Glycyrrhiza prevented MPP+-induced cell death more potently than rhubarb.

NGF-differentiated PC12D cells were treated with various concentrations of rhubarb and Glycyrrhiza (rhubarb:Glycyrrhiza ratio = 1∶0, 8∶1, 4∶1, 2∶1, 1∶1, 1∶2, 1∶4, 1∶8, 0∶1) in the presence of 0.3 mM MPP+ for 48 h. Cell viability was evaluated by trypan blue exclusion assay. Values are the means of three independent experiments; bars, s.d. **p<0.01 compared with MPP+ group cells.