New triterpenoid estersaponins from the root barks of Pittosporum verticillatum subsp. verticillatum and evaluation of cytotoxicities

The phytochemical investigation of the root barks of Pittosporum verticillatum Bojer subsp. verticillatum led to the isolation of three new triterpene saponins, 3-O-[β-d-glucopyranosyl-(1 → 2)]-[α-l- arabinopyranosyl-(1 → 3)]-[α-l-arabinofuranosyl-(1 → 4)]-β-d-glucuronopyranosyl-21-O-(2-acetoxy-2-methylbutanoyl)-R1-barrigenol (1), 3-O-[β-d-glucopyranosyl-(1 → 2)]-[α-l-arabinopyranosyl-(1 → 3)]-[α-l-arabinofuranosyl-(1 → 4)]-β-d- glucuronopyranosyl-21-O-(2-acetoxy-2-methylbutanoyl)-28-O-acetyl-R1-barrigenol (2), 3-O-[β-d-glucopyranosyl-(1 → 2)]-[α-l-arabinopyranosyl-(1 → 3)]-[α-l-arabinofuranosyl-(1 → 4)]-β-d- glucuronopyranosyl-21-O-β,β-dimethylacryloyl-22-O-angeloyl-R1- barrigenol (3), and one known saponin senaciapittoside B (4). Their structures were elucidated mainly by 1D- and 2D-NMR spectroscopy and HRESIMS. Compounds 1-4 were evaluated for their cytotoxicity against one human cancer cell line (SW480) and one rat cardiomyoblast cell line (H9c2).