Silybum marianum

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Milk thistle
Milk thistle flowerhead.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Asterales
Family: Asteraceae
Genus: Silybum
Species:
S. marianum
Binomial name
Silybum marianum
(L.) Gaertn.
Synonyms

Carduus marianusL.

Silybum marianum is a species of thistle. It has various common names including milk thistle, [1] blessed milkthistle, [2] Marian thistle, Mary thistle, Saint Mary's thistle, Mediterranean milk thistle, variegated thistle and Scotch thistle (not to be confused with Onopordum acanthium or Cirsium vulgare ). This species is an annual or biennial plant of the family Asteraceae. This fairly typical thistle has red to purple flowers and shiny pale green leaves with white veins. Once native from Southern Europe through Asia, it has spread throughout the world.

Contents

Description

Illustration Illustration Silybum marianum0.jpg
Illustration

Milk thistle is an upright herb that can grow to be 30 to 200 cm (12 to 79 in) tall and has an overall conical shape. [3] The approximate maximum base diameter is 160 cm (63 in). The stem is grooved and may be covered in a light cottony fuzz. [4] The largest specimens have hollow stems.

The leaves are oblong to lanceolate and 15–60 cm long and typically pinnately lobed, with spiny edges like most thistles. [3] They are hairless, shiny green, with milk-white veins. [3]

The flower heads are 4 to 12 cm long and wide, of red-purple colour. They flower from June to August in the North or December to February in the Southern Hemisphere (summer through autumn). [4] The flower head is surround by bracts which are hairless, with triangular, spine-edged appendages, tipped with a stout yellow spine.

The fruits are black achenes with a simple long white pappus, surrounded by a yellow basal ring. [5] [3] A long pappus acts as a "parachute", supporting seed dispersal by wind. [6]

Distribution and habitat

Silybum marianum is native from around the Mediterranean and much of Europe to Central Asia and India; in Africa it reaches as far south as Ethiopia. [7] It is possibly native near the coast of southeast England. S. marianum has been widely introduced outside its natural range, for example into North America, Hawaii, Australia, New Zealand, and Colombia where it is considered an invasive weed. [4] [8] [9] It also spreads invasively in almost all of Europe as a consequence of field cultivation. [10]

Silybum marianum establishes itself in sunny, warm ruderal meadows in regularly disturbed places such as rubble deposits, at the foot of south-exposed walls or villages and on urban fallow land or on cattle pastures. However, it does not prefer dry, stony soils. [10] [11]

Milk thistle has been potentially observed to modify fire regimes in its invasive range. [12] [13] Its invasion into new habitats may also be encouraged by fire. [14]

Cultivation

Milk thistle is an adaptive crop with low requirements. It is mainly cultivated as a medicinal plant but it is also sometimes used as a food source. [15] [16] It's mainly cultivated in Europe but also in Asia and North America. [17] Milk thistle is a biennial plant, it is normally grown as an annual plant, which simplifies cultivation. When the main requirements of the plant are met, then the milk thistle will blossom in the first year. [15]

Milk thistle has low soil nutrient requirements and is drought resistant. The optimal pH ranges from 5.5 to 7.6, but a wide range is acceptable. The seeds are directly sown into the soil with a sowing depth of 1 to 1.5 cm. For germination, a minimal temperature of 2 °C is needed. Sowing can be done in Autumn or in Spring, depending on the climate conditions. Row spacing is between 40 and 75 cm with a plant space of about 25 cm in the rows. Fertilization is not necessarily needed because of the low nutrient requirements. A standard fertilization rate of 50 kg nitrogen, 30 kg phosphorus and 60 kg potassium per hectare is applied before sowing, to improve yields. Harvest normally occurs in July or August. Since the flower heads don't ripen evenly, optimal harvest time is about a fortnight after 50% of the flower heads are dry. For harvesting a common cereal combine harvester can be used. In Poland, average yields are 1230 kg per ha with an average silymarin content of 26.5 kg per ha. [18]

Chemistry

Silibinin Silibinin skeletal.svg
Silibinin

Traditional milk thistle extract is made from the seeds, which contain approximately 4–6% silymarin. [19] The extract consists of about 65–80% silymarin (a flavonolignan complex) and 20–35% fatty acids, including linoleic acid. [20] Silymarin is a complex mixture of polyphenolic molecules, including seven closely related flavonolignans (silybin A, silybin B, isosilybin A, isosilybin B, silychristin, isosilychristin, silydianin) and one flavonoid (taxifolin). [20] Silibinin, a semipurified fraction of silymarin, is primarily a mixture of 2 diastereoisomers, silybin A and silybin B, in a roughly 1:1 ratio. [20] [21]

Traditional medicine and adverse effects

Although milk thistle has been used in traditional medicine for centuries, there is no clinical evidence that it has any medicinal effect, and the quality of research has been poor. [22] [23] [24] Silymarin is extracted from the milk thistle seeds and available as a standardized extract. [25] In 2019, Cancer Research UK stated: "We need a lot more research with reliable clinical trials before we can be sure that milk thistle will play any part in treating or preventing cancers." [26]

Use of milk thistle may cause stomach upset and produce allergic reactions in some people. [22] Eyelid edema, ocular pruritus, dry eye, diplopia, and blurred vision are among the reported complications based on registered side effects in the WHO global database of adverse drug reactions. [27]

Toxicity

Milk thistle based supplements have been measured to have the highest mycotoxin concentrations of up to 37 mg/kg when compared to various plant-based dietary supplements. [28]

Animal toxicity

Because of nitrate [4] content, the plant has been found to be toxic to cattle and sheep. [4] When potassium nitrate is eaten by ruminants, the bacteria in the animal's stomach breaks the chemical down, producing nitrite ions. Nitrite ions then combine with hemoglobin to produce methemoglobin, blocking the transport of oxygen. The result is a form of oxygen deprivation. [29]

Related Research Articles

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Carduus nutans is a biennial plant in the daisy and sunflower family Asteraceae with the common names musk thistle, nodding thistle, and nodding plumeless thistle. It is native to regions of Europe, Central Asia, and North Africa, where it is a scattered pasture plant. The musk thistle has been declared as invasive in North America, Australia, New Zealand, and South Africa.

<i>Onopordum acanthium</i> Species of flowering plant in the daisy family Asteraceae

Onopordum acanthium is a flowering plant in the family Asteraceae. It is native to Europe and Western Asia from the Iberian Peninsula east to Kazakhstan, and north to central Scandinavia, and widely naturalised elsewhere, with especially large populations present in the United States and Australia. It is a vigorous biennial plant with coarse, spiny leaves and conspicuous spiny-winged stems.

<i>Silybum</i> Genus of plants

Silybum is a genus of two species of thistles in the family Asteraceae. The plants are native to the Mediterranean regions of Europe, North Africa, and the Middle East. One species has been introduced elsewhere, including in North America. The name "milk thistle" derives from a feature of the leaves, which are prominently banded with splashes of white. Historically, these milky bands were said to be Mother Mary's milk, and this is the origin of another common name, St. Mary's thistle. The most widespread species is Silybum marianum.

<i>Cirsium vulgare</i> Species of flowering plant in the daisy family Asteraceae

Cirsium vulgare, the spear thistle, bull thistle, or common thistle, is a species of the Asteraceae genus Cirsium, native throughout most of Europe, Western Asia, and northwestern Africa. It is also naturalised in North America, Africa, and Australia and is an invasive weed in several regions. It is the national flower of Scotland.

<span class="mw-page-title-main">Safflower</span> Species of plant

Safflower is a highly branched, herbaceous, thistle-like annual plant in the family Asteraceae. It is one of the world's oldest crops, and today is commercially cultivated for vegetable oil extracted from the seeds. Plants are 30 to 150 cm tall with globular flower heads having yellow, orange, or red flowers. Each branch will usually have from one to five flower heads containing 15 to 20 seeds per head. Safflower is native to arid environments having seasonal rain. It grows a deep taproot which enables it to thrive in such environments.

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<span class="mw-page-title-main">Silibinin</span> Chemical compound

Silibinin (INN), also known as silybin (both from Silybum, the generic name of the plant from which it is extracted), is the major active constituent of silymarin, a standardized extract of the milk thistle, containing a mixture of flavonolignans consisting of silibinin, isosilibinin, silychristin, silidianin, and others. Silibinin itself is a mixture of two diastereomers, silybin A and silybin B, in approximately equimolar ratio. Silibinin is used in pure forms as a medication, and more frequently as an active ingredient in milk thistle–derived herbal supplements.

<i>Oenothera biennis</i> Species of flowering plant

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<i>Cirsium arvense</i> Species of flowering plant

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<i>Centaurea benedicta</i> Species of plant

Centaurea benedicta, known by the common names St. Benedict's thistle, blessed thistle, holy thistle, spotted thistle or blessed knapweed, is a thistle-like plant in the family Asteraceae, native to the Mediterranean region, from Portugal north to southern France and east to Iran. It is known in other parts of the world, including parts of North America, as an introduced species and often a noxious weed.

<i>Amaranthus caudatus</i> Species of flowering plant

Amaranthus caudatus is a species of annual flowering plant. It goes by common names such as love-lies-bleeding, pendant amaranth, tassel flower, velvet flower, foxtail amaranth, and quelite.

<i>Sonchus asper</i> Species of flowering plant in the daisy family Asteraceae

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<i>Lactuca serriola</i> Species of flowering plant in the daisy family Asteraceae

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<i>Sonchus oleraceus</i> Species of flowering plant in the family Asteraceae

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<i>Sonchus arvensis</i> Species of flowering plant in the daisy family Asteraceae

Sonchus arvensis, the field milk thistle, field sowthistle, perennial sow-thistle, corn sow thistle, dindle, gutweed, swine thistle, or tree sow thistle, is a species of flowering plant in the family Asteraceae. S. arvensis often occurs in annual crop fields and may cause substantial yield losses.

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<i>Silphium perfoliatum</i> Species of flowering plant

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<span class="mw-page-title-main">Silychristin</span> Natural chemical compound

Silychristin is a natural product and one of the constituents of silymarin, the standardized, active extract of the fruit of milk thistle, Silybum marianum. It is the second most abundant constituent in silymarin, after silybin. Silychristin is a flavonolignan, along with many other silymarin constituents, meaning it is composed up of a flavonoid and a lignan. It is estimated that up to 65–80% of silymarin extract is made up of flavonolignans, like silychristin, which give silymarin its well known potent antioxidant and hepatoprotective properties. Silychristin can exist as two stereoisomers, silychristin A and silychristin B. The marianum variety of S. marianum includes silychristin A as a major flavonolignan constituent, while the lesser known and studied albiflorum variety includes unique flavonolignans, including silyhermin, (–)-silandrin, and (+)-silymonin.

References

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  29. http://ucanr.edu/sites/UCCE_LR/files/180507.pdf Tucker JM, et al. Nitrate Poisoning in Livestock (1961)

Further reading