Abstract: BJECTIVE: To assess the anti_human hepatoma effects of five sesquiterpene lactones from the roots of Inula helenium, and to explore the relationship between structure and activity and the possible mechanism of antitumor action. METHODS: Using MTT assay to evaluate the antitumor activities of five sesquiterpene lactones on the human hepatoma cell line HLE, and to explore the cytotoxicity on human embryonic lung cells. The rate of cell proliferation was determined by grafted tumor assay in vivo. RESULTS: Isoalantolactone exhibited significant anti_proliferative activities to hepatoma cell, while other compounds demonstrated weak anti_proliferative activities. Isoalantolactone significantly inhibited tumor growth of H22 tumor_bearing mice. Isoalantolactone showed no toxicity to human embryonic lung cell line in vitro. CONCLUSION: These results clearly demonstrated that the anti_tumor activities had close relationship with the structures, β_unsaturated five_membered lactone ring was necessary for the activities. When β_unsaturated five_membered lactone become saturated or the bond between C_5 and C_10 of ring_A and ring_B broken to form a 10_membered macroring, anti_proliferative activity was either diminished or lost.

Key words: inula helenium, sesquiterpenes, human hepatoma cell line, anti_proliferative activity, structure_activity relationship