Astragalus What Is It Used For？

Astragalus is a treasure of traditional Chinese medicine. It is the dried root of the perennial herb Astragalus membranaceus or Astragalus mongholicus, also known as Huangqi or Mianqi. Mongolian milkvetch root is mainly distributed in parts of northern China, such as the Inner Mongolia Autonomous Region, Hebei Province and Shanxi Province; membranous milkvetch root is widely distributed in the three northeastern provinces of China, as well as in northern China (Hebei Province, Inner Mongolia Autonomous Region, Shanxi Province) and northwestern China (Shaanxi Province, Gansu Province).

Astragalus Membranaceus Root has a wide range of bioactive ingredients, including flavonoids, saponins, amino acids and trace elements [1]. Traditional Chinese medicine shows that Astragalus is mild in nature and sweet in taste. It can replenish the qi, stop sweating, reduce swelling, detoxify, and has many other clinical effects. It is mainly used to treat symptoms such as qi deficiency and weakness, yin deficiency and night sweating, qi deficiency and edema, hypertension, high blood sugar, and long-term wounds that do not heal [2-3].

At present, the processing and utilization of astragalus mainly focuses on the pharmaceutical field, mainly researching the extraction of active ingredients and pharmacological effects. Since astragalus was only approved as a dual-use resource in 2020, there are currently few astragalus foods on the market, and it is more commonly used in healthcare or medicine. In recent years, there have been more and more reports on the research of ordinary foods such as compound functional drinks, biscuits, and yogurt made from Astragalus. This paper reviews the bioactive components of Astragalus and the research on its application in foods, providing a reference and basis for the further development and utilization of Astragalus resources.

1 Bioactive components of Astragalus extract

To date, more than 100 compounds have been isolated and identified from Astragalus. The main effective bioactive ingredients include polysaccharides, saponins, flavonoids, folic acid, alkaloids, and a small amount of trace elements [4].

1.1 Astragalus polysaccharide

Astragalus polysaccharide is an important indicator for the standardized quality control of astragalus, and is one of the main active ingredients with the highest content in astragalus. Although the composition, content, chemical composition, and structure of astragalus polysaccharide vary due to differences in raw material sources and extraction techniques, it is roughly divided into heteropolysaccharides, glucan, and acidic polysaccharides [5-6].

Among them, glucan is divided into two types according to its water solubility: one is water-soluble glucan, and the other is water-insoluble glucan. Heteropolysaccharides are mostly acidic polysaccharides, and their monosaccharide composition includes rhamnose, arabinose, glucose, galactose, mannose, and xylose [7].

Some studies have shown that there are structural differences in astragalus polysaccharides from different raw materials, but the monosaccharides are mainly glucose and mannose, which account for more than 90% of the total. Based on this, an NMR fingerprint spectrum of astragalus polysaccharides can be established, and the quality of astragalus polysaccharides can be evaluated based on the type and content of monosaccharides.

The molecular structure of astragalus polysaccharides has been studied relatively well, and recent research has focused on the extraction and purification of astragalus polysaccharides and their pharmacological effects.

1.2 Saponins

Astragalus saponins are an important class of active ingredients in astragalus [8]. So far, more than 50 chemical substances have been isolated from astragalus. Among Astragalus and its closely related plants, saponins are mainly divided into eight types of astragalosides, three types of isofraxidin, three types of cycloastragenol, four types of astragalosides IV and soybean saponins, etc. [9], while the rest are all of the aglycone type of tetracyclic triterpenoid saponins and the 9, 19-cyclolanostane type, collectively referred to as astragaloside or astragalus total saponin [10-11]. One of the main active ingredients of astragaloside is astragaloside IV, which has the effect of regulating body metabolism and immune function. Astragalosides I–III in astragalus have the effect of enhancing immunity and promoting bone differentiation; isomucronulatol has the pharmacological effect of reducing high-glucose-induced cell damage in the human glomerular system, treating neurodegenerative diseases and neuroinflammation [12].

Astragaloside IV in astragaloside is the main indicator for quality control of astragalus, and its content is only about one thousandth of astragalus. Therefore, when preparing astragalus extract, it is required to efficiently extract astragaloside from astragalus. At this stage, there have been further developments in the extraction process and research on astragaloside, such as supercritical CO2 extraction, water-saturated n-butanol extraction, ultrasonic-assisted extraction technology, and perforated adsorption resin methods [8]. Therefore, research on rapid and efficient extraction processes and technologies for astragaloside is particularly important.

1.3 Flavonoids

Nearly 40 types of flavonoids have been found in Astragalus membranaceus, including mainly the four major types of flavonoids, isoflavonoids, isoflavanones and pterocidanosides [13]. Among these, isoflavonoids are the most numerous, and are widely distributed in the rhizomes, leaves and flowers of Astragalus membranaceus. A large number of studies have shown that the secondary metabolites of flavonoids are similar in different parts of the plant, but the content varies greatly. According to numerous literature reports, the roots of Astragalus contain the most active ingredients, and there has been a lot of research on the roots of Astragalus in terms of food and medicine. Xu Zhen et al. [14] used ultra-high performance liquid chromatography-tandem mass spectrometry to analyze and determine the flavonoid components in Astragalus membranaceus from Hunyuan, Shanxi Province. Astragalus membranaceus contains six flavonoid active ingredients. Further comparison found that the content of astragaloside in the underground part is 1/4 times that of the above-ground part, and the total flavonoid content of the underground part of Astragalus membranaceus is slightly higher than that of the above-ground part.

At present, more and more domestic and foreign scholars are conducting in-depth research and analysis on the effective active ingredients of flavonoids in Astragalus membranaceus, and the optimization process for the efficient extraction and purification of Astragalus flavonoids, in order to lay a foundation for further better development and utilization of Astragalus flavonoids.

2. Application of Astragalus extract in food

Studies have shown that astragalus and its extracts have physiological effects such as improving immunity, anti-tumor, hypoglycemic, and antioxidant. Therefore, in addition to being used as traditional Chinese medicine, the application value of astragalus and its extracts in food is increasingly being valued. In 2020, the National Health Commission approved astragalus to be managed according to the tradition of being both a food and a traditional Chinese medicine substance, laying a legal foundation for astragalus to be developed as a functional food ingredient. Table 1 lists the foods containing astragalus that have been reported in the literature since 2017.

2.1 Astragalus drinks

The preparation of drinks using astragalus as the raw material is the most common way to develop and utilize astragalus. Studies have shown that the combination of astragalus and wolfberry can enhance the health-promoting function of astragalus [28]. Therefore, Xu Lin et al. [15] optimized the process of water-extracting Astragalus by targeting the content of astragaloside IV. The compound Astragalus drink developed by them uses Astragalus extract and concentrated wolfberry juice as the main raw materials. Animal experiments have shown that the drink has the functions of relieving physical fatigue and anti-oxidation.

Zhou Wenjing et al. [29] used the content of astragaloside IV and sensory evaluation as indicators, mixed astragalus, Luo Han Guo and pears, and extracted them with hot water to develop a beverage with the effect of anti-smog and clearing the lungs. By constructing a mouse model of smog, the efficacy of the anti-smog and lung-clearing drink was evaluated by the pathological conditions of the lungs and the contents of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) content in lung tissue to evaluate the efficacy of the anti-smog lung-clearing drink.

The results showed that the anti-smog lung-clearing drink had a significant effect on improving the pathological damage to the lung tissue of smog-exposed mice. Compared with the model group, the content of IL-6 and TNF-α in the treatment group was significantly reduced (P<0.01), which may play a role by reducing inflammation. In addition, Astragalus can also be compounded with dates [30], hawthorn [31], wintergreen [32], chestnuts [33], roses [34], etc. to prepare drinks with different functions. Astragalus can be compounded with other raw materials of medicinal foods, and the water extract can be obtained by decoction. After concentration and drying, a solid drink can also be prepared [35-37].

As a food product, it must have a good flavor. Astragalus extract has a slightly sweet taste and is a good ingredient for making beverages. On the other hand, even if Astragalus extract is used, some of the inherent volatile “Chinese medicine flavor” will remain when it is processed into a beverage, making it difficult for consumers to accept. Therefore, how to eliminate the “Chinese medicine flavor” of Astragalus will be a difficult problem to solve in the processing of Astragalus drinks. At present, many traditional Chinese medicine enterprises are developing and producing oral Astragalus membranaceus liquid or granules. Although these are also ordinary foods, the concept of using traditional Chinese medicine in food production actually requires more food enterprises to develop and produce Astragalus membranaceus drinks from a food perspective.

2.2 Astragalus membranaceus wine

In the production of wine, functional factors can be introduced by adding different raw materials to produce functional wines with physiological activity. Astragalus can be used to develop health-promoting beer [38] and yellow wine [39] due to its unique physiological activity. Astragalus can be added at different stages during the preparation of astragalus wine. It can be fermented together with other raw materials or added after fermentation to prepare the wine, forming a fermented or prepared astragalus wine, respectively. Yang Lihua et al. [40] used yellow rice and glutinous rice as the main ingredients, steamed the rice with Astragalus extract, and then added koji to ferment it, optimizing the best fermentation process for astragalus wine. The final astragalus rice wine sample had plump and even grains, a delicious sweet and sour taste, a light aroma, and a sweet and mellow mouthfeel.

Oats have excellent medicinal and health benefits, reducing the accumulation of cholesterol in the cardiovascular system and lowering blood lipids. They are also effective against atherosclerosis, coronary heart disease and hypertension. Liu Quanliang et al. [26] used high-quality local oats as the main raw material, added astragalus, and used the raw material fermentation process to develop and produce oat astragalus wine. In the process of preparing astragalus wine using apple pomace and chestnut pomace, astragalus is extracted with edible alcohol and added to distilled wine to obtain the prepared wine [41].

2.3 Astragalus enzyme

An enzyme is a fermented liquid produced by fermenting one or more grains, fruits, vegetables, herbs, etc., with probiotics. The fermented liquid can also be dried and ground to make products in the form of enzyme powder or enzyme capsules [42]. Hu Xiaoli [43] used Angelica sinensis, Astragalus membranaceus, Codonopsis pilosula, and Glycyrrhiza uralensis as raw materials, and prepared functional enzymes using a method of adding exogenous cellulase, amylase, and glucoamylase for fermentation. This enzyme product not only has the effect of activating blood circulation and moistening the intestines of Angelica sinensis effect of activating blood circulation and moistening the bowels, but also retains the effect of astragalus in strengthening the spleen and kidney qi and enhancing the body's protective function, as well as the effect of codonopsis in tonifying qi and nourishing blood and the effect of licorice in clearing away heat and detoxifying. The enzyme prepared from astragalus as raw material embodies the health preservation concepts of Chinese medicine diet, food nourishment, and food therapy, and combines the medicinal effects of food and medicine of the same origin with the nutritional and health care functions of enzyme foods. Therefore, it has broad development prospects [44].

Fermented foods have a special flavor. Further research is needed to understand how the flavor of the enzyme prepared from fermented Astragalus membranaceus changes, how to coordinate the “Chinese medicinal flavor” of Astragalus membranaceus with the flavor of other foods, and the functionality of the enzyme.

2.4 Astragalus membranaceus chewable tablets

Chewable tablets are a type of tablet product that can be swallowed without water after chewing in the mouth. They have the advantages of being easy to eat and carry, and having a long shelf life. At present, Astragalus can be used alone or in combination with other raw materials such as wolfberry [45], codonopsis [46], and cordyceps [47] to develop into chewable tablets. Cen Nana et al. [25] extracted Astragalus with 70% ethanol and dried it to obtain an extract powder. It was mixed with wolfberry in a ratio of 3.5:6.5, and milk powder, mannitol, lactose, citric acid as flavoring agents, microcrystalline cellulose as a filler, magnesium stearate as a lubricant, and distilled water as a wetting agent to obtain a medlar astragalus chewable tablet chewing tablets.

Jin Yuanyuan [48] extracted selenium-rich astragalus with 45% ethanol to obtain an extract powder, and optimized the optimal formula for selenium-rich astragalus chewing tablets through response surface testing. The results showed that when the amount of selenium-rich astragalus extract powder was 20%, microcrystalline cellulose 10%, mannitol 51%, lactose 17%, citric acid and magnesium stearate were added at 1% respectively, and 75% ethanol was used as a wetting agent. The resulting chewable tablets had a smooth surface, uniform color, moderate hardness, and a pleasant texture.

Sun Yunxia [49] used water to extract a powdered extract from a combination of ginseng and astragalus, based on the characteristics of ginseng in “supporting the positive and dispelling the negative” and astragalus in “strengthening the immune system and reinforcing the body's defences”. The extract was mixed with the excipients mannitol and sucrose, the flavouring agents aspartame and citric acid, the lubricant magnesium stearate, and 85% ethanol as a wetting agent, and the mixture was compressed to obtain Astragalus and Ginseng Chewable Tablets. In a mouse spleen cell proliferation experiment, it was found that the chewable tablets can significantly promote mouse spleen cell proliferation in the presence of concanavalin A (Con A) or lipopolysaccharide (LPS), indicating that they can enhance mouse mouse cellular immune function. A study of mouse humoral immunity using this chewable tablet showed that it significantly increased the spleen index and antibody titer in mice, indicating that it has the function of enhancing mouse humoral immunity.

3 Conclusion

With the increase of modern life pressure, the proportion of people suffering from obesity, hyperglycemia, hyperlipidemia, reduced immunity, and fatigue as the main sub-health symptoms continues to expand, and consumers are increasingly concerned about foods with adjuvant health effects. Although milk vetch root has been developed as the main ingredient in beverages, wine, biscuits, and other foods, some milk vetch root products also contain other Chinese medicinal herbs and are not suitable for consumption as ordinary foods.

There has been a lot of research on the pharmacological properties and preparations of Astragalus, and extensive research on the mechanisms of action of Astragalus extracts or individual physiologically active ingredients. However, there has been less research on the functionality and mechanisms of action of Astragalus foods, and most of the functionality is based on deductions from traditional Chinese medicine theory or research results in the field of traditional Chinese medicine. Therefore, it is necessary to better explore the efficacy and mechanism of astragalus food from a modern scientific perspective, clarify issues such as the changes in the bioactive components of astragalus during food processing and the mechanism of interaction with other food components, and further develop astragalus products with higher added value. Astragalus, as a traditional medicinal and edible food that “strengthens the qi and reinforces the body's defenses,” is in line with the national concept of self-care for chronic non-communicable diseases in the context of health promotion, which advocates “prevention” and “nourishing the body through diet.” Therefore, astragalus food products have broad development prospects in the future.

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