Astragalus Extract What Is It Good For?

Astragalus membranaceus is a perennial herb in the family Fabaceae. It is divided into two species: Astragalus membranaceus and Astragalus mongholicus. It was first recorded in the Shennong Bencao Jing (Shennong's Classic of Materia Medica) and has been used for more than 2,000 years. It is mainly produced in Gansu Province, Inner Mongolia Autonomous Region, Heilongjiang Province and Shanxi Province. Modern pharmacological studies and extensive clinical practice have confirmed that astragalus has a variety of biological activities, including immunomodulation, anti-oxidation, anti-inflammation, anti-tumor, anti-aging, lowering blood lipids, protecting the liver, expectorant and diuretic effects [1-3].

Studies have shown that astragalus contains more than 200 chemical components, of which isoflavonoids, saponins, and astragalus polysaccharide (APS) are the main active ingredients. Isoflavonoids such as astragaloside IV, astragaloside III, and astragaloside II and their glycosides have the effect of strengthening the immune system and the body. Astragaloside IV is a saponin that is used as a representative indicator of the quality of astragalus because of its significant pharmacological activity. In addition, astragalus also contains amino acids,

vitamins and trace elements [4-6].

Recent studies have shown that astragalus polysaccharides have a growth-promoting effect on a variety of probiotics and have the potential to become a prebiotic in traditional Chinese medicine. In addition, it is worth noting that the animal health function of astragalus polysaccharides has also become a research hotspot. Given its unique efficacy, astragalus polysaccharides, as a new type of feed additive, can improve the immune function of animals by exerting antibacterial, antiviral, and immunomodulatory effects. This is of great significance for improving the quality of animal products and promoting the sustainable development of animal husbandry [7-8]. A large number of studies have confirmed that the biological activity of astragalus polysaccharides is mainly manifested in the following aspects.

1 Antitumor effect

Studies have found that the alcohol-soluble polysaccharides (APS) in Astragalus membranaceus can effectively change the levels of serum cellular immune factors (TNF-α, IL-2 and IFN-γ) and the activity of various immune cells (macrophages, lymphocytes and NK cells), inhibit the growth and proliferation of H22 liver cells in mice, and thus cause apoptosis of tumor cells, thereby was greatly reduced [9]. APS4 can inhibit the proliferation of human gastric cancer MGC-803 cells by inducing DNA damage, cell cycle disorders, damage to mitochondrial membrane potential and excessive production of ROS [10]. APS can activate macrophages to release NO and TNF-α, thereby blocking the growth of MCF-7 cancer cells [11].

Yan Lijun et al. [12] treated lung cancer NCI-H460 cells with different concentrations of APS and intervened in their in vitro antitumor experiments. After detection by MTT method and Western blot method, the results showed that compared with the control group, after 48 hours of APS treatment, the apoptosis rate (early apoptosis rate, late apoptosis rate, total apoptosis rate) and the expression level of apoptosis proteins (Caspase-3, Bax/Bcl-2 ratio) were significantly increased after 48 h of APS treatment compared to the control group. It is speculated that the mechanism by which APS inhibits the proliferation of NCI-H460 cells and induces apoptosis may be related to cell cycle arrest and the mitochondrial apoptosis pathway.

Li Caihong et al. [13] investigated the effect of APS on ovarian cancer cells by combining different doses of APS with DDP chemotherapy in vitro. The results showed that APS could mediate the sensitization of ovarian cancer cells to DDP chemotherapy. It can be seen that APS may exert its pro-apoptotic effect on ovarian cancer cells by increasing the expression of apoptosis-related factors, suggesting that APS may have anti-ovarian cancer function.

2 Immune regulation

The Ca2+-cAMP pathway is thought to be one of the ways in which APS and PSP exert their immunomodulatory effects in body cells. A moderate amount of astragaloside IV can effectively inhibit Salmonella infection in mice, promote the body's production of the anti-inflammatory factor IL-10, and enhance the mouse's own immune function. APS can reduce OTA-induced immune stress in vivo and in vitro by activating the AMP K/SIRT-1 signal transduction pathway to reduce OTA-induced immune stress in vivo and in vitro [14].

Zhou et al. [15] found that oral administration of Astragalus polysaccharide for 25 days to two types of tumor-bearing mice, C57BL/10J and C57BL/6J,  activate the MyD88-dependent immune signal and transmission pathway mediated by TLR4 to regulate the host's own immune function, significantly increase the apoptosis rate of tumor cells, the index of immune organs and the level of pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) in the blood, and reduce the weight of the tumor. Shen Dongdong et al. [16] studied the effect of APS on immune function by establishing an SD rat model. After intraperitoneal injection, the results showed that the lesion degree of small intestinal tissue in rats with intestinal ischemia-reperfusion injury in the Astragalus polysaccharide intervention group was significantly reduced, and the CD3+/CD 4+ ratio was significantly higher, and the levels of TNF-α, ICAM-1, and IL-6 were significantly lower, suggesting that Astragalus polysaccharide may improve the immune function of the body by regulating the expression levels of T lymphocyte subsets and related factors in injured rats.

3 Hypoglycemic effect

Diabetes is a metabolic disease characterized by elevated blood glucose, which can easily lead to a variety of complications, such as diabetic nephropathy, ketoacidosis, retinopathy, etc. Studies have shown that when the active ingredients of astragalus were extracted, a new type of polysaccharide composed of AERP1 and AERP2 components (AERP) was found [17]. In diabetic mice, this new polysaccharide has a hypoglycemic effect, can reduce blood glucose levels, reduce tissue damage, and effectively inhibit cognitive impairment, change the intestinal microbiota and regulate the composition of SCFAs.

Wu Yingping et al. [18] established a model of diabetic rats and intervened with insulin and astragalus polysaccharide. After 6 weeks of continuous gavage administration, the content of TNF-α in the rats was determined by ELISA. The results compared with the insulin group, the content of TNF-α in the serum of the combined group was significantly reduced, suggesting that APS can reduce insulin resistance by reducing the expression level of TNF-α and reducing the degree of damage to pancreatic β cells.

4 Cardiovascular protective effect

Saikun et al. [19] found that APS has a certain hypolipidemic activity in rats by giving rats a high-fat diet containing different doses of APS, which can promote cholesterol and bile acid metabolism in rats and significantly cause a decrease in the serum TC, LDL and TG levels in the blood serum, thereby exerting a hypolipidemic effect. Debin et al. [20] found that APS can inhibit cell apoptosis to reduce or alleviate the growth of cardiomyocyte volume, thereby reducing cardiomyocyte apoptosis caused by MVRI. At the pathological level, APS can improve myocardial damage induced by CVB3, dilated cardiomyopathy, chronic myocardial fibrosis and inflammation in mice [21].

At the same time, APS can regulate the expression of the Keap1/Nrf2-ARE signaling pathway in AA rats, increase the antioxidant capacity of cardiomyocytes, reduce oxidative stress and inflammation, and improve cardiac function [22]. He Lihong et al. [23] found that astragalus polysaccharide significantly affects the cycle of human umbilical vein endothelial cells (HUVEC) and the expression of vascular endothelial growth factor (VEGF). Within the range of 0–100 μg·mL-1 APS concentration, the proliferation activity of HUVEC cells increases with the increased with increasing APS concentration. When the concentration was 100 μg·mL-1, APS had the best ability to promote VEGF expression, suggesting that APS may promote the proliferation of HUVEC cells by inducing the cell cycle to transition from the G0/G1 phase to the G2/M phase and S phase and upregulating the expression level of the cell growth promoting factor VEGF.

5 Anti-inflammatory effect

It is currently believed that an imbalance in the Th1/Th2 and Th17/Treg cell ratios is the main cause of asthma attacks. APS can reduce the levels of the inflammatory cytokines IL-4 and IL-8 in the blood serum and increase the level of IFN-γ to balance the Th1/Th2 cell ratio and exert its anti-inflammatory effect, thereby reducing airway inflammation and enhancing the therapeutic effect of asthma in mice [24]. At the same time, APS can also regulate the levels of the cytokines IL-10 and IL-17 to balance the Th17/Treg cell ratio, reduce the infiltration and damage of Neu and Eos to lung tissue, and play a protective role [25].

Liu Danhua et al. [26] studied the regulatory mechanism of astragalus polysaccharide (APS) on the inflammation of lipopolysaccharide (LPS)-induced DF-1 cells. It was found that under the intervention of APS, compared with the LPS group, the phosphorylation level of NF-κBp65 and the protein content of TNF-α and IL-1β in DF-1 cells in the APS combined LPS group were significantly reduced, and the mRNA expression of SOCS3 was significantly increased. It can be seen that the anti-inflammatory effect of APS can be achieved by promoting the high expression of SOCS3 to inhibit the activation pathway of the NF-κBp65 signal pathway.

6 Antioxidant effect

A large number of studies have shown that antioxidant substances can effectively remove excess free radicals in the body, which is an important way to prevent aging. Sun Chen et al. [27] systematically studied the antioxidant activity of different polar parts of Astragalus and its polysaccharides. The absorbance values of APS and the butanol fraction of astragalus increased significantly with increasing mass concentration, as determined using the o-phenanthroline-Fe3+ method.

It is therefore speculated that astragalus polysaccharides and the butanol fraction of astragalus have strong antioxidant capacity. Hu Bijun [28] studied the process of microwave-assisted extraction of astragalus polysaccharides and their antioxidant activity. It was found that in the range of APS concentrations of 0.5–2.0 g/L, the DPPH · radical scavenging rate was positively correlated with the APS concentration; and in the range of 0.5–2.5 g/L, with the increase of APS concentration, the OH · radical scavenging rate also increased significantly. It is therefore believed that within a certain concentration range, APS has a certain scavenging capacity for the two free radicals DPPH· and OH· and is dose-dependent.

7 Radiation resistance test

Zhou Nina et al. [29] cultured human bone marrow mesenchymal stem cells (HM⁃SC-bm) in vitro and used 2 Gy of X-rays and APS to intervene. The results showed that the optimal intervention concentration of the drug was 50 μg/mL APS. Compared with the irradiation group (IR) alone, the irradiation group (IR+APS) with added drug significantly increased the proliferation and viability of HMSC-bm cells, effectively reducing the micronucleus rate of cells after 2Gy X-ray irradiation and the number of 53BP1 foci in cells. It can be seen that the protective effect of APS can be achieved by increasing the radiation resistance of HMSC-bm to X-rays and promoting the process of genomic DNA repair.

8 Prebiotic activity

As early as 1995, Glenn Gibson et al. defined prebiotics as “an indigestible food component that beneficially affects the host by selectively stimulating the growth or activity of one or a limited number of bacteria in the colon, thereby improving host health.” In 2000, Lactobacillus and Bifidobacterium were considered to be “preferred target organisms for prebiotics” [30-31]. Since then, the definition of prebiotics has been continuously refined. In 2017, the ISAP consensus group considered prebiotics to be essentially “a substrate that is selectively utilized by host microorganisms and has health benefits.”

Previous studies in China have found that APS has a probiotic effect on Lactobacillus intestinalis, and that 2.5% astragalus polysaccharide has the most significant probiotic effect on Lactobacillus rhamnosus [32]. Cai Hainan [33] found that APS has a probiotic effect on Lactobacillus curvulus, and that the effect is dose-dependent. These results all initially revealed that APS has significant prebiotic activity. The physicochemical properties of the various components of the extracted astragalus polysaccharides vary greatly depending on the purification method, and so do their biological activities in the intestine. Although preliminary studies have shown that astragalus polysaccharides have prebiotic activity, it is still unclear which components of astragalus polysaccharides have this effect, the effects of each component on the intestinal flora, the relevant metabolic mechanisms and the action mechanisms.

9 Future research hotspots and directions for astragalus

Astragalus polysaccharides have a wide range of biological effects, including anti-tumor, immune regulation, lowering blood sugar, cardiovascular protection, anti-inflammatory, anti-oxidation, anti-radiation, prebiotic activity, etc. As a safe and effective Chinese herbal medicine, the clinical efficacy of astragalus is mainly due to isoflavones, saponins and their metabolites, while the role of polysaccharides is not well understood. The molecular mechanism of the interaction between astragalus and its ingredients and the intestinal flora after entering the body is not yet clear. Due to the wide variety and complex structure of the compounds contained in astragalus, the drug target molecules also show corresponding diversity and complexity.

As research into microecology gradually deepens, the relationship between it and traditional Chinese medicine is constantly being discovered and expanded. Practical research into the relationship between traditional Chinese medicine and microecology is also emerging in an endless stream, such as the impact of traditional Chinese medicine on the human microecology, the mechanism of action of traditional Chinese medicine as a microecological regulator, clinical application research of traditional Chinese medicine microecological preparations, the role of normal flora in the body's absorption and utilization of the active ingredients of traditional Chinese medicine, and research into the role of microecology in traditional Chinese medicine clinical, acupuncture and other aspects. It can be seen that a new and emerging interdisciplinary subject combining traditional Chinese medicine and Western medicine traditional Chinese medicine microecology is quietly emerging and will flourish.

With the in-depth development of traditional Chinese medicine microecology, it will surely provide a broader scientific connotation and a more direct reference model for the combination of traditional Chinese medicine and Western medicine. Given its special role in regulating intestinal flora, the application of astragalus polysaccharides in microecology is likely to become a breakthrough point in unlocking the mysteries of traditional Chinese medicine.

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