Neurotrophic and neuroprotective actions of ginsenosides Rb(1) and Rg(1)

The ginsenosides have many pharmacological actions, including various actions on the nervous system. Our previous studies have demonstrated that two ginsenosides, Rb(1) and Rg(1) improve performance in a passive avoidance-learning paradigm and enhance cholinergic metabolism. The present study was designed to examine the cellular neurotrophic and neuroprotective actions of two pure ginsenosides in two model systems. PC12 cells were grown in the absence or presence of nerve growth factor (NGF) as a positive control, and different concentrations of Rb(1) or Rg(1). To assess neurotrophic properties, neurite outgrowth was quantified for representative fields of cells. After 8 days in culture, both ginsenosides enhanced neurite outgrowth in the presence of a sub-optimal dose of (2 ng/ml) NGF, but did not significantly stimulate neurite outgrowth in the absence of NGF. However, after 18 days in culture, both ginsenosides increased neurite outgrowth in the absence of NGF. SN-K-SH cells were grown in the absence or presence of MPTP or beta-amyloid to assess neuroprotection. Rb(1) and Rg(1) both reversed MPTP-induced cell death. beta-Amyloid-induced cell death was not reversed by either ginsenoside, but Rg(1) produced a modest enhancement of cell death in this model. These results suggest that these two ginsenosides have neurotrophic and selective neuroprotective actions that may contribute to the purported enhancement of cognitive function.