Computer-assisted design and synthesis of novel aldose reductase inhibitors

The design and synthesis of phenalene 26 (AY-31,358), an unsubstituted analogue of a tolrestat/ICI-105,552 computer-generated hybrid (7), are reported. Compound 7 was designed by the superimposition of the putative low-energy conformers of tolrestat (1) and ICI-105,552 (6). The more rigid aldose reductase inhibitor sorbinil (2) was used as a template to help discern a common pharmacophore in the three inhibitors. Compound 26 was synthesized as a model and was evaluated as an inhibitor of bovine lens aldose reductase. It was found to exhibit good in vitro activity as well as some in vivo activity in the nerve. It was expected that introduction of the trifluoromethyl and methoxy substituents would enhance the biological activity of model compound 26. As a result of a positive Ames test with 26, however, work has now been directed toward modifying the template in a way so as to eliminate the mutagenicity with retention of biological activity.     

In vitro aldose reductase inhibitory activity of substituted N-benzenesulfonylglycine derivatives

A number of N-benzenesulfonylglycines, alanines, sarcosine, and prolines, which contain the minimum pharmacophore moieties necessary for aldose reductase inhibitory activity, were prepared and tested in the rat lens assay. In this assay, the benzenesulfonylglycines are considerably more potent than the corresponding alanine and sarcosine derivatives which, in turn, are more active than the proline analogues. Of the monosubstituted benzenesulfonylglycines, the 2-nitro and 4-amino derivatives were most active with 50% inhibitory concentration (IC50) values of 13 and 16 microM, respectively. The most potent derivatives evaluated were the beta- and alpha-naphthylenesulfonylglycines with IC50 values of 0.4 and 1.3 microM, respectively. The structure-activity data obtained from evaluation of the benzenesulfonylamino acids suggests that the aromatic ring and ring substituents, as well as the sulfonamide group and carboxylate moiety, all contribute to the inhibitory potency through direct interaction with complimentary binding sites present on aldose reductase.     

Protein structure-based de novo design and synthesis of aldose reductase inhibitors.

Aldose reductase has been implicated in the etiology of diabetic complications. Due to the limited number of currently available drugs for the treatment of diabetic complications, we have carried out a structure-based de novo design and synthesis in an attempt to identify new aldose reductase inhibitors. With the LEGEND program, we have designed 200 chemical structures that fit into the ligand binding site of the crystal structure of the enzyme. After their visual inspection and assessment of synthetic feasibility, four compounds were chosen to be synthesized. These compounds were all found to have reasonable inhibitory activities (IC50 = 17-91 microM), indicating the first successful generation of nonpeptide drug leads that have been obtained using a rational de novo design approach.     

Oxadiazolo pyrrolidine carboxamides as enoyl-ACP reductase inhibitors: design, synthesis and antitubercular activity screening

Pyrrolidine carboxamides have been recognized as potent direct enoyl-acyl carrier protein reductase inhibitors. In our study, the search for new pyrrolidine carboxamides incorporated with various heterocyclic moieties, possessing antitubercular activities is been done. A series of oxadiazolyl pyrrolidine carboxamides (2a–e) were synthesized by reacting pyrrolidine carboxylic acid and oxadiazole amines using HBTU as amide forming agent. The purity of the synthesized compounds was confirmed by physical characterization like melting point and thin layer chromatography. The functional group identification was done based on spectral characterization utilizing, FT-IR, ¹H NMR, ¹³C NMR, mass spectral data and elemental analysis. Invitro antitubercular screening was performed by alamar blue assay method on mycobacterium tuberculosis H37Rv.     

On the synthesis of bioisosters of o-benzothiazolyloxybenzoic acids and evaluation as aldose reductase inhibitors

In continuation of our attempts to develop novel aldose reductase inhibitors (ARIs), a number of compounds characterized by bioisosteric replacement of pharmacophors were prepared. On the one hand, the acidic function was formally replaced by an oxime or a nitro group and on the other hand the lipophilic substituent was modified. The results of the biological evaluation of these derivatives enabled us to gain insight into structural features critical for the aldose reductase inhibition.     

Synthesis and biological evaluation of substituted benzenesulfonamides as novel potent membrane-bound phospholipase A2 inhibitors

A novel series of 4-[N-methyl-N-[(E)-3-[4-(methylsulfonyl)phenyl]-2- propenoyl]amino]benzenesulfonamides has been prepared and evaluated as membrane-bound phospholipase A2 inhibitors. A structure-activity relationship study indicated that the optimum potency was realized with the N-(phenylalkyl)piperidine derivatives 3 and 4. These compounds inhibited the liberation of arachidonic acid from the rabbit heart membrane fraction with IC30 values of 0.028 and 0.009 microM, respectively. Several compounds (3, 4, and 28), which proved to be potent inhibitors in vitro, significantly reduced the size of myocardial infarction in coronary occluded rats by iv administrations prior to the ligation. N-(1-Benzyl-4-piperidinyl)-4-[N-methyl-N-[(E)-3-[ 4-(methylsulfonyl)phenyl]-2-propenoyl]amino]-benzenesulfonamide (3, ER-3826), which showed the protective in vivo effects at doses higher than 0.3 mg/kg iv, was finally chosen as a leading candidate.     

Effects of aldose reductase inhibitors on antioxidant defense in rat and rabbit liver.

Aldose reductase has been implicated in the etiology of diabetic complications, atherosclerosis, and ischemia-reperfusion injury. Aldose reductase inhibitors are known to have species-dependent differences in biotransformation enzyme induction. Whether aldose reductase inhibitors, which have antioxidant potential, alter the oxidative stress pathway is unknown. This study has determined whether four daily ip treatments of either low (10 mg/kg) or high (50 mg/kg) doses of AL-1576 or AL-4114 alter the activities of the antioxidant defense enzymes catalase, glutathione reductase, glutathione peroxidase, superoxide dismutase, and the concentrations of reduced and oxidized glutathione in livers of normal rats and rabbits. There was no change in the concentration of thiobarbituric acid reactive substances in either rat or rabbit livers, indicating that lipid peroxidation was not increased by any treatment. Hepatic catalase, superoxide dismutase, and glutathione peroxidase activities and concentrations of reduced and oxidized glutathione were not significantly altered in rat, though glutathione reductase activity was increased after high doses of both drugs. However, in rabbit liver, glutathione reductase activity decreased in a dose-dependent manner after AL-4114 treatment, while superoxide dismutase and glutathione peroxidase activities decreased only after the low dose of AL-4114. Although AL-4114 and AL-1576 did not directly generate increased lipid peroxidation within normal rat and rabbit livers, some of the enzymes responsible for oxidative defense were altered, particularly in rabbit livers.     

Pyrido[1,2-a]pyrimidin-4-one derivatives as a novel class of selective aldose reductase inhibitors exhibiting antioxidant activity

2-Phenyl-pyrido[1,2-a]pyrimidin-4-one derivatives bearing a phenol or a catechol moiety in position 2 were tested as aldose reductase (ALR2) inhibitors and exhibited activity levels in the micromolar/submicromolar range. Introduction of a hydroxy group in position 6 or 9 gave an enhancement of the inhibitory potency (compare 18, 19, 28, and 29 vs 13 and 14). Lengthening of the 2-side chain to benzyl determined a general reduction in activity. The lack or the methylation of the phenol or catechol hydroxyls gave inactive (10-12, 21, 22, 25-27) or scarcely active (15, 17, 20) compounds, thus demonstrating that the phenol or catechol hydroxyls are involved in the enzyme pharmacophoric recognition. Moreover, all the pyridopyrimidinones displayed significant antioxidant properties, with the best activity shown by the catechol derivatives. The theoretical binding mode of the most active compounds obtained by docking simulations into the ALR2 crystal structure was fully consistent with the structure-activity relationships in the pyrido[1,2-a]pyrimidin-4-one series.     

Spirohydantoin inhibitors of aldose reductase inhibit iron- and copper-catalysed ascorbate oxidation in vitro

Transition metal-catalysed oxidations have been implicated in the complications of diabetes. We report here that some experimental inhibitors of the enzyme aldose reductase (implicated in diabetes mellitus via its ability to catalyse glucose reduction to sorbitol) are also potent inhibitors of transition metal-catalysed ascorbate oxidation. The inhibition appears to be dependent upon the presence of a spirohydantoin group. It is conceivable that the copper- and iron-binding capacity of these compounds may contribute to some of their observed biological effects and may provide a starting point for a new generation of experimental drugs for the treatment of diabetes mellitus.     

Discovery of novel aldose reductase inhibitors using a protein structure-based approach: 3D-database search followed by design and synthesis

Aldose reductase (AR) has been implicated in the etiology of diabetic complications. Due to the limited number of currently available drugs for the treatment of diabetic complications, we have carried out structure-based drug design and synthesis in an attempt to find new types of AR inhibitors. With the ADAM&EVE program, a three-dimensional database (ACD3D) was searched using the ligand binding site of the AR crystal structure. Out of 179 compounds selected through this search followed by visual inspection, 36 compounds were purchased and subjected to a biological assay. Ten compounds showed more than 40% inhibition of AR at a 15 microg/mL concentration. In a subsequent lead optimization, a series of analogues of the most active compound were synthesized based on the docking mode derived by ADAM&EVE. Many of these congeners exhibited higher activities compared to the mother compound. Indeed, the most potent, synthesized compound showed an approximately 20-fold increase in inhibitory activity (IC(50) = 0.21 vs 4.3 microM). Furthermore, a hydrophobic subsite was newly inferred, which would be useful for the design of inhibitors with improved affinity for AR.     

Permeability characteristics of novel aldose reductase inhibitors using rat jejunum in vitro.

The aim of this study was to estimate in vivo permeability and bioavailability of epalrestat and newly synthesized compounds with possible therapeutic activity as aldose enzyme inhibitors (ARIs). For this purpose permeability in vitro using rat jejunum mounted in side-by-side diffusion cells was determined. Tested substances were found to be low and moderately permeable and some of them were also substrates for efflux transporters. It was shown, that the higher efflux for some derivatives was due to MRP-2, but not Pgp involvement. Tested ARIs do not share the same efflux transporter with epalrestat, the only ARI currently on the market in Japan. The most permeable compound, a 2,6-difluoro-4-pyrrol-1ylphenol derivative, is not a substrate for efflux transporters and would therefore be the most promising lead compound for further investigation of potent ARIs.     

Synthesis and aldose reductase inhibitory activity of substituted 2-oxoquinoline-1-acetic acid derivatives

A number of 2-oxoquinoline-1-alkanoic acids that contain the N-acylglycine fragment found in several known inhibitors of aldose reductase were synthesized and tested in the rat lens assay. All of the target compounds were prepared by alkylation of the appropriate 2-oxoquinoline intermediates with a halo ester, followed by hydrolysis of the intermediate esters. In the rat lens assay, the 1-acetic acid derivatives 9a-e display the highest level of aldose reductase inhibitor activity with IC50 values of 0.45-6.0 microM. Modification of the 1-acetic acid moiety by esterification, substitution of an alpha-methyl group, or insertion of an additional methylene unit results in reduced inhibitory potency. Structure-activity data also suggests that both the benzene and 2-oxopyridine rings of 9a-e contribute substantially toward activity and that inhibitory potency is influenced by aromatic ring substituents.     

A new series of pyridazinone derivatives as cholinesterases inhibitors: Synthesis,in vitro activity and molecular modeling studies

BackgroundThe pyridazinone nucleus has been incorporated into a wide variety of therapeutically interesting molecules to transform them into better drugs. Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are known to be serine hydrolase enzymes responsible for the hydrolysis of acetylcholine (ACh). Inhibition of cholinesterases is an effective method to curb Alzheimer’s disease. Here, we prepared 12 new 6-substituted-3(2H)-pyridazinone-2-acetyl-2-(nonsubstituted/4-substituted benzenesulfonohydrazide) derivatives and evaluated their inhibitory effects on AChE/BChE in pursuit of potent dual inhibitors for Alzheirmer’s Disease. We also tried to get insights into binding interactions of the synthesized compounds in the active site of both enzymes by using molecular docking approach.MethodWe obtained our compounds by the reaction of various substituted/nonsubstituted benzenesulfonic acid derivatives with 6-substitutedphenyl-3(2H)-pyridazinone-2-yl acetohydrazide and determined their anticholinesterase activities according to the Ellman’s method. Molecular docking studies were done using Glide and the results were evaluated on Maestro (Schrödinger, LLC, New York, NY, 2019).ResultsThe title compounds showed moderate inhibition at 100 μg/ml against both enzymes, yet with better activity against BChE. Compound VI_2a emerged as a dual inhibitor with 25.02% and 51.70% inhibition against AChE and BChE, respectively.ConclusionThis study supports that novel pyridazinone derivates may be used for the development of new BChE inhibitory agents. It was less potent than the reference drugs, yet promising for further modifications as a lead. The ability of the compounds to adopt energetically more favourable conformations and to engage in more key interactions in the ECBChE active gorge explains their better activity profile against ECBChE.     

Design,synthesis, and biological activity evaluation of BACE1 inhibitors with antioxidant activity

The proteolytic enzyme β-secretase (BACE1) plays a central role in the synthesis of the pathogenic β-amyloid peptides (Aβ) in Alzheimer's disease (AD), antioxidants could attenuate the AD syndrome and prevent the disease progression. In this study, BACE1 inhibitors ( D1 – D18 ) with free radical-scavenging activities were synthesized by molecular hybridization of 2-aminopyridine with natural antioxidants. The biological activity evaluation showed that D1 had obvious inhibitory activity against BACE1, and strong antioxidant activity in 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS^+•) assay, which could be used as a lead compound for further study.     

Design, synthesis and in vitro activity of glycinamide-bearing compounds as DPP-IV inhibitors

To research the structure-activity relationship (SAR) of glycinamide-bearing compounds that used as inhibitors of dipeptidyl peptidase IV (DPP-IV), P32/98 and compound A were chosen as the leading compounds, heterocycles containing nitrogen atom were introduced to form amide, and different residues on a-position of carbonyl were designed. The nineteen designed compounds were synthesized by a simple route and were evaluated as inhibitors of DPP-IV. All of the structures were characterized by 1H NMR and HRMS. The preliminary SAR result was obtained.     

Comparison of aldose reductase inhibitors in vitro. Effects of enzyme purification and substrate type

Aldose reductase (EC 1.1.1.21) was purified approximately 5000-fold from bovine lens by ammonium sulphate fractionation and chromatography on DEAE-Sephacel and Matrex OA. Inhibition of this enzyme was found to depend upon the assay substrate. Tested against the purest form of enzyme, the inhibitor Sorbinil gave IC50 values of approximately 100 microM with the model substrate 4-nitrobenzaldehyde (4NB) and 0.4-1.4 microM with the physiological substrate glucose. A similar effect of substrate was found for the inhibitor Statil (IC50 450-750 nM with 4NB, 26-71 nM with glucose substrate). The implications of these results towards the assessment of aldose reductase inhibitors in vitro are discussed.     

Synthesis of novel benzoic acid derivatives with benzothiazolyl subunit and evaluation as aldose reductase inhibitors

Several methyl benzothiazolyloxybenzoates, S-isosters, and the corresponding benzoic acids were synthesized and tested as aldose reductase inhibitors (ARIs). Out of this series, the ester derivative 2a-7 was found to exhibit the highest enzyme-inhibitoric activity. In order to investigate this unexpected result, further modifications were carried out which allowed us to explain this finding and to open a path to a novel class of ARIs.     

Novel inhibitors of rat lens aldose reductase: N-[[(substituted amino)phenyl]sulfonyl]glycines

A number of N-[[(substituted amino)phenyl]sulfonyl]glycines 3a-n were synthesized as analogues of the simple (phenylsulfonyl)glycines 1a-c with increased lipophilic character and therefore greater aldose reductase inhibitory potential. The 2-benzoylamino derivative 3c was found to be less potent than the corresponding amine 1c as an inhibitor of rat lens aldose reductase, but both the 3- and 4-benzoylamino analogues, 3b and 3a, are substantially more potent than their amines 1b and 1a; compound 3a is the most effective inhibitor of this series, with an IC50 of 0.41 microM. The 4-benzoylamino derivative 3a is also significantly more active than the 4-acetylamino analogue 3d and the 4-benzylamino (3e) and 4-dimethylamino (3f) derivatives, suggesting that both the additional carbonyl moiety and aromatic ring present in this compound may bind to complementary sites present on the enzyme. Furthermore, structure-activity studies reveal that increasing the number of atoms between the carbonyl and aromatic moieties of 3a results in a decrease in inhibitory activity. Kinetic studies demonstrate that 3a, like other known inhibitors of aldose reductase, functions as an uncompetitive inhibitor with respect to the substrate and therefore may interact at the proposed common inhibitor binding site of this enzyme.     

Gossypol and derivatives: a new class of aldose reductase inhibitors

Gossypol and 17 derivatives were tested as inhibitors of aldose reductase from human placenta. Gossypol and a number of the derivatives were potent inhibitors. The order of inhibitory activity was interpreted in relation to the Kador-Sharpless pharmacophor model for the aldose reductase inhibitor site. The structural but not the electronic aspects of the model were found to apply to this series of compounds.     

A flavone from Manilkara indica as a specific inhibitor against aldose reductase in vitro

Isoaffinetin (5,7,3',4',5'-pentahydroxyflavone-6-C-glucoside) was isolated from Manilkara indica as a potent inhibitor of lens aldose reductase by bioassay-directed fractionation. This C-glucosyl flavone showed specific inhibition against aldose reductases (rat lens, porcine lens and recombinant human) with no inhibition against aldehyde reductase and NADH oxidase. Kinetic analysis showed that isoaffinetin exhibited uncompetitive inhibition against both dl-glyceraldehyde and NADPH. A structure-activity relationship study revealed that the increasing number of hydroxy groups in the B-ring contributes to the increase in aldose reductase inhibition by C-glucosyl flavones.