Provided herein is a crystallized ternary structure of human aldose reductase (AR) bound to NADPH and .gamma.-glutamyl-S-(1,2-dicarboxyethyl)cysteinylglycine (DCEG). Also provided are specific inhibitors of glutathione-aldehyde binding to aldose reductase which are designed via at least computer modeling of the ternary AR:NADPH:DCEG structure and methods of designing and of screening the inhibitors for inhibition of glutathione-aldehyde binding to aldose reductase.