Aerial parts and roots of three Digitalis species (Digitalis davisiana Heywood, Digitalis viridiflora Lindley and Digitalis grandiflora Miller; Plantaginaceae) were investigated from the viewpoint of cytotoxicity to identify the biologically active parts. Playing a role in cell proliferation and tumor growth, LXRα agonist activity also has become of interest to researchers investigating its relationship with the cytotoxicity.
Materials and methods
Cytotoxicity of aqueous extracts was determined through HEp-2, HepG2 and 3Y1 cells using MTT method. LXRα agonist activity was determined through luciferase reporter gene assay on HEK293 cells.
Tested extracts showed strong cytotoxicity on HEp-2 cells with IC50 values between 19.7 and 79.6 μg/mL. Cytotoxicity on HepG2 cells was found to be lower (IC50; 211.4–2152.9 μg/mL). On 3Y1 cells, extracts showed concentration dependent cytostatic activity (IC50; 87.9–772.3 μg/mL). Extracts showed cytotoxicity on HEK293 cells at a concentration of 100 μg/mL; therefore, dilutions were made. However, due to dilutions, LXRα agonist activity was found to be low.
The extracts exhibited selective cytotoxicity on cancer and non-cancerous cells. Moreover, the selectivity was seen between different cancer cells. Any relationship could not be found between cytotoxicity and LXRα agonist activity, due to the low agonist effects. Further investigations are needed to clarify the mechanism of activity.