Figure 2: Effect of co-treatment with SYR + Fe (II) or SYR + Cu (II) on the cell viability of HEK 293 and HepG2 after 24 h (upper) and 72 h (lower) of incubation. (A) SYR (125 and 250 μM) + Fe (II) 100 μM in HepG2 cells; (B and C) SYR (125 and 250 μM) + Cu (II) (100 and 250 μM) in HEK 293 and HepG2 cells. Cell viability was determined using MTT assay. The data are expressed as mean ± SD of at least three independent experiments and analyzed by one-way analysis of variance followed by Dunnett post-test. *P < 0.05; ***P < 0.001 compared with the control group. +++P < 0.001 compared with the Cu (II) (100 μM) group. #P < 0.05; ###P < 0.001 compared with the Cu (II) (250 μM) group.