Inhibition of Aldose Reductase and Red Blood Cell Sorbitol Accumulation by Extract of Capparis spinosa

Activation of polyol pathway, due to increased aldose reductase (ALR2) activity, is one of the several mechanisms that have been involved in the development of secondary complications of diabetes. Therefore, ALR2 inhibition has been recognized as a potential therapeutic goal in the prevention and treatment of various secondary complications of diabetes, such as cataract. In this study, we aimed to evaluate the inhibitory effects of hydro alcoholic Capparis spinosa extract (CSE) on ALR2 and sorbitol accumulation in red blood cells (RBCs). The hydroalcoholic extract of Capparis spinosa (C. spinosa) was prepared and its inhibitory effects were evaluated by using the partial purified bovine lens ALR2 and its specificity was checked by comparing with its inhibitory effect on aldehyde reductase (ALR1), the other member of aldo-keto reductases family. Because RBC sorbitol accumulation is strongly correlated with the blood glucose level, the effect of CSE on sorbitol accumulation in human RBCs, preincubated with high serum glucose concentration, was determined. The CSE inhibited ALR2 activity, with an IC50 of 0.54 mg/mL and it was seven and a half times greater than that of ALR1 inhibition, indicating the specificity of CSE for ALR2, rather than ALR1. Also, CSE, at a concentration of 0.54 mg/mL, could reduce sorbitol accumulation in erythrocytes, by 46.8%. These results demonstrated that CSE, mainly through inhibition of ALR2, could prevent or delay the diabetic complications, like cataract formation, as a result of sorbitol accumulation.