Bioassay-guided isolation of aldose reductase inhibitors from Artemisia dracunculus

An ethanolic extract of Artemisia dracunculus L. having antidiabetic activity was examined as a possible aldose reductase (ALR2) inhibitor, a key enzyme involved in diabetic complications. At 3.75 microg/mL, the total extract inhibited ALR2 activity by 40%, while quercitrin, a known ALR2 inhibitor, inhibited its activity by 54%. Bioactivity guided fractionation and isolation of the compounds that inhibit ALR2 activity was carried out with the total ethanolic extract yielding four bioactive compounds with ALR2 inhibitory activity ranging from 58% to 77% at 3.75 microg/mL. Using LC/MS, (1)H NMR, (13)C NMR and 2D NMR spectroscopic analyses, the four compounds were identified as 4,5-di-O-caffeoylquinic acid, davidigenin, 6-demethoxycapillarisin and 2',4'-dihydroxy-4-methoxydihydrochalcone. This is the first report on their isolation from A. dracunculus and the ALR2 inhibitory activity of 4,5-di-O-caffeoylquinic acid, 6-demethoxycapillarisin and 2',4'-dihydroxy-4-methoxydihydrochalcone. These results suggest a use of the extract of A. dracunculus for ameliorating diabetic complications.