Triterpenoid saponins from Pteleopsis suberosa stem bark

Thirteen oleanane saponins (1-13), four of which were new compds. (1-4), were isolated from Pteleopsis suberosa Engl. et Diels stem bark (Combretaceae). Their structures were detd. by 1D and 2D NMR spectroscopy and ESI-MS spectrometry. The compds. were identified as 2α,3β,19α,23,24-pentahydroxy-11-oxo-olean-12-en-28-oic acid 28-O-β-D-glucopyranosyl ester (1), 2α,3β,19β,23,24-pentahydroxy-11-oxo-olean-12-en-28-oic acid 28-O-β-D-glucopyranosyl ester (2), 2α,3β,19α,23-tetrahydroxy-11-oxo-olean-12-en-28-oic acid 28-O-β-D-glucopyranosyl ester (3), and 2α,3β,6β,19α,24-pentahydroxy-11-oxo-olean-12- en-28-oic acid 28-O-β-D-glucopyranosyl ester (4). The presence of α,β-unsatd. carbonyl function was not common in the oleanane class and the aglycons of these compds. were not found previously in the literature. Moreover, the isolated compds. were tested against Helicobacter pylori std. and vacA, and cagA clin. virulence genotypes. Results showed that compd. 6 has an anti-H. pylori activity against three metronidazole-resistant strains (Ci 1 cagA, Ci 2 vacA, and Ci 3).