Triterpenoid Saponins from the Cultivar ``Green Elf'' of Pittosporum tenuifolium

Four oleanane-type glycosides were isolated from a horticultural cultivar ``Green Elf `` of the endemic Pittosporum tenuifolium (Pittosporaceae) from New Zealand: three acylated barringtogenol C glycosides from the leaves, with two previously undescribed 3-O-beta-d-glucopyranosyl-(1 & RARR;2)-[alpha-l-arabinopyranosyl-(1 & RARR;3)]-beta-d-glucuronopyranosyl-21-O-angeloyl-28-O-acetylbarringtogen ol C, 3-O-beta-d-galactopyranosyl-(1 & RARR;2)-[alpha-l-arabinopyranosyl-(1 & RARR;3)]-beta-d-glucuronopyranosyl-21-O-angeloyl-28-O-acetylbarringtogen ol C, and the known 3-O-beta-d-glucopyranosyl-(1 & RARR;2)-[alpha-l-arabinopyranosyl-(1 & RARR;3)]-beta-d-glucuronopyranosyl-21-O-angeloyl-28-O-acetylbarringtogen ol C (Eryngioside L). From the roots, the known 3-O-beta-d-glucopyranosyl-(1 & RARR;2)-beta-d-galactopyranosyl-(1 & RARR;2)-beta-d-glucuronopyranosyloleanolic acid (Sandrosaponin X) was identified. Their structures were elucidated by spectroscopic methods including 1D- and 2D-NMR experiments and mass spectrometry (ESI-MS). According to their structural similarities with gymnemic acids, the inhibitory activities on the sweet taste TAS1R2/TAS1R3 receptor of an aqueous ethanolic extract of the leaves and roots, a crude saponin mixture, 3-O-beta-d-glucopyranosyl-(1 & RARR;2)-[alpha-l-arabinopyranosyl-(1 & RARR;3)]-beta-d-glucuronopyranosyl-21-O-angeloyl-28-O-acetylbarringtogen ol C, and Eryngioside L were evaluated.