Curcumin Analogues with Aldose Reductase Inhibitory Activity: Synthesis, Biological Evaluation, and Molecular Docking

Curcumin, a constituent of Curcuma longa, has shown numerous biological and pharmacological activities, including antidiabetic effects. Here, a novel series of curcumin analogues were synthesized and evaluated for in vitro inhibition of aldose reductase (AR), the first and rate-limiting enzyme of the polyol pathway, which plays a key role in the onset and progression of diabetic complications. Biological activity studies showed that all the curcuminoids exhibited moderate to good AR inhibitory (ARI) activities compared with that of the quercetin standard. Importantly, compounds 8d, 8h, 9c, 9e, and 10g demonstrated promising ARI activities, with the 50% inhibitory concentration (IC50) values of 5.73, 5.95, 5.11, 5.78, and 5.10 mu M, respectively. Four other compounds exhibited IC50 values in the range of 6.04-6.18 mu M. Methyl and methoxy derivatives showed a remarkable ARI potential compared with that of other substitutions on the aromatic ring. Molecular docking experiments demonstrated that the most active curcuminoid (10g) was able to favorably bind in the active site of the AR enzyme. The potent ARI activities exhibited by the curcuminoids were attributed to their substitution patterns on the aromatic moiety, which may provide novel leads in the development of therapeutics for the treatment of diabetic complications.