Medicinal plant extracts for the treatment of dementia : A review of their pharmacology, efficacy and tolerability

Various active compounds derived primarily from Oriental and European medicinal plants, including Ginkgo biloba, Panax ginseng, Nicotiana tobaccum, Huperzia serrata, Galanthus nivalis and Salvia officinalis, have been assessed for their efficacy in dementia, primarily in Alzheimers disease. These plants may be used individually or, particularly in traditional Chinese or Ayurvedic formulations, in combination. The mechanisms of action of medicinal plant extracts in Alzheimers disease have yet to be fully determined, but are thought to involve anticholinesterase, anti-inflammatory, antioxidant and estrogenic activity, and cholinergic receptor activation. Robust clinical trial data are currently scarce. However, those that are available confirm the effectiveness of G. biloba in delaying deterioration or inducing symptomatic improvement in patients with Alzheimers disease. In addition, the extract does not appear to be associated with adverse or toxic effects. The active component of G. nivalis, the selective acetylcholinesterase inhibitory alkaloid galantamine (galanthamine), is currently commercially available in Austria and is preregistrational in a number of other countries for the symptomatic treatment of mild/moderate Alzheimers disease. Currently available data indicate galantamine to be well tolerated in the long term, with a relative lack of toxicity at clinically effective dosages. Future development of effective novel therapeutic strategies for dementia may benefit from the combination of conventional Western medical science and traditional Oriental medical practices.