Four new oleanane-type triterpene saponins, xanifolia-Y0 (1), xanifolia-Y2 (2), xanifolia-Y3 (3), and xanifolia-Y7 (4), were isolated from the husks of Xanthoceras sorbifolia along with two known analogues, xanifolia-Y8 (5) and xanifolia-Y10 (6). The structures of 1-4 were determined by spectroscopic data interpretation and chemical degradation. Compounds 1-6 were evaluated for their cell-growth inhibition activity toward human ovarian cancer cells (OVCAR3) by a MTT assay, and the IC50 values ranged from 4 to 13 microM. On the basis of the results obtained, it is concluded that a C-3 trisaccharide with a galactose and acylation with an angeloyl group at both C-21 and C-22 are important for cell inhibition activity for this class of compounds.

Protoaescigenin, an aglycone of the Olean-12-en, was esterified with tigloyl chloride. Three esterification products: Tig-N, with esterification at C-24 position; Tig-R, with esterification at C-24 and C-28 positions and Tig-S, with esterification at C-24 and C-21 were found to have cell-growth inhibition activity with human ovarian cancer cells (ES2). The IC 50 values for Tig-N, Tig-R and Tig-S are 8.6±5.1µg/ml, 3.6±1.7µg/ml and 0.17±0.20µg/ml, respectively. All compounds have a common C-24 esterification, but Tig-S with the both (C-24 and C-21) esterification has the highest activity. Tig-S induces cell-death by the apoptosis and the drug-treated cells were arrested in the S-phase of cell cycles. Treatment with the esterified products of Protoaescigenin inhibits DNA synthesis in K562 cells in dose and time dependent manner. A drug-combination study of Tig-R with three anticancer drugs: Cytarabine, Camptothecin and Daunomycin, indicated that the drug effect of Tig-R is additive to the drug effect of these agents. This is the first report to show that protoaescigenin esterified with tigloyl groups inhibits DNA synthesis and inhibits cell-growth.