Ursolic acid, a natural pentacyclic triterpenoid carboxylic acid, is a major component of some traditional medicine herbs, foods, and other plants that is known to possess a wide range of biological functions, such as antioxidative, antimicrobial, anti-inflammatory, and anticancer activities. Ursolic acid inhibits Na+/K+-ATPase activity (IC50 = 24.7 μM) and blocks NF-κB activation in various human cancer cells lines (10-100 μM), inhibiting cell proliferation and inducing apoptosis.