Proanthocyanidins from Whole Spenceria ramalana Plants and Their Effects on AGE Formation in Vitro and 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), were isolated from the whole plant of Spenceria ramalana, together with three known compounds (4 – 6). The inhibitory effects of isolated compounds (1 – 6) on the formation of AGE were examined in vitro; compounds 3 and 6 showed the strongest inhibition, with IC50 values of 17.4 ± 0.9 and 14.1 ± 2.8 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.