Figure 4

The screening effect of IκB–EGFP drug discovery system assayed on propolis. Taiwan propolis (propolis 1 and 2), Brazil red propolis (propolis 3 and 4), and Brazil green propolis (propolis 5 and 6) were dissolved in 80% ethanol and used as test samples to verify the ability of the pIκB–EGFP drug discovery system. pIκB–EGFP-transfected 293 cells were used as a control group; PMA (50 ng/ml) and curcumin were other control groups used for initiating or inhibiting IκB–EGFP degradation. Ethanol (80%) was added into pIκB–EGFP-transfected 293 cells to verify if the fluorescence increase was due to the background effect of solvent used. After 24-h incubation of the propolis, the amount of IκB–EGFP proteins (shown as EGFP expression fold compared to control group) was measured by flow cytometry (results expressed as mean ± standard deviation).