Protection of HT22 neuronal cells against glutamate toxicity mediated by the antioxidant activity of Pueraria candollei var. mirifica extracts

Neuronal degeneration is known to be due to oxidative stress acting through a pathway involving the excessive activation of glutamate receptors. We studied the neuroprotection potential of an ethyl acetate-ethanol extract of Pueraria mirifica (P. candollei var. mirifica) root (PM extract). PM extract was evaluated for its antioxidant and neuroprotective activities against glutamate toxicity in mouse hippocampal HT22 neuronal cells. The extract at concentrations of 10 and 50 mu g/ml exhibited considerable antioxidant activity with significant neuroprotection, based on the microscopic observations of cell morphology and the determination of cell viability and cell number. Studies of the possible mechanisms of action indicated that the neuroprotection exerted by PM extract was related to its scavenging activity against H2O2 and related reactive oxygen species. High-performance liquid chromatography (HPLC) and thin-layer chromatography (TLC) analyses showed that the extract contained daidzein and genistein as identified constituents, as well as additional components with antioxidant activity. While daidzein and genistein individually and in combination were observed not to be neuroprotective, we propose that the antioxidant and neuroprotective activities of PM extract are derived from the combined properties of its constituents.