Scientific Name(s): Cnicus benedictus
Common Name(s): Cardin, Carduus benedictus, Holy thistle, Spotted thistle, St. Benedict's thistle
Blessed thistle is native to southern Europe, western Asia, and North Africa, and has been naturalized throughout the United States and Europe. It is considered a noxious weed and grows mostly in stony, uncultivated areas. It is an annual, growing about 0.7 m in height with leathery, hairy leaves 30 cm long and 8 cm wide. The entire plant is covered with down and bears pale yellow flowers in dense, prickly flower heads. Blessed thistle should not be confused with Silybum marianum, which is commonly referred to as "milk thistle."Duke 2002, Khan 2009, Ulbricht 2008, USDA 2016 Synonyms are Centaurea benedicta and Cirsium pugnax.
The plant was widely cultivated during the Middle Ages in Europe and was used in many herbal formulations of the period.Blumenthal 2000 Its medicinal use as a healing herb was mentioned by Shakespeare in his play Much Ado About Nothing.Shakespeare 1914 It was thought to be useful against the bubonic plague; however, its main uses were for treatment of digestive complaints, gout, fever, and headache.Duke 2002, Khan 2009 Blessed thistle was also recommended as an emmenagogue and galactogogue, and for the treatment of intestinal worms.Duke 2002, Khan 2009 The plant's dried leaves, stems, and flowers have been used medicinally. Blessed thistle, used in flavoring Bénédictine liqueur, has generally recognized as safe (GRAS) status as a flavoring agent. It is available as a single herb and in homeopathic preparations. Blessed thistle is approved by the German Commission E for treatment of dyspepsia and loss of appetite, and is a minor component of a multiherb cancer remedy formulation.Blumenthal 2000
The most prominent constituent of blessed thistle is the bitter sesquiterpene lactone ester cnicin. The leaves and plant parts contain tannins, sesquiterpenes, a high mineral content (primarily potassium, manganese, magnesium, and calcium), phytosterols, triterpenoids, and small amounts of volatile oil.Blumenthal 2000, Duke 1992, Jaiswal 2011, Khan 2009 Linoleic and oleic acid have been identified in the seed.Duke 1992
Uses and Pharmacology
Limited studies suggest cytotoxicDuke 2002, Erel 2011, Vanhaelen-Fastrè 1972, Vanhaelen-Fastré 1978 and antimicrobial activityBroekaert 1993, Bruno 2003, Duke 2002, Panagouleas 2003 of extracts of the plant and of the chemical constituent cnicin. Cnicin has been shown to have anti-inflammatory properties in vitro and in rat paw edema tests, with similar efficacy to indomethacin.Duke 2002, Erel 2011 Inhibition of acetylcholinesterase and antioxidant activity has also been demonstrated by an ethanol extract of the plant.Paun 2015
Use of blessed thistle is largely based on the ability of the bitter principle cnicin to stimulate secretion of gastric juices and saliva, and potentially bile; however, research reveals no clinical data regarding use of this plant for any indication.
No clinical studies exist to provide dosing recommendations for blessed thistle. Doses of 4 to 6 g daily have been traditionally used. The leaves (1.5 to 2 teaspoons per cup of water) and dried flowering shoots (1.5 to 3 g 3 times/day) have also been used.Blumenthal 2000, Duke 2002
Pregnancy / Lactation
Avoid use. Blessed thistle has been traditionally used as an emmenagogue and should not be used in pregnancy. Although traditionally used to promote lactation, information regarding safety and efficacy in lactation is lacking.Blumenthal 2000, Duke 2002, Khan 2009, Ulbricht 2008
Allergy and hypersensitivity to blessed thistle have been reported.Ulbricht 2008 Use caution in people sensitive to other asteraceous plants. Blessed thistle extract was found to be strongly sensitizing in a study of 12 species in the Asteraceae family.Blumenthal 2000, Duke 2002, Ulbricht 2008
At high doses (5 to 6 g), blessed thistle is a known emetic.Blumenthal 2000, Duke 2002, Ulbricht 2008 Avoid use in persons with gastric ulcers, as stimulation of gastric acid secretion has been reported.Blumenthal 2000, Duke 2002, Ulbricht 2008
Clinical information is limited. The oral, median lethal dose of cnicin in mice was 1.6 to 3.2 mmol/kg.Khan 2009
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