DNA content of HepG2 cells detected by flow cytometry. Untreated HepG2 cells (purple square); HepG2-treated eurycomanone (red square) and HepG2-treated vinblastine sulfate (orange square); for 24, 48 and 72 hours (a). A = G0 phase; B = G1 phase; C = S phase; D = G2/M phase. Untreated cells showed the highest peak in the region of G1 phase and a small low peak in G2/M phase. HepG2 cells treated with eurycomanone increased at G2/M peak suggested that, eurycomanone arrested HepG2 cell cycle at G2/M phase. Following vinblastine treatment, as a control drug, the G2/M peak dramatically increased. The significant accumulation of cells clearly indicates that vinblastine sulfate efficiently arrested the cell cycle progress in HepG2 cells at the G2/M phase.