Design, synthesis and binding properties of novel and selective 5-HT3 and 5-HT4 receptor ligands

In-Silico Screening of Novel Synthesized Thienopyrimidines Targeting Fms Related Receptor Tyrosine Kinase-3 and Their In-Vitro Biological Evaluation

The present investigation describes the design strategy and synthesis of novel thienopyrimidine compounds in addition to their anticancer activity targeting tyrosine kinase FLT3 enzyme. The synthesized compounds were subjected to a cytotoxic study where compounds 9a and 9b showed the most potent cytotoxicity against HT-29, HepG-2, and MCF-7 cell lines reflected by their IC₅₀ values for 9a (1.21 ± 0.34, 6.62 ± 0.7 and 7.2 ± 1.9 μM), for 9b (0.85 ± 0.16, 9.11 ± 0.3 and 16.26 ± 2.3 μM) and better than that of reference standard which recorded (1.4 ± 1.16, 13.915 ± 2.2, and 8.43 ± 0.5 μM), respectively. Compounds’ selectivity to malignant cells was determined using selectivity assay, interestingly, all the tested compounds demonstrated an excellent selectivity index (SI) range from 20.2 to 99.7. Target in-silico prediction revealed the FLT3 kinase enzyme was the kinase enzyme of highest probability. Molecular docking studies were performed on the prepared compounds which showed promising binding affinity for FLT3 kinase enzyme and the main interactions between the synthesized ligands and kinase active site were similar to those between the co-crystallized ligand and the receptor. Further biological exploration was performed using in-vitro FLT3 kinase enzyme inhibition assay. The results showed that the 2-morpholinoacetamido derivative 10a exhibited highest FLT3 inhibitory activity among the tested compounds followed by compound 9a then 12. Pharmacokinetic assessment disclosed that all the investigated compounds were considered as “drug-like” molecules with promising bioavailability.

Synthesis and the biological evaluation of 2-benzenesulfonylalkyl-5-substituted-sulfanyl-[1,3,4]-oxadiazoles as potential anti-hepatitis B virus agents

Current treatments for chronic hepatitis B virus (HBV) infection include the use of interferon-alpha and of nucleoside analogs lamivudine, adefovir and entecavir. However, the use of interferon-alpha has many side effects while that of nucleosidic inhibitors can lead to the emergence of resistant viruses. Hence, new drugs for the treatment of HBV infection are still highly desired. Oxadiazoles have been observed to exhibit antiviral activities against RNA viruses. In this study, a facile synthesis of 2-benzenesulfonylalkyl-5-substituted-sulfanyl-[1,3,4]-oxadiazoles is reported. The compounds were then evaluated for their anti-HBV activity. 1-[2-[5-(1-Benzenesulfonyl-propyl)-[1,3,4]oxadiazol-2-yl-sulfanyl]-ethyl]-4-(2-methoxy-phenyl)-piperazine (1i) was able to inhibit the expression of the viral antigens, HBsAg and HBeAg in a concentration-dependent manner with no cytotoxic effects and without any effects on the expression of viral transcripts. Concentration- and time-dependent reductions in virion production were also observed. The inhibition of virion production was comparable to that of lamivudine and EC(50) values of 1.63 and 2.96 microM were obtained for compound 1i and lamivudine, respectively. Thus, in addition to the antiviral effects on RNA viruses, oxadiazoles also have anti-HBV activities.

Hydrophobic Molecular Similarity from MST Fractional Contributions to the Octanol/water Partition Coefficient

The use of a recently proposed hydrophobic similarity index for the alignment of molecules and the prediction of their differences in biological activity is described. The hydrophobic similarity index exploits atomic contributions to the octanol/water transfer free energy, which are evaluated by means of the fractional partitioning scheme developed within the framework of the Miertus-Scrocco-Tomasi continuum model. Those contributions are used to define global and local measures of hydrophobic similarity. The suitability of this computational strategy is examined for two series of compounds (ACAT inhibitors and 5-HT3 receptor agonists), which are aligned to maximize the global hydrophobic similarity using a Monte Carlo-simulated protocol. Indeed, the concept of local hydrophobic similarity is used to explore structure-activity relationships in a series of COX-2 inhibitors. Inspection of the 3D distribution of hydrophobic/hydrophilic contributions in the aligned molecules is valuable to identify regions of very similar hydrophobicity, which can define pharmacophoric recognition patterns. Moreover, low similar regions permit to identify structural elements that modulate the differences in activity between molecules. Finally, the quantitative relationships found between the pharmacological activity and the hydrophobic similarity index points out that not only the global hydrophobicity, but its 3D distribution, is important to gain insight into the activity of molecules.

Synthesis and binding properties of novel selective 5-HT3 receptor ligands

This work reports on the synthesis and affinities for the 5-HT(3) versus the 5-HT(4) receptor of new piperazinyl-substituted thienopyrimidine derivatives 20-45 with a view to identify potent and selective ligands for the 5-HT(3) receptor. Some of the new compounds show good affinity for the 5-HT(3) receptor and, notably, do not display any affinity for the 5-HT(4) receptor. 4-(4-Methyl-1-piperazinyl)-2-methylthio-6,7-dihydro-5H-cyclopenta[4,5]thieno[2,3-d]pyrimidine 31 exhibits the highest affinity for the 5-HT(3) receptor (Ki = 33 nM) and behaves as noncompetitive antagonist.

Potential antidepressant properties of IDN 5491 (hyperforin-trimethoxybenzoate), a semisynthetic ester of hyperforin

Hyperforin is one of the possible active principles mediating the antidepressant activity of Hypericum perforatum L. extracts. The ester derivative IDN 5491 (hyperforin-trimethoxybenzoate) showed antidepressant-like properties in the forced swimming test (FST) in rats, with no effect on open-field activity, when given as three intraperitoneal injections in 24 h at 3.125 and 6.25 mg/kg. The plasma concentrations of IDN 5491 were 30-50 microM, and those of hyperforin much lower but still close to those after effective doses of hyperforin-dicyclohexylammonium and Hypericum extract. This suggests that hyperforin plays a role in the antidepressant-like effect of the ester and of Hypericum extract. In vitro binding and uptake data showed that IDN 5491 is inactive on a wide panel of CNS targets at a concentration (14 microM) much higher than that measured in the brain of treated rats (0.3 microM). Like the extract, the antidepressant-like effect of IDN 5491 was blocked by (-)-sulpiride, a selective D2 receptor antagonist and by BD-1047, a selective sigma1 antagonist. Ex-vivo binding studies showed that brain sigma1 receptors are occupied after in vivo treatment with IDN 5491, possibly by an unknown metabolite or by endogenous ligand induced by hyperforin.

Combining NMR and molecular modelling in a drug delivery context: investigation of the multi-mode inclusion of a new NPY-5 antagonist bromobenzenesulfonamide into β-cyclodextrin

NMR spectroscopic and molecular modelling methods have been employed to describe the complexation of trans-N-4-[N'-(4-chlorobenzoyl)hydrazinocarbonyl]cyclohexylmethyl-4-bromobenzenesulfonamide, a new chemotype of NPY-5 antagonist, and beta-cyclodextrin, revealing the coexistence of two different kinds of 1:1 complexes where conformational changes of the guest compound with respect to the free state are also detected.

Combining molecular modeling with experimental methodologies: mechanism of membrane permeation and accumulation of ofloxacin

The interaction between ofloxacin, as a model drug of the fluoroquinolone class, and biomembranes was examined as the possible initial step in a transmembrane diffusion process. Dipalmitoylphosphatidylcholine was used for the preparation of biomembrane models. The influence of environmental conditions and protonation on molecular physicochemical behavior, and hence on the membrane interaction, was investigated by differential scanning calorimetry (DSC). This technique has been shown to be very effective in the interpretation of interactions of drug microspeciations with biomembranes. These findings suggest that the interaction occurred owing to ionic and hydrophobic forces showing how the passage through the membrane is mainly favored in the pH interval 6-7.4. It was demonstrated that a pH gradient through model membranes may be responsible for a poorly homogeneous distribution of ofloxacin (or other related fluoroquinolones), which justifies the in vivo accumulation properties of this drug. DSC experiments, which are in agreement with computational data, also showed that the complexing capability of ofloxacin with regard to Mg(++) or Ca(++) may govern the drug entrance into bacterial cells before the DNA Girase inhibition and could ensure the formation of hydrophobic and more fluid phospholipid domains on the surface of the model membrane. These regions are more permeable with regard to various solutes, as well as ofloxacin, allowing a so-called 'self-promoted entrance pathway'. The combination of experimental methodologies with computational data allowed a further rationalization of the results and opened new perspectives into the mechanism of action of ofloxacin, namely its interaction with lipid bilayers and drug-divalent cation complex formation, which might be extended to the entire fluoroquinolone class. Ofloxacin accumulation within Escherichia coli ATCC 25922 was measured as a function of time. Also in this example, the environmental conditions influenced ofloxacin penetration and accumulation. The in vitro experiments, reported here, show that a suitable balance of hydrophilic and hydrophobic fluoroquinolone properties needs to occur for there to be increased drug permeation.

Synthesis and molecular modeling of new 1-aryl-3-[4-arylpiperazin-1-yl]-1-propane derivatives with high affinity at the serotonin transporter and at 5-HT(1A) receptors

It has been proposed that 5-HT(1A) receptor antagonists augment the antidepressant efficacy of selective serotonin (5-HT) reuptake inhibitors. In a search toward new and efficient antidepressants, 1-(aryl)-3-[4-arylpiperazin-1-yl]-1-propane molecular hybrids were designed, synthesized, and evaluated for 5-HT reuptake inhibition and 5-HT(1A) receptor affinity. The design was based in coupling structural moieties related to inhibition of serotonin reuptake, such as benzo[b]thiophene derivatives to arylpiperazines, typical 5-HT(1A) receptor ligands. In binding studies, several compounds showed affinity at the 5-HT transporter and at 5-HT(1A) receptors. Molecular modeling studies predicted the pharmacophore elements required for high affinity binding and the features that enable to discriminate between agonist, partial agonist, or antagonist action at 5-HT(1A) receptors and 5-HT transporter inhibition. Solvent interactions in desolvation prior to the binding step along with enthalpy and enthropy compensations might be responsible to explain agonist, partial agonist, and antagonist character. Hydrogen-bonding capability seems to be important to break hydrogen interhelical hydrogen bonds or alternatively to form other bonds upon ligand binding. Partial agonists and antagonists are unable to do this as the full agonist, which interacts closely by long-range forces or directly. The compounds showing the higher affinity at both the 5-HT transporter (K(i) < 50 nM) and the 5-HT(1A) receptors (K(i) < 20 nM) were further explored for their ability to stimulate [(35)S]GTPgammaS binding or to antagonize 8-hydroxy-2-di-n-propylamino-tetralin (8-OH-DPAT)-stimulated [(35)]GTPgammaS binding to rat hippocampal membranes, an index of agonist/antagonist action at 5-HT(1A) receptors, respectively. Compound 8g exhibited agonist activity (EC(50) = 30 nM) in this assay, whereas compounds 7g and 8h,i behaved as weak partial agonists and 7h-j and 8j,l antagonized the R(+)-8-OH-DPAT-stimulated GTPgammaS binding. Functional characterization was performed by measuring the antagonism to 8-OH-DPAT-induced hypothermia in mice.