Herbal therapy: a new pathway for the treatment of Alzheimer's disease

The ultimate aim of Alzheimer's disease (AD) therapy is to stop or slow down the disease progression. Cholinesterase inhibitors have a modest clinical effect on the symptoms, however, and memantine - the currently available N-methyl-D-aspartate receptor antagonist - does not prevent the deterioration of dementia [1,2]. Finding an effective method to treat AD still poses a significant clinical challenge.Herbal medicine has long been used in China as therapy for dementia. The Complete Work of Jingyue published in 1624 contains the earliest known description in the world of a herbal therapeutic strategy for dementia. In the past 10 years, however, herbal drugs have seldom been approved for use alone in treating dementia. Overall, systematic review has identified a few single herbs and herbal formulations as possible effective medicine for AD (Table 1). According to the current evidence, some of these therapies show promising results in terms of their cognitive benefits. In the present commentary we discuss whether herbal therapy could be a novel pathway to treat AD, on the basis of the results from clinical trials, and the implications for potential therapy of AD pathophysiology.Ginkgo biloba extract is among the most widely used complementary therapies. A Cochrane review included 36 trials of gingko biloba, but most trials were small and of duration <3 months [3]. Nine trials were of 6 months duration and of adequate size, and were conducted to a reasonable standard. Of the four most recent trials to report results, three studies found no difference between Ginkgo biloba, at different doses, and placebo [3], and one study found very large treatment effects in favor of Ginkgo biloba, but the trial sample size was very small [4]. Another recent trial reported negative results in reducing cognitive decline in older adults with normal cognition or with mild cognitive impairment [5]. The current overall evidence that Ginkgo has a predictable and clinically significant bene