Helenalin induces cell cycle arrest in G1 phase and modulates apoptosis in a time-dependent manner. (A) 1.85 × 105 cells/ml were seeded onto 6-well plates and incubated for 24 h. 2uM of helenalin was added to the culture medium and incubated for 4,8,12 and 24 h. Cells were harvested and analyzed by flow cytometry. The cell cycle phase distribution was determined using CellQuest software. Figures represent data from three independent experiments. (B) Percent of cells in Sub-G1 after the indicated timepoints representing three biological experiments.