Semi-Synthesis of Kaurenoic Acid Derivatives and Their In Vitro Cytotoxic Activities

The cytotoxic activities of the diterpene kaurenoic acid ( 1 ) and its 15 semi-synthesis derivatives were assessed on human cell cultures. The human tumor cells used comprised colon (SW620 and SW480), pancreatic (PANC-1 and BxPC-3), stomach (SGC-7901), esophageal (Eca-109), and leukemia (K562 and HL-60). Kaurenoic acid was inactive against the tumor cell lines; however, its derivatives which contain α,β -unsaturated ketone rendered compounds with cytotoxic activity. Compounds 5 – 14, 17 – 19 , and 24 with a substitution at the C-4 position showed significant inhibitory activity against the tested cell lines, while compound 3 , without a substitution at the C-4 position, was slightly less active in these cell lines. The SW620 colon cancer cell was highly susceptible to all of the tested derivatives.