Effect of the taccalonolides on cell cycle distribution. HeLa cells were treated with vehicle (A), 12 nM paclitaxel (B), 3.5 µM taccalonolide A (C), 0.8 µM taccalonolide B (D), 2.5 µM taccalonolide E (E), 1.3 µM taccalonolide N (F), 111 µM taccalonolide R (G), 3.5 µM taccalonolide T (H), 0.6 µM taccalonolide Z (I), 0.32 µM taccalonolide AA (J) or 13.5 µM taccalonolide AB (K) for 18 h and stained with Kirshan’s reagent. Open and filled arrowheads denote the populations of cells with 2N (G1) and 4N (G2/M) DNA content, respectively.