CYTOTOXICITY OF FLAVONOIDS AND SESQUITERPENE LACTONES FROM ARNICA SPECIES AGAINST THE GLC(4) AND THE COLO-320 CELL-LINES

The cytotoxicity of 21 flavonoids and 5 sesquiterpene lactones, as pre sent in Arnica species, was studied in GLC(4), a human small cell lung carcinoma cell line, and in COLO 320, a human colorectal cancer cell line, using the microculture tetrazolium (MTT) assay. Following contin uous incubation, most flavonoids showed moderate to low cytotoxicity, as compared with the reference compound cisplatin (IC50 = 1.1 mu M aga inst GLC(4) and 2.9 mu M against COLO 320). Their IC50 values varied f rom 17 to > 200 mu M. The most toxic compound was the navone jaceosidi n. Of the sesquiterpene lactones tested, helenalin, possessing both th e reactive alpha-methylene-gamma-lactone moiety and a reactive alpha,b eta-unsubstituted cyclopentenone ring, displayed the strongest cytotox icity. For 2 h exposure, its IC50 value was 0.44 mu M against GLC(4) a nd 1.0 mu M against COLO 320. COLO 320 was more sensitive than GLC4 fo r many flavonoids (especially for flavones), but more resistant to the cytotoxic effect of the sesquiterpene lactones bearing an exocylic me thylene group fused to the lactone function.