醛糖还原酶抑制剂非达司他的合成

目的：合成醛糖还原酶抑制剂非达司他。方法：以4-氟苯甲醚为起始原料，经傅克-酰基化取代、环合、酰氯化、拆分、水解、乙内酰脲化、醇酯化、氨解得目标化合物非达司他。结果：目标化合物经红外光谱、核磁共振氢谱、质谱确证其化学结构，总收率为14．5％。结论：在制备中间体2和7时，改进了工艺，提高了产率。     

Structure of aldehyde reductase holoenzyme in complex with the potent aldose reductase inhibitor fidarestat: implications for inhibitor binding and selectivity

Structure determination of porcine aldehyde reductase holoenzyme in complex with the potent aldose reductase inhibitor fidarestat was carried out to explain the difference in the potency of the inhibitor for aldose and aldehyde reductases. The hydrogen bonds between the active-site residues Tyr50, His113, and Trp114 and fidarestat are conserved in the two enzymes. In aldose reductase, Leu300 forms a hydrogen bond through its main-chain nitrogen atom with the exocyclic amide group of the inhibitor, which when replaced with a Pro in aldehyde reductase, cannot form a hydrogen bond, thus causing a loss in binding energy. Furthermore, in aldehyde reductase, the side chain of Trp220 occupies a disordered split conformation that is not observed in aldose reductase. Molecular modeling and inhibitory activity measurements suggest that the difference in the interaction between the side chain of Trp220 and fidarestat may contribute to the difference in the binding of the inhibitor to the enzymes.     

Ponalrestat: a potent and specific inhibitor of aldose reductase

Many of the complications of diabetes appear to be closely linked to increased conversion of tissue glucose to sorbitol which is catalysed by aldose reductase (aldehyde reductase 2, ALR2). Inhibition of ALR2 could, therefore, lead to a reduction in the development of diabetic complications. Ponalrestat ["Statil" (a trademark, the property of Imperical Chemical Industries PLC), "Prodiax" (a trademark, the property of Merck, Sharp and Dohme), ICI 128436, MK538] inhibits ALR2 from a number of sources. Until now, the mechanism of this inhibition has not been fully elucidated. In this paper, we present a detailed mechanism for inhibition of bovine lens ALR2 by ponalrestat. Treatment of humans with some ALR2 inhibitors leads to side-effects, some of which may result from interactions with other enzymes. Aldehyde reductase (ALR1) is probably the most closely related enzyme to ALR2. Inhibition of ALR1 from bovine kidney was, therefore, investigated in order to assess the specificity of ponalrestat. The values of Ki and Kies (apparent dissociation constants for inhibitor from enzyme-inhibitor and enzyme-inhibitor-substrate complexes, respectively) for the interactions of ponalrestat with ALR1 and ALR2 has been calculated by non-linear fitting of kinetic data. These values indicate that ponalrestat does not compete with binding of glucose of NADPH to ALR2, nor with binding of glucuronate or NADPH to ALR1. Lack of competition and the structural dissimilarity of substrates and inhibitor make it unlikely that ponalrestat will utilize substrate binding sites on other enzymes, and so produce undesirable side-effects via such a mechanism. Ponalrestat is a potent inhibitor (Ki = Kies = 7.7 nM) of ALR2 and follows a pure noncompetitive mechanism with respect to glucose. Efficacy, therefore, will not be decreased by development of hyperglycaemia. The compound is a mixed noncompetitive inhibitor of ALR1 when glucuronate is varied. The values of Ki and Kies are 60 microM and 3 microM, respectively, so that inhibition tends towards uncompetitive. The selectivity of ponalrestat in favour of ALR2, therefore, lies in the range 390 to 7,800-fold, being higher at lower concentrations of glucuronate. The high selectivity of ponalrestat in favour of ALR2 rather than ALR1 suggests that the compound is unlikely to inhibit other enzymes which have less homology with ALR2.     

Ranirestat (AS-3201), a potent aldose reductase inhibitor, reduces sorbitol levels and improves motor nerve conduction velocity in streptozotocin-diabetic rats

Ranirestat (AS-3201) is a novel aldose reductase (AR) inhibitor with potentially beneficial effects on diabetic sensorimotor polyneuropathy. In this study, we performed a kinetic analysis to determine the mode of inhibition of ranirestat on AR and investigated the effects of ranirestat on sorbitol levels in the sciatic nerves and lens of streptozotocin (STZ)-diabetic rats. We also evaluated the effects on motor nerve conduction velocity (MNCV) in STZ-diabetic rats. Kinetic analyses revealed that the ranirestat inhibition of AR is uncompetitive and reversible. In the sciatic nerve and lens of STZ-diabetic rats, single oral administration of ranirestat slightly reduced sorbitol levels. However, repeated oral administration of ranirestat for 5, 21, or 60 days enhanced the reducing effect of the ranirestat on sorbitol levels in the sciatic nerves and lens of STZ-diabetic rats with maximum effects after 21 days of treatment. Finally, repeated oral administration of ranirestat for 21 or 42 days dose-dependently improved the STZ-induced decrease in MNCV in STZ-diabetic rats. These findings demonstrate that repeated oral administration of ranirestat reduces sorbitol accumulation and improves MNCV in STZ-diabetic rats, indicating that ranirestat is an agent for the management of diabetic sensorimotor polyneuropathy.     

Inhibitory effects of fidarestat on aldose reductase and aldehyde reductase activity evaluated by a new method using HPLC with post-column spectrophotometric detection

A new method to assay the activity of aldose reductase (AR) and aldehyde reductase (AHR) by high-performance liquid chromatography is described. The separation of AR and AHR from tissue extracts using an anion-exchange column was followed by chromatographic measurement of the activity in the elute. AR and AHR activity were expressed as the area under the peak obtained by post-column spectrophotometric detection of the decrease of coenzyme (NADPH) in each enzyme reaction. In the enzyme preparation from rat or human tissues obtained by this method, two active peaks were identified as AR and AHR. The correlation coefficient between the injection volume of the enzyme preparation from each tissue and each peak area was 0.998 or greater. In addition, the within-day preservation rate of AR or AHR activity from each tissue was over 95%. In a comparative study of fidarestat with other AR inhibitors using this method, it was confirmed that the inhibitory effect of fidarestat on AR activity from each rat tissue was more potent than that produced by sorbinil and equipotent to that of epalrestat and zenarestat. Fidarestat was also found to inhibit AR activity more potently than AHR activity in human erythrocytes. Therefore, this method is applicable to studies of the selective inhibition of AR or AHR by test compounds.     

醛糖还原酶抑制剂依帕司他胶囊和片剂的人体生物等效性

目的 :评价依帕司他胶囊和片剂的人体生物等效性。方法 :2 0名健康男性受试者 ,随机分为 2组 ,分别于早晨空腹一次口服依帕司他胶囊或片剂5 0mg。 1wk后再交叉服药。用HPLC法测定依帕司他血药浓度。结果 :依帕司他胶囊和片剂的主要药动学参数 ,Tmax为 (1.7±s 0 .4 )h和 (1.6± 0 .6 )h ,Cmax为 (4 .0± 0 .9)mg·L- 1和 (4 .3± 1.1)mg·L- 1,MRT为 (1.6± 0 .3)h和 (1.6± 0 .4 )h ,T1/2 为(1.7± 0 .6 )h和 (1.4± 0 .3)h ,AUC0 8为 (10 .9±2 .1)mg·h·L- 1和 (11.4± 2 .8)mg·h·L- 1,AUC0 ∞为 (11.1± 2 .2 )mg·h·L- 1和 (11.5± 2 .8)mg·h·L- 1。依帕司他胶囊相对生物利用度为 (10 0±2 2 ) %。结论 :依帕司他胶囊与片剂具有生物等效性     

Synthesis of flavonoids and their effects on aldose reductase and sorbitol accumulation in streptozotocin-induced diabetic rat tissues

Aldose reductase, the key enzyme of the polyol pathway, and oxidative stress are known to play important roles in the complications of diabetes. A drug with potent inhibition of aldose reductase and oxidative stress, therefore, would be a most promising drug for the prevention of diabetic complications. The purpose of this study was to develop new compounds with these dual-effects through synthesis of chalcone derivatives and by examining the structure-activity relationships on the inhibition of rat lens aldose reductase as well as on antioxidant effects. A series of 35 flavonoid derivatives were synthesized by Winget's condensation, oxidation, and reduction of appropriate acetophenones with appropriate benzaldehydes. The inhibitory activity of these derivatives on rat lens aldose reductase and their antioxidant effects, measured using Cu2+ chelation and radical scavenging activities on 1,1-diphenyl-picrylhydrazyl in-vitro, were evaluated. Their effect on sorbitol accumulation in the red blood cells, lenses and sciatic nerves of streptozotocin-induced diabetic rats was also estimated. Among the new flavonoid derivatives synthesized, those with the 2',4'-dihydroxyl groups in the A ring such as 2,4,2',4'-tetrahydroxychalcone (22), 2,2',4'-trihydroxychalcone (11), 2',4'-dihydroxy-2,4-dimethylchalcone (21) and 3,4,2',4'-tetrahydroxychalcone (18) were found to possess the highest rat lens aldose reductase inhibitory activity in-vitro, their IC50 values (concentration of inhibitors giving 50% inhibition of enzyme activity) being 1.6 x 10(-7), 3.8 x 10(-7), 4.0 x 10(-7) and 4.6 x 10(-7) M, respectively. All of the chalcones tested except 3, 18, 23 with o-dihydroxy or hydroquinone moiety showed a weak free radical scavenging activity. In the in-vivo experiments, however, compound 18 with o-dihydroxy moiety in the B ring showed the strongest inhibitory activity in the accumulation of sorbitol in the tissues. It also showed the strongest activity in transition metal chelation and free radical scavenging activity. Of the 35 4,2'-dihydroxyl and 2',4'-dihydroxyl derivatives of flavonoid synthesized, including chalcone, flavone, flavanone, flavonol and dihydrochalcone, some chalcone derivatives synthesized were found to possess aldose reductase inhibition and antioxidant activities in-vitro as well as inhibition in the accumulation of sorbitol in the tissues in-vivo. 3,4,2',4'-Tetrahydroxychalcone (18, butein) was the most promising compound for the prevention or treatment of diabetic complications.     

L-669,262, a potent HMG-CoA reductase inhibitor

The microbial transformation of simvastatin (MK-733) by Nocardia autotrophica subspecies amethystina yielded iso-simvastatin-6-one as a minor component. This transformation product is a dienone and is one of the more potent inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase found to date.     

Determination of tolrestat, a novel aldose reductase inhibitor, in serum and tissues

An ultraviolet spectrophotometric method and a high-performance liquid chromatographic (HPLC) method were developed for the determination of tolrestat, a novel aldose reductase inhibitor, in serum. The limits of detection of the methods are 15 micrograms/ml and 0.2 microgram/ml, respectively. With human serum, a modification of the HPLC method provides sensitivity to 25 ng/ml. The specificity of the methods were compared. The HPLC method can be applied to the lens and the sciatic nerve.     

Development of potent aldose reductase inhibitors having a hydantoin structure

Seventeen hydantoin derivatives were tested as inhibitors of aldose reductase, an enzyme believed to participate in the initiation of diabetic complications. Nine compounds with high inhibitory activities (IC50 values against purified rat lens aldose reductase less than or equal to 1.06 X 10(-6)M) were tested further for their abilities to prevent sorbitol accumulation induced by exposure of excised rat lens and sciatic nerve to a high glucose concentration (50 mM). Seven active compounds among them inhibited sorbitol accumulation by about 50% or more at a concentration of 10(-5)M. These seven compounds were given orally to streptozotocin-induced diabetic rats at a dose of 50 mg/kg/day and were assessed for their abilities to prevent both sorbitol accumulation in two tissues (lens and sciatic nerve) and myo-inositol depletion in the sciatic nerve. 1-[(2,4,5-Trichlorophenyl)sulfonyl]hydantoin, 1-[(2,5-dichlorophenyl)sulfonyl]hydantoin, and 1-[(beta-naphthyl)sulfonyl]hydantoin were found to be the most effective: they inhibited sorbitol accumulation in the sciatic nerve completely and that in the lens by more than 92%. It is conceivable from this study that the three compounds are promising for further investigation targeted to the treatment of diabetic complications.     

Reversal of stage-I sugar cataract by Sorbinil, an aldose reductase inhibitor

Aldose reductase is implicated in the pathogenesis of sugar cataracts; therefore, inhibition of this enzyme subsequent to cataractogenesis may represent a therapeutic approach for the restoration of lens physiology despite the persistence of diabetes or galactosemia. In the present study, the effect of aldose reductase inhibition subsequent to stage-I cataract formation was investigated in the galactose-maintained rat. Our results indicated that despite continuation of galactose feeding the aldose reductase inhibitor, Sorbinil, a spirohydantoin, arrested further progression and promoted a reparative process. Quantitative analysis of scanning electron micrographs indicated that the afflicted lens regions were contained and their cellular components stabilized with regard to fiber hydration and interdigitation. The reparative process involved: decrease in lens dulcitol, gradual recovery of fiber thickness and partial restoration of lens myo-inositol content. At this stage of cataractogenesis, despite continuance of galactose feeding, the effects of Sorbinil treatment were comparable to the reparative process achieved by restoration of a normal diet.     

Diuretic and natriuretic effects of sorbinil, an aldose reductase inhibitor

The renal effects of sorbinil, an aldose reductase inhibitor that interferes with the conversion of glucose to sorbitol, were studied in rats and rabbits before and after fluid deprivation. The intracellular osmolar solute, sorbitol, is found in increasing concentrations from cortex to medulla in the kidney and may be involved in the urinary concentrating mechanism. Oral administration of sorbinil in the rabbit resulted in significant increases in urine flow rate and sodium excretion with a tendency toward decreased urine osmolality and increased potassium excretion both before and after water deprivation. When fluid intake was controlled in the rat study, significant increases in urine flow rate and sodium and potassium excretion and a significant decrease in urine osmolality occurred only in response to fluid deprivation. Thus, sorbinil has diuretic and natriuretic properties and may prevent the normal concentration of urine in the antidiuretic animal.     

High-resolution structures of human aldose reductase holoenzyme in complex with stereoisomers of the potent inhibitor Fidarestat: stereospecific interaction between the enzyme and a cyclic imide type inhibitor

Structure determinations of human aldose reductase holoenzyme in complex with the 2S4R-,2R4S- and 2R4R-isomers of the potent inhibitor Fidarestat ((2S,4S)-6-fluoro-2',5'-dioxospiro[chroman-4,4'-imidazoline]-2-carboxamide) were carried out in order to elucidate the binding modes responsible for the differences in their inhibitory potencies. In the complex structure with the 2R4S-isomer the cyclic imide moiety formed hydrogen bonds with the side-chains of Trp111, Tyr48 and His110. In the attempt to determine the complex structure with the least potent 2R4R-isomer this ligand was not observed, and instead, the active site was simultaneously occupied by two citrate molecules (occupancies of 60% and 40%). In the case of 2S4R, the active site was occupied by a citrate molecule which anchors the 2S4R-isomer from its carbamoyl group. The structures of the complexes suggest that the differences in the interactions between the cyclic imide rings and carbamoyl groups of the compounds with residues His110, Trp111, Trp219 and Cys298 account for differences in their inhibitory potencies.     

Long-term treatment with ranirestat (AS-3201), a potent aldose reductase inhibitor, suppresses diabetic neuropathy and cataract formation in rats

We investigated the chronic functional and histopathological changes in the sciatic nerve and lens of streptozotocin (STZ)-diabetic rats and evaluated the preventive effects of ranirestat (AS-3201), a potent aldose reductase inhibitor, on these changes. Sorbitol levels in the sciatic nerve and lens, motor nerve conduction velocity (MNCV), and development of cataracts were measured in STZ-diabetic rats given a ranirestat-admixed diet (0.0005%) for 35 weeks. Ranirestat reduced sorbitol accumulation in the sciatic nerve and improved the decrease in MNCV of STZ-diabetic rats. Morphological and morphometric examination of changes in sural nerve revealed that treatment with ranirestat prevented both the deformity of myelinated fibers and the decrease in their axonal and myelin areas (atrophy). Ranirestat also averted the changes in the size frequency histogram of myelinated fibers. Finally, STZ-diabetic rats developed early lens opacities 8 weeks after STZ injection and had cataract by the end of the experimental period. However, in the ranirestat-treated diabetic rats, no lens opacity was observed in any rat throughout the entire experimental period. This study suggests that the polyol pathway plays an important role in the progress of diabetic neuropathy and cataract formation in STZ-diabetic rats. Ranirestat should be a promising agent for the treatment of complications associated with diabetes, especially neuropathy.     

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.     

Inhibition of human lens aldose reductase by flavonoids,sulindac and indomethacin

The inhibition of human lens aldose reductase by flavonoids has been studied. Quercetin, the major pentahydroxyflavone, was observed to inhibit human lens aldose reductase by 50% at a concentration of 5 × 10^?6 M. The inhibitory activity of its 3-O-glucoside was similar to that of the parent aglycon. Glycosidation with l-sugar (quercitrin and guaijaverin), however, inproved the inhibitory activity (the IC₅₀ values being 1 × 10^?6 M and 2.5 × 10^?6 M respectively). The improvement in inhibitory activity with glycosidation with l-sugar was also apparent from the high inhibitory activity of myricitrin as compared to myricetin, although the improvement in this case of hexahydroxy flavone glycosidation was significantly less than in the case of penthahydroxy flavone glycosidation. The structure-activity relationship observed for human lens enzyme was similar to that reported previously for rat lens enzyme. Inhibitory activity on the whole however, was lower with human lens enzyme. Some known inhibitors of cyclo-oxygenase such as indomethacin, aspirin and sulindac also inhibited human lens aldose reductase. Thus, an inhibitor of one of the enzymes may actually inhibit both and. when administered, may exert mixed physiological effects.     

Muscarinic receptor density is reduced in diabetic rat atria, an effect prevented by the aldose reductase inhibitor, Statil

Binding assays using [3H]quinuclidinyl benzilate (QNB) as a muscarinic receptor ligand were carried out on atrial tissue from 6 control and 11 six-week streptozocin-diabetic rats. Five of the latter had received the aldose reductase inhibitor, Statil (25 mg kg-1 day-1 orally). Dissociation constants for specific (atropine displaceable QNB) binding were not changed either by diabetes or Statil treatment. Muscarinic receptor numbers, as estimated by Bmax values, were, however, significantly depressed in tissues from the untreated diabetic group, compared with tissues from either the controls or the Statil-treated diabetic group. These results may explain the reduced sensitivity to muscarinic agonists previously observed in atria from similarly diabetic rats and indicate the involvement of the sorbitol pathway in the change. Possible mechanisms are discussed.     

Inhibition of sorbitol formation in human erythrocytes by calcium dobesilate

The effects of calcium dobesilate (Doxium, a drug already known to prevent or reverse the retinal microvascular lesions of diabetes mellitus) on sorbitol formation in human erythrocytes was studied, and compared with the effects of tetramethylene glutaric acid (TMGA), a specific aldose reductase inhibitor. Both compounds inhibited sorbitol formation. In a 29 mmol/l glucose medium, calcium dobesilate in concentrations of 2 and 10 mmol/l caused, 50 and 100% inhibition of sorbitol formation, respectively, whereas TMGA completely inhibited sorbitol formation at a concentration of 0.1 mmol/l. These results suggest that calcium dobesilate may exert, at least in part, its beneficial effect on diabetic microangiopathy by inhibiting the formation of sorbitol. The inhibition of sorbitol synthesis may be mediated by an inhibitory action of calcium dobesilate on aldose reductase.     

Inhibitory effects of isorhamnetin-3-O-beta-D-glucoside from Salicornia herbacea on rat lens aldose reductase and sorbitol accumulation in streptozotocin-induced diabetic rat tissues

The inhibitory effects of compounds from Salicornia herbacea (Chenopodiaceae) on rat lens aldose reductase (RLAR) and sorbitol accumulation in streptozotocin-induced diabetic rat tissues were investigated. The various fractions from the MeOH extract of S. herbacea were tested for their effects on RLAR in vitro. Among them, the EtOAc fraction was found to exhibit a potent RLAR inhibition (IC(50)=0.75 microg/ml), from which an active principle as a potent AR inhibitor was isolated and its chemical structure was elucidated as isorhamnetin-3-O-beta-D-glucoside (1) by spectral analysis. Compound 1 exhibited a potent RLAR inhibition in vitro, its IC(50) being 1.4 microM. Compound 1, when administered orally at 25 mg/kg in streptozotocin (STZ)-induced diabetic rats, caused not only a significant inhibition of serum glucose concentration but also sorbitol accumulation in the lenses, red blood cells (RBC), and sciatic nerves. These results indicate that compound 1 from S. herbacea is a leading compound for further study as a new drug for the prevention and/or treatment of diabetes and its complications.