Structure elucidation of an acetylated saponin of Blighia welwitschii by NMR spectroscopy

A new glycosylated triterpene has been isolated from the fruit of Blighia welwitschii. The structural analysis of its peracetylated derivative (1) was performed by 2D homonuclear and heteronuclear NMR spectroscopy. The saponin was shown to contain hederagenin and five sugar residues forming two glycosyl chains. The complete structure of the saponin was established to be 3-0-[β-d-Glcp-(1 → 3)-α-l-Rhap-(1 → 2)- α-l-Arap]-28-O-[β-d-Glcp-(1 → 6)-β-d-Glcp]hederagenin.