Bacopa monniera Wettst. (Scrophulariaceae), known by the common name ‘brahmi’, has been used in Ayurvedic medicine for almost 3000 years as a nerve tonic and to improve intellect and memory. Various investigations have attempted to substantiate and identify a scientific basis for the reputed effects. A number of in vivo studies have shown Bacopa monniera extracts to improve cognitive function. The mode of action to explain these effects has yet to be fully elucidated. Some studies suggest that the antioxidant effects of Bacopa monniera may protect the CNS from oxidative damage. Extracts of Bacopa monniera have been reported to induce a dose-related increase in superoxide dismutase, catalase and glutathione peroxidase activities in the rat frontal cortex, striatum and hippocampus, to dose-dependently inhibit nitric oxide (nitric oxide)-related toxicity (DNA damage) in cultured rat astrocytes and to inhibit aluminium-induced neurotoxicity in the rat brain. The antioxidant effects of Bacopa monniera have also been suggested to alter amyloid plaque formation. In addition to antioxidant effects, Bacopa monniera has also shown anti-inflammatory activity in vivo. It is reported to modulate the cholinergic system and has an anxiolytic action. It is therefore possible that Bacopa monniera may exert multiple effects on the CNS.
Although the majority of relevant studies which have investigated the reputed cognitive-enhancing effects of Bacopa monniera have focused on extracts rather than isolated constituents, it is the triterpenoid saponins, reported to occur in the aerial parts of Bacopa monniera, which have been associated with the activity. The dammarane-type triterpenoid saponins, a mixture known as bacoside A which includes bacoside A3, have been shown to protect rat brains from smoking-induced apoptosis and from structural and functional impairment of mitochondria.
Clinical studies have so far only been undertaken on healthy volunteers. In one double-blind, placebo-controlled study with normal healthy subjects treated with Bacopa monniera extract, no acute effects on cognitive function were observed. However, a double-blind, randomised, placebo-controlled study on patients aged 40 to 65 years showed that those given a standardised extract of Bacopa monniera resulted in a significant improvement in retention of new information but no difference in the rate of learning, attention, and verbal and visual short-term memory. Another similar study investigated the speed of visual information processing, learning rate and memory consolidation and concluded that the Bacopa monniera extract improved higher-order cognitive processes such as learning and memory.