Acylated Triterpenoid Saponins from the Stem Bark of Foetidia a fricana

Nine new acylated triterpenoid saponins (4−12) were isolated from the stem bark of Foetidia africana. They all possess barringtogenol C as the aglycone, esterified by acetic and/or isovaleric acids. The sugar chain consists of up to three units: d-glucuronic acid (GlcUA) linked to C-3 of the aglycone and substituted by d-galactose (Gal) (at GlcUA C-2) and/or l-rhamnose (Rha) (at GlcUA C-4). The structures were established by acid and alkaline hydrolysis, by NMR experiments including 1H−H (COSY, HOHAHA, ROESY) and 1H−13C (HSQC, HMBC) spectroscopy, and by mass spectrometry (ESIMS, ESIMSn).