Triterpenoid saponin from the bark of Guaiacum officinale L

A new triterpenoid saponin, guaianin R (1) was isolated from the n-BuOH extract of bark of Guaiacum officinale L. It was characterized as akebonic acid-3-O-alpha-L-rhamnopyranosyl-(1 --> 3)-beta-D-glucopyranosyl-(1 --> 3)-alpha-L-rhamnopyranosyl-(1 --> 2)-alpha-L-arabinopyranoside]-28-O-beta-D-glucopyranosyl]-ester. The structure was established with the help of a comparative study of 1D and 2D 1H- 13C NMR methods. A number of other saponins were isolated and reported from the same species.