Ridaifen (RID)‐B‐induced apoptosis is caspase dependent. (a) Jurkat cells were incubated with 4 µM RID‐B for the indicated times. The cells were lysed and subjected to caspase‐3, caspase‐8, and caspase‐9 assay. The results are presented as a comparison with the 0‐h treatment. Data are representative of three independent experiments. (b) Jurkat cells were incubated with or without the indicated doses of acetyl (Ac)‐DEVD‐CHO for 1 h, and thereafter incubated with or without 4 µM RID‐B for 4 h. The cells were lysed and subjected to caspase‐3, caspase‐8, and caspase‐9 assay. The results are presented as a comparison with the 0‐h treatment. Data are representative of three independent experiments. (c) Jurkat cells were incubated with or without the indicated doses of Ac‐DEVD‐CHO for 1 h, and thereafter incubated with or without 4 µM RID‐B for 4 h. DNA fragmentation assay was carried out by agarose gel electrophoresis.