Triterpene saponins from Antonia ovata leaves

Six pentacyclic triterpenoid saponins, named antoniosides E-J along with two known alkaloids, were isolated from the leaves of Antonia ovata. Their structures were determined by the extensive use of 1D and 2D-NMR experiments along with HRESIMS analysis and acid hydrolysis. All isolated saponins contained the same pentasaccharide chain: 3-O-[beta-D-glucopyranosyl-(1 -> 2)]-[beta-D-glucopyranosyl-(1 -> 4)]-[beta-D-glucopyranosyl-(1 -> 3)-alpha-L-arabinopyranosyl(1 -> 6)]-beta-D-glucopyranoside, linked at C-3 of esterified derivatives of polyhydroxyoleanene triterpenoids (theasapogenol A and 15 alpha-hydroxy-theasapogenol A). Isolated compounds were evaluated for their cytotoxic activity against KB cell line by a WST-1 assay, and the IC50 values ranged from 3.3 to 5.3 mu M.