artichoke

What are artichokes

The globe artichoke (Cynara cardunculus var. scolymus) is a variety of a species of thistle cultivated as a food 1).

Left alone, an unpicked artichoke will blossom into a striking purple flower. The edible portion of the plant consists of the flower buds before the flowers come into bloom. The budding artichoke flower-head is a cluster of many budding small flowers (an inflorescence) together with many bracts, on an edible base. Once the buds bloom, the structure changes to a coarse, barely edible form. Another variety of the same species is the cardoon, a perennial plant native to the Mediterranean region. Both wild forms and cultivated varieties (cultivars) exist.

Artichoke (Cynara scolymus) extracts obtained from different parts of the plant (leaves, fruits and roots) have been used as medicaments since ancient times 2), 3), 4). Traditional medicine made use of the artichoke a choleretic, diuretic, laxative, appetite-stimulant, anti-gout medication and depurative (purifying and detoxifying effects) 5).

In the 1960s, one of the active ingredients found in the artichoke –called cynarin – was identified and successfully marketed as a liver-protecting agent. In a short time, this active ingredient was isolated, and some Italian researchers identified its chemical structure, thus enabling its synthesis. Some cynarin-based synthetic preparations were used to treat liver and gallbladder disorders, as well as to reduce lipid and cholesterol values, even if, over the years, they were then replaced by drugs that were more specific for these diseases. In the last ten years, however, the aqueous extract from artichoke leaves has regained an acknowledged medical value in Germany: it has been officially certified as safe and effective if it is obtained through a process complying with the relevant international pharmaceutical regulations 6). The artichoke leaf extract has been used as a dietary supplement indicated for treatment of hyperlipidemia 7), 8). In addition, Pharmacopoeias have approved its use as a hepatic stimulant and appetite stimulant, particularly in children 9), 10), 11), 12). Artichoke leaves, whether fresh or dry, are presently included in the official European monographs on herbal products, and the plant is mentioned in the most important collections of medicinal herbs and phytotherapy and general pharmacognosy books 13), 14), 15), 16), which approve use of artichoke as a choleretic, diuretic, hepatoprotective and liver-stimulating substance.

Nutritional value of artichokes

One medium artichoke (128 grams) has just 60 calories, more than six grams of fiber, and four grams of protein. Artichokes also provide a good source of magnesium, potassium, and folate, nutrients that help improve muscle function and heart health.

Table 1. Artichokes (globe or french), raw nutrition facts

[Source: United States Department of Agriculture Agricultural Research Service 17)]

Table 2. Artichokes (Jerusalem-artichokes), raw nutrition facts

[Source: United States Department of Agriculture Agricultural Research Service 18)]

Chemistry of the biologically active molecules found in the artichoke

From a chemical point of view, artichoke leaves contain different molecules with important pharmacological activities: caffeic acid derivatives, flavonoids, sesquiterpenic lactones, anthocyans, in particular cyanidin and tannins, volatile oils, including terpenoids, carotenoids, saturated, unsaturated and polyunsaturated fatty acids, including linoleic, palmitic, oleic and stearic acids, other unsaturated compounds, like hydroxymethyl acrylic acid and polyacetylene, citric, malic, lactic, succinic and glycemic acids, monosaccharides, oligosaccharides and polysaccharides of different kinds, such as, for example, various sugars, mucilages, pectins, inulin, amino acids and proteins, like L-asparagine, and a large number of enzymes, including oxidase, peroxidase, cynarase, ascorbinase,  protease, ashes, potassium, magnesium, calcium and traces of other metals 19).

Caffeic acid derivatives

Many of the pharmacological activities of artichoke leaf extracts were attributed – at least initially – to the presence of caffeoylquinic acids 20). In literature, these compounds are also called, more generically, “caffeic acid derivatives” or “ortodihydrophenols”; they are synthetically obtained from the condensation of a quinic acid molecule with one or two caffeic acid molecules. The highest content in caffeoylquinic acids can be found in the leaf at the end of the first vegetation year 21). But these acids can also be found in small quantities in all the other parts of the plant. Pharmacologically, these compounds have exhibited choleretic effects (that is, they stimulate the biliary flow) and, in part, a cholesterol-reducing action.

Flavonoids

The chief flavonoids identified in leaves (0.1 to 1%) are luteolin 22) and three luteolin glycosides: cynaroside (luteolin-7-O-glucopiranoside), scolymoside (luteolin-7-O-rutinoside), and cynarotrioside (luteolin-7-O-rutinosil-4-O-glucopiranoside).

In addition, recent analyses also highlighted the presence of rutin, apigenin, quercetin and other flavonoids together with luteolin and its glycosides 23). It now seems to have been ascertained that these compounds – in particular luteolin – seem to exert a pharmacological effect on cholesterolemia through at least two different mechanisms: on the one hand they modulate cholesterol absorption and on the other, they slow down endogenous cholesterol synthesis by inhibiting HMG-CoA-reductase synthesis. In addition, these substances can also enhance the production of biliary acids and exhibit a marked antioxidant activity in the liver and serum 24).

Sesquiterpenic lactones

In addition to flavonoids and caffeoylquinic acid derivatives, artichoke leaves also contain a number of sesquiterpenic lactones (cynarotriol, cynaropicrin), which are responsible for the typical bitter taste of the artichoke 25). The highest contents in these substances were measured in young leaves immediately after flowering; on the contrary, they are absent in roots, ripe fruits and flowers. These components are endowed with hypocholesterolemizing antiinflammatory activity 26).

Other components

Other components found in the artichoke include: anthocians, and in particular cyanidin and tannins 27); more than 30 volatile oils, including terpenoids 28), carotenoids 29); saturated, unsaturated and polyunsaturated fatty acids, including linoleic, palmitic, oleic and stearic acids 30); other unsaturated compounds, such as hydroxymethyl acrylic acid and polyacetylene 31); citric, malic, lactic, succinic and glycemic acids 32); monosaccharides, oligosaccharides and polysaccharides of different kinds, such as, for example, various sugars, mucilages, pectins, inulin 33); amino acids and proteins, like L-asparagine, and a large number of enzymes 34), including oxidase, peroxidase, cynarase, ascorbinase, protease 35); ashes, potassium, magnesium, calcium and traces of other metals.

Benefits of artichokes

Hypercholesterolaemia and Artichoke leaf extract

Hypercholesterolaemia is directly associated with an increased risk of coronary heart disease (coronary artery disease) and other sequelae of atherosclerosis 36). Cardiovascular diseases are a major cause of death, and 49% of deaths due to cardiovascular disease are from coronary heart disease in particular 37). Effective non-pharmacologic treatment consists largely of dietary interventions and increased physical activity, and is considered the treatment of choice for primary and secondary prevention of coronary artery disease 38).

Artichoke leaf extract has been suggested as such an option. Artichoke (Cynara scolymus) is a herbaceous perennial native to southern Europe, northern Africa and the Canary islands. It contains 1% caffeic acid derivatives, 1% flavonoids, volatile and sesquiterpene 39). For medicinal purposes, extracts of the leaf are used. Artichoke leaf extract has traditionally been used as a diuretic and choleretic as well as for jaundice and liver insufficiency. Artichoke contains the bioactive agents apigenin and luteolin 40). The total antioxidant capacity of artichoke flower heads is one of the highest reported for vegetables 41). Cynarine is a chemical constituent in artichoke (Cynara scolymus). The majority of the cynarine found in artichoke is located in the pulp of the leaves, though dried leaves and stems of artichoke also contain it. It inhibits taste receptors, making water (and other foods and drinks) seem sweet 42).

In animal studies artichoke leaf extract has been shown to reduce plasma cholesterol and triglycerides 43) and to prevent the development of atherosclerotic plaque 44). The anti-atherosclerotic effects are presumed to be linked to the antioxidant effects of artichoke leaf extract, which reduce low-density lipoprotein (LDL-“Bad” Cholesterol) oxidation 45) on the one hand, and the inhibition of cholesterol synthesis on the other. In test tube studies on cultured hepatocytes (liver cells), for instance, suggested that artichoke leaf extract inhibits the incorporation of 14C-labelled acetate into the non-saponifiable lipid fraction and thus reduces the cholesterol biosynthesis 46). Other studies suggested indirect inhibitory effects exerted at the level of HMG-CoA reductase 47). Luteolin was found to play a major role in the inhibition of cholesterol synthesis 48). Quantitative measurements show that artichoke extract inhibits cholesterol biosynthesis in a concentration-dependent manner 49). Cholesterol- lowering effects of artichoke leaf extract are also reported in several case reports and uncontrolled studies 50), 51), 52), 53), 54).

In the Petrowicz 1997 study 55), there were no significant effects on serum cholesterol levels in the total sample. Subgroup analyses were performed in 24 patients with baseline total cholesterol levels of more than 200 mg/dL. The data suggest that patients with an initial total cholesterol level of more than 230 mg/dL experienced a significant reduction in total cholesterol levels compared with patients who received placebo. Total cholesterol levels at baseline are reported for the two groups together and therefore it was not possible to assess whether baseline data were comparable for both groups. No major adverse events were reported in either group.

In the Bundy 2008 study 56), the total cholesterol level in participants receiving artichoke leaf extract decreased by 4.2% from 7.16 mmol/L at baseline to 6.86 mmol/L after 12 weeks, and increased from 6.90 mmol/L to 7.04 mmol/L in patients receiving placebo; the total difference in change between groups was statistically significant. No further statistically significant differences between groups were observed for HDL-“good” cholesterol, LDL-“bad” cholesterol and triacylglycerol (triglyceride).

In the Englisch 2000 trial 57), total cholesterol levels for patients on artichoke leaf extract decreased by 18.5% or 1.43 mmol/L (from 7.74 mmol/L at baseline to 6.31 mmol/L after 42 ± 3 days of treatment). Total cholesterol levels for patients taking placebo also decreased by 8.6% or 0.66 mmol/L (from 7.69 mmol/L at baseline to 7.03 mmol/L). The difference between the artichoke and placebo groups was statistically significant. LDL-cholesterol levels were also significantly lower for patients receiving artichoke leaf extract, showing a mean decrease of 1.26 mmol/L compared with patients taking placebo where the mean decrease was 0.33 mmol/L. There were no differences between placebo and artichoke leaf extract group for the blood levels of either HDL-“good” cholesterol or triglyceride. Although dietary habits were recorded, the food intake was not strictly controlled in the entire patient sample. In the sample, which included out-patients as well as hospitalised patients, the latter received a standardised and constant hospital diet.

The three reviewed trials indicate the absence of serious adverse events in patients treated with 1.2 to 1.9 g of artichoke leaf extract daily. In all studies, adverse events were described as mild and transient. Englisch 2000 58) reports 28 adverse events; 26 are mild changes in laboratory values, with unlikely relationship to the investigated product and 2 definitely not related to artichoke leaf extract. Petrowicz 1997 59) reports no changes in safety parameters and no major adverse clinical reactions, but provides no further details. Only in the Bundy 2008 60) study are the adverse events described; most of them occurred in both the artichoke leaf extract and placebo groups with higher incidences in the placebo group. Only constipation was mentioned by 3 in the artichoke leaf extract group versus 0 in the placebo group. Others are flatulence (2 versus 3), headache (0 versus 2), diarrhoea (1 versus 2), tiredness (2 versus 4), dry mouth (2 versus 4), forgetfulness (0 versus 1), and bloating (1 versus 0). Positive side effects concern gastrointestinal tract function (4 versus 1), improved appetite, reduced nausea, and cessation of hot flashes (1 versus 0, respectively) 61).

Although artichoke leaf extract-containing preparations are today promoted as aids to reduce cholesterol levels and are freely available over the counter or through the Internet, their effectiveness in treating hypercholesterolaemia is unclear, and results from randomized controlled trials need to be evaluated to establish a cause-and-effect relationship. A 2013 Cochrane Review 62) showed some data from clinical trials assessing artichoke leaf extract for treating hypercholesterolaemia exist. The available evidence is not compelling enough to recommend artichoke leaf extract as a treatment option for hypercholesterolaemia. The limited data on safety suggest mild, transient and infrequent adverse events with the short term use of artichoke leaf extract.

Liver and Gastro-Intestinal Effects of artichoke extract

Experiments conducted in vitro demonstrated that the dry aqueous extract from artichoke leaves in primary hepatocyte cultures can induce bile secretion from biliary canaliculi, and that pure or more or less diluted juices squeezed from fresh leaves exert a dose-dependent choleretic effect on the isolated, perfused rat liver 63). Much more recently, in 1993, the choleretic action of the standardized extract was investigated by Kirchhoff 64) in a cross-over, doubleblind, randomised, placebo controlled pilot study. A single 1.92 g dose was administered in 20 male patients (mean age 26 years), divided into two groups: the first group (A) received the active treatment and then placebo after an 8-day washout period; the second group (B) received placebo in the first stage and the active treatment in the second. The mean increase in secreted bile volume was considerably higher in treated individuals than in the placebo groups; in particular, the greatest effect was reached after 1 hour, but the effects were still evident after 3 hours.

In 1998, Schulz reported the results of a small placebo-controlled clinical trial. The administration of 1,920 mg artichoke extract in 20 volunteers increased bile flow by 127.3% and 151.5% after 30 and 60 minutes respectively. The effects of the artichoke on gastrointestinal disorders associated to poor elimination of biliary acids were investigated in an observation study conducted by Held 65) in 1991, in which 403 patients affected by hepatic insufficiency and disorders in the biliary duct were treated for 4 weeks with standardised artichoke extract containing 375 mg dry extract per tablet. The overall results were considered as good by 46.9% of the patients. Twelve patients (2.9%) dropped out of the study – 4 because of diarrhoea and 2 because of excessive flatulence. The same extract was used in a similar study conducted by Wegener in 1994. The extract was administered at the average dose of 4.75 tablets a day (corresponding to 1,520 mg) in 170 patients affected by different gastrointestinal disorders, including dyspepsia (34%), irritable colon (16%), constipation (22%), functional biliary duct disorders (21%), and others. After 6 weeks’ treatment, there was an unexpected marked reduction of vomiting (95%), nausea (85%) and abdominal pain (75.5%). Abdominal pain, inappetence and meteorism also improved. According to the patients, the results were generally considered as excellent (22%) or good (67%). Unwanted side effects (weakness and a sensation of hunger) were observed only in 1.2% of the patients.

Another large multicentre phase IV clinical trial, with treatment lasting 43.5 days on the average, was conducted by Fintelmann and Menßen 66) in 1996 in 553 patients (mean age 54.7 years) suffering from dyspepsia. The administration of 3 to 6 tablets of standardised extract containing 375 mg dry extract per tablet resulted in the significant reduction of dyspeptic symptoms within 6 treatment weeks and the improvement of general symptoms in 70% of the cases. In comparison with baseline values, the subjective reduction of symptoms was about 66% for meteorism, 76% for abdominal pain, 82% for nausea and 88% for vomiting. According to the physician’s opinion, the general average therapeutic efficacy, on the basis of a classification scale ranging from 1 (excellent) to 5 (poor), amounted to 1.95. The effects were considered as “good” or “excellent” in about 87% of the patients and occurred within 10 days from treatment. Only light side effects were recorded (weakness and flatulence). Other more recent studies were also conducted to ascertain the capability of the artichoke extract of improving dyspepsia symptoms.

Best way to cook artichokes

In the US, large globe artichokes are frequently prepared by removing all but 5–10 mm (0.2–0.4 in) or so of the stem. After washing under cool water, snap off tough outer leaves close to the stem until you see pale-green layers. To remove thorns, which may interfere with eating, around a quarter of each scale can be cut off. Use kitchen shears to cut off the sharp tips from all exposed leaves; you will only need to trim about half an inch. Using a sharp paring knife, slice off enough of thick stem to form a flat base so the artichoke can sit upright in the steamer basket and on the plate.

To cook, the artichoke is boiled or steamed. A cooked, unseasoned artichoke has a delicate flavor, reminiscent of fried egg white. The core of the stem tastes similar to the artichoke heart, and is edible.

Salt may be added to the water if boiling artichokes. Covered artichokes, in particular those that have been cut, can turn brown due to the enzymatic browning and chlorophyll oxidation. Placing them in water slightly acidified with vinegar or lemon juice can prevent the discoloration.

Leaves are often removed one at a time. To eat, pull off leaves one by one. Dip in sauce (hollandaise, vinegar, butter, mayonnaise, aioli, lemon juice, or other sauces). The fibrous upper part of each leaf is usually discarded. Then spoon out and discard prickly choke. Cut up the tender heart and dip in sauce. The heart is eaten when the inedible choke has been peeled away from the base and discarded.

In Italy, artichoke hearts in oil are the usual vegetable for “spring” section of the “Four Seasons” pizza (with olives for summer, mushrooms for autumn, and prosciutto for winter). A recipe well known in Rome is Jewish-style artichokes, which are deep-fried whole. The softer parts of artichokes are also eaten raw, one leaf at the time dipped in vinegar and olive oil, or thinly sliced and dressed with lemon and olive oil.

Stuffed artichoke recipes are abundant. A common Italian stuffing uses a mixture of bread crumbs, garlic, oregano, parsley, grated cheese, and prosciutto or sausage. A bit of the mixture is then pushed into the spaces at the base of each leaf and into the center before boiling or steaming.

In Spain, the tenderer, younger, and smaller artichokes are used. They can be sprinkled with olive oil and left in hot ashes in a barbecue, sauteed in olive oil with garlic, with rice as a paella, or sautéed and combined with eggs in a tortilla (frittata).

Another way to use artichokes is to completely break off all of the leaves, leaving the bare heart. The leaves are steamed to soften the fleshy base part of each leaf to be used as the basis for any number of side dishes or appetizing dips, or the fleshy part is left attached to the heart, while the upper parts of the leaves are discarded. The remaining concave-shaped heart is often filled with meat, then fried or baked in a savory sauce. Frozen artichoke hearts are a time-saving substitute, though the consistency and stronger flavor of fresh hearts when available is preferred.

Throughout North Africa, the Middle East, Turkey, and Armenia, a favorite filling for stuffed artichoke hearts includes ground lamb. Spices reflect the local cuisine of each country. In Lebanon, for example, the typical filling would include lamb, onion, tomato, pinenuts, raisins, parsley, dill, mint, black pepper, and allspice. A popular Turkish vegetarian variety uses only onion, carrot, green peas, and salt. Artichokes are often prepared with white sauces and other sauces.

Summary

The lipid-lowering effects of artichoke leaf extract are supported by in vitro and animal experiments. A 2013 Cochrane Review 67) showed some data from clinical trials assessing artichoke leaf extract for treating hypercholesterolaemia exist. The available evidence is not compelling enough to recommend artichoke leaf extract as a treatment option for hypercholesterolaemia. The limited data on safety suggest mild, transient and infrequent adverse events (e.g. constipation, flatulence, bloating, tiredness, weakness, hunger, dry mouth, memory loss) with the short term use of artichoke leaf extract. Better clinical trials assessing larger patient samples over longer intervention periods, particularly in patients with highly rather than moderately elevated cholesterol levels, are needed to establish whether artichoke leaf extract is an effective and safe treatment option for patients with hypercholesterolaemia.

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