Proanthocyanidins from Spenceria ramalana and their effects on AGE formation in vitro and hyaloid-retinal vessel dilation in larval zebrafish in vivo.

Three new A-type proanthocyanidins (1-3), ent-epiafzelechin-(2α→O→7,4α→8)-ent-afzelechin 3'-O-β-D-glycopyranoside (1), ent-epiafzelechin-(2α→O→7,4α→8)-ent-epiafzelechin-(2α→O→7,4α→8)-ent-afzelechin (2), and ent-epiafzelechin-(2α→O→7,4α→8)-ent-epicatechin-(2α→O→7,4α→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 μM, 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 μM, respectively, versus the HG-treated control group.