Spiro hydantoin aldose reductase inhibitors

Sorbitol formation from glucose, catalyzed by the enzyme aldose reductase, is believed to play a role in the development of certain chronic complications of diabetes mellitus. Spiro hydantoins derived from five- and six-membered ketones fused to an aromatic ring or ring system inhibit aldose reductase isolated from calf lens. In vivo these compounds are potent inhibitors of sorbitol formation in sciatic nerves of streptozotocinized rats. Optimum in vivo activity is reached in spiro hydantoins derived from 6-halogenated 2,3-dihydro-4H-1-benzopyran-4-ones (4-chromanones). In 2,4-dihydro-6-fluorospiro[4H-1-benzopyran-4,4'-imidazolidine]-2',5 '-dione, the activity resides exclusively in the 4S isomer, compound 115 (CP-45,634, USAN: sorbinil). This compound is currently being used to test, in humans, the value of aldose reductase inhibitors in the therapy of diabetic complications.     

Spiro oxazolidinedione aldose reductase inhibitors

Spiro oxazolidinediones (2) derived from five- and six-membered ring aralkyl ketones are potent aldose reductase inhibitors in vitro and in vivo. Their novel and general synthesis has been devised with alpha-hydroxyimidates (5) and 4-alkoxy-2-oxo-3-oxazolines (6) as key intermediates, since traditional synthetic routes through alpha-hydroxy amides (8) usually led to alpha, beta-unsaturated amides (9). Resolution with cinchonidine afforded optically active spiro oxazolidinediones. Optimum biological activity resided in (4S)-6-chlorospiro [4H-2,3-dihydrobenzopyran-4,5'-oxazolidine]-2',4'-dione (21) and its 6,8-dichloro congener (23).     

Spiro hydantoin aldose reductase inhibitors derived from 8-aza-4-chromanones

A series of spiro hydantoins derived from 8-azachromanones (2,3-dihydro-4H-pyrano[2,3-b]pyridin-4-ones) has been prepared and tested for aldose reductase inhibitory activity. The standard Bucherer-Bergs conditions had to be drastically modified to increase yields from less than 1% to an acceptable 50% range. One of the most potent compounds was cis-6'-chloro-2',3'-dihydro-2'-methylspiro[imidazolidine-4,4'-4'H- pyrano[2,3-b]pyridine]-2,5-dione; resolution of this compound showed that the 2'R,4'S enantiomer 16 was the most active spiro hydantoin in this series with an IC50 of 7.5 x 10(-9) against human placenta aldose reductase.     

1,2,4]Triazino[4,3-a]benzimidazole acetic acid derivatives: a new class of selective aldose reductase inhibitors.

Acetic acid derivatives of [1,2,4]triazino[4,3-a]benzimidazole (TBI) were synthesized and tested in vitro and in vivo as a novel class of aldose reductase (ALR2) inhibitors. Compound 3, (10-benzyl[1,2,4]triazino[4,3-a]benzimidazol-3,4(10H)-dion-2-yl)acetic acid, displayed the highest inhibitory activity (IC(50) = 0.36 microM) and was found to be effective in preventing cataract development in severely galactosemic rats when administered as an eyedrop solution. All the compounds investigated were selective for ALR2, since none of them inhibited appreciably aldehyde reductase, sorbitol dehydrogenase, or glutathione reductase. The activity of 3 was lowered by inserting various substituents on the pendant phenyl ring, by shifting the acetic acid moiety from the 2 to the 3 position of the TBI nucleus, or by cleaving the TBI system to yield benzimidazolylidenehydrazines as open-chain analogues. A three-dimensional model of human ALR2 was built, taking into account the conformational changes induced by the binding of inhibitors such as zopolrestat, to simulate the docking of 3 into the enzyme active site. The theoretical binding mode of 3 was fully consistent with the structure-activity relationships in the TBI series and will guide the design of novel ALR2 inhibitors.     

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.     

Some new thiazolyl thiazolidinedione derivatives as aldose reductase inhibitors

In diabetes, increased flux through the polyol pathway has been implicated in the development of diabetic complications such as cataract, retinopathy, neuropathy, and nephropathy. Aldose reductase (AR) appears to be the key factor in the reduction of glucose to sorbitol. Aldose reductase inhibitors have been found to prevent sorbitol accumulation in tissues. A series of thiazolyl-2,4-thiazolidinediones was prepared by Knoevenagel reaction of substituted benzyl-2,4-thiazolidinediones with chlorothiazolecarbaldehydes and were evaluated for their ability to inhibit rat kidney AR by an in vitro spectrophotometric assay. Results showed that compounds containing piperidine at the C-2 position of thiazole ring showed better inhibitory activity than thiazole compounds having 4-chlorobenzylsulfanyl at the same position.     

Curcumin analogs as potent aldose reductase inhibitors

In the present study, curcuminoids isolated from curcuma longa were demonstrated to possess inhibitory activities on bovine lens aldose reductase. In order to find more potent aldose reductase inhibitor, curcumin analogs were synthesized and evaluated for their ability to inhibit bovine lens aldose reductase enzyme. The results indicated that the compounds with tetrahydroxyl groups, 2,6-bis(3,4-dihydroxybenzylidene)cyclohexanone (A(2)), 2,5-bis(3,4-dihydroxybenzylidene)cyclopentanone (B(2)), 1,5-bis(3,4-dihydroxyphenyl)-1,4-pentadiene-3-one (C(2)), and 3,5-bis(3,4-dihydroxybenzylidene)-4-piperidone (D(2)) showed remarkably potent inhibitory effects on aldose reductase with IC(50) of 2.9 microM, 2.6 microM, 3.4 microM, and 4.9 microM, respectively. The structure-activity relationship revealed that the curcumin analogs with ortho-dihydroxyl groups could form a more tight affinity with aldose reductase to exert more potential inhibitory activities.     

Synthesis and aldose reductase inhibitory activity of a new series of benz[h]cinnolinone derivatives

Following our previous studies on pyridazinone carboxylic acids as potent and selective aldose reductase (ALR2) inhibitors, a new series of benzo[h]cinnolinone carboxylic acids, variously substituted at the positions 4, 7-10 and differently modified both at the central ring and at the acidic side chain, were synthesized and tested as inhibitors of ALR2. Comparison with previously synthesized compounds allows us to define more precisely structure-activity relationships for this class of compounds. In fact, in addition to the importance of the acidic side chain, their properties are highly influenced by the substituents present on the benzo[h]cinnolinone nucleous, with potency ranging from that of Sorbinil to very weakly active compounds.     

Selective irreversible inhibitors of aldose reductase.

A series of 5-substituted-1,3-dioxo-1H-benz[de]isoquinoline-2(3H)-acetic acid analogues have been examined as irreversible inhibitors of aldose reductase. The 5-alpha-bromoacetamide and 5-alpha-iodoacetamide analogues 5 and 6 gave irreversible inhibition of aldose reductase while the 5-alpha-chloroacetamide analogue 3 did not show this type of inhibition. Protection studies indicate that irreversible inhibitions are occurring at the inhibitor binding site. Comparative irreversible inhibition studies with rat lens aldose reductase (RLAR) and rat kidney aldehyde reductase (RKALR) indicate that 5-alpha-haloacetamide analogues 5 and 6 are much more effective inhibitors of RLAR.     

Isoxazolo-[3,4-d]-pyridazin-7-(6H)-one as a potential substrate for new aldose reductase inhibitors.

The isoxazolo-[3,4-d]-pyridazin-7-(6H)-one (2) and its corresponding open derivatives 5-acetyl-4-amino-(4-nitro)-6-substituted-3(2H)pyridazinones (3, 4) were used as simplified substrates for the synthesis of new aldose reductase inhibitors with respect to the previously reported 5, 6-dihydrobenzo[h]cinnolin-3(2H)one-2 acetic acids (1). Moreover, a few derivatives lacking the 5-acetyl group were prepared. Several compounds derived from 2 displayed inhibitory properties comparable to those of Sorbinil. In this class the presence at position 6 of a phenyl carrying an electron-withdrawing substituent proved to be beneficial, independently from its position on the ring (5g,j-l). Acetic acid derivatives were more effective than propionic and butyric analogues. On the contrary, all the monocyclic compounds (6-8) were either inactive or only weakly active. The 3-methyl-4-(p-chlorophenyl)isoxazolo-[3,4-d]-pyridazin-7-(6H )-one acetic acid (5g), which proved to be the most potent derivative, was also investigated in molecular modeling studies, to assess possible similarities in its interaction with the enzyme, with respect to the model 1.     

Naphtho[1,2-d]isothiazole acetic acid derivatives as a novel class of selective aldose reductase inhibitors

Acetic acid derivatives of naphtho[1,2-d]isothiazole (NiT) were synthesized and tested as novel aldose reductase (ALR2) inhibitors. The parent compound 11 exhibited a fair inhibitory activity (IC(50) = 10 muM), which was enhanced by 2 orders of magnitude by introducing a second carboxylic group at position 4 (13 and 14: IC(50) = 0.55 and 0.14 muM, respectively). Substitution of the acetic acid function with an apolar group gave inactive (29) or poorly active (25, 26, 30) compounds, thus demonstrating that the 2-acetic group is involved in the enzyme pharmacophoric recognition while the 4-carboxylic moiety has only an accessory role. The potent compounds 11, 13, 14, 26 all proved to be selective for ALR2, since none of them inhibited aldehyde reductase, sorbitol dehydrogenase, or glutathione reductase. The isopropyl ester 31, a prodrug of 14, was found to be effective in preventing cataract development in severely galactosemic rats, when administered as an eyedrop solution. The theoretical binding mode of 13 and 14, obtained by docking simulations into the ALR2 crystal structure, was fully consistent with the structure-activity relationships in the NiT series.     

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.     

Inhibition kinetics of human kidney aldose and aldehyde reductases by aldose reductase inhibitors

Kinetic patterns of inhibition of homogenous human kidney aldose reductase (AR, EC 1.1.1.21) and aldehyde reductase II (AR II, EC 1.1.1.19) by statil, ICI 105552 [1-(3,4-dichlorobenzyl)-3-methyl-1,2-dihydro-2-oxoquinol-4-yl acetic acid], tolrestat, alrestatin, chromone carboxylic acid (CCA), quercetin, phenobarbital and sorbinil were studied. On the basis of the kinetic nature of inhibition, the inhibitors were classified into four distinct categories. For aldose reductase, sorbinil and phenobarbital were noncompetitive (NC; category I) and CCA and alrestatin were uncompetitive (UC; category II) to both the aldehyde substrate and NADPH. Quercetin and ICI 105552 were NC to the aldehyde and UC to NADPH (category III) and tolrestat and statil were UC to the aldehyde and NC to NADPH (category IV). For AR II, sorbinil and alrestatin were category I inhibitors, ICI 105552 and statil belong to category II, phenobarbital, tolrestat and CCA to category III, and quercetin to category IV. To determine the specificity of inhibition, the ratios of the inhibition constants (Kii) for AR and AR II were calculated. A lower ratio indicates greater specificity. With aldehyde as the varied substrate the specificity ratios were: statil less than ICI 105552 less than alrestatin less than tolrestat less than quercetin less than CCA less than sorbinil less than phenobarbital, and with NADPH as the varied substrate, ICI 105552 less than statil less than alrestatin less than tolrestat less than quercetin less than CCA less than sorbinil less than phenobarbital. For AR, double-inhibition plots generated for one inhibitor from each kinetic category versus sorbinil showed that AR inhibitors of categories I-III bind to the same site on the protein molecule as sorbinil. However, tolrestat seemed to bind to a site different from the sorbinil binding site. For AR II, inhibitors from all the four categories appeared to bind to the same inhibitor binding site.     

Quinazolineacetic acids and related analogues as aldose reductase inhibitors

A variety of 2,4-dioxoquinazolineacetic acids (10, 11) were synthesized as hybrids of the known aldose reductase inhibitors alrestatin (8), ICI-105,552 (9), and ICI-128,436 (2) and evaluated for their ability to inhibit partially purified bovine lens aldose reductase (in vitro) and their effectiveness to decrease galactitol accumulation in the 4-day galactosemic rat model (in vivo). In support to SAR studies, related analogues pyrimidinediones (12), dihydroquinazolones (13), and indazolidinones (14,15) were synthesized and tested in the in vitro and in vivo assays. All prepared compounds (10-15) have shown a high level of in vitro activity (IC50 approximately 10(-6) to 4 x 10(-8) M). However, only the 2,4-quinazolinedione analogues 10 and 11, with similar N-aralkyl substitution found in 2 and 9, have exhibited good oral potency. The remaining compounds were either inactive or had only a marginal in vivo activity. The structure-activity data support the presence of a secondary hydrophobic pocket in the vicinity of the primary lipophilic region of the enzyme.     

Presence of aldose reductase inhibitors in tea leaves

Water extract from commercial English tea has a potent inhibitory activity against human placenta aldose reductase (NADPH oxidoreductase, E.C.1.1.1.21.). Inhibitory activity was separated into five major fractions by one-step chromatography with a C-18 reverse phase column. The most active fraction was further subjected to reverse phase column chromatography. As a result, a well-known flavone-glycoside, isoquercitrin, was isolated as the most potent chemical. The inhibitory character of isoquercitrin for aldose reductase was a mix of uncompetitive and noncompetitive inhibitions, and its IC50 was 1 x 10(-6) M. In rat sciatic nerve tissue preparations, sorbitol accumulation in the presence of high concentrations of glucose (30 mM) was inhibited by 38% at 5 x 10(-4) M of isoquercitrin. The flavone-glycoside isoquercitrin is the active inhibitor of aldose reductase inhibitor present in English tea. Given the ability of aldose reductase inhibitors to prevent diabetic complications, an epidemiological study of the effect of tea consumption on the pathogenesis and progression of diabetic complications would be interesting.     

醛糖还原酶抑制剂筛选的研究进展*

醛糖还原酶是多元醇通路中的关键限速酶,高血糖浓度下,此通路代谢旺盛,与糖尿病并发症的发生和恶化有密切关系。醛糖还原酶抑制剂因此而成为糖尿病并发症的药物治疗因子,它主要是通过山梨醇通路降低体内血糖浓度,减少山梨醇在体内组织中的堆积达到治疗目的。目前已从植物、微生物中或化学合成获得了许多醛糖还原酶抑制剂,其中2个分别在日本和爱尔兰上市,还有部分正进行临床试验。现主要概述醛糖还原酶抑制剂筛选的研究进展。     

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.     

Diabetic nephropathy,renal hemodynamics,and aldose reductase inhibitors

Diabetic kidney disease or diabetic nephropathy is the leading cause of renal failure in the United States today. This review presents a brief overview of diabetic nephropathy—its current statistics, histopathology, natural history, and main risk factors, including hyperglycemia, hyperfiltration, and hypertension. Pathogenic mechanisms by which hyperglycemia, severe hyperfiltration, and capillary hypertension might cause renal injury are discussed. Evidence is reviewed indicating a potentially useful role for aldose reducatase inhibitors (ARIs) to normalize or reduce the impact of two possible risk factors for diabetic nephropathy, namely, elevated polyol pathway metabolism and severe hyperfiltration. Measurements in experimental models of whole kidney blood flow (⁵⁷Co-microspheres, clearance methods), superficial cortical blood flow (laser Doppler flowmetry), and single nephron hemodynamic parameters (renal micropuncture) concordantly indicate that the beneficial effect of ARIs on hyperfiltration is based on protection or restoration of normal renal microvascular resistance. Since ARIs affect neither blood sugar levels nor mean arterial pressure, ARIs have no increased risk attributable to hypoglycemia or hypotension. It is concluded that ARIs warrant further experimental and clinical research in early diabetic nephropathy.