Synthesis and in vitro evaluation of new benzothiazole derivatives as schistosomicidal agents

Design, Synthesis and Biological Activities of (Thio)Urea Benzothiazole Derivatives

(Thio)ureas ((T)Us) and benzothiazoles (BTs) each have demonstrated to have a great variety of biological activities. When these groups come together, the 2-(thio)ureabenzothizoles [(T)UBTs] are formed, improving the physicochemical as well as the biological properties, making these compounds very interesting in medicinal chemistry. Frentizole, bentaluron and methabenzthiazuron are examples of UBTs used for treatment of rheumatoid arthritis and as wood preservatives and herbicides in winter corn crops, respectively. With this antecedent, we recently reported a bibliographic review about the synthesis of this class of compounds, from the reaction of substituted 2-aminobenzothiazoles (ABTs) with iso(thio)cyanates, (thio)phosgenes, (thio)carbamoyl chlorides, 1,1'-(thio)carbonyldiimidazoles, and carbon disulfide. Herein, we prepared a bibliographic review about those features of design, chemical synthesis, and biological activities relating to (T)UBTs as potential therapeutic agents. This review is about synthetic methodologies generated from 1968 to the present day, highlighting the focus to transform (T)UBTs to compounds containing a range substituents, as illustrated with 37 schemes and 11 figures and concluded with 148 references. In this topic, the scientists dedicated to medicinal chemistry and pharmaceutical industry will find useful information for the design and synthesis of this interesting group of compounds with the aim of repurposing these compounds.

New N-acyl Thiourea Derivatives: Synthesis, Standardized Quantification Method and In Vitro Evaluation of Potential Biological Activities

New N-acyl thiourea derivatives with heterocyclic rings have been synthesized by first obtaining isothiocyanate, which further reacted with a heterocyclic amine, characterized by (FT-IR, NMR spectroscopy and FT-ICR) and tested for their in vitro antimicrobial, anti-biofilm and antioxidant activities to obtain a drug candidate in a lead-optimization process. From the tested compounds, those bearing benzothiazole (1b) and 6-methylpyridine (1d) moieties revealed anti-biofilm activity against E. coli ATCC 25922 at MBIC values of 625 µg/mL. Compound 1d exhibited the highest antioxidant capacity (~43%) in the in vitro assay using 1,1-diphenyl-2-picrylhydrazyl (DPPH). Considering the in vitro results, the highest anti-biofilm and antioxidant activities were obtained for compound 1d. Therefore, a reversed-phase high-performance liquid chromatography (RP-HPLC) method has been optimized and validated for the quantitative determination of compound 1d. The detection and quantitation limits were 0.0174 μg/mL and 0.0521 μg/mL, respectively. The R² correlation coefficient of the LOQ and linearity curves were greater than 0.99, over the concentration range of 0.05 μg/mL-40 μg/mL. The precision and accuracy of the analytical method were within 98-102%, confirming that the method is suitable for the quantitative determination of compound 1d in routine quality control analyses. Evaluating the results, the promising potential of the new N-acyl thiourea derivatives bearing 6-methylpyridine moiety will be further investigated for developing agents with anti-biofilm and antioxidant activities.

Multi technique investigation on interaction between 5-(2-thiazolylazo)-2,4,6-triaminopyrimidine and HSA and BSA

In research laboratories and in various industries, azo compounds are among the most effective and commonly used organic dyes. The association between human (HSA) and bovine (BSA) serum albumins with 5-(2-thiazolylazo)-2,4,6-triaminopyrimidine (TTP) was investigated in this research using spectroscopy methods and molecular modeling study. The fluorescence quenching results showed that the quenching mechanisms were static and dynamic processes for HSA and BSA, respectively. From the thermodynamic observations, it is clear that the binding process is a spontaneous molecular interaction, in which van der Waals and hydrogen bonding interactions for HSA and hydrophobic interaction for BSA play the major roles. According to Förster energy transfer, non-radiative energy transferred from HSA and BSA to TTP, is provided by close distance (r₀) between TTP and Trp residues of HSA and BSA. The synchronous fluorescence spectroscopy, FT-IR findings and UV-Vis absorption data confirm that TTP can induce conformational and micro environmental changes in both the proteins. Furthermore, docking results predicted the probable binding site of TTP in subdomain IIA of HSA and BSA molecules where Trp residues are located. Types of amino acid residues surrounding the TTP molecule supported that van der Waals forces, hydrophobic forces and electrostatic forces play important roles in stabilization of drug-protein complexes formed.Communicated by Ramaswamy H. Sarma.

Computational Study of Benzothiazole Derivatives for Conformational, Thermodynamic and Spectroscopic Features and Their Potential to Act as Antibacterials

Benzothiazole analogs are very interesting due to their potential activity against several infections. In this research, five benzothiazole derivatives were studied using density functional theory calculations. The optimized geometry, geometrical parameters and vibrational spectra were analyzed. The charge distribution diagrams, such as FMO (HOMO-LUMO), energies of HOMO-LUMO, polarizability, hyperpolarizability, MESP and density of states, were calculated. The computed energies of HOMO and LUMO showed that the transfer of charge occurred within the compound. The effect of the change of substituents on the ring on the value of the HOMO-LUMO energy gap was also observed. It was observed that, in this series, compound 4 with CF3 substituent had the lowest energy gap of HOMO-LUMO, and compound 5 with no substituent had highest HOMO-LUMO energy gap. From the energies of HOMO and LUMO, the reactivity descriptors, such as electron affinity (A), ionization potential (I), chemical softness (σ), chemical hardness (ƞ), electronic chemical potential (μ), electrophilicity index (ω), were calculated. In addition, the 13C and 1H NMR chemical shifts of the molecules were calculated using the gauge-independent atomic orbit (GIAO) method; the shifts were in good agreement with the experimental values. The anti-bacterial potential of compounds 1 to 5 was tested by molecular docking studies toward target proteins 2KAU and 7EL1 from Klebsiella aerogenes and Staphylococcus aureus. Compounds 3 and 1 showed high affinity toward 2KAU and 7EL1, respectively.

Benzothiazoles from Condensation of o-Aminothiophenoles with Carboxylic Acids and Their Derivatives: A Review

Nowadays, organic chemists are interested in the field of heterocyclic chemistry due to its use in the synthesis of a great variety of biologically active compounds. Heterocyclic compounds are widely found in nature and are essential for life. Among these, some natural nitrogen containing heterocyclic compounds have been used as chemotherapeutic agents. Their attachment to sugar molecules either as thioglycosides or as nucleosides analogues plays an important role in vital biological processes as well as in synthetic organic chemistry. Molecules containing benzothiazole (BT) nuclei are of this interesting class of compounds because some of them have been found to have a wide variety of biological activities. In this sense, we selected this topic to review and to then summarize the procedures related to the condensation reactions of o-aminothiophenoles (ATPs) as well as their disulfides with carboxylic acids, esters, orthoesters, acyl chlorides, amides, and nitriles. The condensation reactions with carbon dioxide (CO₂) are included. Conventional methods with the use of acid and metal catalysts as well as recent green techniques, such as microwave irradiation, the use of ionic liquids, and ultrasound (US) chemistry, which have proven to have many advantages, were found in the review.

Design, synthesis and evaluation of benzothiazole derivatives as multifunctional agents

Oxidative stress is the product or aetiology of various multifactorial diseases; on the other hand, the development of multifunctional compounds is a recognized strategy for the control of complex diseases. To this end, a series of benzothiazole derivatives was synthesized and evaluated for their multifunctional effectiveness as antioxidant, sunscreen (filter), antifungal and antiproliferative agents. Compounds were easily synthesized via condensation reaction between 2-aminothiophenols and different benzaldehydes. SAR study, particularly in position 2 and 6 of benzothiazoles, led to the identification of 4g and 4k as very interesting potential compounds for the design of multifunctional drugs. In particular, compound 4g is the best blocker of hERG potassium channels expressed in HEK 293 cells exhibiting 60.32% inhibition with IC₅₀ = 4.79 μM.

Synthesis, molecular docking, binding free energy calculation and molecular dynamics simulation studies of benzothiazol-2-ylcarbamodithioates as Staphylococcus aureus MurD inhibitors

A new series of benzothiazol-2-ylcarbamodithioate functional compounds 5a-f has been designed, synthesized and characterized by spectral data. These compounds were screened for their in vitro antibacterial activity against strains of Staphylococcus aureus (NCIM 5021, NCIM 5022 and methicillin-resistant isolate 43300), Bacillus subtilis (NCIM 2545), Escherichia coli (NCIM 2567), Klebsiella pneumoniae (NCIM 2706) and Psudomonas aeruginosa (NCIM 2036). Compounds 5a and 5d exhibited significant activity against all the tested bacterial strains. Specifically, compounds 5a and 5d showed potent activity against K. pneumoniae (NCIM 2706), while compound 5a also displayed potent activity against S. aureus (NCIM 5021). Compound 5d showed minimum IC₅₀ value of 13.37 μM against S. aureus MurD enzyme. Further, the binding interactions of compounds 5a-f in the catalytic pocket have been investigated using the extra-precision molecular docking and binding free energy calculation by MM-GBSA approach. A 30 ns molecular dynamics simulation of 5d/modeled S. aureus MurD enzyme was performed to determine the stability of the predicted binding conformation.

In vitro activity, ultrastructural studies and in silico pharmacokinetic properties of indol-3-yl-thiosemicarbazones derivatives and analogues against juvenile and adult worms of S. mansoni

The present work aimed to carry out in vitro biological assays of indol-3-yl derivatives thiosemicarbazones (2a-e) and 4-thiazolidinones (3a-d) against juvenile and adult worms of S. mansoni, as well as the in silico determination of pharmacokinetic parameters for the prediction of the oral bioavailability of these derivatives. All compounds were initially screened at a concentration of 200 μM against S. mansoni adult worms and the results evidenced the good activity of compounds 2b, 2d and 3b, which caused 100% mortality after 24, 48 and 72 h, respectively. Subsequent studies with these same compounds revealed that compound 2b was able to reduce the viability of the parasites by 85% and 83% at concentrations of 200 and 100 μM, respectively. In relation to the juvenile worms, all compounds (2b, 2d and 3b) were able to cause mortality, but compound 2b demonstrated better activity causing 100% mortality in 48 h. Additionally, it was possible to observe reduction in the viability of juvenile worms of 85%, 81% and 64% at concentrations of 200, 100 and 50 μM, respectively. Several ultrastructural damages were observed when adult and juvenile S. mansoni worms were exposed to compound 2b (200 μM) that was characterized by extensive destruction by the integument, which may justify the mortality rate of cultured parasites. In the DNA interaction assay, fragmentation of the genetic material of adult worms when treated with compound 2b (200 μM) was evidenced, indicating the apoptosis process as mechanism of parasite death. Regarding pharmacokinetic properties, all derivatives are according to the required parameters, predicting good oral bioavailability for the studied compounds. The results presented in this study reveal the good activity of compound 2b in both adult and juvenile worms of S. mansoni, pointing this compound as promising in the development of further studies on schistosomicidal activity.

Inhibition of cervical cancer cell metastasis by benzothiazole through up-regulation of E-cadherin expression

The present study was aimed to investigate the effect of benzothiazole on the invasive and metastasis potential of HeLa DH cervical cancer cells and the underlying mechanism. HeLa DH cervical cells were cultured with 5, 10, 15, 20, 25 and 30 μM concentrations of benzothiazole for 48 h. Benzothiazole treatment did not induce any cytotoxic effect on HeLa DH cells after 48 h of incubation. The results from wound healing assay revealed that migration potential of HeLa DH cells was reduced to 4% on treatment with 20 μM concentration of benzithiazole compared to 99% in the control cells. The invasion potential of HeLa DH cells was reduced to 13% on treatment with 20 μM concentration of benzithiazole. Inhibition of HeLa DH cell migration was also significantly (p < 0.002) higher in the benzithiazole treated cell cultures compared to the control cells. HeLa DH cervical cancer cells on treatment with various concentrations of benzithiazole for 48 h showed a significant (p < 0.05) increase in the expression of E-cadherin in a dose dependent manner. Among the various concentrations of benzithiazole used, western blot assay revealed that the increase in E-cadherin was maximum at 20 μM. Analysis of the levels of mRNA corresponding to E-cadherin by RT-qPCR showed significant increase in HeLa DH cervical cancer cells on treatment with 20 μM concentration of benzithiazole. Thus benzithiazole treatment suppresses the invasive and metastasis potential of HeLa DH cervical cells through upregulation of E-cadherin expression. Therefore, benzithiazole has a potential to be used for the treatment of cervical cancer.

A novel platinum(ii) anticancer complex of danysl bis(2-benzothiazolylmethyl)amine with dimethyl sulfoxide as a leaving group: synthesis, cytotoxicity, interaction with DNA and human serum albumin

A novel mononuclear platinum(ii) anticancer complex of danysl bis(2-benzothiazolylmethyl)amine with a dimethyl sulfoxide as a leaving group was reported.

Novel benzothiazine-piperazine derivatives by peptide-coupling as potential anti-proliferative agents

In an attempt to develop potential and selective anti-proliferative agents, a series of novel benzothiazine-piperazine derivatives 8a-i and 10a-g were synthesized by coupling of 2H-1,4-benzothiazin-3(4H)-one with various amines 7a-i and 9a-g in excellent yields and evaluated for their in vitro anti-proliferative activity against four cancer cell lines, HeLa (cervical), MIAPACA (pancreatic), MDA-MB-231 (breast) and IMR32 (neuroblastoma). In vitro inhibitory activity indicated that compounds 8a, 8d, 8g, 10a, 10b, 10e, 10f were found to be good anti-proliferative agents. Among them the derivatives 8g, 10e and 10f were found to be the most active members exhibiting remarkable growth inhibitory activity. Molecular docking was undertaken to investigate the probable binding mode and key active site interactions in HDAC8 and EHMT2 proteins. The docking results are complementary to the experimental results.

A Green Ultrasound Synthesis, Characterization and Antibacterial Evaluation of 1,4-Disubstituted 1,2,3-Triazoles Tethering Bioactive Benzothiazole Nucleus

The synthesis of N-(benzo[d]thiazol-2-yl)-2-(4-substituted-1H-1,2,3-triazol-1-yl)acetamides 5a–r via the 1,3-dipolar cycloaddition reaction between 2-azido-N-(benzo[d]thiazol-2-yl)acetamide derivatives 3a–c and different alkynes were performed in the presence and absence of ultrasound irradiation. The synthesis was carried out using t-BuOH/H₂O (1:1, v/v) as reaction solvents and CuSO₄·5H₂O/sodium ascorbate as the catalyst. The copper catalyst was implemented to provide the regioselective 1,4-disubstituted 1,2,3-triazoles 5a–r. Significant reductions in reaction times with comparably higher yields were observed when the reactions were carried out under ultrasound irradiation. The structures of the newly synthesized 1,2,3-triazoles were elucidated by IR, NMR, MS, and elemental analyses. They were also screened for their antimicrobial activity against three gram-positive (Streptococcus pneumonia, Bacillus subtilis, and Staphylococcus aureus), three gram-negative (Pseudomonasaeuroginosa, Escherichia coli, and Klebsiella pneumonia), and two fungal strains (Aspergillus fumigates and Candida albicans). Most of the tested compounds displayed promising antimicrobial activities at a Minimum Inhibition Concentration (MIC) of 4–16 μg/mL.

Novel benzothiazole based sulfonylureas/sulfonylthioureas: design, synthesis and evaluation of their antidiabetic potential

Twenty-eight benzothiazole based sulfonylureas/sulfonylthioureas were synthesized and were found to be effective against diabetes as PPAR-γ agonists.

Efficient and convenient synthesis of pyrido [2,1-b]benzothiazole, pyrimidopyrido[2,1-b]benzothiazole and benzothiazolo[3,2-a][1,8]naphthyridine derivatives

New 3-aryl-pyrido[2,1-b][1,3]benzothiazole derivatives 2a–e were synthesized in excellent yields via the reaction of benzothiazoleacetonitrile (1) with different aromatic aldehydes. The treatment of 2-(benzo[d]thiazol-2-yl)-3-(pyridin-4-yl)acrylonitrile (6) with malononitrile afforded 1-amino-3-(pyridin-4-yl)-3H-pyrido[2,1-b][1,3]benzothiazole-2,4-dicarbonitrile (7), which was allowed to react with a variety of reagents to provide pyrimido[5′,4′:5,6]pyrido[2,1-b][1,3]benzothiazole 8, 9 and [1,3]benzothiazolo[3,2-a][1,8]naphthyridine 10, 15 derivatives. All synthesized products were confirmed by elemental analysis, IR, 1H-NMR, 13C-NMR, and mass spectral data.

Design, facile synthesis and anthelmintic activity of new O-substituted 6-methoxybenzothiazole-2-carbamates

Hypothesis for designing 6-substituted benzothiazolecarbamate prototype anthelmintics having diversities in flexibility and rigidity of substituents with different polar nature and hydrophilic–lipophilic properties.

DFT study of conformational and vibrational characteristics of 2-(2-hydroxyphenyl)benzothiazole molecule

The conformational and IR and Raman spectral studies of 2-(2-hydroxyphenyl)benzothiazole have been carried out by using the DFT method at the B3LYP/6-311++G(**) level. The detailed vibrational assignments have been done on the basis of calculated potential energy distributions. Comparative studies of molecular geometries, atomic charges and vibrational fundamentals of all the conformers have been made. There are four possible conformers for this molecule. The optimized geometrical parameters obtained by B3LYP/6-311++G(**) method showed good agreement with the experimental X-ray data. The atomic polar tensor (APT) charges, Mulliken atomic charges, natural bond orbital (NBO) analysis and HOMO-LUMO energy gap of HBT and its conformers were also computed.

DFT simulation, quantum chemical electronic structure, spectroscopic and structure-activity investigations of 2-benzothiazole acetonitrile

The Fourier transform infrared and FT-Raman spectra of 2-benzothiazole acetonitrile (BTAN) have been recorded in the range 4000-450 and 4000-100 cm(-1) respectively. The conformational analysis of the compound has been carried out to obtain the stable geometry of the compound. The complete vibrational assignment and analysis of the fundamental modes of the compound are carried out using the experimental FTIR and FT-Raman data and quantum chemical studies. The experimental vibrational frequencies are compared with the wavenumbers derived theoretically by B3LYP gradient calculations employing the standard 6-31G(**), high level 6-311++G(**) and cc-pVTZ basis sets. The structural parameters, thermodynamic properties and vibrational frequencies of the normal modes obtained from the B3LYP methods are in good agreement with the experimental data. The (1)H (400 MHz; CDCl3) and (13)C (100 MHz;CDCl3) nuclear magnetic resonance (NMR) spectra are also recorded. The electronic properties, the energies of the highest occupied and lowest unoccupied molecular orbitals are measured by DFT approach. The kinetic stability of the molecule has been determined from the frontier molecular orbital energy gap. The charges of the atoms and the structure-chemical reactivity relations of the compound are determined by its chemical potential, global hardness, global softness, electronegativity, electrophilicity and local reactivity descriptors by conceptual DFT methods. The non-linear optical properties of the compound have been discussed by measuring the polarisability and hyperpolarisability tensors.

Design, synthesis and mode of action of some benzothiazole derivatives bearing an amide moiety as antibacterial agents

Schematic outline of the most potent compound, benzothiazole bearing amide moiety A07, showing antibacterial activity and its mode of action.

Recent advances in the synthesis of 2-substituted benzothiazoles: a review

Recent advances in various synthetic protocols of 2-substituted benzothiazole derivatives.

Efficient synthesis of 2-amino-6-arylbenzothiazoles via Pd(0) Suzuki cross coupling reactions: potent urease enzyme inhibition and nitric oxide scavenging activities of the products

In general, benzothiazole derivatives have attracted great interest due to their pharmaceutical and biological importance. New 2-amino-6-arylbenzothiazoles were synthesized in moderate to excellent yields via Suzuki cross coupling reactions using various aryl boronic acids and aryl boronic acid pinacol esters and the antiurease and nitric oxide (NO) scavenging activity of the products were also examined. The most active compound concerning urease enzyme inhibition was 6-phenylbenzo[d]thiazole-2-amine 3e, with an IC₅₀ value of 26.35 µg/mL. Compound 3c, 6-(4-methoxyphenyl) benzo[d]thiazole-2-amine, exhibited the highest nitric oxide percentage scavenging at 100 µg/mL.

Synthesis and Antimicrobial Evaluation of a New Series ofN-1,3-Benzothiazol-2-ylbenzamides

Enterococcus faecalisis a Gram-positive commensal inhabitant of the intestinal tract of humans, animals, and insects. However, it is also an opportunistic pathogen and has emerged as a leading cause of hospital-acquired extraintestinal infections. Fluoroquinolones have been frequently used to treatE. faecalisinfections, and the emergence of fluoroquinolone-resistantE. faecalisstrains has recently been reported in several countries. Thus, the identifications of new antibiotics specifically directed toE. faecalismay be envisaged. In this paper, a new series ofN-1,3-benzothiazol-2-ylbenzamides have been designed, synthesized, and evaluated for theirin vitroantimicrobial activities. Among the tested compounds,3iwas active againstE. faecalis.

Exploration of Newer Possibilities to the Synthesis of Diazepine and Quinoline Carboxylic Acid Derivatives

Heterocyclic systems containing benzothiazoles, carbazole (and azacarbazole) moieties have attracted the attention of chemists owing to these nuclei having been identified in the literature as most promising pharmacophores in drug design and synthesis. Based on these observations, it could be anticipated that incorporation of the bioactive azepine moiety and quinoline moiety into the molecular framework of benzothiazoles fused to carbazole (and azacarbazoles) could produce interesting series of compounds9–12with enhanced biological activities, whose structure was unequivocally established from its microanalyses and spectral data.

2-(5-Chloro-1,3-benzothia-zol-2-yl)-4-meth-oxy-phenol

In the mol-ecule of the title compound, C(14)H(10)ClNO(2)S, the dihedral angle between the almost planar benzothia-zole ring system [maximum deviation = 0.005 (2) Å] and the benzene ring is 1.23 (9)°. The conformation of the mol-ecule is stabilized by an intra-molecular O-H⋯N hydrogen bond, forming an S(6) ring motif. In the crystal, mol-ecules are linked into layers parallel to the ac plane by C-H⋯O hydrogen bonds and π-π stacking inter-actions [centroid-centroid distance = 3.7365 (12) Å].

5-Chloro-2-phenyl-1,3-benzothiazole

In the structure of the title compound, C₁₃H₈ClNS, the dihedral angle between the benzothia­zole ring system and the phenyl ring is 7.11 (8)°. In the crystal, mol­ecules are arranged parallel to the c axis.

Schistosoma mansoni: In vitro schistosomicidal activity of piplartine

Schistosomiasis is one of the world's greatly neglected tropical diseases, and its control is largely dependent on a single drug, praziquantel. Here, we report the in vitro effect of piplartine, an amide isolated from Piper tuberculatum (Piperaceae), on Schistosoma mansoni adult worms. A piplartine concentration of 15.8 μM reduced the motor activity of worms and caused their death within 24h in a RPMI 1640 medium. Similarly, the highest sub-lethal concentration of piplartine (6.3 μM) caused a 75% reduction in egg production in spite of coupling. Additionally, piplartine induced morphological changes on the tegument, and a quantitative analysis carried out by confocal microscopy revealed an extensive tegumental destruction and damage in the tubercles. This damage was dose-dependent in the range of 15.8-630.2 μM. At doses higher than 157.6 μM, piplartine induced morphological changes in the oral and ventral sucker regions of the worms. It is the first time that the schistosomicidal activity has been reported for piplartine.