The memory enhancing effect of brahmi was traced to a mixture of triterpenoid saponins, designated as bacosides A and B. Both bacoside A and B showed single spots on TLC over silica gel, while bacoside A (Chatterjee et al., 1963, 1965) was obtained as colorless needles, bacoside B (Chatterjee et al. 1963) was a colorless powder.

In the investigations, taken up later (TLC and HPLC on reversed phase) showed that bacoside A was a mixture of at least three saponins which were designated as bacogenin A1, (Kulshreshtha and Rastogi, 1973), bacogenin A2 (Kulshreshtha and Rastogi, 1974) and bacogenin A3 (Chandel et al. 1977).

Methods have been developed for quantitative determination bacoside A content in the extract by UV spectroscopy (Pal and Sarin, 1992) and HPLC (Pal et al. 1998).

The final structure of bacoside A was determined as 3(a-L-arabinopyranosyl)-O-ß-D-glucopyransoid-10,20-dihydroxy-16-keto-d ammarene.

The structure of bacogenin-A1, the major constituent of bacoside A is as follows:

It is essential for plant extracts in order to be therapeutically effective to have all the constituents in tact because the therapeutic effect is generally the result of concerted activity of several active compounds as well as the inert accompanying substances.
Though these inert accompanying components do not directly affect the pathological mechanism, it is reasonable to use the complex mixture of components provided by a medicinal plant because these inert components might influence bioavailability and excretion of the active component.

Further, by inert plant components the stability of the active component might be increased and possible side effects minimized. If there are different active compounds present in a plant drug, they might have additive or potentiating effect (Handa, 1997).
The memory enhancing effect of brahmi is more than can be explained by its bacoside content. Similar observations have been made with several other plants as well (Dhawan, 1997).
To monitor the seasonal variations of bacosides, fresh plant material was collected every month, extracted with ethanol and fractionated.

It was carried over a period of fourteen months commencing from March'93. TLC of n-butanol fractions of the ethanolic extracts of the plant was used to monitor bacosides. From this study it was concluded that bacoside A predominates in March and April whereas both bacosides A and B are available in May.

In the rest of the months other compounds start appearing and disappearing (Rastogi et al. 1996).

PHARMACEUTICAL STANDARDS

The brahmi extract has the following pharmaceutical specifications:

1. Description Greenish brown powder
2. Identification Positive for bacosides in HPLC and TLC finger prints.
3. Sulphated ash Not more than 10% w/w
4. Assay

a) Bacosides content: 55±5% w/w
b) Shelf Life: About 2 years
c) Storage: Store in a closed container and avoid heat.