Fig. 2. Cytotoxic activity of luteolin against A549 cells. (A) 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay after 24 h treatment.

(B) Phase contrast microscopy and Hoechst 33342 staining after 24 h treatment (scale bar = 100 µm). White arrowheads indicate the apoptotic cells. (C) The number of apoptotic cells. Data are shown as mean ± SEM from four independent experiments. ^*P < 0.001 versus the control.