Enhancing Action of Positive Allosteric Modulators through the Design of Dimeric Compounds.

The present study describes the identification of highly potent dimeric 1,2,4-benzothiadiazine 1,1-dioxide (BTD)-type positive allosteric modulators of the AMPA receptors (AMPApams) obtained by linking two monomeric BTD scaffolds through their respective 6-positions. Using previous X-ray data from monomeric BTDs cocrystallized with the GluA2 ligand-binding domain (LBD), a molecular modeling approach was performed to predict the preferred dimeric combinations. Two 6,6-ethylene-linked dimeric BTD compounds (16 and 22) were prepared and evaluated as AMPApams on HEK293 cells expressing GluA2o( Q) (calcium flux experiment). These compounds were found to be about 10,000 times more potent than their respective monomers, the most active dimeric compound being the bis-4-cyclopropyl-substituted compound 22 [6,6'-(ethane-1,2-diyl)bis(4-cyclopropyl-3,4-dihydro-2 H-1,2,4-benzothiadiazine 1,1-dioxide], with an EC50 value of 1.4 nM. As a proof of concept, the bis-4-methyl-substituted dimeric compound 16 (EC50 = 13 nM) was successfully cocrystallized with the GluA2o-LBD and was found to occupy the two BTD binding sites at the LBD dimer interface.

Synthesis and characterisation of neem leaf extract, 2, 3-dehydrosalanol and quercetin dihydrate mediated silver nano particles for therapeutic applications.

The utility of green silver nanoparticles (AgNPs) in veterinary medicine is steadily increasing as they have many therapeutic applications against pathogens and arthropods of livestock. In this study, green AgNPs using neem (N-AgNPs), 2,3-dehydrosalanol (2,3-DHS-AgNPs) and quercetin dihydrate (QDH-AgNPs) were synthesised and characterised. Synthesised compounds were characterised by UV-Vis spectroscopy and the peak absorbance was recorded at 370 nm for neem extract. For N-AgNPs, 2,3-DHS-AgNPs and QDH-AgNPs, the maximum absorbance peaks were at 430, 230 and 220 nm, respectively. The FTIR analysis confirmed the synthesis of green AgNPs. The XRD pattern of N-AgNPs showed the peaks corresponding to whole spectra of 2 θ values ranging from 10-80. The relatively higher intensity of (111, 222) planes in face centred cubic crystalline structure supports the formation of synthesised AgNPs. In DLS analysis, the hydrodynamic diameter of neem leaf extract was found to be 259.8 nm, followed by 5.3, 6.7 and 261.8 nm for 2,3-DHS-AgNPs, N-AgNPs and QDH-AgNPs, respectively. Based on the transmission electron microscopy and scanning electron microscopy image analyses, confirmed the formation of N-AgNPs, 2,3-DHS-AgNPs and QDH-AgNPs. These eco-friendly phyto-AgNPs may be of use as an effective alternative to chemical control methods against the arthropods of livestock.

Insight into the structural requirements of benzothiadiazine scaffold-based derivatives as hepatitis C virus NS5B polymerase inhibitors using 3D-QSAR, molecular docking and molecular dynamics.

Hepatitis C virus (HCV) infection is a significant world health threat with frequently ineffective problem existed in the present treatment, thus representing a major unmet medical need. The nonstructural viral protein 5B (NS5B), one of the best-studied polymerase, has emerged as an attractive target for the development of novel therapeutics against hepatitis C virus. In this work, both ligand- and receptor- based three-dimensional quantitative structure activity relationship (3D-QSAR) studies were carried out using comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) techniques on 360 benzothiadiazine scaffold-based derivatives as HCV GT-1b NS5B polymerase allosteric inhibitors. The resultant optimum 3D-QSAR model exhibited R(2)(ev) of 0.54, R(2)(nev) of 0.72 and the predictive ability was validated by using an independent test set of 90 compounds which gave R(2)(pred) value of 0.64. In addition, docking analysis and molecular dynamics simulation (MD) were also applied to elucidate the probable binding modes of these inhibitors at the allosteric site of the enzyme. Interpretation of the 3D contour maps in context of the topology of the allosteric binding site of NS5B provided insight into NS5B-inhibitor interactions. The information obtained from this work can be utilized to accurately predict the binding affinity of related analogues and also facilitate the future rational design of novel inhibitors with improved activity.

Anti-tubercular agents. Part 5: synthesis and biological evaluation of benzothiadiazine 1,1-dioxide based congeners.

In an effort to discover new and effective chemotherapeutic agents from this laboratory for the treatment of tuberculosis, here in we describe the synthesis and biological evaluation of a series of novel benzothiadiazine 1,1-dioxide (BTD) based congeners by using rifampicin, streptomycin; ciprofloxacin and amphotericin as positive controls. Further, to understand structural requirements for exploring the structure activity relationship of BTDs, cytotoxicity and in vivo study of recently reported potent molecule 4 (MIC = 1 microg/mL) is also discussed.

Chloro-substituted 3-alkylamino-4H-1,2,4-benzothiadiazine 1,1-dioxides as ATP-sensitive potassium channel activators: impact of the position of the chlorine atom on the aromatic ring on activity and tissue selectivity.

The synthesis of 5-chloro-, 6-chloro-, and 8-chloro-substituted 3-alkylamino/cycloalkylamino-4H-1,2,4-benzothiadiazine 1,1-dioxides is described. Their inhibitory effect on the insulin releasing process and their vasorelaxant activity was compared to that of previously reported 7-chloro-3-alkylamino/cycloalkylamino-4H-1,2,4-benzothiadiazine 1,1-dioxides. "5-Chloro" compounds were found to be essentially inactive on both the insulin-secreting and the smooth muscle cells. By contrast, "8-chloro" and "6-chloro" compounds were found to be active on insulin-secreting cells, with the "6-chloro" derivatives emerging as the most potent drugs. Moreover, the "6-chloro" analogues exhibited less myorelaxant activity than their "7-chloro" counterparts. 8-Chloro-3-isopropylamino-4H-1,2,4-benzothiadiazine 1,1-dioxide (25b) and 6-chloro-3-cyclobutylamino-4H-1,2,4-benzothiadiazine 1,1-dioxide (19e) were further identified as K(ATP) channel openers by radioisotopic measurements conducted on insulin-secreting cells. Likewise, current recordings on HEK293 cells expressing human SUR1/Kir6.2 channels confirmed the highly potent activity of 19e (EC(50) = 80 nM) on such types of K(ATP) channels. The present work indicates that 6-chloro-3-alkylamino/cycloalkylamino-4H-1,2,4-benzothiadiazine 1,1-dioxides appear to be more attractive than their previously described 7-chloro-substituted analogues as original drugs activating the SUR1/Kir6.2 K(ATP) channels.

Inhibitors of HCV NS5B polymerase: synthesis and structure-activity relationships of N-alkyl-4-hydroxyquinolon-3-yl-benzothiadiazine sulfamides.

Substituted N-alkyl-4-hydroxyquinolon-3-yl-benzothiadiazine sulfamides were investigated as inhibitors of genotype 1 HCV polymerase. Structure-activity relationship patterns for this class of compounds are discussed.

2,1,3-Benzothiadiazine derivatives: synthesis and screening versus PDE4 enzyme.

A series of N-1,3 disubstituted 2,1,3-benzothiadiazine derivatives (BTDs) were synthesized and evaluated for their inhibitory activity versus enzymatic isoform PDE4 extracted from U937 cell line. Some of the tested compounds showed a high PDE4 inhibitory activity at 100 microM and the IC(50) value of the most interesting terms were evaluated. The structure-activity relationships of these compounds showed that the 3,5-di-tert-butyl-4-hydroxybenzyl moiety at N-1 position is important to obtain activity at micromolar level as previously reported. For the same compounds the antioxidant activity were evaluated highlighting 14 as the most significative one. The introduction of other bulky substituents in N-1 position is detrimental.

Formation of bound residues of 8-hydroxybentazon by oxidoreductive catalysts in soil.

This study was performed to determine which oxidoreductive catalysts were most efficient in catalyzing the binding of 8-hydroxybentazon to soil humic substances. 8-Hydroxybentazon was completely transformed by an oxidoreductive enzyme, laccase of Myceliophthora thermophila, at pH 3.0-7.0 within 30 min. When abiotic catalysts, manganese(IV), iron(III), and aluminum oxides were used in the same pH range, 8-hydroxybentazon was completely transformed only by manganese(IV) oxide (delta-MnO2), but a relatively small amount of 8-hydroxybentazon was transformed by iron(III) oxide and aluminum oxide. The adsorption of 8-hydroxybentazon in the soil showed an H-type and coincided well with the Langmuir isotherm. To better understand the factors involved in the rapid and strong binding of 8-hydroxybentazon with soil humic substances, 8-hydroxybentazon transformation by oxidoreductive catalysts was studied in various soil conditions: air-dried, preincubated, sterilized, and iron(III) oxide and manganese(IV) oxide free. 8-Hydroxybentazon was completely transformed within 24 h in the decreasing order of preincubated, air-dried, and sterilized soils. However, little transformation was observed in the iron(III) oxide and manganese(IV) oxide free soils. These results suggest that the major catalyst responsible for the rapid and strong binding of 8-hydroxybentazon to soil humic substances is a metal oxide, manganese(IV) oxide, not a soil oxidoreductive enzyme.

(S)-2,3-dihydro-[3,4]cyclopentano-1,2,4-benzothiadiazine-1,1-dioxide: (S18986-1) a positive modulator of AMPA receptors enhances (S)-AMPA-mediated [3H]noradrenaline release from rat hippocampal and frontal cortex slices.

The present study describes the effect of (S)-2,3-dihydro-[3, 4]cyclopentano-1,2,4-benzothiadiazine-1,1-dioxide (S18986-1), a positive allosteric modulator of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors with cognitive-enhancing effects, on (S)-AMPA-induced [3H]noradrenaline release in rat hippocampal and frontal cortex slices. (S)-AMPA significantly increased [3H]noradrenaline release in rat hippocampus and frontal cortex slices, whereas S18986-1 (3-1000 microM) alone, was inactive. However, S18986-1 between 30 and 1000 microM potently enhanced (+200%) (S)-AMPA-mediated [3H]noradrenaline release in both hippocampal and frontal cortex slices. The capacity of S18986-1 to potentiate [3H]noradrenaline release was specific for AMPA receptors as S18986-1 failed to potentiate either kainate and N-methyl-D-aspartate (NMDA)-mediated release of [3H]noradrenaline in rat hippocampal slices. Moreover, 1, 2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide (NBQX) and 1-(4-aminophenyl)-3-methylcarbamoyl-4-methyl-3, 4-dihydro-7,8-methylenedioxy-5H-2,3-benzodiazepine (GYKI-53655) but not (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5, 10-imine ((+)-MK-801), inhibited (S)-AMPA and S18986-induced stimulation of (S)-AMPA-mediated [3H]noradrenaline release. In addition, S18986-1-induced stimulation of (S)-AMPA-evoked [3H]noradrenaline release was markedly attenuated in the presence of tetrodotoxin (1 microM) and in Ca(2+)-free buffer. S18986-1 enhanced (S)-AMPA-mediated [3H]noradrenaline release to a greater extent than its corresponding (R)-enantiomer S19024-1 and racemic mixture S17951-1. However, positive allosteric modulators of AMPA receptors such as aniracetam failed to potentiate AMPA-mediated noradrenaline release in hippocampal slices, whereas cyclothiazide potently enhanced (S)-AMPA-mediated [3H]noradrenaline release. These results suggest that the capacity of S18986-1 to enhance AMPA receptor-mediated release of noradrenaline in rat hippocampus and frontal cortex, could contribute to the cognition enhancing mechanisms of S18986-1.

Benzyl derivatives of 2,1,3-benzo- and benzothieno[3,2-a]thiadiazine 2,2-dioxides: first phosphodiesterase 7 inhibitors.

The synthesis of a new family of benzyl derivatives of 2,1,3-benzo- and benzothieno[3,2-a]thiadiazine 2,2-dioxides was achieved. The biological data revealed the first heterocyclic family of compounds with PDE 7 inhibitory properties appearing to be a new objective for the treatment of T-cell-dependent disorders. The IC(50) values or percent inhibition values of the compounds against PDE 7 were calculated by testing them against human recombinant PDE 7 expressed in S. cerevisiae. In this expression system the only cyclic nucleotide hydrolyzing activity present in cell extracts corresponded to human PDE 7. Isoenzyme selectivity PDE 7 versus PDE 4 and PDE 3 was also measured. Considering simultaneously inhibition of the three different isoenzymes, monobenzyl derivatives 15 and 23 showed interesting PDE 7 potency (around 10 microM); although not statistically significant, a trend toward selectivity with respect to PDE 3 and PDE 4 was obtained. Benzothiadiazine 16, although less potent at PDE 7 (IC(50) = 25 microM), also showed a trend of selectivity toward PDE 3 and PDE 4. These compounds are considered the best leads for further optimization.