Fig. 3

Cytotoxicity of betulin after (A) 24, (B) 48 and (C) 72 h of cells exposure (SRB assay)

Cytotoxicity expressed as the percentage of the total cellular protein content in control (nontreated) cells. Betulin concentrations in µg/mL. All data expressed as means ± SD (standard deviation) for n = 3 independent experiments. Asterisks refer to statistically significant differences between control and treatments analyzed by one-way ANOVA followed by Dunnett’s posttest; * p<0.05, ** p<0.01, *** p<0.001. Lower case letters indicate significant differences between the two cell lines at the same time points determined using Student’s t-test; ^ap<0.05, ^bp<0.01. NT – betulin concentration not tested (for NIH/3T3 cells)