Suppressive effects of vietnamese ginseng saponin and its major component majonoside-R2 on psychological stress-induced enhancement of lipid peroxidation in the mouse brain.

We investigated the in vivo effects of Vietnamese ginseng saponin (VG saponin) and its major component majonoside-R2 (MR2) on psychological stress-induced enhancement of lipid peroxidation in the mouse brain. Psychological stress exposure using a communication box system for 4 h significantly increased the content of thiobarbituric acid reactive substance (TBARS), an index of lipid peroxidation activity, in the brain. Pretreatment with VG saponin (15-25 mg/kg, PO) and MR2 (1-10 mg/kg, IP) significantly attenuated the psychological stress-induced increase in TBARS content in the brain. The aglycone of MR2 (MR2-aglycone: 1.2 mg/kg, IP), at the equivalent dose of MR2 (i.e., 3 mg/kg, IP), also produced the suppressive effect on the increase in the TBARS content. The in vivo suppressive effect of MR2 was dose dependently attenuated by flumazenil (3 and 10 mg/kg, IP), a benzodiazepine receptor antagonist, and pregnenolone sulfate (10 mg/kg, IP), a neurosteroidal negative allosteric modulator of GABA(A) receptors. These findings suggest that VG saponin and its major component MR2 have preventive effects on the psychological stress-induced brain cell membrane damage, and that the effect of MR2 is partly due to enhancement of GABA(A)-ergic systems in the brain.