Polyphenols from Euphorbia pekinensis Inhibit AGEs Formation In Vitro and Vessel Dilation in Larval Zebrafish In Vivo

To identify active compounds in the roots of Euphorbia pekinensis for treatment of diabetic complications, an active column fraction from a 70% EtOH extract of E. pekinensis root was purified by preparative reversed-phase high-performance liquid chromatography, leading to the isolation of a new ellagic acid derivative, 3,3-di- O -methylellagic acid 4- O -(6- O -galloyl)- -D-galactopyranoside ( 1 ), along with three known compounds, geraniin ( 2 ), 3,3-di- O -methylellagic acid 4- O - -D-xylopyranoside ( 3 ), and ellagic acid 3,3-dimethyl ether ( 4 ). The structure of the new compound was established by extensive spectroscopic studies and chemical evidence. The inhibitory effects of isolated compounds 1 - 4 on advanced glycation end-products (AGEs) formation were examined. All compounds exhibited considerable inhibition of AGEs formation and IC (50) values of 0.41-12.33 mu M, compared with those of the positive controls aminoguanidine (IC (50) =1122.34 mu M) and quercetin (IC (50) =27.80 mu M). In addition, the effects of 2 and 4 on the dilation of hyaloid-retinal vessels induced by high glucose (HG) in larval zebrafish were investigated; both compounds significantly reduced the HG-induced dilation of hyaloid-retinal vessels relative to the HG-treated control group.