Abstract In traditional practices of medicine, numerous plants have been used to
alleviate memory impairment both in healthy individuals and those with disease
states which are now recognised as specific cognitive disorders such as Alzheimer’s
disease (AD).
An ethnopharmacological approach has provided leads to identify plants and their compounds that may have potential to modulate cognitive abilities by different modes of action. A variety of therapeutic targets have been identified as relevant in the treatment of cognitive disorders, including modulation of the cholinergic system, which may be achieved by the inhibition of acetylcholinesterase (AChE), and neuroprotection against glutamate-induced overstimulation
of N-methyl-D-aspartate (NMDA) receptors, by the use of NMDA receptor
modulators.
Other activities considered to be relevant in the alleviation of cognitive
impairment include anti-inflammatory, antioxidant and estrogenic activities. Two of
the currently licensed drugs used to treat cognitive symptoms in AD, galantamine
and rivastigmine, were derived from plant sources and have been characterised as
inhibitors of AChE.
However, some plant extracts which occur as a complex mixture of components, such as Ginkgo biloba L. extract, have demonstrated relevant biological activities in relation to cognitive function, but the compounds responsible for the observed effects or the mechanisms of action have not been well characterised.
Amongst the many plants reputed to enhance cognitive function in a variety
of traditional medicines including Ayurvedic, Chinese, European, African and
South American medicines, relatively few have been extensively studied to determine
any pharmacological basis for their historical uses. Some of those plants that
have generated particular interest in understanding and establishing their potential
for alleviating cognitive impairment are discussed.
