Piptadenin, a Novel 3,4-Secooleanane Triterpene and Piptadenamide, a New Ceramide from the Stem Bark of Piptadeniastrum africanum (Hook.f.) Brenan.

Piptadenin (1), a new triterpene along with piptadenamide (10), a new ceramide, have been isolated from the AcOEt-soluble fraction of the MeOH extract of the stem bark of Piptadeniastrum africanum along with nine known compounds, 1-O-[(3β,22β)-3,22-dihydroxy-28-oxoolean-12-en-28-yl]-β-d-glucopyranose (2), 22β-hydroxyoleanic acid (3), oleanic acid (4), lupeol (5), betulinic acid (6), 5α-stigmasta-7,22-dien-3β-ol (7), 5α-stigmasta-7,22-dien-3-one (8), (3β)-stigmast-5-en-3-yl β-d-glucopyranoside (9) and 2,3-dihydroxypropyl hexacosanoate (11). Except for compound 11, all the isolated compounds are reported for the first time from this plant. The structures of the isolated compounds were elucidated by spectroscopic data including 1D and 2D NMR. The pure compounds 1 – 11 were subjected to the pharmacological screening and compounds 2, 5 – 7 and 9 exhibited potent urease inhibitory activity with IC50 value of 25.8, 28.9, 30.1, 31.8 and 32.7 μm, respectively, whereas compound 1 showed moderate activity (IC50 = 98.7 μm). The potent urease inhibitory activity supplemented the previous literature reports and medicinal uses of this plant.