Scatter plots of Ann/PI-untreated HepG2 cells under four situations in quadrant analysis. They are living cells (A3), apoptotic cells (A4), late apoptotic or dead cells (A2) and necrotic or dead cells (A1). Exposed for 24 hours (1); exposed for 48 hours (2); exposed for 72 hours (3)(a). The graph summarized the number of cells in each quadrant (b). The values of the bars represented mean ± S.D. of three independent experiments. P < 0.05.