Bioactive Compounds from Cardoon as Health Promoters in Metabolic Disorders

Cardoon (Cynara cardunculus L.) is a Mediterranean plant and member of the Asteraceae family that includes three botanical taxa, the wild perennial cardoon (C. cardunculus L. var. sylvestris (Lamk) Fiori), globe artichoke (C. cardunculus L. var. scolymus L. Fiori), and domesticated cardoon (C. cardunculus L. var. altilis DC.). Cardoon has been widely used in the Mediterranean diet and folk medicine since ancient times. Today, cardoon is recognized as a plant with great industrial potential and is considered as a functional food, with important nutritional value, being an interesting source of bioactive compounds, such as phenolics, minerals, inulin, fiber, and sesquiterpene lactones. These bioactive compounds have been vastly described in the literature, exhibiting a wide range of beneficial effects, such as antimicrobial, anti-inflammatory, anticancer, antioxidant, lipid-lowering, cytotoxic, antidiabetic, antihemorrhoidal, cardiotonic, and choleretic activity. In this review, an overview of the cardoon nutritional and phytochemical composition, as well as its biological potential, is provided, highlighting the main therapeutic effects of the different parts of the cardoon plant on metabolic disorders, specifically associated with hepatoprotective, hypolipidemic, and antidiabetic activity.


Introduction
Mediterranean plants have been used since ancient times by humans; the knowledge about these plants and their benefits has been accumulated and transmitted over several generations. Mediterranean plants are used for many purposes, such as medicine, food, spices, and ritual components [1,2]. In addition to their nutritional value, Mediterranean plant-based foods are seen as a simple way to introduce the concepts of wellness and health in our daily diet via the consumption of natural products. This is associated with the content of various bioactive compounds, such as phenolic compounds, inulin, vitamins, and minerals, being described as possessing great biological potential, such as antioxidant, anti-inflammatory, antimutagenic, anticancer, and neuroprotective activity [3][4][5][6].
One of the most prominent Mediterranean plants in recent years has been Cynara cardunculus L., due to its high biological and industrial potential [7][8][9].

Carbohydrates
Carbohydrates are the most common biomolecules in the world, defined as simple sugars.
The free sugars found in cardoon's vegetal parts are reported in Table 2. In general, sucrose was the sugar reported in higher concentrations (seeds, bracts, and heads), with contents ranging from "not detected" to 8.77 g/100 g of d.w. [7,43,46]. Sugars play an important role in the defense reactions of plants. Additionally, it has been reported that glucose, sucrose, and trehalose can regulate an important number of processes related to plant metabolism and growth, acting independently of the basal functions; furthermore, they can also act as signaling molecules [51].
Another important sugar present in higher amounts in the roots of cardoon is inulin, with contents ranging from 22.4 to 49.6 g/100 g d.w. [32,39] (Table 2), being considered the main reserve sugar in roots of C. cardunculus L. [32]. Inulin, a linear fructan, i.e., a polymer of fructose units, usually with a glucose molecule at the end, is a reserve carbohydrate that is accumulated mainly in the roots and tubers of several plants of the Asteraceae family, such as cardoon [52]. This polymer has been exploited by nutraceutical and pharmaceutical industries and for other biorefining applications [32,39,40]. Several purposes have been reported, such as prebiotics, a nutritional supplement as low caloric soluble dietary fiber, and a mediate sugar for lipid metabolism in diabetic and hypercholesterolemia [53]. Additionally, inulin can be used as a diagnostic agent for the determination of kidney function [54], for the production of fructose by enzymatic hydrolysis of inulin from inulin-rich biomass, and for ethanol production [55][56][57]. Table 1. Nutritional composition of raw cardoon [48].
Lignocellulosic biomass (cellulose, hemicellulose, and lignin) is the most abundant renewable resource on earth. This biomass is resistant to enzymatic and chemical degradation and possesses a protective function against natural agents and microbial attacks [59,60]. Cardoon is a lignocellulosic plant, in which lignocellulosic residues represent around 70-80% of the cardoon plant [61]. The contents of their vegetal parts range from 4.6 to 55.2 g/100 g d.w. Stems were revealed to have higher amounts (Table 3) [10,35,45,58,60,62,63].
Lignocellulose is naturally recalcitrant, whereby enzymatic hydrolysis of cellulose is extremely difficult compared to the breakdown of other renewable vegetal materials, such as starch [58,60]. Developing methods for primary fractionation depends on their economic assessment and environmental impact [58,59]. Cellulose is probably the most abundant and valuable component of lignocellulosic biomass; it is a long-chain polymer, described as the most structural component in plant cells and tissues [64,65]. Its content in cardoon vegetal parts varies between 10.33% and 51.7%, with its greatest content being found in the stems [10,35,45,58,60,62,63]. Cellulose is a versatile polymer, being utilized by several sectors, such as veterinary foods, wood and paper, fiber and clothes, and cosmetics and pharmaceuticals as an excipient [65]. Cellulose and cellulose derivatives play important roles in pharmaceuticals, with properties related to extended and delayed-release coated dosage forms, extended and controlled release matrices, bioadhesives and mucoadhesives, compression tablets as compressibility enhancers, osmotic drug delivery systems, liquid dosage forms as thickening agents and stabilizers, granules and tablets as binders, semisolid preparations as gelling agents, and several other applications, as reviewed by Shokri and Adibkia [65].
The hemicellulose of cardoon is composed of 90-95% xylan polysaccharide, which may be used as an important source of xylose, a raw material for xylitol production [59]. Moreover, the residual cellulose is a great source of cellulosic fibers, which can be submitted to a saccharification process to obtain a valuable source of fermentable sugars, such as glucose, used for bioethanol production and other industrial applications [59]. The content of hemicellulose in cardoon materials varies between 4.6% and 55.2% (Table 3), with the stalks having the greatest content [10,35,45,58,60,62,63].
Lignin is another important chemical compound that requires proper and adequate valorization. Cardoon vegetal parts possess amounts of lignin that range from 8.7-28.8%, with the stalks being richest in lignin [10,35,45,58,60,62,63]. This valorization may be aimed at producing biobased products, such as antioxidants and polymers, while their use as resins is a very attractive market. Furthermore, lignin, mainly as lignosulfates, is used as a binding dispersant agent, with application in different industries [33,66].
Crop residues and forest products, as a rentable raw material in view of the principles of the circular economy and their economic impact, are very important, mainly for biorefinery approaches with an integral valorization of the biomass for bioethanol production and other high-value products [67].

Proteins and Amino Acids
Proteins are chains of amino acids linked via amide bonds (commonly -known as peptide linkages). Proteins have many roles in the human body, like helping to repair and build our body's tissues, providing a structural framework, and maintaining the pH and fluid balance. Furthermore, they also keep our immune system strong, transport and store nutrients, and can act as a source of energy, if needed.
Amino acids are defined as organic compounds containing both amino and acid groups. They are classified as essential or nonessential. Essential amino acids must be supplied from our exogenous daily diet because the human body lacks the metabolic pathways necessary to synthesize them [68,69].
The most-reported proteins found in cardoon are aspartic proteases, which can be found in flowers from cardoon; they have gained special attention in dairy technology, used for milk coagulation and cheesemaking [70]. The industrial application of proteases in cheese manufacturing promotes acceptability by the vegetarian community and may improve nutritional intake [22]. The milk-clotting enzymes are known as cardosins and are isolated from cardoon flowers; nine enzymes (A-H) have been studied and characterized so far [71]. The crude extract of C. cardunculus flowers contains approximately 75% cardosin A and 25% cardosin B; however, cardosin A enzyme revealed a higher proteolytic activity [72]. Cardosin A is described as similar to chymosin, cleaving the same peptide bond of casein kappa [73,74]. On the other hand, cardosin B is similar to pepsin [73]. The ratio of cardosin A/cardosin B varies between thistles; for example, Cynara humilis only contains cardosin A [73].

Fatty Acids and Sterols
Fatty acids are essential for human wellbeing; however, they cannot be synthesized by humans, given the lack of desaturase enzymes. For this reason, they have to be provided by the diet [75]. Table 4 presents the lipid content of vegetal parts of cardoon, as well as the total saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), and polyunsaturated fatty acids (PUFAs), with a total of 30 fatty acids identified. In general, palmitic (C16:0; 0.03-55.9%), oleic (C18:1n9c; 0.58-46.6%), linoleic (C18:2n6c; 0.3-30.6%), and gamma-linoleic (C18:3n6; 0.0-70.41%) acids are the main compounds (Table 4). Seeds present the highest amounts of lipids, being also rich in MUFAs, which are useful to produce important intermediates such as azelaic and pelargonic acids. MUFAs are highly sought after by the synthetic fertilizer industry, as well as the cosmetic industry, being particularly attractive due to their low price [76,77].  In addition to fatty acids, vegetable oils are good sources of tocopherols and sterols. Phytosterols are cholesterol-like molecules found in most plant foods, and they are found in higher concentrations in vegetable oils. They can be found in free and esterified forms and can be acylated. β-Sitosterol, campesterol, and stigmasterol are reported as the more abundant ones in nature. Phytosterols are well recognized due to their capacity to lower blood cholesterol levels, provide protection against certain types of cancer, and possess immune-modulating activity [78]. Several sterols have been reported in several vegetal parts of cardoon but in low quantities (Table 5).  [44]; B [44]; C [44]; D [46,47]; E [43,44]; F [7].
Tocopherols are a group of fat-soluble antioxidants and can be divided into α-, β-, γ-, and δ-forms; on the other hand, sterols constitute a major portion of the unsaponifiable fraction of oils [79,80]. The crucial effects of tocopherols and sterols toward oxidative reactions are very well documented [80].

Organic Acids
Organic acids are primary metabolites present in high amounts in all plants, especially in fruits and vegetables. These compounds have a strong influence on the organoleptic characteristics of fruits and vegetables, especially with regard to flavor, color, and aroma [81].
Five organic acids were reported in the seeds, bracts, and heads of cardoon [7,43,46,47], namely, oxalic, quinic, and malic acids, followed by citric and fumaric acids which were detected in lower amounts. Bracts and heads were the plant parts with the highest acid contents ranging from 1.96 to 15.6 and 0.89 to 15.7 g/100 g d.w., respectively ( Table 6).

Micronutrients
Micronutrients are essential elements required by the organism to maintain a healthy status. The requirement for micronutrients differs depending on the individual need, which varies due to the different metabolic conditions within the life cycle (age, lifestyle, hormonal activity, exercise, etc.) [82]. They cannot be synthesized within the body, being all the essential micronutrients supplied via our diet [83].

Minerals
Mineral micronutrients are involved in several biochemical processes, such as controlling blood pressure and decreasing the risk of cardiovascular problems; an adequate intake of these chemical compounds is essential to the prevention of deficiency-related diseases [83]. For example, calcium is crucial for the human body, particularly for bone mass; on the other hand, an inadequate intake of potassium and/or sodium is related to the development of hypertension [84].
A total of seven minerals have been reported in raw cardoon, as well as the flowers and seeds of cardoon, namely, K, Na, Ca, Mg, Mn, Fe, and Zn [45,47]. Considerable amounts of K, Ca, Mg, and Fe have been reported in seeds, while the Na level is considerably low (12 to 24 mg/100 g of d.w.) [47], being very important from a nutritional point of view. On the other hand, raw cardoon and flowers present higher amounts of Na (170 and 200-300 mg/100 g of d.w., respectively) [45,48]. Flowers also present high amounts of K (1600-1710 mg/100 g of d.w.), Ca (580-1010 mg/100 g of d.w.), and Mg (150-170 mg/100 g of d.w.) ( Table 7) [45].

Vitamins
Plants are a major source of vitamins, which maintain health in humans and animals, as well as play important roles in plant growth and development. Vitamins include two major groups: fat-soluble (A, D, E, and K) and water-soluble vitamins (thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), biotin (B7), folate (B9), cobalamin (B12), and C families) [85]. Despite being minority compounds found in fruits, vegetables, and other foods, vitamins are essential for the maintenance and function of the organism and normal growth [86]. Cardoon has several vitamins reported in its raw material, contributing to its bioactive effects, e.g., antioxidant activity, decreasing the loss of vision and blurry vision, and supporting normal growth [85,86]. Vitamin C is the most abundant vitamin in cardoon and artichoke, with contents of 2.0 and 11.7 mg/100 g raw edible portion, respectively, followed by pantothenic acid (0.338 and 0.34 mg/100 g raw edible portion, respectively) and niacin (0.3 and 0.9 mg/100 g raw edible portion, respectively). Other vitamins reported in cardoon and artichoke are thiamine, riboflavin, pyridoxine, folate, vitamin A, and vitamin E (Table 8).
Vitamin C is an essential nutrient which cannot be synthesized by humans due to the lack of a key enzyme in the biosynthetic pathway. Vitamin C is crucial in the metabolism of proteins and the biosynthesis of some neurotransmitters [87,88]. Ongoing research is studying whether vitamin C, due to its antioxidant activity, can help prevent or delay the development of diseases in which oxidative stress plays an important role.

Volatile Compounds
The plant release of volatile compounds is involved in a broad class of ecological functions since volatiles play an important role in plant interactions with biotic and abiotic factors. Volatile compounds in plant materials can be derived from amino acids, fatty acids, and carbohydrates [90]. They vary widely across species and maintain differences in ecological strategy. They are released by almost any kind of tissue and type of vegetation (trees, shrubs, grass, etc.) as green leaf volatile compounds, nitrogen-containing compounds, and aromatic compounds. Plant volatiles can be emitted constitutively or in response to a variety of stimuli [91].
Sesquiterpene lactones represent one of the most prevalent and biologically relevant groups of secondary metabolites reported in plants. They are responsible for the phytotoxic, cytotoxic, fungicidal, antiviral, and antimicrobial activity of cardoon [92]. Cynaropicrin is a guaianolide sesquiterpene lactone found in the stalks, receptacle, bracts, and leaves of cardoon [44], as well as in globe artichoke [93], being an interesting compound due to its availability and great biological potential, such as antitumoral, antifeedant, and anti-inflammatory activity [44,94,95]. Grosheimin was found in higher amounts in leaves, with minor amounts in the stalks. Furthermore, deacylcynaropicrin was only reported in the leaves of cardoon, but in lower concentrations [44]. Both compounds are less studied than cynaropicrin.
Long-chain aliphatic alcohols were described as being in low concentrations, accounting for 1-5% in vegetal parts of cardoon [44]. This family of compounds has been recognized to present several biological and pharmacological effects in animals and humans. For ex-ample, octocosan-1-ol was reported to have several properties such as antioxidant activity, a cholesterol-lowering effect, lipid peroxidation, neurological functions, antiangiogenic and antitumor activity, prevention of inflammation and pain, antifatigue function, ergogenic properties, and improving athletic performance in exercise-trained rats, being used in food, medicine, and cosmetics, as reviewed by Kabir [96].
Pentacyclic triterpenes are ubiquitously distributed throughout the plant kingdom in a free form as aglycones or in combined forms, and they have long been known to have several biological effects. These compounds are the major family of lipophilic compounds found in the capitula, receptacle, and bracts (Table 9), in amounts that vary from 8% to 84% in the vegetal parts of cardoon [44]. Compounds such as α, β-amyrins have been reported to possess several pharmacological effects, such as anxiolytic, anti-depressant, anticancer, anti-inflammatory, antimicrobial, and antiviral activity [86].
Aromatic compounds and others were found in lower amounts in the vegetal parts of cardoon (contents ranging from 0.3% and 4% of the total detected compounds) [44]. 3-Vanillylpropanol was the major compound found in leaves, followed by benzoic acid. Furthermore, scopoline was only reported in the capitula and florets [44]. Aromatic compounds have been described as antioxidant and antimicrobial agents [97]. These compounds have been studied due to their advantages over antibiotics as growth promoters, being reported as residue-free and generally recognized as safe (GRAS) [98].   The consumption of medicinal plants, fruits, and vegetables is associated with a wide array of benefits in human health, linked to the consumption of non-nutrient bioactive compounds, such as phenolic compounds, for which various biological activities have been described, such as antioxidant, anti-inflammatory, regulator of glucose levels, antimutagenic, anticancer, and neuroprotective potential [5,30,100].
The composition of phenolic compounds in cardoon, wild cardoon, and globe artichoke is associated with several factors, such as different cultivars, genotypes, growing conditions, edaphoclimatic conditions, plant parts, plant age, harvest time factors, and handling and storage factors [7,30,31,43,46,102,103].
Cardoon presents mono-and di-isomers of caffeoylquinic acid, such as 1,5-dicaffeoylquinic acid (cynarine) and flavonoid O-glycosides (luteolin and apigenin derivatives) as the main compounds responsible for its biological effects [13,102,104]. Cynarine has been greatly investigated due to its high capacity to inhibit cholesterol biosynthesis and LDL oxidation, consequently reducing the risk of cardiovascular diseases [37]. Additionally, the anti-obesity effect of chlorogenic acid was reported in mice [105]. Furthermore, several reports also showed further biological potential of artichoke and cardoon extracts, rich in phenolic compounds, such as antimicrobial [106][107][108][109], anti-inflammatory [110], and antitumor properties [111,112].
In general, the compounds mostly detected in cardoon leaves and heads are chlorogenic acid and 1,5-O-dicaffeoylquinic acid [7,31,102,113,114]. Immature heads revealed a higher phenolic content compared with mature ones [7,31], proving that the maturity stage possesses a significant influence on the phenolic profile [31,115]. Apigenin derivatives were reported in the highest concentrations in both wild and cultivated cardoon immature inflorescences [116]. Furthermore, high contents of hydroxycinnamic acids, mainly dicaffeoylquinic acids, in receptacle and bracts, and apigenin and luteolin derivatives, in capitulum florets and leaves, respectively, were reported in different plant tissues of cardoon [114] (Table 10).      [114] tr, traces (below the limit of quantification); n.d., not detected.
Several studies reported the phenolic composition of artichoke, with caffeic acid derivatives identified as the major class of phenolics. 5-O-Caffeoylquinic acid is the most abundant, followed by 1,5-O-dicaffeoylquinic acid, and 3,4-O-dicaffeoylquinic acid, while it is also rich in flavonoids, with luteolin-7-O-glucoside being the major flavonoid reported [9,17]. These compounds were also found in higher amounts in raw artichoke and in their vegetal parts, as seen in cardoon vegetal parts [7,9,17,30,31,43,46].

Cynara cardunculus and Its Effect on Metabolic Disorders
Metabolic disorders are a common problem in industrialized countries, associated with an unhealthy lifestyle, such as a sedentary routine, high levels of stress, and unhealthy eating habits [119]. These disorders are related to several factors, such as obesity, diabetes, hypertension, and dyslipidemia [120].
According to the WHO, more than 100 million Europeans rely on traditional and complementary medicine [121]. Plants have been widely described as having activity against several metabolic disorders. Their activity against these disorders is linked to their composition in several bioactive compounds, which, via various mechanisms of action, are related to the regulation of oxidative processes, improving the antioxidant activity, decreasing the production of proinflammatory cytokines, and interacting in intracellular signaling pathways [122,123].
Thus, C. cardunculus L. is one of the plants that has been described in the literature with therapeutic purpose [124]. Its extracts have been used in traditional medicine, due to their hepatoprotective (Table 11), lipid-lowering (Table 12), and antidiabetic (Table 13) activities. Furthermore, C. cardunculus L. extracts possess antimicrobial [125][126][127], antioxidant [125,127,128], and anti-inflammatory [127,129] properties, as extensively described in the literature. The possible mechanism supporting the biological activity of C. cardunculus might be due to its content of vitamins, flavonoids, and polyphenols, since they are potent free-radical scavengers that prevent oxidative stress, which is intrinsically connected to the hepatoprotective, hypolipidemic, and antidiabetic activity [130,131].

Hepatoprotective Activity
The liver plays a relevant role in a variety of regulatory and metabolic activities; some of its functions influence the metabolism of carbohydrates, lipids, and proteins, while this organ is also crucial in endocrine activity and the elimination of toxins from the organism [132]. However, liver functions can be easily compromised, since hepatic damage can be triggered by prescription drugs, over-the-counter medications, dietary supplements, environmental factors, and alcohol [133].
Researchers have been exploring the hepatoprotective effect of C. Cardunculus taxa. Several studies demonstrated through in vitro assays, in vivo assays, and clinical trials that C. cardunculus L. (wild cardoon, domesticated cardoon, and globe artichoke) possesses hepatoprotective activity, as summarized in Table 11.
The in vitro hepatoprotective activity of C. scolymus on a human hepatocellular carcinoma cell line (HepG2 cells) was demonstrated by Youssef and colleagues [134], with the synergic activity resulting from the combination of three extracts (C. cardunculus L. var. scolymus L. Fiori, Ficus carica L. (fig), and Morus nigra L. (blackberry)) which were able to normalize the enzyme levels in the cells after the induction of hepatoxicity using carbon tetrachloride (CCl4), which caused an increase in aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels and a reduction in glutathione (GSH) and superoxide dismutase (SOD).
Furthermore, El Morsy and collaborators [135] studied the potential protective effect of artichoke leaf extract (ALE) against hepatotoxicity triggered by paracetamol overdose in rats. The authors observed that rats pretreated with ALE had lower values of serum ALT and AST, which were previously raised by paracetamol. Furthermore, hepatotoxicity due to paracetamol also causes oxidative damage. For this reason, the ALE effect on enzymatic antioxidants was also studied, and the authors found that ALE increased hepatic GSH, which reversed oxidative stress parameters, DNA damage, and necrosis. Moreover, it is important to emphasize that ALE had a higher impact on the restoration of GSH, nitric oxide, and antioxidant enzyme levels compared to N-acetylcysteine, a reference drug for the treatment of paracetamol overdose [135]. In a similar study, Elsayed Elgarawany and colleagues [136] investigated the effect of artichoke leaves, silymarin, and both compounds in acetaminophen-induced liver damage in mice. The treatment with artichoke, silymarin, or their combination resulted in a significant decrease in liver weight and enzymes. However, the reduced expression of proliferative cell nuclear antigen happened in the group using ALE and silymarin, which was attributed to the capacity of silymarin to increase the activity of glutathione reductase [136].
On the other hand, Tang and colleagues evaluated the effect of ALE on the alcoholic liver disease animal model; results showed that the levels of hepatic enzymes were reduced, and there was a suppression of the Toll-like receptor (TLR) 4 and nuclear factor-kappa B (NF-κB) pathway, which ultimately mitigated the oxidative stress and the inflammatory pathway [137].
Additionally, the hepatoprotective effect of bergamont polyphenolic fraction (Citrus bergamia) and C. cardunculus var. scolymus L. Fiori extract was also studied in a clinical trial conducted by Musolino and collaborators. After 16 weeks of supplementation, both extracts alone (300 mg/daily) and in combination (150 mg/kg of each extract) demonstrated the potential to decrease serum ALT and AST; nevertheless, the combination of both extracts exhibited better results [138].
Some mechanisms of action of artichoke extract have been described as being related to the ability to influence the lipid profile, leading to a hepatoprotective effect. For this reason, one of the mechanisms of action underlying the hepatoprotective activity might be related to the suppression of the TLR 4 and NF-κB pathway, which can ultimately hinder the release of proinflammatory cytokines and subsequently prevent the damage of the cell membrane, thus avoiding the leakage of AST and ALT into the bloodstream [139]. The bioactive compounds of Cynara that might be responsible for this hepatoprotective activity are caffeic acid and its derivates (chlorogenic acid and cynarine), as well as luteolin [139][140][141], mainly attributed to the antioxidant properties of the above-stated components [141]. The aqueous infusion of separate flower heads of C. scolymus, fruit of Ficus carica L., and fruit of Morus nigra L. presented reduced levels of liver enzymes and a higher level of antioxidant enzymes. The mixture of the three plants decreased AST and ALT levels and increased GSH and SOD when compared to CCl 4 -treated cells. [134] Ethanol extract from leaves in vivo Wistar Rats with high-fat diet (HFD)-induced obesity The administration of artichoke extract caused a decrease in pancreatic lipase compared to the HFD group and reduced organ weight. In addition, the serum lipid profile and the values of the hepatic enzymes were restored. [142]

Hydroethanolic extract from leaves in vivo
Wistar Rats with phenylhydrazine-induced hemolytic anemia The groups treated with Cynara scolymus extracts exhibited a decrease in the serum liver enzymes levels and, consequently, an improvement of the liver tissue damage. [143] Ethanolic extracts from artichoke (plant part) in vivo ICR mice with acute alcohol-induced liver injury The pretreatment with 1.6 g/kg BW of artichoke had a preventive effect due to its ability to reduce the lipidic profile and MDA while increasing SOD and GSH, as well as the inhibition of the inflammatory pathway by suppressing the expression levels of TLR4 and NF-κB. [137] Methanol extract from leaves in vivo Mice infected with Schistosoma mansoni Upon treatment with ALE either alone or in conjugation with praziquantel, there was an improvement of the liver enzymes. In addition, ALE-treated groups exhibited a reduction in the granuloma size due to the increase in hepatic stellate cell recruitment, ultimately improving liver fibrosis. [144]

Aqueous leaf extract in vivo
High-fat and high-cholesterol diet-induced steatohepatitis and liver damage in mice After ALE treatment, there was a reduction of the hepatic triglyceride level and inflammation, as well as a suppression of the liver damage induced by high-fat and high-cholesterol diet in mice. [145] var. scolymus L. Fiori Ethanol extract from receptacle, stem, inner bract, outer bract, and leaves in vivo

Sprague-Dawley rats with paracetamol-induced hepatotoxicity and nephrotoxicity
There were no significant changes in ALT and AST levels after the treatment with the different parts from artichoke; however, the histopathological data showed that the receptacle and stem extracts of Cynara scolymus significantly improved the pathological changes induced by paracetamol in both organs.
[146] The treatment with fish oil 10% or 1 g of artichoke leaves led to better improvement of DEN-induced changes in the biochemical parameters, such as antioxidant enzymes, angiogenic growth factors, liver function enzymes, and other substances produced by the liver. [147] Ethanol extract from leaves in vivo Albino mice of C57BL/6 with acetaminophen-induced hepatotoxicity After the treatment with ALE, silymarin, or their conjugation, there was an improvement of the serum liver enzymes, a decrease in MDA levels, an increase in glutathione reductase, and a decrease in PCNA expression. Thus, both plant extracts had hepatoprotective activity against acetaminophen. [136] Hydroethanolic extract from leaves in vivo Wistar rats with acutediazinon-induced liver injury The treatment with ALE caused a reduction in serum ALP, AST, ALT, MDA, TNF-α, and protein carbonyl and enhanced liver histopathological changes and hepatic CAT and SOD activities. [130] Aqueous extract from leaves in vivo Sprague-Dawley rats with paracetamol-induced hepatotoxicity Pretreatment with ALE (1.5 g/kg) reduced ALT and AST levels. In addition, the hepatic lipid peroxidation and NO levels also exhibited a reduction, whereas SOD and antioxidant enzymes activity increased.
Furthermore, the pretreated group presented a reduction in DNA damage. [135] Ethanol extract from leaves in vivo Wistar Rats with cadmium (Cd) toxicity-induced oxidative organ damage The ALE-treated rats exhibited a significant reduction in the oxidative stress in the Cd-exposed rats. Furthermore, ALE alone increased the GSH and CAT activity levels in rat liver and reduced liver lesions. [148] var. scolymus L. Fiori

Ethanol extract from leaves in vivo
Sprague-Dawley rats with carbon tetrachloride-induced oxidative stress and hepatic injury After treating rats with ALE, the levels of AST and ALT were decreased by 40% and 52%, respectively, in the curative group compared to the CCl 4 group, normalized to the antioxidant system, due to the decrease in SOD and MDA levels. [149] Luteolin-enriched artichoke leaves in vivo C57BL/6N mice with HFD-induced obesity Luteolin-enriched artichoke leaves and luteolin treatments significantly decreased the hepatic PAP enzyme activity and increased the activity of hepatic CPT. [150] Hydroethanolic extract of artichoke in vivo Wistar rats with lead acetate-induced toxicity Upon the treatment with the ALE, there was a decrease in the lipid profile levels and lead serum levels.

Aqueous extract from leaves in vivo
Rats with 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis After treating the mice with the extract, there was no significant variation in the ALT values comparing with the TNBS-treated mice. [152] Butanolic extract from aerial parts in vivo Male albino rats with paracetamol induced liver injury After 10 days, rats pretreated with the extract (300 mg/kg) prevented the increase in AST, ALT, and ALP caused by paracetamol. [153] var. scolymus L. Fiori Hydroethanolic Extract from Leaves in vivo Liver damage induced by deltamethrin in weanling male rats After 28 days of supplementation with an herbal syrup (sucrose, extract from C. scolymus, and chicory), there was an increase in the oxidative stress enzymes and an improvement of the serum liver enzymes. [154] var. altilis DC.

Leaves extract encapsulated in capsules
Clinical trial Adult patients with a history of at least 12 months of T2DM and NAFLD After 16 weeks, the patients supplemented with C. altilis alone exhibited a reduction in AST and ALT levels. However, the combination of Citrus bergamia and C. altilis had a more significant reduction, leading to liver protection. [138] var. scolymus L. Fiori

Cynarol ® (Leaves extract)
Clinical trial Subjects with nonalcoholic fatty liver disease After the treatment with ALE the hepatic vein flow increased, and portal vein diameter and liver size decreased when compared with placebo. Furthermore, the treatment also reduced both AST and ALT, as well as traditional liver markers and serum lipid profile. [155] -Clinical trial Patients with nonalcoholic steatohepatitis After the treatment with C. scolymus L. extract, there was a decrease in ALT and AST, while it also reduced the serum lipid profile. [141] -, there are no data.

Hypolipidemic Activity
Hyperlipidemia is characterized as an abnormally high concentration of lipids in the blood, such as triglycerides (TG), total cholesterol (TC), and low-density lipoprotein cholesterol (LDL-c) and a reduction in high-density lipoprotein cholesterol (HDL-c) values [156]. This unbalanced lipidic profile is one of the most relevant risk factors for cardiovascular diseases [157]. The most common causes of hyperlipidemia are lifestyle habits (smoking, obesity, and sedentarism), type 2 diabetes, alcohol, lipoprotein lipase mutations, hypothyroidism, and environmental and genetic factors [158]. The beneficial effects of C. cardunculus on the lipidic profile have been the focus of several studies, as described in Table 12.
Ben Salem and collaborators demonstrated the effect of ALE on the lipidic profile, cardiac markers, and antioxidant levels in obese rats [159]. As a result of supplementation of rats with ALE (200 mg/kg and 400 mg/kg), there was an improvement in the lipidic profile due to the decrease in TC, TG, and LDL-c levels and increase in HDL-c levels. In addition, ALE supplementation also reduced the cardiac markers and increased the antioxidant enzyme SOD, GPx, and GSH activities [159]. The effect of artichoke extracts on liver phosphatide phosphohydrolase and lipid profile in hyperlipidemic rats was also evaluated by Heidarian and colleagues. The supplementation with a mix of 10% artichoke in rat pellets for 60 days resulted in a decrease in the lipids in the serum and the phosphatide phosphohydrolase activity, which consequently decreased the levels of TG [151]. Furthermore, Oppedisano and collaborators showed the effect of C. cardunculus var. sylvestris (Lank) Fiori leaf extract in rats fed an HFD. In the animals fed an HFD and supplemented with 10 or 20 mg/kg of C. cardunculus, there was a dose-dependent reduction in TC, TG, and malondialdehyde levels compared with the group that was not supplemented with C. cardunculus var. sylvestris (Lank) Fiori [160].
Furthermore, TC, LDL-c/HDL-c and TC/HDL-c ratio levels suffered a significant reduction in subjects with primary mild hypercholesterolemia and after 8 weeks of supplementation with ALE (2 daily doses of 250 mg). There was a significant increase in HDL-c, which plays an important role in the prevention of cardiovascular diseases [161].
Luteolin and chlorogenic acid are compounds with crucial roles in modulating the lipid profile, according to several authors [139,159]. Luteolin can reduce cholesterol synthesis owing to the inhibition of hydroxy-methyl-glutaryl-coenzyme A (HMG-CoA) reductase, due to the inhibition of liver sterol regulatory element-binding proteins (SREBPs) and acetyl-CoA C-acetyltransferase (ACAT) [139,162]. However, the modulation of the lipidic profile by luteolin is not clear. Kwon and colleagues evaluated the effect of luteolin-enriched artichoke versus artichoke leaf and concluded that artichoke leaf had a higher effect on the lipidic profile than the luteolin-enriched [150].
Chlorogenic acid stimulates AMP-activated protein kinase and consequently inhibits sterol regulatory element-binding protein, which results in a reduction in cholesterol synthesis. Additionally, chlorogenic acid can also increase β-oxidation and inhibit malonyl-CoA, due to carnitine palmitoyl transferase stimulation, which subsequently lowers triglycerides levels [139,141]. Lastly, other authors also mentioned inulin, capable of modulating the lipid profile by increasing the conversion of cholesterol in bile salts, subsequently reducing very-low-density lipoprotein and LDL-c serum levels [139,163]. Oral administration of ALE at two doses 200 and 400 mg/kg decreased lipase pancreatic activity, improved the lipid profile, significantly decreased the cardiac markers, and improved the antioxidant activity and oxidative stress markers. [159] Ethanol extract from leaves in vivo HFD-induced obesity in Wistar rats After the treatment, there was a normalization of serum lipid profile, a decrease in urea, uric acid, and creatinine, a reduction in the formation of lipid accumulation and AOPP, and an increment in the antioxidant activity. [164] Aqueous extract from Leaves in vivo Golden Syrian hamsters After 42 days, the ALE fed hamsters exhibited a decrease in TC, non-HDL, and TG. In addition, there was an increase in the excretion of bile acids and neutral sterols. [165] Aqueous extract from Leaves in vivo Wistar rats fed on high-cholesterol diet The rats fed on high-cholesterol diet treated with ALE exhibited a decrease in the serum lipidic profile. [166] Extract from Leaves in vivo C57BL/6N mice with HFD-Induced Obesity When treated with ALE and luteolin-enriched ALE, there was a decrease in the plasma, hepatic, and fecal lipid profile, as well as a decrease in the hepatic PAP enzyme activity. [150] var. sylvestris (Lank) Fiori Hydroalcoholic extract from leaves in vivo Insulin resistance, hyperlipidemia, and NAFLD in Sprague-Dawley rats fed a hyperlipidemic diet After the treatment with ALE, the rats on a high-fat diet exhibited a decrease in the serum lipid profile in a dose-dependent manner. [160] var. scolymus L. Fiori Ethanol extract from leaf in vivo DNA damage and atherosclerosis in Wistar albino rats fed an atherogenic diet TG and HDL-c showed a significant decrease in the ALE-treated rats, when compared to the control group. [167] var. scolymus L. Fiori

Aqueous extract from leaves in vivo
Hepatic and cardiac oxidative stress in Wistar rats fed on high-cholesterol diet Hypercholesterolemic rats treated with ALE exhibited a decrease in the serum TC and TG levels; however, in the liver, there was no change. On the other hand, this treatment reduced the MDA and diene conjugate levels in the liver and heart tissues, and there was an increase in hepatic vitamin E levels and GSH-Px activities. [168] Aqueous extract from leaves and aqueous extract from stems in vivo Rats fed with HFD and vitamin C supplement Both extracts reduced the lipid profile levels, as well as GOT and GTP values. [169]  [172] Subjects with moderate untreated hypercholesterolemia The group treated with a supplement of red yeast rice, policosanols, and artichoke leaf extracts exhibited a significant decrease in LDL-c, TC, and apo B in healthy subjects with moderate hypercholesterolemia. On the other hand, no effect was demonstrated on other lipid concentrations, and there was no alteration in liver and renal function markers and in the muscle breakdown. [173] var. scolymus L. Fiori

Extract from leaves Clinical trial Patients with nonalcoholic steatohepatitis
After the treatment with ALE, the AST and ALT levels decreased, as well as the TG and TC levels. [141] Extract from leaves Clinical trial Subjects with primary mild hypercholesterolemia The supplemented group exhibited a significant decrease in TC, LDL-c, and LDL/HDL compared with the placebo. Furthermore, the supplementation caused an increase in HDL-c, which might have clinical interest owing to its protective role in cardiovascular disease. [161]

Antidiabetic Activity
Diabetes mellitus (DM) is described as having abnormal blood glucose levels caused by a defect in insulin secretion and/or insulin action. These abnormal glucose levels are associated with lipidic profile dysregulation [174,175]. Several authors have researched the antidiabetic activity of C. cardunculus and its possible mechanisms of action (Table 13).
Ben Salem and colleagues studied the in vitro capacity of different extracts (butanolic, ethanolic, and aqueous) of C. cardunculus var. scolymus L. Fiori to inhibit the activity of α-amylase; the results showed that the ethanolic extract exhibited an IC 50 value of 72.22 µg/mL (compared to acarbose specific inhibitor (IC 50 = 14.83 µg/mL)). Furthermore, the authors investigated the possible anti-diabetic effect of the ethanol leaf extract of C. cardunculus var. scolymus L. Fiori in alloxan-induced stress oxidant Wistar rats. The Wistar rats were supplemented with two daily doses of the ALE extract (200 mg/kg or 400 mg/kg) for 28 days. After the supplementation, ALE decreased the α-amylase levels in the serum of diabetic rats, which consequently lowered the blood glucose rate. Additionally, the administration of ALE also affected the lipidic profile and antioxidative activity in the liver, kidney, and pancreas of diabetic rats [176]. In addition, the antidiabetic activity of infusions (200 mg/L) of Agrimonia eupatoria L. and C. altilis L. was evaluated by Kuczmannová et al., by monitoring the inhibitory effect of α-glucosidase, serum glucose levels, formation of advanced glycation end-products (AGEs), and the activity of butyrylcholinesterase. The artichoke extract did not affect the activity of α-glucosidase, but induced a reduction in the glucose levels and inhibited the formation of AGEs [177]. Similarly, the treatment with an oral administration of ALE (200 and 400 mg/kg) on streptozotocin (STZ)-induced diabetic rats resulted in a significant decrease in serum glucose, TG, and TC levels [178].
In a clinical trial conducted by Ebrahimi-Mameghani and collaborators, the authors examined the effects of supplementation with ALE (1800 mg/daily) in patients with metabolic syndrome for 12 weeks. After the supplementation with ALE, there was a decrease in insulin and in homeostasis model assessment of insulin resistance (HOMA-IR) values [179].
These studies confirmed the antidiabetic activity of cardoon, which might be related to the content of chlorogenic acid, which can suppress glucose 6-phosphate, responsible for regulating blood glucose [180,181], and caffeoylquinic acid, responsible for regulating α-glucosidase activity [181,182]. [183] Methanolic extract from inedible floral stems in vitro and in vivo Suisse albino mice with alloxan-induced diabetes The administration of the extract resulted in a decrease in the serum profile levels and blood glucose. [184] var. altilis DC.

Aqueous extract in vitro and in vivo
Wistar rats with STZ-induced diabetes Both plant extracts presented good anti-glucosidase, antiglycation, and antihyperglycemic properties. In addition, the experiments on isolated aortas exhibited an improvement of vascular dilatory functions in diabetic animals. [177] var. scolymus L. Fiori Ethanolic extract from leaves in vitro and in vivo Wistar rats with alloxan-induced diabetes Both doses of the extract from C. scolymus decreased the activity of α-amylase, consequently reducing the blood glucose rate. [176] Methanol extract of cereal-based chips enriched with omega-3-rich fish oil and artichoke bracts in vitro and in vivo Suisse Albino mice with alloxan-induced diabetes In diabetic mice, the enriched chips normalized the levels of blood glucose and serum markers such as alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, urea, and creatinine. Furthermore, there was an improvement of the serum lipid profile. [185] Butanolic extract from leaves in vivo Albino rats with streptozotocin (STZ)-induced hyperglycemia The treatment caused a decrease in the blood sugar levels in the diabetes induced-rats, compared with the STZ diabetic rats. [186] Hydroalcoholic extract from leaves in vivo Wistar rats with STZ-induced diabetes In the groups with the administration of artichoke extract, compared with the diabetic group, there was an increase in insulin levels, while the serum concentrations of glucagon and glucose were reduced. [187] var. scolymus L. Fiori Ethanolic extract in vivo Wistar rats with STZ-induced diabetes When compared with glibenclamide, the use of artichoke extract decreased the lipid profile, increased HLD-c, and decreased HbA1C. However, compared with the group treated with glibenclamide, fasting blood glucose levels were elevated.
[188] The hypercholesterolemia-induced rats treated with both doses of ALE exhibited a decrease in fasting blood glucose, creatinine, uric acid, and urea. These results show that artichoke extracts can be used as a complementary treatment for renal damage and diabetes. [189] var. scolymus L. Fiori Hydroalcoholic extract from flowering head in vivo Wistar rats and obese Zucker rats Cynara scolymus flowering head extract had the capacity to lower the glycemia in both rat strains; however, the extract had a higher efficacy in Wistar rats than in Zucker rats. [190] Luteolin-enriched artichoke leaves in vivo C57BL/6N mice with high-fatdiet-induced obesity The treatment with ALE and luteolin-enriched ALE reduced the levels of insulin and glucose. [150] Hydroalcoholic extract from flowering head in vivo Wistar rats The combination of both plants extract resulted in a reduction in the food intake, mainly due to the P. vulgaris extract, and a decrease in the glycemia. [181] var. altilis DC.

Hydroalcoholic extract from leaves in vivo
Sprague-Dawley rats with nonalcoholic fatty liver disease induced by high-fat diet The administration of the extract in a high-fat diet reduced the levels of serum glucose, serum lipid profile, and MDA. Moreover, the 20 mg/kg dose was more effective in completely and significantly restoring OCTN1 and OCTN2 expression in rats fed a high-fat diet. [160] var. scolymus L. Fiori Hydroalcoholic extract from leaves Clinical trial Patients with metabolic syndrome The administration of the Cynara extract resulted in a decrease in insulin and in HOMA-IR values in patients with the TT genotype of TCF7L2-rs7903146 polymorphism. However, this supplementation did not have any effect toward the blood glucose levels. [179] -, there is no data

Conclusions
The current review provided the nutritional and phytochemical composition of cardoon and its therapeutic applications in metabolic disorders; specifically, hepatoprotective, hypolipidemic, and antidiabetic properties were highlighted. Cardoon is a plant used in the Mediterranean diet and traditional medicine, composed of several bioactive compounds, such as dietary fibers, sesquiterpenes lactones, and phenolic compounds. C. cardunculus L. is one of the most promising Mediterranean plants, due to its therapeutic potential and industrial applications. Several studies have demonstrated that cardoon has the capacity to act as an anti-inflammatory, antidiabetic, lipid-lowering, antimicrobial, and antitumoral agent due to its phytochemical composition. It is important to exploit cardoon's capacity to be applied as an adjuvant in therapies to prevent or diminish the occurrence of diabetes, as well as cholesterol-related diseases. This yields new insights into the advantages of employing other processing and formulation technologies, such as nanoparticles, microencapsulation, and nanoemulsions, to improve their functionality and to increase the use of nutraceutical products, food supplements, and pharmaceutical formulations. Nevertheless, further studies are needed to fully comprehend the mechanism of action of cardoon metabolites underlying the biological activities stated in this review. It is imperative to conduct more clinical trials to clarify the dose and duration of the therapeutics.