Balázs Balogh

Utility of cyclodextrins in the formulation of genistein. Part 1. Preparation and physicochemical properties of genistein complexes with native cyclodextrins

Isoflavones are suitable guest molecules for inclusion complex formation with cyclodextrins (CDs). The molecular encapsulation with CDs results in a solid, molecularly dispersed form and in a significantly improved aqueous solubility of isoflavones. Genistein, a key isoflavone constituent of Ononidis spinosae radix was found to form a supramolecular, non-covalent inclusion complex with both beta-cyclodextrin (beta-CD) and gamma-cyclodextrin (gamma-CD), while it did not form a stable complex with alpha-CD. The guest genistein was found to spatially located in the less polar cavity of cyclodextrin. The isolated binary genistein/CD complexes appeared novel crystalline lattices. The in vitro dissolution of genistein entrapped into both beta- and gamma-CD, significantly surpassed that of the plain isoflavone.

Semicarbazide-sensitive amine oxidase/vascular adhesion protein-1: a patent survey

Introduction: Vascular adhesion protein-1 (VAP-1)/semicarbazide-sensitive amine oxidase (SSAO) is an adhesion protein involved in leukocyte trafficking and inflammatory processes, with a special amine oxidase activity. Inhibitors have been mainly developed for treating chronic inflammatory disorders. The utility of inhibitors as antiangiogenic agents in ophthalmological and oncological diseases is currently under evaluation. SSAO substrates may mimic several insulin effects, although their utility for the treatment of diabetes is still far from being fully understood. Areas covered: This paper reviews the patent literature of SSAO/VAP-1 inhibitors and substrates, for the period of 1990 – 2010. The current stage of SSAO/VAP-1-interacting agents published in patents is described, along with their chemical structures and pharmacological uses. Expert opinion: SSAO/VAP-1 is a promising anti-inflammatory target. Another important field for therapeutic application of these inhibitors may be ophthalmology, due to their antiangiogenic effects. SSAO substrates might also be of therapeutic value in the treatment of diabetes; however, more extensive research has to be undertaken to validate this approach.

Novel arylalkenylpropargylamines as neuroprotective, potent, and selective monoamine oxidase B inhibitors for the treatment of Parkinson's disease

To develop novel neuroprotective agents, a library of novel arylalkenylpropargylamines was synthesized and tested for inhibitory activities against monoamine oxidases. From this, a number of highly potent and selective monoamine oxidase B inhibitors were identified. Selected compounds were also tested for neuroprotection in in vitro studies with PC-12 cells treated with 6-OHDA and rotenone, respectively. It was observed that some of the compounds tested yielded a marked increase in survival in PC-12 cells treated with the neurotoxins. This indicates that these propargylamines are able to confer protection against the effects of the toxins and may also be considered as novel disease-modifying anti-Parkinsonian agents, which are much needed for the therapy of Parkinsons disease.

Molecular modelling of subtypes (α2A, α2B and α2C) of α2-adrenoceptors: A comparative study

The therapeutic usefulness of current agents that activate the three alpha(2)-adrenoceptors, alpha(2A), alpha(2B) and alpha(2C) is limited by their lack of subtype selectivity. One approach to the development of subtype-selective agents is the in silico docking of potential ligands to the receptors in quantitative molecular modeling studies. Because the crystal structure of the alpha(2)-adrenoceptors is not known, we used homology modeling based on the published structure of bovine rhodopsin. We developed individual models for each of the three receptors, which were found to accurately represent published data from both radioligand binding mutagenesis experiments. Using 18 non-subtype-selective agents to validate the models, the calculated transformed and the experimental binding free energies were satisfactory correlated (r(2)(A)=0.888, r(2)(B)=0.887, r(2)(C)=0.790). The binding pockets differed in size (482-619A(3)) with the alpha(2B) receptor subtype having the largest and the alpha(2c) the smallest cavity. The binding sites for all three subtypes were found to be essentially identical with the exception of two subtype-specific residues, and thus we were unable to identify any significant differences in the interactions of ligands with the three receptor subtypes. Although, the binding properties of all three receptors are very similar, the differences in pocket volume and two subtype-specific residues in the binding pocket might play an as yet undocumented role in subtype selectivity.

SSAO substrates exhibiting insulin-like effects in adipocytes as a promising treatment option for metabolic disorders

BACKGROUND Benzylamine exerts insulin-like effects in adipocytes (e.g., glucose uptake and antilipolysis) and improves glucose handling in rodents. RESULTS In murine adipocytes, benzylamine mimics another insulin action: it enhances apelin expression in a manner that is blocked by the semicarbazide-sensitive amine oxidase/vascular adhesion protein-1 (SSAO/VAP-1) inhibitor semicarbazide. It is shown that in human adipocytes, benzylamine activates glucose transport, but its effects are not additive to maximal insulin stimulation. Benzylamine effects are hydrogen peroxide dependent. They can be reproduced by novel substrates, but not by benzaldehyde. CONCLUSION Owing to the parallelism between the in vitro insulin mimicry and the in vivo improvement of glucose handling elicited by benzylamine in rodents, the SSAO/VAP-1 substrates, with stronger effects on human adipocytes than benzylamine, show promising applications for the treatment of insulin resistance.

Drug Repositioning for Treatment of Movement Disorders: From Serendipity to Rational Discovery Strategies

Movement disorders are a heterogeneous group of both common and rare neurological conditions characterized by abnormalities of motor functions and movement patterns. This work overviews recent successes and ongoing studies of repositioning relating to this disease group, which underscores the challenge of integrating the voluminous and heterogeneous findings required for making suitable drug repositioning decisions. In silico drug repositioning methods hold the promise of automated fusion of heterogeneous information sources, but the controllable, flexible and transparent incorporation of the expertise of medicinal chemists throughout the repositioning process remains an open challenge. In support of a more systematic approach toward repositioning, we summarize the application of a computational repurposing method based on statistically rooted knowledge fusion. To foster the spread of this technique, we provide a step-by-step guide to the complete workflow, together with a case study in Parkinsons disease.

Generation and analysis of the conformational potential energy surfaces of N-acetyl-N-methyl-L-alanine-N'-methylamide. An exploratory ab initio study

Abstract N-methylation is a naturally occurring modification in small peptides, e.g. antibiotics that can effect the conformational preferences of the molecule as well as the ease of trans to cis isomerization of the involved peptide bond. In the present exploratory study we have calculated the potential energy surface of both N -acetyl- l -alanine- N ′-methylamide and N -acetyl- N -methyl- l -alanine- N ′-methylamide at the RHF/3-21G level of theory with a cis – trans or with a trans – trans peptide conformation. With respect to the non-methylated model system our results indicate that N-methylation reduces the number of observable backbone conformers in both amide configurations. The effect of methylation on the ease of trans to cis isomerization was assessed by calculating the energetics of the corresponding transition structures. An increase in the activation energies of the trans to cis isomerization of the relevant peptide bond was observed for the N-methylated moiety.

3D QSAR models for α2a-adrenoceptor agonists

Abstract Three-dimensional structure–activity relationship studies of α 2a -adrenoceptor agonists were carried out by Distance Comparison (DISCOthech) and Comparative Molecular Field Analysis (CoMFA) methods to define the pharmacophore and a quantitative model, respectively, of this class of compounds. The statistical validation of the CoMFA model indicates its high predictive performance for binding affinities of new α 2a -adrenoceptor agonists.

Dietary Phenolic Compounds Interfere with the Fate of Hydrogen Peroxide in Human Adipose Tissue but Do Not Directly Inhibit Primary Amine Oxidase Activity

Resveratrol has been reported to inhibit monoamine oxidases (MAO). Many substrates or inhibitors of neuronal MAO interact also with other amine oxidases (AO) in peripheral organs, such as semicarbazide-sensitive AO (SSAO), known as primary amine oxidase, absent in neurones, but abundant in adipocytes. We asked whether phenolic compounds (resveratrol, pterostilbene, quercetin, and caffeic acid) behave as MAO and SSAO inhibitors. AO activity was determined in human adipose tissue. Computational docking and glucose uptake assays were performed in 3D models of human AO proteins and in adipocytes, respectively. Phenolic compounds fully inhibited the fluorescent detection of H2O2 generated during MAO and SSAO activation by tyramine and benzylamine. They also quenched H2O2-induced fluorescence in absence of biological material and were unable to abolish the oxidation of radiolabelled tyramine and benzylamine. Thus, phenolic compounds hampered H2O2 detection but did not block AO activity. Only resveratrol and quercetin partially impaired MAO-dependent [14C]-tyramine oxidation and behaved as MAO inhibitors. Phenolic compounds counteracted the H2O2-dependent benzylamine-stimulated glucose transport. This indicates that various phenolic compounds block downstream effects of H2O2 produced by biogenic or exogenous amine oxidation without directly inhibiting AO. Phenolic compounds remain of interest regarding their capacity to limit oxidative stress rather than inhibiting AO.

Structure-Based Calculation of Binding Affinities of α2A-Adrenoceptor Agonists

Adrenergic receptors of the a2 type (a2-adrenoceptors) belong to the family of seven transmembrane-spanning G-proteinlinked receptors. a2-Adrenoceptors can be grouped into three highly homologous subtypes (a2A, a2B, and a2C) and, because of the difference in pharmacology, a fourth subtype (a2D) can be formally distinguished, though this is rather a species orthologue. In general, the a2-adrenoceptors are responsible for the presynaptic feedback of the release of adrenaline and noradrenaline, their physiological agonists. Although numerous findings are available on the receptor subtypes from experiments with knockout mice and these results are of some relevance for human pharmacology, the similar patterns of expression of adrenergic receptors in human and mouse tissues do not guarantee similar functions. Thus, the individual roles of the three a2-adrenoceptor subtypes in humans have not been completely elucidated. However, the results of the reported studies do indicate (see Supporting Information) that the a2-adrenoceptor subtypes are involved in various important physiological processes, and further investigations of the differences in their molecular pharmacology are therefore essential. The identification of subtype-specific functions from pharmacological experiments is currently not possible because of the lack of subtype-specific ligands and the cross-reactivity with imidazoline receptors. The development of subtype-selective agonists would be useful as it would facilitate further examinations of the molecular pharmacology of the a2-adrenoceptors. The rational, structure-based design of such agonists requires a precise knowledge of the molecular structure of the binding site. Unfortunately, because of the difficulties inherent in crystallization, atomic-resolution structures of the a2-adrenoceptors are not available in the Protein Databank. In the present study, an atomic-resolution model of the a2Aadrenoceptor was constructed through use of its amino acid sequence and the crystallographic bovine rhodopsin structure as a template. Similar homology models were earlier constructed by other researchers and successfully used to provide qualitative explanations. The a2A-adrenoceptor model in the present study is based on a crystallographic template structure with a resolution of 2.2 ? appropriate for quantitative investigations (for details, refer to the Computational Methods below). In possession of the atomic resolution target structure (a2Aadrenoceptor), 15 known agonist ligands were automatically docked to the presumed binding region of the receptor (Figure 1a). Inspection of the results revealed that the docked ligand conformations are in physical contact with the key residues D3.32 ACHTUNGTRENNUNG(113), S5.42 ACHTUNGTRENNUNG(200), and S5.46 ACHTUNGTRENNUNG(204), previously identified by site-directed mutagenesis studies. As an example, the positively charged amino group of noradrenaline (Figure 1b) or of methylnoradrenaline forms a salt bridge with the negative side-chain carboxylate of D3.32 ACHTUNGTRENNUNG(113). Similar results involving an interaction between the ionic groups were earlier obtained for noradrenaline. For some other ligands (for example, clonidine, Figure 1c), interactions can be observed with E4.39 ACHTUNGTRENNUNG(189) instead of D3.32 ACHTUNGTRENNUNG(113) . Additionally, the binding pocket is formed by hydrophobic amino acids such as V5.39ACHTUNGTRENNUNG(197), F5.47 ACHTUNGTRENNUNG(205), W6.48 ACHTUNGTRENNUNG(258), F6.49 ACHTUNGTRENNUNG(259), F6.52 ACHTUNGTRENNUNG(262), and the key serine residues. The qualitative agreement with the site-directed mutagenesis data indicates the usefulness of the homology model and the docking procedure applied. However, a correct (quantitative) estimation of the binding free energy (DGb) is the real challenge in molecular design. Once a DGb calculator has been developed, the screening-out of potent (tight binding) agonists from the candidate compounds becomes possible. To meet this expectation, quantitative structure–activity relationships (QSARs) were developed by using the docked structures and experimental DGb values of the agonists. As a first attempt, simple linear regression (LR) was performed, involving the modified scoring function values (DGT) of AutoDock 3.0 program package, which includes the intermolecular (enthalpic) terms and a solvation penalty. These values were calculated for the docked agonist–protein complex structures. A detailed discussion on the calculation of DGT is to be found in Ref. [17]. An excellent correlation was obtained for nine ligands not containing chlorine atoms [Eq. (1), Figure 2].