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Diabetic complications including nephropathy, neuropathy, and cataract are leading causes of end-stage renal diseases and neurological disorders. Aldose reductase (AR), the rate-limiting enzyme of the polyol pathway, catalyzes the reduction of glucose to sorbitol via NADPH. Excessive accumulation of intracellular sorbitol found in various tissues of diabetic animals and in cells cultured under high glucose conditions has been proposed to be an important factor for the pathogenesis of diabetic complications. Indole ring-containing AR inhibitors have received considerable attention as potential treatments for diabetic complications. However, these agents have not achieved worldwide use because of limited efficacy or unacceptable adverse effects. In this study, a series of 2-phenylindole derivatives were evaluated via an in vitro spectrophotometric assay for their ability to inhibit rat kidney AR. In addition, the antioxidant and AR inhibitory activities of the compounds under study were compared.

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.

Aldose reductase (AR) is implicated to play a critical role in diabetes and cardiovascular complications because of the reaction it catalyzes. AR enzyme appears to be the key factor in the reduction of glucose to sorbitol. Synthesis and accumulation of sorbitol in cells due to AR activity is the main cause of diabetic complications, such as diabetic cataract, retinopathy, neuropathy and nephropathy. Aldose reductase inhibitors have been found to prevent sorbitol accumulation in tissues. Numerous compounds have been prepared in order to improve the pharmacological prophile of inhibition of aldose reductase enzyme. In this study, seventeen flavonyl-2,4-thiazolidinediones (flavonyl-2,4-TZD) (Ia -e, IIa-e and IIIa-g) were tested for their ability to inhibit rat kidney AR. Compound Ib showed the highest inhibitory activity (88.69^1.46%) whereas Ia, IIa, IIIa, IIIb also showed significant inhibitory activity (49.26^2.85, 67.29^1.09, 71.11^1.95, 64.86^1.21%, respectively).