Oral or intranasal administration of an aqueous A. membranaceus extract to 1000 human subjects decreased the incidence and shortened the course of the common cold (4). Two months of oral administration of the herb significantly increased the levels of IgA and IgG in the nasal secretions of patients susceptible to the common cold (4). Details of these studies were not available.
A hot water extract of A. membranaceus root taken by human subjects was reported to have a pronounced immunostimulant effect (24). Human adults treated with an oral dose of Astragalus root (15.6 g per person per day for 20 days) significantly increased serum IgM, IgE, and cyclic AMP concentrations (24). Extracts of A. membranaceus have been further reported to stimulate the production of interferon, a protein with antiviral activity, in both animals and humans in response to viral infections (21, 25). A hot water extract of the drug administered intramuscularly for 3–4 months to patients with coxsackievirus B myocarditis enhanced natural killer cells, a response which was mediated through interferon induction (15). Furthermore, both natural and recombinant interferons enhanced the antiviral activity of an A. membranaceus extract (26).
References:
4. Chang HM, But PPH, eds. Pharmacology and applications of Chinese materia medica, Vol. 2. Singapore, World Scientific Publishing, 1987.
15. Yang YZ et al. Effect of Astragalus membranaceus on natural killer cell activity and induction of alpha- and gamma-interferon in patients with coxsackie B viral myocarditis. Chung-hua i hseuh tsa chih (English Edition), 1990, 103:304–307.
21. Hou YD et al. Effect of Radix Astragali seu hedysari on the interferon system. Chinese medical journal, 1981, 94:35–40.
24. Institute of Basic Medical Sciences, The Chinese Academy of Medical Sciences. Immunity parameters and blood cAMP changes in normal persons after ingestion of Radix Astragali. Chung hua i hsueh t'sa chih, 1979, 59:31–34.
25. Finter NB. Interferons and interferon-inducers. Amsterdam, North Holland, 1973:363.
26. Peng JZ et al. Inhibitory effects of interferon and its combination with antiviral drugs on adenovirus multiplication. Zhongguo yixue kexueyuan xuebao, 1984, 6:116–119.
Source: WHO Monographs Vol 1, 1999 -2010
