Xanthoceras sorbifolia Bunge (Sapindaceae) is found in the Inner Mongolia region of China. The plant has been used as folk medicine for various diseases. To determine its effect on anti-tumor activity, cancer cell lines derived from 12 different human organs were exposed to the plant extract and their growth properties analyzed with MTT assay. Among the cells studied, OVCAR-3 (derived from ovarian carcinoma) cells were found to be the most sensitive for growth inhibition. The active ingredient was then purified with two times C18 column chromatography. Six active compounds were identified. The IC50 value of the purified products is approximately 1.5 - 4.5 ug/ml. Their chemical structures were determined with NMR (H, C13, HMQC, HMBC, NOESY, HOHAHA) and MS (MALDI-TOF) spectroscopy analysis. These compounds are: Xanifolia-Y1: 3-O-[β-D-galactopyranosyl-(1→2)]-α-L-arabinofuranosyl-(1→3)-β-D-glucuronopyranosyl-21-O-(3,4-diangeloyl)-α-L-rhamnophyranosyl-22-O-acetyl-3β,16α, 21β, 22α, 28-pentahydroxyolean-12-ene. Xanifolia-Y2: 3-O-[β-D-glucopyranosyl-(1→2)]-α-L-arabinofuranosyl-(1→3)-β-D-glucuronopyranosyl-21,22-O-diangeloyl-3β, 15α, 16α, 21β, 22α, 24β, 28-heptahydroxyolean-12-ene. Xanifolia-Y3: 3-O-[β-D-galactopyranosyl-(1→2)]-α-L-arabinofuranosyl-(1→3)-β-D-glucuronopyranosyl-21,22-O-diangeloyl-3β, 15α, 16α, 21β, 22α, 28-hexahydroxyolean-12-ene. Xanifolia-Y8: 3-O-[β-glucopyranosyl (1→2)]-α-arabinofuranosyl (1→3)-β-glucuronopyranosyl-21, 22-O-diangeloyl-3β, 16α, 21β, 22α, 24β, 28-hexahydroxyolean-12-ene. Xanifolia-Y9: 3-O-[β-galactopyranosyl (1→2)]-α-arabinofuranosyl (1→3)-β-glucuronopyranosyl-21-O-(3,4-diangeloyl)-α-rhamnopyranosyl-28-O-acetyl-3β, 16α, 21β, 22α, 28-pentahydroxyolean-12-ene. Xanifoli-Y10: 3-O-[β-galactopyranosyl (1→2)]-α-arabinofuranosyl (1→3)-β-glucuronopyranosyl-21, 22-O-diangeloyl-3β, 16α, 21β, 22α, 28-pentahydroxyolean-12-ene. These active compounds belong to a family of oleanene triterpenoidal saponin. Four of them (Xanifolia Y2, Y3, Y8 and Y10) have a trisaccharide chain attached at C3 of the aglycone and two angeloyl groups are acylated at C21 and C22. Other two (Xanifolia Y1 and Y9) have a trisaccharide chain at C-3 and a monosaccharide at C21 where two angeloyl groups are acylated at C3 and C4 positions. A common feature among these compounds is the presence of the diangeloyl group. To study the structure-function relationship, a compound with a similar structure toY3 but with only one angeloyl group at C22 was investigated. It was found that it has 1/10 of the Y3 activity. Removal of both angeloyl groups from C21 and C22 of Y3 completely abolishes its activity. Results indicate that diangeloyl groups in these compounds are important for anti-tumor activity.
[Proc Amer Assoc Cancer Res, Volume 47, 2006]