Cytotoxicity of Flavonoids and Sesquiterpene Lactones fromArnicaSpecies Against the GLC4and the COLO 320 Cell Lines

Abstract

The cytotoxicity of 21 flavonoids and 5 sesquiterpene lactones, as present in Arnica species, was studied in GLC₄, 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 continuous incubation, most flavonoids showed moderate to low cytotoxicity, as compared with the reference compound cisplatin (IC₅₀ = 1.1 nM against GLC₄ and 2.9 µM against COLO 320). Their IC₅₀ values varied from 17 to >200 µM. The most toxic compound was the flavone jaceosidin. Of the sesquiterpene lactones tested, helenalin, possessing both the reactive α-methylene-γ-lactone moiety and a reactive α,β-unsubstituted cyclopentenone ring, displayed the strongest cytotoxicity. For 2 h exposure, its IC₅₀ value was 0.44 µM against GLC₄ and 1.0 µM against COLO 320. COLO 320 was more sensitive than GLC₄ for many flavonoids (especially for flavones), but more resistant to the cytotoxic effect of the sesquiterpene lactones bearing an exocylic methylene group fused to the lactone function.