Medicinal plants and Alzheimer's disease: Integrating ethnobotanical and contemporary scientific evidence

The use of complementary medicines such as plant extracts in dementia thera py, varies according to the different cultural traditions. In orthodox West ern medicine, contrasting with that in China and the Far East for example, pharmacological properties of traditional cognitive or memory enhancing pla nts have not been widely investigated in the context of current models of A lzheimer's disease. An exception is Ginkgo biloba in which the ginkgolides have antioxidant, neuroprotective, and cholinergic activities relevant to A lzheimer's disease mechanisms. The therapeutic efficacy of Ginkgo biloba ex tracts in Alzheimer's disease in placebo-controlled clinical trials is repo rtedly similar to currently prescribed drugs such as tacrine or donepezil a nd, importantly, undesirable side effects of Ginkgo biloba are minimal. Old European reference books (eg, medical herbals) document a variety of other plants such as Salvia officinalis (sage) and Melissa officinalis (balm) wi th memory improving properties, and cholinergic activities have recently be en identified in extracts of these plants. Precedents for modern discovery of clinically relevant pharmacological activities in plants with long-estab lished medicinal use include, for example, the interaction of alkaloid opio ids in Papaver somniferum (Opium poppy) with endogenous opiate receptors in the brain. With recent major advances in understanding the neurobiology of Alzheimer's disease, and as yet limited efficacy of so-called rationally d esigned therapies, it may be timely to re-explore historical archives for n ew directions in drug development. This article considers not only the valu e of an integrative traditional and modern scientific approach to developin g new treatments for dementia, but also in the understanding of disease mec hanisms. Long before the current biologically based hypothesis of cholinerg ic derangement in Alzheimer's disease emerged, plants now known to contain cholinergic antagonists were recorded for their amnesic and dementia-induci ng properties.