What Are the Health Benefits of Astragalus Root?

Astragalus is the dried root of Astragalus membranaceus (Fisch.) Bge. var. mongholicus (Bge.) Hsiao or As tragalus membranaceus (Fisch.) Bge. of the legume family. It tastes sweet and is slightly warm in nature. It enters the lung and spleen meridians. Astragalus membranaceus (Fisch.) Bge. var. mongholicus (Bge.) Hsiao or As tragalus membranaceus (Fisch.) Bge. is the dried root of Astragalus membranaceus (Fisch.) Bge. var. mongholicus (Bge.) Hsiao or As tragalus membranaceus (Fisch.) Bge., a legume plant with a sweet taste and slightly warm nature. It enters the lung and spleen channels [2].

Astragalus has the reputation of being the “holy medicine for replenishing qi” and has the effects of replenishing qi and strengthening the spleen, benefiting the defense and strengthening the body's resistance, promoting urination to reduce swelling, etc. Modern research has found that the chemical composition of astragalus includes compounds such as polysaccharides, saponins, flavonoids, and amino acids [3]. Astragalus polysaccharide, one of the main active ingredients of astragalus, can enhance immunity, strengthen the heart and protect the liver, lower blood pressure and diuretic, anti-aging and anti-free radical damage [4], is a major research hotspot in recent years. This article summarizes the extraction, isolation and purification of astragalus polysaccharides, as well as the pharmacological effects of astragalus polysaccharides on anti-aging, improving immunity, improving memory, anti-osteoporosis and intervention in type 2 diabetes, with the aim of providing a reference for further research on astragalus polysaccharides.

1.Astragalus polysaccharide extraction methods

(1). Solution extraction method

Guo Huiqing et al. [5] used hot water extraction to extract astragalus polysaccharides and optimized the process. The results showed that when the liquid-to-material ratio was 1:20, the temperature was set to 60 °C, and the extraction was performed twice for 4 h each time, the yield of crude astragalus polysaccharides was the highest, at 13.7%.

A research Research [6] used boiling water to extract astragalus polysaccharides, investigating the effects of water addition, brewing time and number of brews on the extraction rate of astragalus polysaccharides. The results showed that adding 9 times the amount of water and brewing for 3 times for 1 hour each time gave the best extraction rate of astragalus polysaccharides, at 4.81%, which was higher than the extraction rate of astragalus polysaccharides extracted by traditional boiling (4.06%). Xie Dan Dan and others [7] used a 1% NaOH alkaline solution to extract astragalus polysaccharides, optimizing the extraction temperature, liquid-to-material ratio, and extraction time. The results showed that the extraction rate of astragalus polysaccharides could be as high as (15.63±0.36)%.

(2). Ultrasonic extraction method

Sun Yinghua et al. [8] used an ultrasonic extraction method to extract astragalus polysaccharides and compared the results of the extraction rate of astragalus polysaccharides under different experimental conditions. The results showed that when the ratio of the liquid to the material was 1:25, the extraction temperature was set to 30°C, and the ultrasonic wave was applied for 5 minutes, the astragalus polysaccharide content reached 4.92%, which was the optimal extraction rate of astragalus polysaccharides. Ding Jian et al. [9] extracted astragalus polysaccharides with the aid of ultrasound. The results showed that the optimal extraction rate of astragalus polysaccharides was 9.08% when the extraction temperature was 80°C, the liquid-to-solid ratio was 1:15, and the pH value was 9, with ultrasound for 20 minutes.

Li Li et al. [10] used a circulating ultrasonic-assisted method for the extraction of astragalus polysaccharides, and combined it with an orthogonal design method to optimize the process. The results showed that at an extraction power of 1,000 W, an ultrasonic time and interval time was 1:1, and the ultrasonic extraction time was 40 minutes, the highest extraction rate of astragalus polysaccharide was 11.44%, and the extraction rate was higher than that of astragalus polysaccharide obtained by the traditional decoction method. Ben Yongguang et al. [11] extracted total astragalus polysaccharides by ultrasonic combined with enzymatic method, and the results showed that the yield of astragalus polysaccharides extracted by ultrasonic combined with enzymatic method was higher than that of the traditional water extraction method. Wang Dan et al. [12] used an ultrasonic extraction method to extract astragalus polysaccharides and compared the extraction rates of astragalus polysaccharides under different factors. The experiment concluded that when the ultrasonic time was 16 minutes, the material ratio was 1:11, and the ultrasonic power was 430 W, the extraction rate of astragalus polysaccharides was the highest, at 7.58%.

(3). Enzymatic hydrolysis

Deng Zhiyue et al. [13] used a composite enzyme method to extract astragalus polysaccharides, comparing the effects of different pH values, temperatures, reaction times and enzyme addition amounts on the extraction rate of astragalus polysaccharides. The results showed that when the enzyme addition amount was 5.5%, the temperature was 60°C, the pH was 6, and the enzymatic hydrolysis time was 3.5 hours, the extraction rate of astragalus polysaccharides was the highest, reaching 8.58%. Dong Ling et al. [14] used the method of cellulase enzymolysis-microwave for extracting astragalus polysaccharides. The extraction rate of astragalus was investigated under different process parameters during the experiment. The results showed that under the microwave power of 480W, with an enzyme to material ratio of 57.6 U/g, a liquid to solid ratio of 10:1, and an enzymatic hydrolysis time of 1 h, the yield of astragalus polysaccharides was the highest, at 16.07%. The yield of astragalus polysaccharides using the microwave method was higher than that using the enzymatic hydrolysis method alone.

2.Astragalus polysaccharide separation and purification

(1). graded alcohol precipitation and stepwise alcohol precipitation

Graded alcohol precipitation is used to separate astragalus polysaccharides, which makes use of the difference in solubility of astragalus polysaccharides with different molecular weights in methanol or ethanol of different concentrations [15]. Yan Qiao Juan et al. [16] investigated the molecular weight distribution of astragalus polysaccharides and used the stepwise alcohol precipitation method and the graded alcohol precipitation method to separate astragalus polysaccharides.

The results showed that when the alcohol precipitation concentration was higher, the molecular weight of the precipitated polysaccharides was lower. When the added alcohol concentration reached 90%, most of the polysaccharides could be precipitated. Astragalus polysaccharides are unevenly distributed in different alcohol precipitates. The part with a concentration of 90% mostly contains small molecular weight polysaccharides and a small amount of impurities, while the part with a concentration between 10% and 30% mostly contains high molecular weight polysaccharides. Different alcohol concentrations can be used to isolate astragalus polysaccharides of different molecular weights.

(2). Macroporous resin adsorption separation method

Macroporous adsorption resin is a type of polymeric adsorbent that separates astragalus polysaccharides through the principles of adsorption and selectivity [17]. Zhao Fengchun [18] used a macroporous resin adsorption method to separate and purify astragalus polysaccharides and screen the resin. The results showed that X-5 resin can effectively separate and purify astragalus polysaccharides, with a purity of up to 71.3%. Liu Sha et al. [19] used D101 macroporous adsorption resin to separate and purify crude astragalus polysaccharides, obtaining astragalus polysaccharides with a purity of 65.07%.

(3). Gel column chromatography Gel column chromatography has a molecular sieve effect and uses molecules of different sizes to separate astragalus polysaccharides. Dextran gels and agarose gels are the types of gels often used in the test process. A study Studies[15] have found that Astragalus polysaccharides are extracted by the water-soluble alcohol precipitation method, followed by protein removal using the Sevag method, and then chromatographed using a DEAE-Sepharose Fast Flow ion exchange column. Two symmetrical peak components were collected, and gel column chromatography of the collected symmetrical peak components was performed. The results showed that the components obtained by gel column chromatography were homogeneous and relatively pure.

(4). Quaternary ammonium salt complexation method The principle of the quaternary ammonium salt complexation method for separating astragalus polysaccharides is to use the fact that astragalus polysaccharides have different molecular weights and carry anionic charges of different densities. The ability to form precipitates with the same quaternary ammonium salt will differ, achieving the purpose of separating astragalus polysaccharides with different molecular weights. The The quaternary ammonium salt complexation method is often used to separate astragalus polysaccharides using cetyltrimethylammonium bromide and cetylpyridinium [20].

3.Pharmacological effects of astragalus polysaccharides

(1). Anti-aging

Aging is an inevitable part of human life. Numerous studies have shown that traditional Chinese medicine has obvious advantages in anti-aging and anti-oxidation [21]. Many scholars and researchers at home and abroad are studying the anti-aging effects of astragalus polysaccharides [22]. Shi Shenghui et al. [23] created an aging model by injecting D-galactose into rats for 6 consecutive weeks, and then gave the rats an astragalus polysaccharide solution by gavage. The results reduced the level of malondialdehyde and the activity of monoamine oxidase in the rats, and increased the activity of glutathione peroxidase and superoxide dismutase, indicating that astragalus polysaccharide has an anti-aging effect.

Miao Yu Dan et al. [24] demonstrated through experiments that astragalus polysaccharide reduced the content of lipofuscin in mice, and significantly increased the activity of glutathione reductase and glutathione peroxidase in the heart and kidney tissues of aging mice. The anti-aging mechanism of astragalus polysaccharide's anti-aging mechanism may be to enhance the body's antioxidant capacity, thereby removing excess oxygen free radicals in the body and preventing the process of apoptosis in brain cells, thereby playing an anti-aging role [25].

(2). Immune system

Astragalus polysaccharides can promote the metabolic function of cells in the body and also enhance the activity of immune cells in the body, thereby improving the body's immune function [26], thus exerting the effect of astragalus tonifying the middle and benefiting qi. Shi Yong Fang [27] used hydrocortisone to create a mouse model of immunodeficiency, and then injected the mice with astragalus polysaccharide solution.

The results showed that astragalus polysaccharide can promote the production of hemolysin and increase the transformation rate of mouse lymphocytes. It also increased the weight of the thymus and spleen, all of which indicate that astragalus polysaccharide can effectively improve immunity. Liu Jun Qiu [28] found through immunological and plasma metabolomics experiments that astragalus polysaccharide can improve the organ index of the body, increase the proliferation conversion rate and proliferation activity of mouse spleen lymphocytes, thereby improving the body's immunity. Astragalus polysaccharide can improve the body's immune function and play a role in enhancing immunity.

(3). Improves memory

Alzheimer's disease is a disease that produces lesions in the central nervous system, and its main characteristic is hippocampal-dependent learning, memory and behavioral impairments. Ma Guoxiang et al. [29] used Aβ25~35 bilateral ventricle injection to induce an Alzheimer's disease model, then treated the rats with astragalus polysaccharide by gavage, and subsequently subjected the rats to the water maze experiment.

The results showed that astragalus polysaccharide improved the rats' ability to locate and navigate and their memory ability. The pathological results showed that the hippocampal histopathology of the treated rats was significantly improved. Fei Hong et al. [30] used an Aβ1~42 bilateral ventricle injection mouse model to induce Alzheimer's disease, treated with Astragalus polysaccharide by gavage, and performed the Morris water maze experiment to observe the behavioral indicators and learning and memory abilities of the mice. The results showed that Astragalus polysaccharide had a significant effect on improving the memory of mice.

Su Hua et al. [31] constructed a rat model of Alzheimer's disease to explore the effects of astragalus polysaccharide intervention on oxidative stress response and the Wnt pathway after modelling in rats. The results showed that astragalus polysaccharide can significantly reduce the content of malondialdehyde, enhance the activity of superoxide dismutase and catalase, and may inhibit the neurotoxicity caused by β-amyloid by activating the Wnt pathway, thereby protecting the nerves. Astragalus polysaccharides can improve the hippocampal structure of Alzheimer's disease mice, reduce hippocampal tissue damage, and further improve the memory of Alzheimer's disease mice.

(4). Anti-osteoporosis

Osteoporosis is a common disease. A decrease in the number or function of osteoblasts is a major factor in the development of osteoporosis. Therefore, the key to treating osteoporosis is to promote the proliferation and differentiation of osteoblasts. Chai Yi et al. [32] used MC-3T3-E1 osteoblasts as the research object, and used RT-PCR and Western blotting to detect the effect of astragalus polysaccharide on the expression of CYP24 A and CYP27B mRNA and protein expression. The results showed that astragalus polysaccharide promoted the expression of CYP27B mRNA and protein and inhibited the expression of CYP24A mRNA and protein. Vitamin D can promote the formation of osteoblasts and inhibit osteoblast apoptosis, playing an important role in osteoporosis [33]. The results of Wang Yaoyao et al. [34] showed that Astragalus can exert an anti-osteoporosis effect by regulating the vitamin D-FGF-23-Klotho axis in vitamin D-deficient rats. Astragalus polysaccharide plays a role in the prevention of osteoporosis.

(5). Type 2 diabetes intervention

Astragalus is a very common ingredient in traditional Chinese medicine prescriptions for diabetes and is among the most frequently used. Research [35] has shown that astragalus polysaccharide intervention in HepG2 cell insulin resistance models improves cell viability, increases PPARγ expression, reduces intracellular H2O2 concentration, alleviates insulin resistance, and has a certain effect on diabetes. Li Dan et al. [36] constructed a mouse model of aging-induced type 2 diabetes by feeding naturally aging mice a high-fat, high-sugar diet and injecting them with streptozotocin intraperitoneally. Astragalus polysaccharide treatment was administered, and the results showed that the mice's blood glucose and body weight had improved significantly. Research research [37] results show that astragalus polysaccharide can combat liver damage caused by diabetes by improving the deposition of lipid droplets in the liver, thereby achieving the effect of treating type 2 diabetes.

The research results of Tang Simeng et al. [38] show that astragalus polysaccharide can improve the pathological morphology of islet tissue in type 2 diabetic rats, and can also increase the number of islet β cells to achieve the effect of treating diabetes. Astragalus polysaccharide can alleviate endoplasmic reticulum damage by relieving endoplasmic reticulum stress [39], promote the activity of glycogen synthase and the synthesis of insulin signal proteins, and also promote the secretion of insulin, which is suitable for the treatment of type 2 diabetes. Mao Zhu et al. [40] found that astragalus polysaccharide berberine can significantly promote the secretion of insulin-resistant INS-1 (IR-INS-1) cells, and speculate that astragalus polysaccharide berberine may improve insulin resistance by downregulating the expression of miR-126-3p in IR-INS-1 cells.

4. Discussion

Astragalus, one of the traditional Chinese medicines used for both food and medicine, can invigorate the qi and raise yang, reinforce the superficial defense mechanism to stop sweating, promote diuresis to reduce edema, and is widely used in clinical practice. Astragalus polysaccharide is the main active ingredient in astragalus, and has pharmacological effects such as anti-aging, improving immunity, improving memory, anti-osteoporosis, and treating type 2 diabetes. Astragalus polysaccharide extraction methods include hot water extraction, boiling water infusion, alkaline solution extraction, ultrasonic extraction, enzymatic hydrolysis, and the combined use of several extraction methods. The yield of astragalus polysaccharide extracted by different extraction methods is not the same. Even if the same extraction method is used, the final yield of astragalus polysaccharide will be different if the extraction process parameters are different.

Similarly , the yield and purity of astragalus polysaccharide obtained using different separation and purification methods are inconsistent. The results will also be different if the process parameters of the separation and purification are different. How to combine modern technology with the extraction, separation and purification of astragalus polysaccharide to obtain higher yields and purities is the current and future research direction for scholars. Astragalus has a variety of pharmacological effects, but the mechanisms of some pharmacological effects are not yet clear and require further research.

The molecular weight of astragalus polysaccharide ranges widely from large to small. Astragalus polysaccharide products obtained using different extraction, separation and purification methods may differ, and the content and purity of astragalus polysaccharide have an important impact on the effective exertion of its biological activity. Therefore

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