Neuropharmacological review of the nootropic herb Bacopa monnieri

Abstract

This review synthesizes behavioral research with neuromolecular mechanisms putatively involved with the low-toxicity cognitive enhancing action of Bacopa monnieri (BM), a medicinal Ayurvedic herb. BM is traditionally used for various ailments, but is best known as a neural tonic and memory enhancer. Numerous animal and in vitro studies have been conducted, with many evidencing potential medicinal properties. Several randomized, double-blind, placebo-controlled trials have substantiated BM's nootropic utility in humans. There is also evidence for potential attenuation of dementia, Parkinson's disease, and epilepsy. Current evidence suggests BM acts via the following mechanisms-anti-oxidant neuroprotection (via redox and enzyme induction), acetylcholinesterase inhibition and/or choline acetyltransferase activation, β-amyloid reduction, increased cerebral blood flow, and neurotransmitter modulation (acetylcholine [ACh], 5-hydroxytryptamine [5-HT], dopamine [DA]). BM appears to exhibit low toxicity in model organisms and humans; however, long-term studies of toxicity in humans have yet to be conducted. This review will integrate molecular neuroscience with behavioral research.

FIG. 1.

Dose-dependent changes in relative fluorescence intensity of lipofuscin obtained in chloroform fraction of brain tissue homegenate. Results are expressed as mean±standard deviation of 6 rats in each group. (*) p<0.05 for young versus aged; (#) p<0.05 for aged versus aged treated groups. (Reprinted, with permission, from Rastogi et al.)

FIG. 2.

Effect of different doses of bacosides on neurotransmitter acetylcholine content in aged rate brain. Results are expressed as mean±standard deviation of 6 rats in each group. (*) p<0.05 for young versus aged; (#) p<0.05 for aged versus aged treated groups. (Reprinted, with permission, from Rastogi et al.)

FIG. 3.

Amelioration of alterations in monoaminergic neurotransmitters with aging on long-term bacosides treatment. Concentration of serotonin, norepinephrin, and dopamine (ng/gram wet tissue) in the cortex of young, middle-aged, and aged treated or untreated rats. Values are expressed as mean±standard deviation of 6 animals in each group. Level of significance as calculated by one-way analysis of variance (ANOVA) followed by post hoc least significant difference: (*) p<0.05 for young versus aged; (†) p<0.05 for young versus middle-aged treated; and (#) p<0.05 for aged untreated versus aged treated group. 5-HT, 5-hydroxytryptamine; NE, norepinephrine; DA, dopamine. (Reprinted, with permission, from Rastogi et al.)

FIG. 4.

Camera lucida tracings of basolateral amygdaloid neurons from control rats (A) and rats treated with Bacopa monniera for 6 weeks at doses of 20 mg/kg (B), 40 mg/kg (C), and 80 mg/kg (D). (Reprinted, with permission, from Vollala et al.