Two new acylated triterpenoid saponins from Tetrapleura tetraptera

Abstract

Tetrapleura tetraptera (Schum. et Thonn.) Taub. (Mimosaceae) is a tree that grows in the West and Central Africa. This plant has many pharmacological and ethnopharmacological potential uses, such as the treatment against convulsions, leprosy, inflamation, rheumatism [1,2], flatulence, jaundice, fevers [3], and epilepsy [4]. As part of our continuing search for new bioactive triterpene saponins from Cameroonian medicinal plants, a butanol fraction of the methanolic extract of the stem bark of T. tetraptera was submitted to multiple chromatographic steps (VLC, FLASH, MPLC on normal Silica gel and reversed phase Silica gel) affording two new acylated triterpenoid saponins (1) and (2). Their structures characterized as 3-O-{β-D-glucopyranosyl-(1→3)-6-O-[(2E,6S)-2,6-dimethyl-6-hydroxy-octa-2,7-dienoyl]-β-D-glucopyranosyl-(1→2)-β-D-glucopyranosyl-(1→4)]-[β-D-glucopyranosyl-(1→2)]-β-D-glucopyranosyl} 3,27-dihydroxyoleanolic acid (1) and 3-O-{β-D-glucopyranosyl-(1→2)-β-D-glucopyranosyl-(1→3)-β-D-glucopyranosyl(1→4)-[6-O-(E)-feruloyl]-β-D-glucopyranosyl-(1→4)-β-D-glucopyranosyl} 3,27-dihydroxyoleanolic acid (2), were mainly established by extensive analysis of 1D- (1H and 13C/DEPT) and 2D-NMR experiments (COSY, NOESY, TOCSY, HSQC, HMBC) and FAB- and HRESI-mass spectrometry.