Astragalus to improve memory and intelligence?

Note:  Below is an article on astragalus originally appearing in Issue # 24 of Dr. Leung's newsletter, Leung's Chinese Herb News, published in early 2000.

Astragalus root is one of my favorite tonic herbs. I have written about it often in previous issues of this Newsletter. It has a wide variety of traditional properties and modern pharmacological activities. When traditionally used as a tonic, it imparts many of the benefits of Asian ginseng, but few of the latter’s adverse side effects (e.g., hypertension, agitation). Its traditional extracts, if properly prepared and used, can deliver many of its well-known traditional benefits, such as healing (wounds, ulcers, etc.), promoting tissue regeneration, removing toxins, disease prevention (especially cold and flu), and strengthening body qi (vital energy), etc. Biological activities discovered in astragalus root and its extracts include: antioxidant, immunomodulating, antimutagenic, hypoglycemic, antiviral, liver protectant, cardiovascular (hypotensive, vasodilating, etc.), and many others. These effects are not due to a single compound or a single class of compounds but rather, to different types of components, with saponins (triterpene glycosides), polysaccharides, and flavonoids playing a key role, due to their predominance. Other compounds, such as choline, betaine, and amino acids, if selectively extracted, also play a role in the biological activities of astragalus.

The ability of an aqueous extract of astragalus root to improve memory and learning in mice is reported in an article published in the Chinese Journal of Traditional Chinese Drugs by researchers at the Guangxi Research Institute of Traditional Chinese Medicine and Chinese Drugs.3 The root used was identified as that of Astragalus membranaceus by Prof. Luo Jin-Yu of the Department of Chinese Materia Medica. The extract was prepared by boiling the herb 3 times, 30 min each time. The combined extracts were filtered and the filtrate evaporated to a syrupy consistency, which was then refrigerated. Although the dosages of the extract used are reported as 35 g/kg and 50 g/kg, administered ig, there is no indication whether these amounts were based on the raw root or the actual weights of the water extract (of undefined strength). But at least we know the researchers used a hot water extract, unlike many publications in reputable journals, which do not specify what were used in the reported studies [see Issue 18, pp. 1-2; HerbalGram 48, pp. 63-64]. Using the foot-pad-electrical-shock-avoidance method and after conditioning, 4 groups of mice (10 each) were subjected to the following treatments: The control mice, Group A, were given 10 ml/kg distilled water; Group B were given either 10 ml/kg of 40% ethanol or 8 mg/kg of anisodine; Group C were given simultaneously 35 g/kg of the astragalus water extract (extractives) and one of the above drugs; and Group D, as in C, were given simultaneously 50 g/kg of the extract along with one of the drugs. The mice were observed, during a 5-minute period, for the number of times they forgot to remain on the safety pad and leapt to the electrified pad. Compared to the average number of mistakes (100%) made by Group B animals with drug-induced memory loss in both experiments, the astragalus extract reduced the error rate to 80% and 70%, respectively, in alcohol- and anisodine-treated animals (Group C). A higher dose of astragalus extract (Group D) redued the error rate further to 40% in alcohol-treated animals and 50% in anisodine-treated animals. In comparison, the control mice (Group A) had an error rate of 20% in both experiments.

Although this report is flawed, especially in the ambiguity of the amounts of extract administered and the fact that the experiments were only performed once, I find the results rather interesting. If the authors had used the dosage of 50 g/kg to mean 50 g of “extractives from the root”/kg, then, when extrapolated to a person of 60 kg (132 lbs), he/she would have to ingest a concentrated water extract of 3 kg (6.6 lbs) of astragalus, which, depending on the concentration, can be up to 4 l (4 qt) of liquid! This would be equivalent to drinking a gallon of a syrupy brew! Although bulky, it probably may not be deadly, because the authors also report no fatalities in an acute toxicity test using twice the amount. Thus, after mice were administered ig 100 g/kg of the same extract daily for 7 days (accumulative dose, 700 g/kg) and observed for 12 more days, no fatality was observed. There were also no obvious toxic side effects, with the exception the mice were rather calm within an hour after administering the extract! Poor mice! After ingesting even a gallon of that stuff (not to speak of 2 gallons), I would be stuffed and calm too!

(3) G.X. Hong et al., “Studies on Memory-improving Effects of an Aqueous Extract of Astragalus membranaceus (Fisch.) Bge.,” Zhongguo Zhongyao Zazhi, 19(11): 687-688 (1994); Leung, A.Y., and S. Foster, Encyclopedia of Common Natural Ingredients Used in Food, Drugs and Cosmetics, Wiley-Interscience, New York, 1995, pp. 50-53.

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