What Is the Benefit of Dandelion Root Extract?

Dandelion is the dried whole herb of Taraxacum mongolicum Hand.-Mazz., Taraxacum borealisinense Kitam. or several plants of the same genus [1]. The plants in this genus are native to Europe and were introduced to China, where they are widely distributed in provinces such as Hebei, Shanxi, Gansu and Heilongjiang [2]. They have been studied in China for thousands of years. The Ming Dynasty's Compendium of Materia Medica records that dandelion is used to treat boils and scabies. Dandelion clears away heat and toxins, reduces swelling and disperses lumps, and promotes diuresis and urination. It is often used to treat boils, breast abscesses, lung abscesses, intestinal abscesses, scrofula, red eyes, sore throats, damp-heat jaundice, and painful hot urination [1]. Modern research has shown that dandelion contains polysaccharides, essential oils, flavonoids, sterols, phenolic acids, pigments and terpenes, and has pharmacological activities such as protecting the liver and gallbladder, lowering blood sugar, antibacterial, anti-oxidant, anti-inflammatory, anti-tumor and boosting immunity.

In recent years, the widespread clinical use of dandelion as a traditional Chinese medicinal herb, as well as its increased use as a food and health food, has led to a continuous increase in dandelion production to meet the surging market demand. Due to factors such as the different methods of harvesting medicinal herbs, the harvesting period, and the processing methods, the quality of raw medicinal herbs on the market varies greatly. However, the quality control of Chinese medicinal herbs is the basis and guarantee for the safe and effective clinical use of Chinese medicine.

Therefore, in 2016, Academician Liu Changxiao proposed the concept of quality markers (Q-markers), which provides new ideas and methods for the quality control and quality evaluation of Chinese medicine [3]. Based on this, this paper provides a reference for the quality control and in-depth development of dandelion by analyzing and predicting its quality markers based on the traditional efficacy, modern pharmacological efficacy, and the validity and measurability of the chemical constituents of dandelion, in addition to summarizing the chemical composition and pharmacological effects of dandelion.

1 Chemical composition

Dandelion contains a wide variety of chemical components, mainly including flavonoids, phenolic acids, terpenes, sterols, polysaccharides, pigments, essential oils and coumarin compounds. Among these, flavonoids, phenolic acids and terpenes are the main pharmacologically active components of dandelion.

1.1 Flavonoids

Flavonoids are one of the main active ingredients in dandelion plants [3]. At present, 39 flavonoids have been found in dandelion [4, 5], including mainly luteolin and quercetin flavonoids and their derivatives. The total flavonoid content of dandelion in different parts of the same plant at the same time period (flowers>leaves>roots) varies significantly, which is consistent with its traditional medicinal part being the aboveground part [6]; and the flavonoid content of dandelion from different origins also varies greatly, which may be related to its growth environment and harvesting method [7].

1.2 Phenolic acids

Phenolic acids are one of the main active ingredients of dandelion, and they are abundant. The average content in dandelion flowers is 4.09% [8]. Hydroxycinnamic acid derivatives are the most abundant phenolic compounds in dandelion leaves and flowers, such as chicoric acid, caffeic acid, chlorogenic acid and monocaffeoyl tartaric acid [7, 9]. So far, 29 phenolic acids have been isolated from dandelion [10, 11].

1.3 Terpenoids

The terpenoids in dandelion plants are mainly triterpenoids and sesquiterpenoids [12-18], and the bitterness of dandelion mainly comes from terpenoids [19].

1.4 Sterols

Phytosterols are one of the main active substances in dandelion. Phytosterols can be isolated and identified from the whole grass, roots, leaves, flowers, pollen and other parts of dandelion plants. Pollen contains more phytosterols [12, 13]. The individual sterols in medicinal dandelion flowers, in descending order of content, are sitosterol, stigmasterol, and campesterol [20]. Except for stigmasterol and campesterol, other sterols mostly exist in the form of esters and rarely as glycosides [21, 22].

1.5 Polysaccharide compounds

Dandelion polysaccharides are one of the key components of dandelion that exert their pharmacological effects. They are abundant, accounting for about 30% to 50% of the dry weight [23]. The content of polysaccharides in various medicinal parts of dandelion has the following characteristics: root > flower > leaf [24]. Dandelion polysaccharides are composed of D-rhamnose, D-galactose, glucose, D-xylose and D-arabinose [25]. CaiL et al. [26] isolated two polysaccharides, DRP1 and DRP2, from dandelion root extract. Both polysaccharides are α-type polysaccharides and do not contain protein. In addition, dandelion root also contains a large amount of inulin [23].

1.6 Pigments

The flowers of dandelions contain a large amount of tetraterpene pigments, mainly luteolin epoxides [27], such as: apigenin, neoeriocitrin, luteolin, eriocitrin, violaxanthin, chlorophyll, taraxerol and its esters, which often form monoesters or diesters with some common saturated fatty acids [28].

1.7 Volatile oil compounds

The volatile oil of dandelion is complex in composition. Yang Chao et al. [29] extracted the volatile oil of dandelion using supercritical fluid CO2 extraction, and analyzed 26 components using GC-MS, accounting for 83.72% of the total volatile oil components, including linolenic acid, palmitic acid, oleic acid, ethyl palmitate, stearic acid, tricosane, etc.

1.8 Coumarin compounds

The coumarin components contained in dandelions mainly include esculin [10], scopoletin, umbelliferone, coumestrol, wild chicory glycosides, escin [30], luteolin [31], scopoletin, scopolamine, chicoric acid A, and chicoric acid.

In addition, dandelion is also rich in vitamins (A, C, E, K and B) and minerals (calcium, sodium, magnesium, iron, copper, silicon, zinc and manganese) [32].

2 Pharmacological effects

2.1 Antitumor effects

Modern pharmacological studies have shown that dandelion extract exhibits certain antitumor activity [33]. Its antitumor mechanisms of action include inducing apoptosis, inhibiting tumor cell proliferation by inducing apoptosis, inhibiting tumor angiogenesis, and exerting antitumor activity at the mitochondrial and genetic levels [33, 34]. Ovadje et al. [36] found that dandelion root extract can selectively and effectively induce apoptosis and autophagy in chronic myeloid leukemia (CMML) cells and human T-cell leukemia Jurkat cells, in a time- and dose-dependent manner. Aqueous dandelion root extract can activate multiple death pathways in cancer cells and cause them to express genes associated with programmed cell death [37]. The active ingredients in dandelion, including luteolin, β-sitosterol, α-linolenic acid, stearic acid, linolenic acid, palmitic acid, etc., have been shown to have anti-breast cancer effects. The mechanisms of action include blocking the cell cycle, promoting apoptosis and oxidative stress response, and inhibiting energy metabolism in breast cancer cells [39, 40].

2.2 Hepatoprotective and choleretic effects

The hepatoprotective mechanism of dandelion may be antagonizing the damage to lysosomes and mitochondria of hepatocytes caused by endotoxin, relieving the toxic effects of endotoxin released after the action of antibiotics[27], and reducing oxidative stress[40]. In a choleretic experiment, the bile volume of anaesthetized rats increased by more than 40% after administration of dandelion injection or dandelion ethanol extract via the duodenum [41]. Both the dandelion injection group and the dandelion decoction gavage group were able to restore liver damage caused by carbon tetrachloride to some extent.

A water extract of dandelion root can improve antioxidant capacity and reduce lipid peroxidation, thereby protecting HepG2/2E1 cells and mice from alcoholic liver injury. Mice in the dandelion root ethanol aqueous extract group showed no signs of alcohol-induced liver toxicity, and the activities of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase and lactate dehydrogenase in their serum were significantly lower than those in mice given ethanol alone [42]. For hepatitis B, the antiviral properties of dandelion extract may help block protein synthesis steps and DNA replication, as well as improve the ability to cope with oxidative stress, thereby protecting liver cells. It is speculated that caffeic acid and luteolin-7-O-β-D-glucopyranoside may be the main active ingredients [43].

2.3 Broad-spectrum antibacterial effects

Dandelion extract has a significant inhibitory effect on Staphylococcus aureus, hemolytic streptococcus, Staphylococcus epidermidis, and catarrhal streptococcus [4]. Experiments have confirmed that the antibacterial principle of dandelion may be to inhibit the synthesis of cell walls, proteins, and nucleic substances [44]; accelerate the destruction of cell membrane integrity, leading to increased cell permeability, causing the exudation of metal ions, proteins, and saccharides, resulting in cell metabolic disorders, and thus cell death. In addition, dandelion extract has a certain inhibitory effect on Helicobacter pylori (HP), and it has the same effect on HP metronidazole-resistant strains and sensitive strains. It can be used clinically for the treatment of HP infection and as a remedial treatment after HP metronidazole resistance [45].

2.4 Antioxidant effect

The antioxidant effect of dandelion may be related to its high content of phenolic compounds, namely flavonoids and coumarin derivatives. The reducing activity of dandelion polyphenols is equivalent to 40% of ascorbic acid [46], and they have the ability to scavenge DPPH free radicals, ABTS free radicals and reduce iron [47]. Kim MY et al. [48] added a mixed leafy vegetable containing dandelion to a high-fat and high-cholesterol diet in mice. the antioxidant levels and the activities of antioxidant enzymes in mice were increased, and the lipid peroxidation in the plasma, liver, heart and kidney was significantly reduced. The antioxidant activity of dandelion methanol extract was measured by assessing its ability to scavenge DPPH radicals, and the IC50 value was 70.1 μg/mL [49]; moreover, the scavenging rate increased with the increase of sample concentration [50]. In addition, dandelion polysaccharides have also been shown to have certain antioxidant properties. After the wild dandelions in Xinjiang were graded and precipitated, four dandelion polysaccharide samples with antioxidant activity were obtained in sequence. When the polysaccharide mass concentration was 0.5 mg/mL, the DPPH scavenging rate reached 84.32% [51].

2.5 Anti-inflammatory effect

Dandelion can affect the expression of pro-inflammatory mediators. In lipopolysaccharide (LPS)-stimulated macrophages (RAW 264.7 cells), luteolin and luteolin-7-O-β-D-glucoside (<20 μM) contained in dandelion flower extract downregulate the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2), without affecting enzyme activity, affecting the production of nitric oxide, prostaglandin E2 and pro-inflammatory cytokines (TNF-α and IL-1) [46]; this process occurs through the inactivation of mitogen-activated protein kinase (MAPK) signaling and is dose-dependent [52]. The two main components of dandelion, luteolin and chicoric acid, can synergistically inhibit the inflammatory response by inactivating the PI3K/Akt pathway and impairing the transcription of nuclear factor κB (NF-κB) in lipopolysaccharide (LPS)-stimulated macrophages (RAW 264.7 cells) [53]. A high-dose extract of dandelion had a significant inhibitory effect on ear swelling caused by xylene, the formation of cotton ball granulomas, and toe swelling caused by egg white in mice and rats [54]. Histopathological examination also showed that dandelion alcohol can significantly relieve synovial hyperplasia, bone and cartilage damage, and inflammatory cell infiltration [55].

2.6 Immunomodulatory effect

Dandelion can restore the immune function of mice with burns, including cell-mediated immunity, humoral immunity and non-specific immunity, and has a dose-dependent effect [56]. Dandelion polysaccharides are believed to have immunomodulatory activity. They can significantly increase the spleen index, phagocytic index, thymus index, lymphocyte transformation rate and serum hemolysin OD value of mice, and promote the growth and development of mouse immune organs [57, 58].

2.7 Gastrointestinal tract effects

Dandelion extract may have a protective effect on the gastrointestinal tract by inhibiting gastric acid secretion, promoting bile secretion [59] and causing gallbladder contraction [32]. Experiments have shown that dandelion extract (10 g/kg) can inhibit gastric enzyme secretion by up to 97.6% [60]. Dandelion polysaccharides have been shown to regulate the intestinal flora [61], inhibit the production of UA and NO in the serum of mice with ulcerative colitis and dysbiosis, regulate the number of normal flora and probiotics, and have a significant effect on improving the intestinal flora imbalance caused by lincomycin in mice [62].

2.8 Cardiovascular function improvement

2.8.1 Lipid-lowering and anti-atherosclerotic effects

Dandelion can reduce the risk of atherosclerosis by reducing oxidative and inflammatory processes. Its extract has an effect on various risk factors for cardiovascular disease in experimental animals, such as obesity and hyperlipidemia [63]. Dandelion root and leaf extracts can reduce oxidative stress and lower the levels of total cholesterol, triglycerides, and low-density lipoprotein cholesterol in the blood serum, while increasing the level of high-density lipoprotein cholesterol in the blood serum. This can effectively prevent atherosclerosis associated with oxidative stress, reduce atherosclerosis-related indices, limit the extent of atherosclerosis, and researchers attribute these positive changes to chicoric acid [64, 65]. In addition, dandelion leaves are also believed to have a positive effect on the cardiovascular system due to their high potassium content (397 mg/100 g) [32].

2.8.2 Anti-obesity effect

A 60% ethanol extract of dandelion leaves (containing about 123 mg gallic acid per gram of total phenolics) was found to have anti-obesity properties in a rat model [66]; it can improve the lipid profile and the concentrations of aspartate aminotransferase and alanine aminotransferase in obese mice. Consumption of dandelion flower syrup with a normal fat diet does not affect body weight, and the syrup has a positive effect on the antioxidant status and prostaglandin content of obese rat models. Its main components are luteolin and hydroxycinnamic acid [67].

2.8.3 Anticoagulant and antithrombotic effects

Taraxerol, which is abundant in dandelion, has an activating effect on platelets. Taraxerol (50 g/mL) inhibits the adhesion of thrombin-activated platelets to fibrinogen by about 20%, inhibits ADP-activated platelet adhesion by about 40%, and inhibits arachidonic acid metabolism. In addition, dandelion leaf and petal fractions also exhibit anti-adhesion and anti-aggregation effects, and the leaf fraction exhibits stronger anti-platelet activity than the monomer chicoric acid, which may be due to the synergistic effect of phenolic compounds in the fraction [68].

2.9 Diuretic effect

The diuretic effect of dandelion leaf extract in rats is comparable to that of furosemide. Compared with other herbs such as horse chestnut and juniper berries, dandelion extract exhibits a stronger diuretic effect [32]. When dandelion water extract was given to male rats by gavage at a dose of 50 mL/kg, the body weight of the experimental group of rats decreased by about 30%. At the same time, because the high potassium content in dandelion leaves can compensate for the potassium lost with urine, the mice did not experience side effects such as hepatic coma and circulatory system disorders due to potassium loss [69]. Experiments have confirmed that dandelion's ethanol extract has a diuretic effect on the human body [70].

2.10 Hypoglycemic effect

Dandelion extract can significantly reduce the serum glucose concentration in rats after oral administration by improving insulin secretion and inhibiting α-glycosidase activity [71], and inhibit the hydrolysis of maltose and the absorption of glucose in the small intestine [72]. Water-soluble polysaccharide PD1-1 extracted from dandelion exhibits good antioxidant activity in terms of DPPH and hydroxyl radical scavenging capacity, and can inhibit α-glycosidase and α-amylase to reduce blood sugar [73].

2.11 Other effects

Dandelion extract can significantly improve the anti-fatigue ability of mice [74]; antagonize the micronucleus mutation of peripheral blood lymphocytes induced by cyclophosphamide [75] and upregulate the expression of estrogen receptors (ER-a, ER-b), progesterone receptors and follicle-stimulating hormone receptors [76].

3 Predictive analysis of dandelion quality markers (Q-markers)

Quality markers are chemical substances that are closely related to the functional properties of traditional Chinese medicine and are either inherent in traditional Chinese medicinal materials or formed during the processing and preparation of traditional Chinese medicine products (such as traditional Chinese medicine decoctions, traditional Chinese medicine extracts, and traditional Chinese medicine preparations). They are used as marker substances to reflect the safety and efficacy of traditional Chinese medicine [2]. The introduction of the concept of traditional Chinese medicine quality markers has provided new ideas for improving the quality standards of traditional Chinese medicinal materials and perfecting the traditional Chinese medicine quality standard system. Environmental and human factors can cause changes in the types and contents of dandelion's chemical components, and simple evaluation indicators cannot fully reflect the chemical quality of dandelion. Therefore, it is necessary to establish a more scientific and comprehensive dandelion quality evaluation system with exclusivity.

3.1 Q-Marker analysis based on plant kinship and exclusivity

The secondary metabolites of medicinal plants are often the main source of their pharmacological activities, such as phenolic acids, alkaloids, terpenes, etc. Plants of the same or similar origin often have similar pharmacological effects. The dandelion genus is one of the larger genera of the Asteraceae family (Compositae), and it is also one of the most evolved groups of the Asteraceae subfamily (Subfam. Liguliflorae DC.). There are about 300 species and more than 2,000 varieties worldwide. Due to its complex evolutionary relationships, the genus is distributed from the temperate zone of the Northern Hemisphere to tropical South America. Its center of distribution is in Central and Eastern Europe and Central and Eastern Asia[77].

There are a total of 70 species and one variety in China; they are distributed throughout the country except in the southeastern and southern provinces[78]. The chemical composition of Asteraceae mainly contains alkaloids, terpenes and essential oils[79]; the chemical composition of dandelion plants mainly includes flavonoids, phenolic acids, terpenes and polysaccharides, etc., which have pharmacological effects such as antibacterial, antioxidant and antitumor effects, and are similar to the basic chemical composition and pharmacological effects of dandelion. In addition, there are significant differences in the chemical composition of dandelions from different regions. These metabolites that produce differences are mainly phenolic compounds. KEGG pathway enrichment analysis shows that the main metabolic pathways are the biosynthesis of phenylpropanoids and flavonoids [80].

Taraxasterol is one of the unique components of dandelion. It is a pentacyclic triterpenoid compound with multiple biological activities. It has the advantages of high safety, low toxicity and side effects, and clear therapeutic targets, and has high medicinal value. At present, research on its pharmacological effects and mechanisms mainly focuses on anti-inflammatory, antioxidant, and anti-cancer effects [81]. Flavonoids and phenolic acids are one of the main active ingredients in dandelion. The 2020 edition of the Chinese Pharmacopoeia changed the quality control index of dandelion from caffeic acid (C9H804) to chicoric acid (C22H18O12), and the content was also changed from not less than 0.020% to 0.30%. It was determined that the content of chicoric acid in 10 batches of dandelion extracts from different origins ranged from 0.047% to 0.360% [82]. Therefore, both caffeic acid and chicoric acid can to some extent reflect the quality of dandelion medicinal materials.

In summary, based on the analysis of the botanical affinity and exclusive components of dandelion, the chemical components such as flavonoids, terpenoids and phenolic acids, such as dandelion sterols, chicoric acid and caffeic acid, can be used as one of the potential Q-Marker indicators of dandelion.

3.2 Q-Marker analysis based on the validity of chemical composition

3.2.1 Q-Marker prediction analysis based on traditional medicinal properties

The theory of Chinese medicine is based on the concept of the nature and properties of herbs and their relationship with the channels and collaterals. The three-way relationship between nature and properties, efficacy and medicinal substance should also be used as the basis for Q-marker prediction [83]. Dandelion is bitter, sweet, cold in nature and enters the liver and stomach channels. Studies have shown that flavonoids, polysaccharides and volatile oil components are the main substance basis of cold Chinese herbal medicines [84].

Triterpenoids are the main source of the bitter taste of dandelion. Bitter taste can purgative, can lower, can dry, can be firm, has the effect of purging, purging fire, lowering the gas, firm yin, dry dampness, etc. [85]. Traditional Chinese medicine theory believes that the bitter substances in bitter medicine are the active substances [86]. Modern research has found that the chemical components of bitter substances mostly include alkaloids, essential oils, glycosides, flavonoids and picrates, etc.[87]; in terms of pharmacological effects, bitter-tasting medicines mostly have anti-inflammatory and anti-cancer activities[88]. The sweet taste can nourish, soothe and harmonize. Sweet-tasting medicines mostly contain ingredients such as glycosides, proteins, amino acids and vitamins[89]. Modern pharmacological studies have shown that sweet-flavored medicines can regulate human body functions, supplement deficiencies, enhance the body's disease resistance, as well as have antipyretic, bactericidal, diuretic, hypolipidemic, hypotensive, and hypoglycemic effects [90]. In summary, the flavonoids, glycosides, and volatile oil components in dandelion can be used as important Q-Marker options.

3.2.2 Q-Marker prediction analysis based on traditional efficacy

Dandelion is bitter and cold in nature and is a good medicine for clearing away heat and detoxifying the body. It is good at dissipating boils and swellings, and is widely used clinically in treating heat-related diseases such as boils, mastitis, enteritis, bronchitis, etc. At the same time, dandelion has the effect of diuresis and unblocking the urinary tract, clearing dampness and heat, and is often used clinically to treat acute urinary tract infections. The Song Dynasty's “Compendium of Materia Medica” records: “The boiled water and juice are good for treating breast abscesses in women, and they are also good for applying to sores when mashed; they also treat thorns and fox urine thorns.” The Qing Dynasty's Yilin Zanyou records: “Dandelion can resolve heat-related toxins, relieve food poisoning, reduce swelling and abscesses, and treat boils and breast abscesses. It also promotes lactation and is used for its shape.

It strengthens teeth and gums and cools yang and yin.” Dandelion's antibacterial, anti-inflammatory, haemostatic, abscess-reducing and diuretic pharmacological effects are closely related to its traditional efficacy. Modern research has shown that the flavonoids luteolin and luteolin-7-O-β-D-glucoside [53, 91], phenolic acids chlorogenic acid, chicoric acid and caffeic acid [53, 92], the terpene dandelion sterol [93] and dandelion polysaccharides all have antibacterial, anti-inflammatory, antioxidant, and anti-tumor effects. These effects are consistent with the traditional efficacy of dandelion in clearing away heat and toxins, reducing swelling and dispersing knots, diuresis and unblocking the urinary tract, and are the main pharmacological substance basis for the traditional efficacy of dandelion. They can be used as an important basis for screening quality markers of dandelion.

3.2.3 Q-Marker prediction analysis based on modern pharmacological effects

Dandelion and its extracts have been shown to have a variety of biological activities. Dandelion polysaccharides induce apoptosis in breast cancer cells by promoting the expression of P53 and Bax proteins and inhibiting the expression of Bcl-2 proteins, thereby inhibiting their proliferation and exerting an anti-breast cancer effect in vivo [93]; it has a strong scavenging capacity for OH, O2 and DPPH, there is a clear dose-effect relationship in its antioxidant effect [94]; it can significantly reduce Fe3+ and inhibit α-glucosidase activity, reduce blood glucose in diabetic mice, while also reducing MDA levels and increasing SOD and GSH-Px activity [95]; it promotes the growth and development of immune organs [96], enhances the expression level of the cytokine TNF-α secreted by macrophages [58, 97], promotes the proliferation of lymphoid subpopulations, and improves the structure of lymphoid subpopulations [98], thereby enhancing immune function; it can also protect against liver damage by regulating inflammatory responses [99] and reducing oxidative stress [100].

Taraxasterol in dandelion inhibits diabetes-induced endothelial dysfunction by activating the AMPK signaling pathway [101]; it can protect the liver in mice [102] and reduce total cholesterol and triglycerides [103]; it significantly inhibits the adhesion of resting platelets to collagen [104]; it stimulates the immune response by controlling the expression of the CD28/CTLA-4 stimulatory molecules and by regulating the Th1 cytokine IL -12 and inhibiting the expression of IL-10 to stimulate the immune response [105]. In addition, the caffeic acid in dandelion can achieve the effect of anti-hepatitis B virus and liver protection by regulating the synthesis and metabolism of bile acids [106]; it has strong cell antioxidant and immunomodulatory activity [107]. Ferulic acid and oleanolic acid in dandelion can promote gastrointestinal motility, and oleanolic acid is more active [108].

Dandelion contains a large amount of flavonoids, such as luteolin, which can improve oxidative stress and inflammatory response by inhibiting nitric oxide synthase (iNOS) [109]. Luteolin and its glycosides can regulate immune cytokines [110], reduce the inflammatory response by inhibiting inflammatory central mediators such as COX-2 and NF-κB [111]; luteolin-7-O-β-D-glucoside can significantly reduce blood glucose levels (62.33%, p≤0.05) and has no effect on blood glucose levels in non-diabetic mice [112]. Quercetin, luteolin and related flavonoids in dandelion inhibit pancreatic lipase in pigs [113].

Dandelion sterols can induce apoptosis by arresting the cell cycle at the G0/G1 phase, effectively inhibiting the growth of subcutaneous transplanted liver cancer in mice [114]. It also inhibits the proliferation of cancer cells CAL-27 in a concentration-dependent manner [115]; and protects against immune liver damage [116]. In summary, the polysaccharides in dandelion can exert antibacterial, antitumor, hypoglycemic, antioxidant, immunomodulatory, hepatoprotective and anti-fatigue effects; phenolic acids can exert anti-inflammatory, antibacterial, antioxidant, hepatoprotective and choleretic, hypolipidemic and immunostimulatory effects. Flavonoids can exert anti-inflammatory, antibacterial, antioxidant, hypolipidemic and immunomodulatory effects; triterpenoids can exert antibacterial, anti-inflammatory, anti-tumor, hepatoprotective, anti-apoptotic and immunomodulatory properties. Therefore, the dandelion polysaccharides, chicoric acid, caffeic acid, chlorogenic acid, ferulic acid, oleanolic acid, luteolin, luteolin-7-O-β-D-glucoside, quercetin and dandelion sterols in dandelion can be used as important bases for selecting Q-Markers that characterize their efficacy.

3.3 Q-Marker prediction analysis based on different harvesting methods

Dandelion has large differences in traits between wild and cultivated dandelions due to differences in growth and harvesting methods. The Chinese Pharmacopoeia stipulates that the whole grass of the Chinese medicine dandelion should be dug up when the flowers first bloom from spring to autumn, but the above-ground parts of artificially cultivated products are harvested 2-3 times a year, with almost no roots, fewer capitulum, and more leaves. The last harvest of the year is dug up with the roots; the whole grass of wild dandelion is dug up, with more roots, smaller leaves, and more capitulum [117].

Dandelions on the market are mainly cultivated artificially, so the harvesting method and harvesting period have a greater impact on the quality of dandelions. There are certain differences between the chemical compositions of wild and cultivated dandelions. Isochlorogenic acid A and luteolin are the compounds that differentiate wild and cultivated dandelions, and can be used as quality control indicators to identify and distinguish between the two [118]. In a study of wild and domestic dandelion samples from four origins, there was no significant difference in the contents of caffeic acid, chlorogenic acid and total flavonoids between wild and domestic dandelions, but the polysaccharide content of wild products was significantly higher than that of domestic products [194]. Therefore, the determination of isochlorogenic acid A, luteolin and polysaccharide content can be used as one of the quality control indicators for dandelion.

3.4 Q-marker prediction analysis based on the detectability of chemical components

The chemical substances contained in traditional Chinese medicine are complex, and only those that are stable and can be quantitatively measured can be used to better establish a quality control and evaluation system. Based on the above analysis, the flavonoids, phenolic acids, polysaccharides, and triterpenes in dandelion are all important choices for Q-markers. Flavonoids and phenolic acids are usually measured using chromatography, which is easy to operate; polysaccharides are mostly measured using the phenol-sulfuric acid method; and terpenoids are mostly measured using GC-MS, HPLC and mass spectrometry due to their complex composition and difficulty in isolation and identification.

Researchers [120] established a UPLC-MS method to simultaneously determine the contents of four index components in dandelion roots and leaves: coumaric acid, caffeic acid, luteolin, and luteolin-7-O-β-D-glucoside. In another study [121], HPLC fingerprints were established for 42 batches of medicinal dandelion collected from 8 places of origin, and the content of total flavonoids, chlorogenic acid, caffeic acid, chicoric acid and isochlorogenic acid A in the medicinal materials was measured. Dandelion polysaccharides are not yet used as an indicator due to their complex structure and difficulty in isolation and purification. Therefore, caffeic acid, luteolin, luteolin-7-O-β-D-glucoside, chlorogenic acid, chicoric acid and isochlorogenic acid A can be used as potential Q-markers for dandelion medicinal materials due to their good detectability.

4 Conclusion

Dandelion is a plant species with a wide variety of species, abundant resources, low price and definite efficacy. It has a medicinal history of thousands of years in China and is an important medicinal and edible resource with broad application prospects in the fields of medicine, health care and veterinary medicine. However, its quality is uneven due to factors such as planting, cultivation and harvesting methods, and there is currently a lack of systematic quality control standards. There is an urgent need to construct and improve its quality evaluation system.

In this paper, based on a review of the research on the chemical composition and pharmacological effects of dandelion, and guided by the theory of traditional Chinese medicine Q-Marker, the possible basis of medicinal substances is analyzed based on the phylogeny of dandelion plants, the specificity of chemical components, the effectiveness and measurability of chemical components, etc., and the Q-Marker is predicted and analyzed. It is initially inferred that luteolin, luteolin-7-O-β-D-glucopyranoside, caffeic acid, chlorogenic acid, chicoric acid and taraxasterol can be used as potential Q-Markers for dandelion medicinal materials. The construction and improvement of a scientific, reasonable and systematic dandelion quality evaluation system based on quality markers is of far-reaching significance for ensuring the safety and efficacy of clinical medication, and can promote the application of dandelion and the healthy development of the industry.

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