Aldose reductase (AR) is the first enzyme in the polyol pathway. AR has been reported to play an important role in the pathogenesis of diabetic complications. Ursolic acid and fourteen synthetic derivatives with ursane skeleton were tested for recombinant human aldose reductase (rhAR) inhibitory activity for development of diabetic complications. Among them, N-(3beta-hydroxyurs-12-en-28-oyl)-4-aminobutyric acid (XV) showed most potent rhAR inhibitory activity in vitro. Inhibition mode of N-(3beta-hydroxyurs-12-en-28-oyl)-4-aminobutyric acid (XV) was tested uncompetitively by kinetic analysis using the Lineweaver-Burk plots. Ursolic acid derivative N-(3beta-hydroxyurs-12-en-28-oyl)-4-aminobutyric acid is able to inhibit rhAR uncompetitively and could be offered as a lead compound for AR inhibition.