['To investigate the effect of puerarin on lipopolysaccharide (LPS)-activated N9 microglia cells.', 'MTT was used to detect the cytotoxic effect of puerarin and LPS on N9 microglia cells. Flow cytometry was used to determine the effect of puerarin on cellular production of nitric oxide (NO) and reactive oxygen species (ROS), apoptosis and cell cycle in LPS-activated N9 microglia cells. The amount of NO released into the supernatant was detected by Griess assay. The HE staining was used to show the morphological response of LPS-activated N9 microglia cells to puerarin.', 'Morphologically, amoeba-like LPS-activated N9 cells turned to be round in quiescence after treated with puerarin (100-200 micromol/L). Puerarin (50-200 micromol/L) caused less amount of NO released into the supernatant, with 12.43+/-0.11 micromol/L of NO at a dose of 200 micromol/L puerarin compared with 23.45+/-0.19 micromol/L in untreated control (P<0.01). Likewise, puerarin (200 micromol/L) completely abolished the ROS-producing ability of LPS-activated N9 cells, with a basal ROS level comparable to the non-LPS-treated control. Puerarin also exerted an anti-apoptotic effect on the LPS-activated N9 cells and rescued the cells from G(0)/G(1) arrest.'] Does [ Puerarin antagonize activation effect of LPS on N9 microglia cells ]?