Cytotoxicity of diphyllin 1 and cleistanthin B 8. (A) Structure of diphyllin 1; atom numbering is included. (B) Structure of cleistanthin B 8. (C) Cytotoxicities of diphyllin 1 for Vero, PS, UKF-NB-4, BHK-21, Huh-7, and HBCA were expressed as a percentage of cell viability at the indicated drug concentration. The cells were seeded in 96-well plates for 24 h, then treated with diphyllin 1 and incubated for 48 h. Diphyllin 1-treated BHK-21 cells were incubated for 72 h. Cell viabilities were measured by Cell Counting Kit-8. (D) Cytotoxicities of cleistanthin B 8 were expressed as percentage cell viability at the indicated drug concentration. The experimental procedure was the same as in (C). (E) Time-dependent cytotoxic effects of diphyllin 1 on Vero cells. Vero cells were seeded in 96-well plates for 24 h, then treated with diphyllin 1 at the indicated concentrations. Cell viabilities were determined after 48, 72, and 144 h of incubation. (F) Time-dependent cytotoxic effects of cleistanthin B 8 on Vero cells, as determined after 48, 72, and 144 h of incubation.