Novel antiallergic and antiinflammatory agents. Part I: Synthesis and pharmacology of glycolic amide derivatives

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.

2-Mercapto Benzothiazole Derivatives: As Potential Leads for the Diabetic Management

BACKGROUND

Results of our previous studies on antiglycation activity, and the noncytotoxicity of 2-mercapto benzothiazoles, encouraged us to further widen our investigation towards the identification of leads against diabetes mellitus.

METHODS

33 derivatives of 2-mercapto benzothiazoles 1-33 were evaluated for in vitro α- glucosidase inhibitory activity. Mode of inhibition was deduced by kinetic studies. To predict the interactions of 2-mercapto benzothiazole derivatives 1-33 with the binding pocket of α-glucosidase enzyme, molecular docking studies were performed on the selected inhibitors.

RESULTS

Compounds 2-4, 6-7, 9-26, 28 and 30 showed many folds potent α-glucosidase inhibitory activity in the range of IC50 = 31.21-208.63 μM, as compared to the standard drug acarbose (IC50 = 875.75 ± 2.08 μM). It was important to note that except derivative 28, all other derivatives were also found previously to have antiglycating potential in the range of IC50 = 187.12-707.21 μM.

CONCLUSION

A number of compounds were identified as dual nature as antiglycating agent and α- glucosidase inhibitors. These compounds may serve as potential lead candidates for the management of diabetes mellitus.

Synthesis of tert-butyl (substituted benzamido)phenylcarbamate derivatives: anti-inflammatory activity and docking studies

A series of new tert-butyl 2-(substituted benzamido) phenylcarbamate (4a-4j) were synthesized by the condensation of tert-butyl 2-amino phenylcarbamate (3) with various substituted carboxylic acid in the presence of EDCI and HOBt as coupling reagent, obtain in excellent yields. The structures of all newly synthesized compounds were characterized spectroscopically and evaluated for in vivo anti-inflammatory activity compared to the standard drug, indomethacin, by using the carrageenan-induced rat paw edema protocol. Most of the compounds exhibited a promising anti-inflammatory activity within 9 to 12 h, the percentage of inhibition values ranging from 54.239 to 39.021%. The results revealed that the compounds 4i and 4a exhibited better or equivalent anti-inflammatory activity with the percentage of inhibition of 54.239 and 54.130%, respectively, which was comparable to standard drug. In addition to experimental results, in silico docking studies was used as a tool to verify and expand the experimental outcomes.

2-Arylaminobenzothiazole-arylpropenone conjugates as tubulin polymerization inhibitors

A new series of 2-arylaminobenzothiazole-arylpropenone conjugates 5-6(a-r) was designed, synthesized and investigated for their cytotoxic potency against the various human cancer cell lines. Most of these conjugates exhibited cytotoxic activity and inhibited in vitro tubulin polymerization effectively. Conjugates 5d and 6d cause cell cycle blocks in the G2/M phase in HeLa cells and treatments with 5d and 6d manifested increased mRNA and protein levels of the G2/M marker, cyclin B1. Immunocytochemistry revealed loss of intact microtubule structure in cells treated with 5d and 6d. Western blot analysis revealed that these conjugates accumulate more tubulin in the soluble fraction. Moreover, the triggering of apoptotic cell death after mitotic arrest was investigated by studying their effect on Hoechst staining, mitochondrial membrane potential, ROS generation.

Asymmetric synthesis of amino-benzothiazol derivatives by additions of 2-lithiated benzothiazoles to (S)-N-t-butylsulfinyl-ketimines

We reported the asymmetric Mannich reactions between lithium-benzothiazoles and (S)-N-tert-butanesulfinylketimines, which gave unknown type of amino-benzothiazol derivatives of high pharmaceutical potential with up to 96% yields and 99 : 1 diastereoselectivities.

4-[(4-Acetylphenyl)amino]-2-methylidene-4-oxobutanoic acid

In the title compound, C₁₃H₁₃NO₄, the N—C(=O) bond length of 1.354 (2) Å is indicative of amide-type resonance. The dihedral angle between the mean planes of the benzene ring and oxo­amine group is 36.4 (3)°, while the mean plane of the 2-methyl­idene group is inclined by 84.2 (01)° from that of the oxo­amine group. In the crystal, classical O—H⋯O hydrogen bonds formed by the carb­oxy­lic acid groups and weak N—H⋯O weak inter­actions formed by the amide groups and supported by weak C—H⋯O inter­actions between the 2-methyl­idene, phenyl and acetyl groups with the carb­oxy­lic acid, oxo­amine and acetyl O atoms, together link the mol­ecules into dimeric chains along [010]. The O—H⋯O hydrogen bonds form R₂²(8) graph-set motifs.

4-[(4-Bromophenyl)amino]-2-methylidene-4-oxobutanoic acid

In the title compound, C11H10BrNO3, two independent molecules (AandB) crystallize in the asymmetric unit. The dihedral angles between the mean planes of the 4-bromophenyl ring and amide group are 24.8 (7) in moleculeAand 77.1 (6)° in moleculeB. The mean plane of the methylidene group is further inclined by 75.6 (4) in moleculeAand 72.5 (6)° in moleculeBfrom that of the amide group. In the crystal, N—H...O hydrogen bonds formed by amide groups and O—H...O hydrogen bonds formed by carboxylic acid groups are observed and supported additionally by weak C—H...O interactions between the methylidene and amide groups. Together, these link the molecules into chains of dimers along [110] and formR22(8) graph-set motifs.

FT-IR, HF and DFT structural, vibrational analysis of 5-chloro-3-(2-(4-ethylpiperazin-1-yl)-2-oxoethyl)benzo[d]thiazol-2(3H)-one molecule

The optimized molecular geometry, vibrational frequencies, atomic charges, dipole moment, rotational constants and several thermodynamic parameters of 5-chloro-3-(2-(4-ethylpiperazin-1-yl)-2-oxoethyl)benzo[d]thiazol-2(3H)-one (abbreviated as CEOT) molecule in the ground state were calculated using ab initio Hartree-Fock (HF) and Density Functional B3LYP methods (DFT) with 6-311++G(d,p), 6-311G(d,p), 6-31++G(d,p) and 6-31G(d,p) basis sets. The Fourier-transform infrared (FT-IR) spectrum of CEOT has been recorded in the region 4000-400 cm(-1). The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FT-IR spectrum. Energy gap of the molecule was found using HOMO and LUMO calculation, hence the less band gap, which seems to be more stable. The observed and calculated vibrational frequencies are found to be in good agreement.

Anti-infective and herbicidal activity of N-substituted 2-aminobenzothiazoles

In this study, a series of N-substituted 2-aminobenzothiazoles was prepared according to a recently developed method. Twelve compounds were tested for their activity related to the inhibition of photosynthetic electron transport (PET) in spinach (Spinacia oleracea L.) chloroplasts. Primary in vitro screening of the discussed compounds was also performed against fungal, bacterial and mycobacterial species. The biological activities of some compounds were comparable or higher than the standards phenoxymethylpenicillin or pyrazinamide. The most effective compounds demonstrated insignificant toxicity against the human monocytic leukemia THP-1 cell line. For all compounds, the structure-activity relationships are discussed.

Ab initio Hartree-Fock and density functional theory investigations on the conformational stability, molecular structure and vibrational spectra of 5-chloro-3-(2-(4-methylpiperazin-1-yl)-2-oxoethyl)benzo[d]thiazol-2(3H)-one drug molecule

In this work, the experimental and theoretical spectra of 5-chloro-3-(2-(4-methylpiperazin-1-yl)-2-oxoethyl)benzo[d]thiazol-2(3H)-one molecule (abbreviated as 5CMOT) are studied. The molecular geometry and vibrational frequencies are calculated in the ground state of molecule using ab initio Hartree-Fock (HF) and Density Function Theory (DFT) methods with 6-311++G(d,p), 6-31G++(d,p), 6-31G(d,p), 6-31G(d) and 6-31G basis sets. Three staggered stable conformers were observed on the torsional potential energy surfaces. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational modes calculated. The comparison of the theoretical and experimental geometries of the title compound indicated that the X-ray parameters fairly well agree with the theoretically obtained values for the most stable conformer. The theoretical results showed an excellent agreement with the experimental values. The calculated HOMO and LUMO energies show that the charge transfer occurs within the molecule.

Synthesis and antiproliferative evaluation of some new amidino-substituted bis-benzothiazolyl-pyridines and pyrazine

Novel diamidino substituted conformationally restricted derivatives of bis-benzothiazolyl-pyridines and pyrazine were synthesized and their antiproliferative activity against several human cancer cell lines were determinated. The synthetic approach used for preparation of isomeric amidinobenzotiazolyl disubstituted pyridines 3a-3k and pyrazine 3l was achieved by condenzation reaction of commercially available pyridine and pyrazine dicarboxylic acids with amidino- 2a and 2-imidazolinyl-substituted 2-aminothiophenol 2b in polyphosphoric acid in moderate to good yield. The condenzation reaction was greatly optimized. The targeted compounds were converted in the desired water soluble dihydrochloride salts by reaction of appropriate free base with concd HCl in ethanol or acetic acid. Antiproliferative assays revealed significant differences in antiproliferative activities of diamidino- and diimidazolinyl-derivatives, the latter exerting stronger concentration-dependent antiproliferative effects on tested tumor cell lines and thus being a prominent compound class for further chemical optimization and biological studies. Biological studies on SW620 cell line and BJ fibroblasts performed for the diimidazolinyl-derivative 3b revealed oxidative stress as a possible mechanism of antiproliferative action and predicted antineoplastic properties for this class of compounds.

Antiproliferative activity and cell cycle analysis of 2-(3,5-dihydroxyphenyl)-6-hydroxybenzothiazole on MCF-7 breast and HCT-15 colon cancer cell lines

The antiproliferative activity of 2-(3,5-Dihydroxyphenyl)-6-hydroxybenzothiazole (DHB) is reported here. DHB inhibits the growth of human colon cancer HCT-15 with a 50% cell growth inhibition value of 23 μM and breast cancer MCF-7 with a 50% cell growth inhibition value of 41 μM in a dose/time dependent manner by using sulforhodamine B assay. Cell cycle analysis by flow cytometry showed that DHB-induced growth arrest could be associated with apoptosis in both cell lines. Moreover, suppression of clonogenic activity occurs after exposure to DHB at a concentration of 25 μM for HCT-15 and of 40 μM for MCF-7.

Novel diamidino-substituted derivatives of phenyl benzothiazolyl and dibenzothiazolyl furans and thiophenes: synthesis, antiproliferative and DNA binding properties

A series of new diamidino-, diisopropylamidino-, and diimidazolinyl-substituted derivatives of phenyl benzothiazolyl and dibenzothiazolyl furans and thiophenes were successfully prepared and evaluated for their antiproliferative activity on tumor cell lines in vitro, DNA binding propensity, and sequence selectivity as well as cellular distribution. A strong antiproliferative effect of the tested compounds was observed on all tested cell lines in a concentration-dependent response pattern. In general, imidazolinyl-substituted derivatives and/or the thiophene core were in correlation with increased antiproliferative activity. Two compounds (2b and 3b) were chosen for biological studies due to their differential antiproliferative properties. The DNA binding properties of this new series of compounds were assessed and evidenced their efficient minor groove binding properties with preferential interaction at AT-rich sites. Both compounds also present nuclear subcellular localization, suggesting that their cellular mode of action implies localization in the DNA compartment and direct inhibition of DNA replication and induction of apoptosis.

Novel amidino substituted 2-phenylbenzothiazoles: synthesis, antitumor evaluation in vitro and acute toxicity testing in vivo

The efficient synthesis of new bis-substituted nitro-amidino, amino-amidino (10a, 10b-13a, 13b) and previously prepared diamidino 2-phenyl-benzothiazoles (9a, 9b) is described. The compounds 11a and 11b were prepared by recently developed methodology of the key precursors in zwitterionic form 8a and 8b with 4-nitrobenzoylchloride in a very good yield (70%). All compounds except diamidino-substituted 2-phenylbenzothiazole 9a show exceptionally prominent tumor cell-growth inhibitory activity and cytotoxicity, whereby the special selectivity of amino-amidine 2-phenylbenzothiazole 12a towards MCF-7 and H 460 cells makes this compound a prospective lead compound that should be further evaluated in animal models. All in vivo tested compounds (12a, 12b, 13a and 13b) are absorbed from mice gastrointestinal system. LD(50) are between 67.33 and 696.2mg/kg body weight (OECD/EPA toxicity categories 2-3).

Novel cyano- and amidinobenzothiazole derivatives: synthesis, antitumor evaluation, and X-ray and quantitative structure-activity relationship (QSAR) analysis

Synthesis of a series of novel cyano- and amidinobenzothiazole derivatives 3-31 is described. All studied amidino derivatives showed noticeable antiproliferative effect on several tumor cell lines. Cyano derivatives 11-17 showed considerably less pronounced activity because of their poor solubility in aqueous cell culture medium, which was confirmed by the principal components (PC) analysis. Compounds 21, 22, 28, and 29 were tested for their effects on the cell cycle and apoptosis, whereby 22 and 29, having methyl group at the C-6 position in pyridine ring, showed drastic cell cycle perturbations that were both concentration- and time-dependent and induced apoptosis. The QSAR modeling, based on the physicochemical descriptors and on the measured biological activities, indicated the relevance of molecular polarizability and particular distribution of pharmacophores on the molecular surface for activity. In conclusion, benzothiazoles containing either isopropylamidino or imidazolyl groups will be considered as starting compounds for further investigation on lead identification.