Proanthocyanidins from Spenceria ramalana and Their Effects on AGE Formation in Vitro and Hyaloid-Retinal Vessel Dilation in Larval Zebrafish in Vivo

Abstract

Three new A-type proanthocyanidins (1-3), ent-epiafzelechin-(2 alpha -> O -> 7,4 alpha -> 8)-ent-afzelechin 3'-O-beta-D-glycopyranoside (1), ent-epiafzelechin-(2 alpha -> O -> 7,4 alpha -> 8)-ent-epiafzelechin-(2 alpha -> O -> 7,4 alpha -> 8)-ent-afzelechin (2), and ent-epiafzelechin-(2 alpha -> O -> 7,4 alpha -> 8) -ent-epiafzelechin-(2 alpha -> O -> 7,4 alpha -> 8)-ent-afzelechin (3), and three known compounds (4-6) were isolated from the whole plant of Spenceria ramalana. The structures of the new proanthocyanidins were established by spectroscopic and chemical studies. The inhibitory effects of compounds 1-6 on the formation of advanced glycation end products were examined in vitro. Compounds 3 and 6 showed the strongest inhibition, with IC50 values of 17.4 +/- 0.5 and 14.1 +/- 1.6 mu M, respectively. The effects of these isolates on the dilation of hyaloid-retinal vessels induced by high glucose (HG) in larval zebrafish were also investigated. Compound 3 reduced the dilation of HG-induced hyaloid-retinal vessels most effectively. This compound reduced the diameters of HG-induced hyaloid-retinal vessels by about 157.7% and 164.1% at 10 and 20 mu M, respectively, versus the HG-treated control group.