Unusual C,O-Fused Glycosylapigenins from Serjania marginata Leaves

Abstract

A phytochemical study of a Serjania marginata leaf extract with antiulcer activity afforded 15 compounds, including the new 3-O-α-L-arabinopyranosyl(1→3)-α-Lrhamnopyranosyl(1→2)[β-D-glucopyranosyl(1→4)]-α-Larabinopyranosyloleanolic acid (1) and 7,5″-anhydroapigenin 8-C-α-(2,6-dideoxy-5-hydroxy-ribo-hexopyranosyl)-4′-O-β-D-glucopyranoside (4). The structures of the new compounds were determined by spectroscopic analysis, including 1D and 2D NMR techniques, mass spectrometry, and chemical methods. Compound 4 is a C-hexopyranosylapigenin with an unusual cyclic ether linkage between C-5″ and C-7 of apigenin. The isolated proanthocyanidins have high antioxidant activities, and these compounds are probably responsible for the gastroprotective effect of the extract.