*2.6. Determination of Cytotoxic Concentration (CC50) of Extracts and Acteoside*

Cell cytotoxic concentration of herb extracts and acteoside was determined using Cell counting kit-8 Dojindo Molecular Technologies, as described previously [23]. Briefly, HEp2 cells were seeded into 96-well cell culture plates (2.5 <sup>×</sup> 104 cells/well) and incubated for 12 h. Cells were treated with indicated concentrations of herb extracts or acteoside. Next, at 48-h post treatment, 10 μL of CCK-8 solution was added to each well of the plate. Then, it was incubated for 1 h at 37 ◦C, and absorbance was measured at 450 nm using microplate reader (molecular devices).
