AGEs Formation Inhibitory Compounds of Euphorbia pekinensis and Their Effects on Vessel Dilation in Larval Zebrafish In Vivo

This study attempted to identify the active compounds in Euphorbia pekinensis extract for diabetic complications. E. pekinensis extract was applied to a Diaion HP-20 column and was divided into four fractions (I-IV), on the basis of the peaks of UV absorption. Of the four fractions, fraction II, which most significantly inhibited AGEs formation, was purified by preparative RP-HPLC, leading to the isolation of one new ellagic acid derivative, 3,3'-di-O-methylellagic acid 4-O-(6''-O-galloyl)-β-D-galactopyranoside (1), along with three known compounds, geraniin (2), 3,3'-di-O-methylellagic acid 4-O-β-D-xylopyranoside (3), 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 AGEs formation were examined. All compounds markedly inhibited AGE formation with IC₅₀ values of 0.41 – 12.33µM, compared with that of a positive control, aminoguanidine (IC₅₀= 1122.34µM). In addition, the effects of these isolates on the dilation of hyaloid-retinal vessels induced by high glucose (HG) in larval zebrafish were also investigated. Of the tested compounds, compound 2 significantly reduced the dilation of HG-induced hyaloid-retinal vessels. This compound reduced the diameters of HG-induced hyaloid-retinal vessels by about 82.3% and 84.6% at 10 and 20µM, respectively, versus the HG-treated control group, whereas the positive control, VEGFR inhibitor, exhibited 77% inhibition at a concentration of 1µM.