What Is the Use of Dandelion Extract in Animal Nutrition?

Dandelion (Taraxacum mongolicum Hand. Mazz.) , also known as yellow flowered ground elder (Ren Hanshu et al., 2022), is a perennial herb in the Asteraceae family. It is widely used as a wild vegetable and in traditional Chinese medicine, and has now been included in the list of medicinal substances with similar nutritional properties by the National Health Commission (Shi Guohui et al., 2017). Dandelion has strong growth and reproduction capabilities and is resource-rich. Dandelion is bitter, sweet and slightly cold. Studies have shown that dandelion extract mainly contains bioactive ingredients such as flavonoids, polysaccharides, phenolic acids, etc., which have pharmacological effects such as antibacterial, antioxidant, liver protection and choleretic (Zhang Zhenhua et al., 2022).

In modern farming, bacterial and viral infections are always one of the causes of animal death. Currently, the addition of antibiotics to feed has been completely banned, and many Chinese herbal medicines have good antibacterial and antiviral effects without causing animals to become tolerant. Dandelion, as a feed additive, can improve the biological performance of livestock and poultry, and has broad application prospects (Li Zhaojia et al., 2022; Li Aike et al., 2020). This article studies the extraction of effective components of dandelion, their biological functions and their application in animal production, providing a reference for the high value-added utilization of dandelion.

1 Main effective components of dandelion

At present, the extraction of effective components of dandelion mainly focuses on compounds such as polysaccharides, flavonoids, terpenes and phenolic acids.

1.1 Polysaccharide components and their extraction methods

Polysaccharides are one of the main effective components of dandelion extract. They are a class of biological macromolecules widely found in nature and have biological activities such as anti-inflammatory, antibacterial, hypoglycemic and antioxidant (Meng Qinglong et al., 2020). Currently, the methods used to extract dandelion polysaccharides include enzymatic extraction, hot water extraction, ultrasonic-assisted extraction, microwave-assisted extraction, etc. Different extraction methods have different polysaccharide extraction rates (Table 1). As can be seen from Table 1, the microwave-assisted extraction method has the highest extraction rate, but the microwave method has high equipment requirements and is currently mainly used in laboratory-scale research and is not suitable for large-scale industrial production. The hot water extraction method is suitable for large-scale production, but the disadvantage is that the extraction time is long and the efficiency is low. Enzyme extraction is more stringent in terms of temperature requirements and is also more expensive.

1.2 Flavonoids and their extraction methods

Flavonoids are found in the above-ground and underground parts of dandelions, with the above-ground flowers being richer in flavonoids (Sun Shanshan et al., 2018). Flavonoids have anti-cancer, antioxidant, liver-protecting, choleretic and immunity-enhancing effects (Tang Chunli et al., 2021). Currently, commonly used methods for extracting dandelion flavonoids include ultrasonic-assisted extraction and microwave-assisted extraction. Different extraction methods have different flavonoid extraction rates (Table 2). Overall, the microwave-assisted extraction method has the highest extraction rate and the shortest time, and can be used as the optimal method for extracting total dandelion flavonoids.

1.3 Phenolic acids and their extraction methods

More than 30 phenolic acids have been isolated from dandelion, mainly including chlorogenic acid, caffeic acid, p-hydroxybenzoic acid, coumarin, etc., among which the phenolic acid content in dandelion leaves is much higher than that in the roots (Li Lingna, 2019). Phenolic acids have antibacterial, antioxidant, hypolipidemic, anticancer, and anti-inflammatory effects (Zhang et al., 2018). The current research on the extraction of phenolic acids from dandelion includes ultrasonic extraction, ethanol reflux, and other methods. Different extraction methods have different phenolic acid extraction rates (Table 3). At present, the extraction of phenolic acid components is mainly concentrated on chlorogenic acid, and other components are rarely involved.

1.4 Other compounds and their extraction methods

Sterol compounds are widely found in all parts of dandelion, especially in pollen (Chen Ruijun et al., 2021). Dong Changying et al. (2011) used reflux extraction to extract crude sterols from dandelion, with an extraction rate of 8.761%. Cui Yanping et al. (2021) used an ultrasonic microwave method to extract polyphenols from dandelion, and the polyphenol extraction rate was 2.96%. At present, research on the extraction of effective components of dandelion mainly focuses on polysaccharides, flavonoids and phenolic acids, while there is very little research on its terpene polyphenols and other components.

2 Biological function research on the effective components of dandelion

2.1 Antioxidant effect

Dandelion is rich in flavonoid polysaccharide volatile oil and phenolic substances, which have a good antioxidant effect. It can reduce body damage by scavenging free radicals. Zhang Zhi et al. (2018) showed in an in vitro study that dandelion total flavonoids have a good scavenging rate for DPPH, and the scavenging rate is proportional to the mass concentration of dandelion total flavonoids. Cui Yanping et al. (2021) found that dandelion polyphenol extract has a good scavenging rate for both DPPH free radicals and ABTS free radicals, but as the concentration of the polyphenol extract increases, the rate of scavenging ABTS free radicals is faster than that of DPPH.

Kamal et al. (2022) found that dandelion essential oil can protect the liver and kidneys of mice from acetaminophen-induced oxidative stress damage by enhancing catalase superoxide dismutase (SOD) and glutathione and reducing malondialdehyde levels. A study by Kang Wenjin et al. (2020) found that dandelion polysaccharides can upregulate the relative expression of antioxidant stress factors Cu-Zn SOD Mn-SOD GPX-1 and GPX-4 mRNA, increase the activity of antioxidant enzymes, and thus remove the damage to the body caused by free radical ions.

2.2 Antibacterial effect

Dandelion has a broad-spectrum antibacterial effect, but the antibacterial effect of different parts varies. Pang Jiwei et al. (2021) showed that the antibacterial effect of the water extract of the whole dandelion herb at the same concentration was better than that of the root water extract, and the antibacterial effect on Staphylococcus aureus was stronger than that on Escherichia coli. Yang Qian et al. (2019) studied the effects of alcohol extracts from different parts of dandelion on two common cariogenic bacteria. Among them, the stem had the best inhibitory effect on Streptococcus mutans, while the flowers and whole grass had the strongest inhibitory effect on Actinomyces viscosus.

Yang Xiaojie et al. (2012) showed that dandelion polysaccharides have different degrees of inhibitory effects on bacteria and fungi, and the inhibitory effect on bacteria is stronger than that on fungi. The antibacterial effect of dandelion extract using different solvents is also different. The dandelion alcohol extract has a strong inhibitory effect on Staphylococcus aureus, Escherichia coli and Shigella dysenteriae, but has no significant inhibitory effect on yeast (Jia Meizhen and Feng Xin, 2013). Qiu Zhihong et al. (2018) showed that dandelion water extract has varying degrees of inhibitory effects on clinical pathogenic bacteria (Staphylococcus aureus, Acinetobacter baumannii, Pseudomonas aeruginosa, Escherichia coli, etc.).

2.3 Anti-inflammatory effect

Dandelion has a good anti-inflammatory effect, which is related to its rich content of triterpenes, flavonoids, sterols, polysaccharides and other ingredients. Research by Che Lu (2020) shows that dandelion sterols can reduce the levels of inflammation and oxidative stress in mice with ulcerative colitis, and can inhibit apoptosis of mouse colonic epithelial cells. Dandelion water extract has a therapeutic effect on ethanol-trinitrobenzene sulfonic acid-induced ulcerative colitis, and the mechanism may be to reduce the body's inflammatory response by regulating the secretion of inflammatory cytokines and increase the expression of pro-repair factors (Mao Yeqin et al., 2022). Chu Aijing et al. (2019) found that dandelion extract can reduce the pathological changes of endotoxin-induced mastitis in mice by regulating the NF-κB and MAPKs signaling pathways. Zhu Zhengwang et al. (2021) showed that dandelion total flavonoids can reduce liver damage caused by CCl 4 in rats by increasing SODGSH activity, lowering the levels of ASTALT TBILALP in rat serum, and reducing the MDA content in the liver.

2.4 Hypoglycemic effect

The phenolic acids and polysaccharides in dandelion have a hypoglycemic effect. Yin Jiale (2021) found that chlorogenic acid in dandelion leaves has a high binding capacity with sodium cholate by simulating the gastrointestinal environment, and has a significant hypolipidemic function. Guo Huijing et al. (2021) used an ultrasound-assisted method to extract dandelion polysaccharides, and used different volume fractions of ethanol for alcohol precipitation. It was found that the polysaccharides obtained at different alcohol precipitation concentrations all had a certain inhibitory effect on the glucoamylase, but the polysaccharides obtained by alcohol precipitation with 80% ethanol had the strongest inhibitory effect on the glucoamylase, and its IC50 was 0.56 mg/mL. Guo et al. (2019) showed that Dandelion polysaccharides have strong inhibitory effects on α-amylase and α-glucosidase in vitro, and exhibit good hypoglycemic activity, which is concentration-dependent. El-Nagar et al. (2022) found that dandelion seed extract can reduce the pathophysiological parameters of elevated cholesterol and improve steatosis inflammation and fibrosis.

2.5 Antitumor effect

From the current research, the anticancer effect of dandelion is mainly in breast cancer, gastric cancer, and ovarian cancer. Liu Siji (2022) found that dandelion phenolic acids can inhibit the proliferation and migration of gastric cancer MGC803 and liver cancer HepG2 cells, but the inhibition of migration in gastric cancer MGC803 is more obvious. Dandelion flavonoids can inhibit the proliferation of breast cancer MCF-7 cells and promote their apoptosis, possibly by regulating the expression of P53Bax and Bcl-2 (Sun Yumin, 2020). Wang et al. (2019) demonstrated that dandelion extract can interfere with glycerophospholipid and unsaturated fatty acid metabolism by inhibiting CHKA/P13K/AKT/FADS2, resulting in the death of triple-negative breast cancer cells. Menke et al. (2019) found that dandelion extract inhibited the cell viability of ovarian cancer cells, migrated mitochondrial integrity and induced apoptosis. Choi et al. (2009) studied the ethanol extract of dandelion flowers and found that it promoted apoptosis in ovarian cancer SK-OV-3 cells. The above study shows that dandelion has a good anti-tumor effect, providing a basis for the development of anti-tumor drugs.

3 Application of dandelion in animal production

3.1 Application in chicken production

Chicken meat and eggs are very important sources of protein in people's daily diet, and their quality is of increasing concern. Current research has found that the factors affecting the quality of chicken meat and eggs mainly include oxidative stress, disease resistance, apparent metabolic rate, and immune function. Yao Dongyun (2020) found that as a daily health care measure, adding 500 to 1000 mg/kg dandelion crude extract to chicken feed can increase the average egg weight of eggs, reduce the rate of broken eggs and breakage, and at the same time alleviate the oxidative stress that occurs during the breeding process. Li, Zhao Jia, et al. (2022) research shows that adding 1% dandelion to the feed can reduce the cholesterol content in eggs and increase the lecithin content; enhance antioxidant capacity and enhance the protective effect on the liver. Wang Shuyan et al. (2021) showed that adding dandelion extract to drinking water can improve the thymus index, spleen index and post-immunization antibody levels of three yellow chickens, and enhance their resistance to avian influenza.

Mao et al. (2022) showed that adding 500 mg/kg dandelion to the diet can improve the growth performance of broilers by improving intestinal barrier function. Dandelion can be added to the diet as an antibiotic alternative to improve production in the poultry industry. Wang et al. (2018) found that adding 3–5 g/L dandelion water extract to the water significantly increased the total serum IgG antioxidant capacity (T-AOC), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) levels in chickens. This may be related to the main active ingredient in dandelion, flavonoids, which have good antioxidant properties. They can reduce oxidative stress by scavenging free radicals and enhance the body's antioxidant capacity (He Jiayi et al., 2022).

3.2 Application in pig production

Du Xuelin (2021) showed that adding 1% dandelion dry powder to the diet of weaned pigs can significantly increase the daily weight gain of pigs and improve their disease resistance. Yu Wenhui et al. (2015) and Wu Suhao et al. (2012) showed that dandelion has an inhibitory effect on Streptococcus suis in vitro and can inhibit the formation of Streptococcus suis biofilms. The main component that exerts this inhibitory effect is chlorogenic acid. Li Yurong (2019) found that adding 500 g/t dried dandelion powder to the feed of fattening pigs can reduce the diarrhea rate, lower the content of triglycerides and total cholesterol, and improve the growth performance and quality of pigs.

Wang et al. (2019) showed that adding 6 g/L dandelion water extract to pig drinking water increased the serum anti-inflammatory cytokine IL-10 and decreased the pro-inflammatory cytokines IL-8, IL-22, and TNF-α, thereby reducing intestinal inflammatory damage in weaned pigs. Zhao et al. (2019) added dandelion root extract (CHE) to the feed of weaned pigs, which reduced the incidence of diarrhea in pigs. In addition, it also improved the concentration of SCFAs in pig feces and immune function, and shaped the fecal microbiota of weaned pigs.

3.3 Application in cattle production

The rumen is an important digestive organ of ruminants, rich in microorganisms, and is an important guarantee of ruminant health. With the rapid development of China's animal husbandry, feeders often add high-quality feed to maintain high milk production in dairy cows, but long-term use can lead to abnormal rumen metabolism and cause mastitis and digestive diseases in dairy cows. Sun Yawang (2021) found that adding dandelion extract to high-concentrate feed can enhance the antioxidant capacity of the mammary gland through Nrf2 regulation factors, increase the pH in the rumen, and reduce the production of lipopolysaccharides.

Wang et al. (2022) found that vomitoxin can promote the expression of BAXCaspase-3 and inhibit the expression of Bcl-2 in bovine milk epithelial cells, thereby accelerating apoptosis. Dandelion sterols can antagonize vomitoxin and inhibit apoptosis. Sun et al. (2015) found that a water extract of dandelion can be used to treat mastitis in cows instead of antibiotics. Cho et al. (2015) found that adding dandelion to the feed of cows can increase the milk protein milk urea nitrogen (MUN) and free fatty acid (FFA) content in milk, thereby improving the production performance of cows. Shi Chengyu et al. (2019) found that dandelion can interfere with the reproduction of Streptococcus mutans and promote the remineralization of teeth. The mechanism of action may be the result of the synergistic effect of antibacterial substances in dandelion. Adding 6% dandelion to the feed can help improve the blood metabolic indicators of beef cattle, increase the serum albumin content, increase the weight gain of grazing cattle, and improve their immune performance.

3.4 Application in fish production

Adding dandelion extract to fish feed can not only promote fish growth and improve meat quality, but also enhance fish immunity. Li Meiju (2020) found that adding 0.4% dandelion extract to tilapia feed can increase the average final weight of tilapia, reduce fattening and mesenteric fat index, and at the same time affect the blood biochemical indicators of tilapia (serum globulin concentration increases, while triglyceride and cholesterol concentrations decrease). Peng Xiaoyu et al. (2010) found that adding 2% dandelion extract to crucian carp feed can promote the growth of crucian carp, improve meat quality, enhance digestive enzyme activity and immunity. Salem et al. (2021) found that the use of dandelion at a rate of 0.5% in trout farming will help prevent oxidative stress and positively affect the feed conversion rate of fish. Li et al. (2022) showed that dandelion extract can reduce lipopolysaccharide (LPS)-induced inflammation in RAW264.7 macrophages and CuSO4-induced inflammation in zebrafish larvae. Xue et al. (2022) added 5.42% dandelion extract to the feed of carp, which improved the growth performance, non-specific immunity and antioxidant capacity of carp. In summary, dandelion extract, as a low-cost feed additive with good biological activity, can be reasonably applied in fish farming.

4 Conclusion

Dandelion is widely distributed, inexpensive, and studies at home and abroad have confirmed that dandelion has antibacterial, growth-promoting, and antioxidant effects, and can be used as a new feed additive in animal production. However, there is not much research on the mechanism of action and the extraction of effective ingredients in dandelion in animals, especially sterol compounds, which require further in-depth research. In addition, the extraction process of some compounds is too complicated and the extraction cost is high, which is not suitable for large-scale extraction and production. Only by developing an extraction method that can be mass-produced and popularized can the wide application of dandelion in animal production be ensured.

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