Place of origin: Radix Astragali is mainly divided into Mongolia Astragalus and Astragalus Membranaceus Bunge ^[1], both of which are mainly cultivated in several places including Shanxi, Inner Mongolia, Northeast China and Hebei province. The genuine medicinal materials ofAstragalus Membranaceus Bunge come from Shanxi province while those of Mongolia Astragalus come from Inner Mongolia ^[13], where the quality of the latter is better.

Radix Astragali was mainly produced in Sichuan, Shaanxi and Gansu provinces before Tang Dynasty. After Song Dynasty, Radix Astragali from Shanxi (Astragalus Membranaceus Bunge) was the best, listed as the genuine medicinal material. In Qing Dynasty, Radix Astragali from Inner Mongolia was also listed as the genuine medicinal material, which was consistent with the modern situation of Radix Astragali. Their morphology is extremely similar. Radix Astragali likes dryness and sunshine, whose soil for planting should be sandy soil under neutral and slightly alkaline condition. Mongolia Astragalus is often planted on the hillsides or under open forests, and Astragalus Membranaceus Bunge is often found on the hillsides towards sunrise, edges of brushwood or in sandy soil at the riverside ^[1].

Radix Astragali: It has cylindrical shape with few branches, whose upper end is thicker. Its surface has longitudinal wrinkles and horizontal long lenticels, with the color of grayish yellow or light brown. The texture is flexible and not easy to break. The cross section is fibrous and powdery. It has a slight odor, sweet taste, and has a slight bean-fishy taste when chewed ^[2].

The counterfeits of Radix Astragali are more than 10. However, the varieties listed below can also be used as Radix Astragali.

Astragalus chrysopterus Bunge: It has long cylindrical shape, whose main root is mostly dichotomous branch. Its surface has fine circular lines and obvious longitudinal wrinkles, with the color from pale yellow to dark brown. The texture is dense and tough. The cross section is fibrous and powdery. It has a slight odor, sweet taste, and has strong bean-fishy taste ^[2].

Astragalus floridus Bunge: It has long cylindrical shape and many twists, whose upper end has the shape of rotten wood. Its surface has obvious longitudinal wrinkles, with the color of brownish yellow or tan. The texture is hard and tough. The cross section is fibrous and slightly powdery. It has a slight odor, and weak and slightly bitter taste ^[2].

Astragalus ernestii Comb: It has cylindrical shape and many branches. Its surface has less wrinkles, whose skin is easy to fall off, with the color of dark brown or tan. The texture is loose and flexible, not easy to break. The cross section is fibrous and powdery. It has a slight odor, sweet taste, and has slight bean-fishy taste ^[2].

Astragalus tongolensis: It has long conical shape with small branches. Its surface has the marks of fibrous root and bulges wrinkles, with the color of pale yellow and dark yellow. The texture is dense and hard. The cross section is weak fibrous and powdery. It has a slight odor, sweet taste, and has slight bean-fishy taste ^[2].

Radix Astragali was firstly recorded in Variorum of Shennong’s Classic of Materia Medica, listed with top grade ^[3]. Li Shizhen described that “Radix Astragali has the advantage of restoratives”. The clinical application of Radix Astragali was recorded in the ancient Chinese medical books. Huang Qi Jian Zhong Tang, recorded in Synopsis of Golden Chamber, can be used to treat the symptoms such as insufficient Qi and blood, abdominal contraction, spontaneous perspiration or night sweats. The medicinal diet therapy of Radix Astragali recorded in Handbook of Prescriptions for Emergencies can be used to treat the diseases including Deficiency-heat, cough and purulent blood ^[1].

1. Polysaccharides

There were about 24 kinds of polysaccharides found in Radix Astragali ^[4]. In vivo experimental studies showed that Astragalus polysaccharides (APS) significantly promoted the early development of immune organs such as thymus and spleen ^{[5] [6]}. APS interacted with immunoglobulin on the surface of B cells to induce the proliferation of B cells, and induced the differentiation of T cells to activate T cells and regulate the immune system ^[4][11]. The studies also found that, APS in combination with probiotics can have a synergistic effect on intestinal microbes and the immune system ^[8]. In addition, APS reduced the expression of pro-inflammatory cytokines, cytotoxicity and apoptosis and avoided immune stress of spleen cells by activating protein kinases involved in the related signal pathway ^[7].

Radix Astragali has a protective effect on the hematopoietic system. The researchers found that APS can promote the generation of granulocyte and erythrocyte lines in human bone marrow cells through in vitro experimental studies ^[14].

2. Saponins

Cyclolanosterane saponins are active substances related to immune regulation. Astragaloside IV (AST) was proved to with good anti-oxidant and anti-inflammatory effects ^[4]. For innate immunity, astragaloside can promote the activation and phagocytosis of macrophages by enhancing the secretion of macrophage releasing factors and the expression of the related genes^[9]. The cell experiments showed that AST IV could enhance the activity of T cells. Animal experiments also proved that it can reduce the activity of Treg cells in mice with lung cancer and enhance the “killing effect” of immune cells ^[4].

3. Flavonoids

Flavonoids are the main immune-modulatory components in Radix Astragali. A large proportion in Radix Astragali was the flavonoid containing glycosides ^[4]. Flavonoids in Radix Astragali could enhance the phagocytosis index of macrophages in vivo experiment ^[10]. Flavonoids in the stems and leaves of Radix Astragali could increase the total number of T cells and improve the activity of LAK cells ^[4].

The steaming method on Radix Astragali was recorded in Lei Gong’s Treatise on Preparation and Boiling of Materia Medica. The honey-frying method commonly applied nowadays was recorded in Profound Treatise on Eye Diseases of Tang Dynasty. Subsequently, the processing with salt method and the processing with wine method were gradually developed ^[12].

Raw Radix Astragali: Remove the impurities from Radix Astragali, wash it and moisten it thoroughly, cut it into thick slices, and then sift out the debris after drying ^[12].

Honey-fried Radix Astragali: The honey is diluted with boiling water, pour the honey into the clean slices of Radix Astragali, mix well and moisten them, place them in the frying container, heat them gently and fry them to dark yellow, take them out and cool them after they are not stick to hands ^[12].

Fried Radix Astragali: Place Radix Astragali in a pot and gently fry it until it is dark yellow with occasional burnt spots then take it out and cool it ^[12].

The main function of raw Radix Astragali is to induce diuresis, reduce edema, promote pus discharge and tissue regeneration, reinforce Qi and strengthen the exterior. Honey-fried Radix Astragali can mainly play a role in replenishing Qi and strengthen the middle warmer, which is mainly used to treat the disorders such as Qi deficiency of spleen and lung, reduced appetite and loose stool, shortness of breath, lack in strength and constipation due to Qi deficiency. The main efficacy of fried Radix Astragali is to replenish spleen and reinforce Qi without stasis, which is mainly used to treat the disorders such as poor appetite, loose stool and abdominal distention due to insufficiency of spleen ^[12].

Radix Astragali was listed as top-grade material in Variorum of Shennong’s Classic of Materia Medica. However, it is noted that the patients with Yin deficiency and Yang hyperactivity should take it with care. In addition, Radix Astragali should be taken carefully for the patients with the symptoms including superficies excess due to prosperous pathogen, retention of dampness due to Qi stagnation, and stagnation due to dyspepsia ^[1]. Radix Astragali is one of the herbal medicines that can be used in healthcare food announced by National Health Commission of the People’s Republic of China. Yue Meizhong, the expert of Traditional Chinese Medicine, has used the diet therapy method, Compound astragalus porridge, to treat the diseases.

Modern medicine has confirmed through clinical studies that the slices of Radix Astragali and oral decoction of Radix Astragali have the effect of preventing and treating colds. In addition, Astragalus injection has also been used in clinical studies to treat hepatitis B and chronic hepatitis with obvious therapeutic effect, that is, the patients’ symptoms are disappeared or improved significantly. In the clinical study, 174 patients were treated with Astragalus injection for chronic hepatitis B. After two months of treatment, 79 cases were cured and 52 cases were significantly improved. Furthermore, Astragalus injection has obvious and good long-term curative effect on other chronic hepatitis. For lung diseases and trachea diseases, such as tuberculosis, night sweats, bronchial asthma and chronic bronchitis, all of the effective rate of Astragalus Compound are higher than 85% ^[15].

In addition, Astragalus Compound (Origin-Preserving Decoction) showed significant efficacy in the treatment of chronic aplastic anemia. Among 17 patients, 4 cases were significantly alleviated and 7 cases were basically alleviated. It can promote the proliferation of hematopoietic stem cells ^[15].

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9. Guo, Z., Xu, H. Y., Xu, L., Wang, S. S., & Zhang, X. M. (2016). In vivo and in vitro immunomodulatory and anti-inflammatory effects of total flavonoids of Astragalus. African Journal of Traditional, Complementary and Alternative Medicines, 13(4), 60-73.
10. Qin, Q., Niu, J., Wang, Z., Xu, W., Qiao, Z., & Gu, Y. (2012). Astragalus membranaceus extract activates immune response in macrophages via heparanase. Molecules, 17(6), 7232-7240.
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