Fig. 1
Effect of harpagoside on microglial cells viability and scavenger effect on hypoxia-enhanced microglial cells activation. From this study, harpagoside has no significant cytotoxicity on microglial cells; while there is significant difference observed between treated cells (10−5, 10−6, 10−7, 10−8, and 10−9 M harpagoside) with that of the control (n = 4; p < 0.05) at 1, 3, and 7 days’ culture. We chose 10−8 M harpagoside for the further evaluation because there was maximal viability of microglial cells at this concentration (112.9 % of control, p < 0.01) at the 1st day’s culture. Under hypoxia condition (1 % O2), active proliferation of microglial cells was observed when compared with that of normoxic control (n = 4; p < 0.05). With 1 h pre-incubation with harpagoside, hypoxia-enhanced active proliferation of microglial cells was scavenged (n = 4). Similar to previous results, we chose 10−8 M harpagoside for the further evaluation because there was persistent effect throughout the 1st day’s culture