DECREASED HELENALIN-INDUCED CYTOTOXICITY BY FLAVONOIDS FROM ARNICA ASSTUDIED IN A HUMAN LUNG-CARCINOMA CELL-LINE

The effect of the flavones apigenin, luteolin, hispidulin and eupafoli n, and of the flavonols kaempferol, quercetin, 6-methoxykaempferol and patuletin from Amica spp, on the cytotoxicity of the sesquiterpene la ctone helenalin was studied in the human lung carcinoma cell line GLC( 4) using the microculture tetrazolium (MTT) assay. The tumour cells we re exposed to the test compounds for 2 h. Helenalin concentrations aro und its control IC50 value, 0.5 mu M, were combined with flavonoid con centrations ranging from 0.01 to 20 mu M. At non-toxic concentrations, up to 10 mu M, all flavonoids except kaempferol significantly reduced the helenalin-induced cytotoxicity. Hispidulin and patuletin displaye d their modulating effect on helenalin-induced cytotoxicity in the bro adest concentration range. The strongest effect was found with 5 and 1 0 mu M hispidulin, 0.05 mu M quercetin, and 1 mu M patuletin, increasi ng the IC50 value of helenalin with circa 40%. No dose-dependency was found in the concentration range tested.