Abstract
During the course of our screening of bioactive natural products, three new saponins named periandradulcins A (1), B (2) and C (3) were isolated as phosphodiesterase (PDE, EC 3.1.4.17) inhibitors from 80% MeOH extract of the roots of Periandra dulcis MART. (Leguminosae) by a combination of column chromatography and reversed- and normal-phase high-performance liquid chromatography (HPLC). On the basis of -1H, 13C- and two-dimensional nuclear magnetic resonance (NMR) spectral data and chemical evidence, their chemical structures were characterized as 3-O-β-[α-L-rhamnopyranosyl(1→2)-β-D-xylopyranosyl(1→2)-β-D-glucuronopyranosyl]-30-hydroxyl-25-formylolean-18-ene-22β-O-syringate, 3-O-β-[α-L-rhamnopyranosyl(1→2)-β-D-xylopyranosyl(1→2)-β-D-glucuronopyranosyl]-22β-hydroxyl-25-formylolean-12-ene and 3-O-β-[α-L-rhamnopyranosyl(1→2)-β-D-glucopyranosyl(1→2)-β-D-glucuronopyranosyl]-22β-hydroxyl-25-formylolean-18-ene, respectively.The concentrations of periandradulcins A, B and C required to give 50% inhibition (IC50 values) of PDE from bovine heart, were 0.033, 7.6 and 7.7 μM, respectively. Compound 1 was the most potent among the known PDE inhibitors; it inhibited PDE-I (IC50 : 0.0022 μM) twenty and forty times more effectively than PDE-II and -III, respectively.
