Evaluating the traditional Chinese literature for herbal formulae and individual herbs used for age-related dementia and memory impairment

Natural products are the basis of many systems of traditional medicine and continue to provide sources for new drugs. Ethnobiological approaches to drug discovery that have proven productive in the past include the investigation of traditional medical literatures. This study describes a broadly applicable method for locating, selecting and evaluating citations in the traditional Chinese herbal medicine literature of the dynastic period (until 1911) for specific symptoms or disorders. This methodology is applied to evaluate multi-herb formulae for age-related dementia and memory impairment. Of the 174 multi-herb formulae located in the searches, 19 were for disorders broadly consistent with amnestic Mild Cognitive Impairment (MCI) and/or Age Associated Memory Impairment (AAMI). These appeared in books written between c. 650 to 1911. Of the 176 herbs that appeared in these 19 formulae, those with the highest frequencies were tabulated and hierarchical cluster analysis was undertaken. Chinese pharmacopoeias were consulted to determine the botanical identity of the herbs and also which herbs within the formulas were specific for memory disorders. This study found that the top ten herbs, in terms of frequency of inclusion in multi-herb formulae specific for age-related memory disorders, were all listed in the pharmacopoeias for memory disorders and these formed three clusters. The herbs identified in this study may warrant further experimental and clinical evaluation both individually and in combination.