further exploration of different substitution patterns at the benzothiazole heterocycle and the basic 4-phenylpiperazine resulted in the discovery of high dually acting D_2SR and D₃R ligands. Moreover, the methoxy substitution at 2-position of 4-phenylpiperazine resulted in significantly (22-fold) increased D_2SR binding affinity as compared to the parent ligand 1, and improved physicochemical and drug-likeness properties of ligands 3-11. However, the latter structural modifications failed to improve the drug-able properties in ligands having un-substituted 4-phenylpiperazine analogs (12-20). Accordingly, compound 9 showed in addition to high dual affinity at the D_2SR and D₃R [K_i (hD_2SR) = 2.8 ± 0.8 nM; K_i (hD₃R) = 3.0 ± 1.6 nM], promising clogS, clogP, LE (hD_2SR, hD₃R), LipE (hD_2SR, hD₃R), and drug-likeness score values of −4.7, 4.2, (0.4, 0.4), (4.4, 4.3), and 0.7, respectively. Also, the deaminated analog 10 [K_i (hD_2SR) = 3.2 ± 0.4 nM; K_i (hD₃R) = 8.5 ± 2.2 nM] revealed clogS, clogP, LE (hD_2SR, hD₃R), LipE (hD_2SR, hD₃R) and drug-likeness score values of −4.7, 4.2, (0.4, 0.4), (3.9, 3.5), and 0.4, respectively. The results observed for the newly developed benzothiazole-based ligands 3-20 provide clues for the diversity in structure activity relationships (SARs) at the D_2SR and D₃R subtypes.

Green ultrasound-assisted three-component click synthesis of novel 1H-1,2,3-triazole carrying benzothiazoles and fluorinated-1,2,4-triazole conjugates and their antimicrobial evaluation

The present study describes an efficient and ecofriendly, ultrasound, one-pot click cycloaddition approach for the construction of a novel series of 1,4-disubstituted-1,2,3-triazoles tethered with fluorinated 1,2,4-triazole-benzothiazole molecular conjugates. It involved three-component condensation of the appropriate bromoacetamide benzothiazole, sodium azide and 4-alkyl/aryl-5-(2-fluorophenyl)-3-(prop-2-ynylthio)-1,2,4-triazoles 4a-e through a Cu(I)-catalyzed 1,3-dipolar cycloaddition reaction. This approach involves in situ generation of azidoacetamide benzothiazole, followed by condensation with terminal alkynes in the presence of CuSO4/Na-ascorbate in aqueous DMSO under both conventional and ultrasound conditions. Some of the designed 1,2,3-triazole conjugates 6a-o were recognized for their antimicrobial activity against some bacterial and fungal pathogenic strains.

Synthesis, ADMET Properties, and Biological Evaluation of Benzothiazole Compounds Targeting Chemokine Receptor 2 (CXCR2)

Herein we describe the synthesis and biological evaluation of a series of novel benzothiazoles based on a diaryl urea scaffold previously reported in some allosteric chemokine receptor 2 (CXCR2) inhibitors. From a library of 41 new compounds, 17 showed significant inhibition of CXCR2, with IC₅₀ values less than 10 μm and selectivity over CXCR4. Our ADMET simulations suggest favorable drug-like properties for the active compounds. Importantly, we developed a predictive model that can distinguish active from inactive compounds; this will serve as a valuable tool to guide the design of optimized compounds to be evaluated in preclinical models.

Discovery of a Nanomolar Multikinase Inhibitor (KST016366): A New Benzothiazole Derivative with Remarkable Broad-Spectrum Antiproliferative Activity

Herein we report the discovery of compound 6 [KST016366; 4-((2-(3-(4-((4-ethylpiperazin-1-yl)methyl)-3-(trifluoromethyl)phenyl)ureido)benzo[d]thiazol-6-yl)oxy)picolinamide] as a new potent multikinase inhibitor through minor structural modification of our previously reported RAF kinase inhibitor A. In vitro anticancer evaluation of 6 showed substantial broad-spectrum antiproliferative activity against 60 human cancer cell lines. In particular, it showed GI50 values of 51.4 and 19 nm against leukemia K-562 and colon carcinoma KM12 cell lines, respectively. Kinase screening of compound 6 revealed its nanomolar-level inhibitory activity of certain oncogenic kinases implicated in both tumorigenesis and angiogenesis. Interestingly, 6 displays IC50 values of 0.82, 3.81, and 53 nm toward Tie2, TrkA, and ABL-1 (wild-type and T315I mutant) kinases, respectively. Moreover, 6 is orally bioavailable with a favorable in vivo pharmacokinetic profile. Compound 6 may serve as a promising candidate for further development of potent anticancer chemotherapeutics.

Benzothiazole Amphiphiles Ameliorate Amyloid β-Related Cell Toxicity and Oxidative Stress

Oxidative stress from the increase of reactive oxygen species in cells is a common part of the normal aging process and is accelerated in patients with Alzheimer's disease (AD). Herein, we report the evaluation of three benzothiazole amphiphiles (BAMs) that exhibit improved biocompatibility without loss of biological activity against amyloid-β induced cell damage compared to a previously reported hexa(ethylene glycol) derivative of benzothiazole aniline (BTA-EG6). The reduced toxicity of these BAM agents compared to BTA-EG6 corresponded with their reduced propensity to induce membrane lysis. In addition, all of the new BAMs were capable of protecting differentiated SH-SY5Y neuroblastoma cells from toxicity and concomitant oxidative stress induced by AD-related aggregated Aβ (1-42) peptides. Binding and microscopy studies support that these BAM agents target Aβ and inhibit the interactions of catalase with Aβ in cells, which, in turn, can account for an observed inhibition of Aβ-induced increases in hydrogen peroxide in cells treated with these compounds. These results support that this family of benzothiazole amphiphiles may have therapeutic potential for treating cellular damage associated with AD and other Aβ-related neurologic diseases.

Comparison of experimental and DFT-calculated NMR chemical shifts of 2-amino and 2-hydroxyl substituted phenyl benzimidazoles, benzoxazoles and benzothiazoles in four solvents using the IEF-PCM solvation model

A comparative study of experimental and calculated NMR chemical shifts of six compounds comprising 2-amino and 2-hydroxy phenyl benzoxazoles/benzothiazoles/benzimidazoles in four solvents is reported. The benzimidazoles showed interesting spectral characteristics, which are discussed. The proton and carbon chemical shifts were similar for all solvents. The largest chemical shift deviations were observed in benzene. The chemical shifts were calculated with density functional theory using a suite of four functionals and basis set combinations. The calculated chemical shifts revealed a good match to the experimentally observed values in most of the solvents. The mean absolute error was used as the primary metric. The use of an additional metric is suggested, which is based on the order of chemical shifts. The DP4 probability measures were also used to compare the experimental and calculated chemical shifts for each compound in the four solvents. Copyright © 2015 John Wiley & Sons, Ltd.

coli

The resistance-nodulation-division (RND) family efflux pumps are important in the antibiotic resistance of Gram-negative bacteria. However, although a number of bacterial RND efflux pump inhibitors have been developed, there has been no clinically available RND efflux pump inhibitor to date. A set of BSN-coded 2-substituted benzothiazoles were tested alone and in combinations with ciprofloxacin (CIP) against the AcrAB-TolC overexpressor Escherichia coli AG102 clinical strain. The results indicated that the BSN compounds did not show intrinsic antimicrobial activity when tested alone. However, when used in combinations with CIP, a reversal in the antibacterial activity of CIP with up to 10-fold better MIC values was observed. In order to describe the binding site features of these BSN compounds with AcrB, docking studies were performed using the CDocker method. The performed docking poses and the calculated binding energy scores revealed that the tested compounds BSN-006, BSN-023, and BSN-004 showed significant binding interactions with the phenylalanine-rich region in the distal binding site of the AcrB binding monomer. Moreover, the tested compounds BSN-006 and BSN-023 possessed stronger binding energies than CIP, verifying that BSN compounds are acting as the putative substrates of AcrB.

baumannii

RND family efflux pumps are important for multidrug resistance in Gram-negative bacteria. To date no efflux pump inhibitors for clinical use have been found, so developing the specific inhibitors of this pump system will be beneficial for the treatment of infections caused by these multidrug-resistant pathogens. A set of BSN-coded 2-substituted benzothiazoles were tested alone and in combination with ciprofloxacin (CIP) against the RND family efflux pump AdeABC overexpressor Acinetobacter baumannii SbMox-2 strain. The results indicated that the BSN compounds did not have antimicrobial activity when tested alone. However, if they were applied in combination with CIP, it was observed that the antibiotic had antimicrobial activity against the tested pathogen, possessing a minimum inhibitory concentration value that could be utilized in clinical treatment. A 3D-common features pharmacophore model was applied by using the HipHop method and the generated pharmacophore hypothesis revealed that the hydrogen bond acceptor property of nitrogen in the thiazole ring and the oxygen of the amide substituted at the second position of the benzothiazole ring system were significant for binding to the target protein. Moreover, three hydrophobic aromatic features were found to be essential for inhibitory activity.

EGFR tyrosine kinase targeted compounds: in vitro antitumor activity and molecular modeling studies of new benzothiazole and pyrimido[2,1-b]benzothiazole derivatives

In this study, we illustrate computer aided drug design of new benzothiazole and pyrimido[2,1-b]benzothiazole derivatives as epidermal growth factor receptor tyrosine kinase (EGFR-TK) inhibitors. Compounds 1-5 were screened at NCI, USA, for antitumor activity against non-small cell lung cancer (NCI-H522), colon cancer (HCT-116, HCT-15 and HT29) and breast cancer (MDA-MB-468 and MDA-MB-231/ATCC) cell lines in which EGFR is overexpressed in varying levels. Results indicated that these compounds are more potent antitumor agents compared to erlotinib against HT29 and MDA-MB-231/ATCC cell lines. Compound 3 showed GI50 value of 22.3 nM against NCI-H522 cell line, while erlotinib exhibited GI50 value of 1 µM against the same cell line. In addition, these compounds were studied for their EGFR tyrosine kinase inhibitory activity. Virtual screening utilizing molecular modeling and QSAR techniques enabled the understanding of the pharmacophoric requirements for antitumor activity. Docking the designed compounds into the ATP binding site of EGFR-TK domain was done to predict the analogous binding mode of these compounds to the EGFR-TK inhibitors.

Identification of benzothiazole derivatives and polycyclic aromatic hydrocarbons as aryl hydrocarbon receptor agonists present in tire extracts

Leachate from rubber tire material contains a complex mixture of chemicals previously shown to produce toxic and biological effects in aquatic organisms. The ability of these leachates to induce Ah receptor (AhR)-dependent cytochrome P4501A1 expression in fish indicated the presence of AhR active chemicals, but the responsible chemicals and their direct interaction with the AhR signaling pathway were not examined. Using a combination of AhR-based bioassays, we have demonstrated the ability of tire extract to stimulate both AhR DNA binding and AhR-dependent gene expression and confirmed that the responsible chemicals were metabolically labile. The application of CALUX (chemical-activated luciferase gene expression) cell bioassay-driven toxicant identification evaluation not only revealed that tire extract contained a variety of known AhR-active polycyclic aromatic hydrocarbons but also identified 2-methylthiobenzothiazole and 2-mercaptobenzothiazole as AhR agonists. Analysis of a structurally diverse series of benzothiazoles identified many that could directly stimulate AhR DNA binding and transiently activate the AhR signaling pathway and identified benzothiazoles as a new class of AhR agonists. In addition to these compounds, the relatively high AhR agonist activity of a large number of fractions strongly suggests that tire extract contains a large number of physiochemically diverse AhR agonists whose identities and toxicological/biological significances are unknown.