From The October 2000 Issue of Nutrition Science News

Astragalus Asserts Immunity

by The American Herbal Pharmacopoeia

Astragalus (Astragalus membranaceus) is most commonly used as a general tonic for those practicing Chinese herbal medicine, and specifically for immune enhancement. Most research on astragalus has focused on its immunostimulatory activity and its seemingly remarkable ability to restore the activity of a suppressed immune system. Clinical trials as well as pharmacological data provide evidence for its usefulness in the prevention of the common cold and as an adjunct to cancer therapies. It is useful as a complementary treatment during chemotherapy, radiation therapy and immune deficiency syndromes.^1-3

There is also evidence for cardiovascular system improvement, particularly in clinical parameters associated with angina, congestive heart failure and acute myocardial infarct. This may be due to the herb's antioxidant activity. Its use in the treatment of hepatitis in modern Chinese medicine is supported by the demonstration of hepatoprotective activity in animal studies.

In traditional Chinese medicine and Western clinical herbal medicine, astragalus is usually used in combination with other botanicals and is very seldom used as a single agent. Pharmacological research of astragalus in combination with ligustrum (Ligustrum lucidum) provides evidence for activity against cancers of the breast, cervix and lung.

Many of the pharmacological studies included here were published in Chinese and as a result have been cited from translations, review articles or English abstracts, rather than from the complete primary literature. Numerous original studies were also reviewed. The reports obtained from secondary sources are considered to be authoritative, and the findings cited are consistent with the clinical use of astragalus in the United States and Asia. Several Chinese pharmacologists who are experts in astragalus have reviewed this material to ensure its accuracy. Nevertheless, a critical evaluation of much of the secondary literature was not conducted.

Immunomodulatory Effects
A number of clinical studies have been reported regarding the use of astragalus for colds and upper respiratory infections. A prophylactic effect against the common cold was reported in an epidemiological study in China involving 1,000 subjects.

Administration of astragalus, given either orally or as a nasal spray, decreased the incidence of illness and shortened the length of its course. Studies exploring this protective effect found that a two-week oral administration of the preparation enhanced subjects induction of interferon by peripheral white blood cells. Levels of IgA and IgG (immunoglobulin) antibodies in nasal secretions increased following two months of treatment.⁴

The effect of astragalus on the induction of interferon was studied in another placebo-controlled study involving 28 people. Fourteen volunteers were given an extract equivalent to 8 g dried root per day and 14 were given placebos. Blood samples were drawn before treatment, then two weeks and two months after treatment. Interferon production by leukocytes was statistically increased after both time periods.⁵

In China, astragalus is widely used in the treatment of cancer, both as a primary treatment and as an adjunct to conventional therapies. It is most often combined with other similarly acting immune-enhancing botanicals. A number of randomized prospective clinical studies of cancer patients were conducted using an undisclosed quantity combination of astragalus and ligustrum. Examples of these data are provided here since they are representative of the use of astragalus in modern Chinese medicine. However, these effects are considered to be due to the cumulative effects of the two botanicals and cannot be presumed to occur with astragalus alone.

According to a review article, breast cancer patients given a combination of astragalus and ligustrum as an adjunct to irradiation treatments showed a statistically significant decrease in deaths from one in two to one in 10. The authors cited an additional study in which patients with stage II and stage III cervical carcinoma who were given the herbs as an adjunct to irradiation showed a slight, though not statistically significant, increase in survival and disease-free state. In another study of patients with advanced non-small-cell lung cancer, the effectiveness of conventional chemotherapy (chemotherapeutic regimen not reported) was compared to the effectiveness of chemotherapy in conjunction with the same astragalus-ligustrum preparation. Those with squamous carcinoma of the lung showed a significant increase in mean survival time from 204 to 465 days, and those with adenocarcinoma showed a less significant increase in survival time from 192 to 324 days.⁶

In another review, it was reported that 53 cases of chronic leukopenia responded favorably to an astragalus extract (1:1; 2 mL daily intramuscularly for one to two weeks). Improvements in symptoms and white blood cell counts were observed, but specific data were lacking.⁴

Cardiovascular Effects
Various cardioactive properties have been reported in the literature. It is important to note here that, in both clinical and animal studies, astragalus was administered by injection, which may preclude application of these findings to dietary supplement products.

In one study, 92 patients with ischemic heart disease were given an unidentified preparation of astragalus. Marked relief from angina pectoris and some improvements as measured by electrocardiogram (EKG) and impedance cardiogram were reported. Improvement in the EKG index was reported as 82.6 percent. Overall improvement was significant as compared with the control group.⁷

Similar improvement in cardiac performance was reported by other groups of researchers. In one study, 43 patients were hospitalized within 36 hours of acute myocardial infarct. After administration of an astragalus preparation (undefined profile), the ratio of pre-ejection period/left ventricular ejection time (PEP/LVET) was decreased, the antioxidant activity of superoxide dismutase of red blood cells was increased, and the lipid peroxidation content of plasma was reduced.⁸

In another study, 20 patients with angina pectoris were given an undefined astragalus preparation. Cardiac output, as measured by Doppler Echocardiogram, increased from 5.09 to 5.95 L/minute two weeks after administration of astragalus. In this study, no improvement in left ventricular diastolic function and no inhibition of adenosine triphosphate was observed.⁹ Intravenous administration of astragalus (undefined preparation) was also reported to significantly shorten the duration of ventricular late potentials in cardiac patients from 39.8 ms vs. 44.5 ms.¹⁰

Patients with congestive heart failure were treated for two weeks with injections (unspecified amount) of astragaloside IV, a primary triterpene of astragalus. Symptoms, such as tightness in the chest, difficulty breathing and decreased exercise capacity, improved. Radionuclide ventriculography showed that left ventricular modeling improved and left ventricular end-diastolic and left ventricular end-systolic volume diminished significantly. The authors concluded that astragaloside IV is an effective positively inotropic agent.¹¹

The effect of astragalus on erythrocyte sodium content and sodium transport in patients with coronary heart disease was investigated. Intravenous administration of 24 g/day of astragalus infused into a 5 percent glucose solution (250 mL) significantly decreased erythrocyte sodium and significantly increased sodium pump activity.¹²

Hepatoprotective Effects
In China, astragalus is widely used in the treatment of chronic hepatitis. According to a review article, elevated serum levels of glutamate pyruvate transaminase (GPT) returned to normal, and symptoms associated with the disease subsided within one to two months of treatment with an unspecified astragalus preparation.¹³

In another report, an aggregate effective rate of 85.7 percent (significantly effective rate 61.2 percent) was observed in 49 cases of chronic hepatitis. Normalization of GPT levels was observed in 80 percent of the responsive patients within one to two months of treatment with an undefined injectable astragalus preparation.⁴ More detailed data regarding these findings were not available. Positive effects of oral administration of astragalus polysaccharides for treatment of hepatitis were reported by a group of researchers who demonstrated enhanced interferon production in a manner similar to that demonstrated in in vitro studies.¹⁴

A single in vitro study exploring the possible effects of astragalus in the treatment of hepatitis B reported significant inhibition of viral protein expression and little effect on viral DNA synthesis.¹⁵ No additional data regarding this study were available.

From the studies cited here, it is evident that astragalus preparations have significant therapeutic potential. More studies are warranted, especially human clinical trials exploring the possible benefits of astragalus to cancer patients and immunocompromised individuals.

Sidebars:
Astragalus Safety Profile

Excerpted with permission from American Herbal Pharmacopoeia and Therapeutic Compendium, a bimonthly series of peer-reviewed monographs. Complete monographs are available individually or by subscription and are published by the American Herbal Pharmacopoeia, Santa Cruz, Calif., 1999.

References

1. Rou M, Renfu X. The effect of radix Astragali on mouse marrow hemopoesis. J Trad Chin Med 1983;3(3):199-204.

2. Sun Y, et al. Immune restoration and/or augmentation of local graft-versus-host reaction by traditional Chinese medicinal herbs. Cancer 1983;52(1):70-3.

3. Sun Y, et al. Preliminary observations on the effects of the Chinese medicinal herbs Astragalus membranaceus and Ligustrum lucidum on lymphocyte blastogenic response. J Biol Respon Modif 1983;2(3):227-37.

4. Chang HM, But PH, editors. Pharmacology and applications of Chinese materia medica. Yeung S, et al, translators. Singapore: World Sci; 1987, vol. 2. 1,320

5. Hou Y, et al. Interferon induction and lymphocyte transformation stimulated by Astragalus membranaceus in mouse spleen cell cultures. Zhonghua Weisheng Wuxue Hemian Yixue Zazhi 1981;1(2):137-9.

6. Morazzoni P, Bombardelli E. Astragalus membranaceus (Fisch) Bunge. Scientific documentation 30 Mar 1994. Milano (Italy): Indena SpA. 1994 Mar:1-18.

7. Li SQ, et al. Clinical observation on the treatment of ischemic heart disease with Astragalus membranaceus. Chung Kuo Chung His I Chief Ho Tsa Chih 1995;15(2):77-80.

8. Chen LX, et al. Astragalus membranaceus on left ventricular function and oxygen free radical in acute myocardial infarction patients and mechanisms of its cardiotonic action. Chung Kuo Chung His I Chief Ho Tsa Chih 1995;15(3):141-3.

9. Lei ZY, et al. Action of Astragalus membranaceus on left ventricular function of angina pectoris. Chung Kuo Chung His I Chieh Ho Tsa Chih 1994;14(4):199-202.

10. Shi HM, et al. Primary research on the clinical significance of ventricular late potentials (VLPs), and the impact of mexiletine, lidocaine, and Astragalus membranaceus on VLPs. Chung His I Chief Ho Tsa Chih 1991;11(5):265-7.

11. Luo HM, et al. Nuclear cardiology study on effective ingredients of Astragalus membranaceus in treating heart failure. Chung Kuo ChungHis I Chief Ho Tsa Chih 1995;15(12):707-9.

12. Jin C, Dai RH. Effect of Astragalus membranaceus on erythrocyte sodium content and sodium transport in the coronary heart disease. Chung His I Chief Ho Tsa Chih 1991;11(11);651-3.

13. Tang W, Eisenbrand G. Chinese drugs of plant origin: chemistry, pharmacology, and use in traditional and modern medicine. Berlin: Springer-Verlag; 1992. 1,056 p.

14. Zhang F, et al. Preparation of astragalus polysaccharide and its therapeutic effect on hepatitis. Yaowu Shengwu Jishu 1995;2(2):26-8.

15. Fan T, et al. The inhibitory effect of some Chinese herbs on hepatitis B virus replication in vitro and its mechanism. Chin J Exper Clin Virol 1996;10(1):27-30.