Structure Elucidation of Triterpenoid Saponins Found in an Immunoadjuvant Preparation of Using Mass Spectrometry and H and C NMR Spectroscopy.

An immunoadjuvant preparation (named Fraction B) was obtained from the aqueous extract of leaves, and further fractionated by consecutive separations with silica flash MPLC and reverse phase HPLC. Two compounds were isolated, and their structures elucidated using a combination of NMR spectroscopy and mass spectrometry. One of these compounds is a previously undescribed triterpene saponin (), which is an isomer of , the unique adjuvant saponin employed in human vaccines. The other compound is a triterpene saponin previously isolated from bark, known as . The structure of consists of a quillaic acid residue substituted with a β-d-Gal-(1→2)-[β-d-Xyl-(1→3)]-β-d-GlcA trisaccharide at C3, and a β-d-Xyl-(1→4)-α-l-Rha-(1→2)-[α-l-Ara-(1→3)]-β-d-Fuc moiety at C28. The oligosaccharide at C28 was further substituted at O4 of the fucosyl residue with an acyl group capped with a β-d-Xyl residue.