3-O-(E)-p-coumaroyl tormentic acid may be promising lead compound for developing an effective drug for treatment of leukemia, it induces apoptotic cell death in human leukemia (HL60) via mainly mitochondrial pathway by, at least in part, Topo I inhibition. 3-O-trans-p-coumaroyltormentic acid shows cytotoxicity against four human tumor cell lines (A549, SK-OV-3, SK-MEL-2, and HCT-15) in vitro, the IC50 values of 13.72, 14.29,14.61, 14.04 uM, respectively. 3beta-O-cis-p-Coumaroyltormentic acid, and 3beta-O-trans-p-coumaroyltormentic acid are weakly selective for vancomycin-resistant Enterococcus (VRE) compared with eukaryotic cells, with an MIC of 59.4microg/mL and a 50% inhibitory concentration (IC50) of 72.0microg/mL for monkey kidney epithelial (MA104) cells. A mixture of 3-O-cis-p-coumaroyltormentic acid and 3-O-trans-p-coumaroyltormentic acid shows an inhibitory effect comparable to (-)-epigallocatechin gallate (EGCG) of green tea on the activation of Epstein-Barr virus early antigen (EBV-EA) induced by 12-O-tetradeca--noylphorbol-13-acetate (TPA).