Herb Research Foundation

BOTANICAL DESCRIPTION

Silybum marianum, a member of the Aster family (Asteraceae or Compositae), is an annual or biennial which grows from 4 to 6 feet. Stems are glabrous, simple or little branched. Leaves are to 2 1/2 feet long, 6-12 inches across, clasping, green marbled or streaked with white veins; sharp-spined. Heads are 2-2 1/2 inches across, involucral bracts spreading to reflexed, acuminate; achenes smooth, mottled with brown. Flowers are purple tufts; receptacle densely bristle-spined. Plant flowers from June through September. It grows mainly in Mediterranean region where it is a wayside herb of uncultivated ground and waste places. It is naturalized and a weed in the Eastern United States, California and South America.

Morazzoni and Bombardelli describe the plant as follows: S. marianum has a stem 20-150 cm high, rarely shorter, glabrous or slightly downy, erect and branched in the upper part. The leaves are alternate, large, white-veined, glabrous with strongly spiny margin. The inflorescences are large and round capitula, solitary at the apex of the stem or its branches, surrounded by thorny bracts. The florets are hermaphrodite, tubular in shape with corolla red-purple. The fruits are hard-skinned achenes 6 to 8 mm long, shiny, generally brownish in color with a white silk-like pappus at the apex. The fruits are harvested in July-August after blooming. (Morazzoni, 1995, pp.5-6)

OTHER NAMES

Silybum marianum: Carduus Marianus, Cnicus marianus, St. Mary's Thistle, Marian Thistle, Milk Thistle, Holy Thistle ( not to be confused with Blessed Thistle Cnicus benedictus).

USES

Part used: seeds, whole plant.

Young leaves (with spines removed) are eaten as a vegetable in spring salads and as a spinach substitute. Young stalks, peeled and soaked, are eaten like asparagus. The roots, soaked in water overnight to remove bitterness, are eaten like salsify. Milk Thistle's flower receptacle, resembling an artichoke, was cooked and eaten like artichokes. (Foster, 1991)

Traditionally, tea made from whole plant used to improve appetite, allay indigestion, restore liver function. Used for cirrhosis, jaundice, hepatitis, liver poisoning from chemicals or drug and alcohol abuse.

Silymarin, a seed extract, dramatically improves liver regeneration in chronic viral hepatitis, cirrhosis, mushroom poisoning, and other hepatopathies. German research suggests that silybin, a flavonoid component of the seed, is clinically useful in treating severe Amanita mushroom poisoning. Silymarin has demonstrated significant activity against exposure to halogenated hydrocarbons. While used clinically in Europe, its use in the U.S. is not well known. Commercial preparations of the seed extracts are manufactured in Europe. (Foster and Duke, 1990, p. 198; Morazzoni, 1995)

Adverse effects from ingesting any of the plant parts of Silybum marianum are generally lacking from the literature. Animal experiments have shown that seed extracts are safe, even in large doses, with practically no side effects, as well as no embryo toxic effect (Weiss, 1988).

The most recent clinical investigations have demonstrated that the flavonolignan silibinin is the most effective compound. Future breeding activities should be directed to the production of genotypes and lines that produce silibinin. (Hetz et al, 1995)

In all references, it appears that this plant is used in particular in the treatment of diseases of the liver.

ENVIRONMENT

Silybum marianum is native to the Mediterranean area. It is grown and used medicinally in France, Italy, Germany, Hungary, Greece and Poland. It is also present in Canary Islands, Madeira and naturalized in the hot, dry areas of Central Europe, North and South America, in Central and East Asia and Southern Australia. It also grows wild in Egypt in the Nile Valley. It is not generally found in Northern Italy, but it is frequent in the central and southern regions and in the islands.

In Italy S. marianum is found on roadsides, waste places and cultivated ground and it is distributed from the sea to the submountain regions to 700-1100 m of altitude. It is cultivated for ornament and naturalized or casual throughout a large part of Europe. (Morazzoni, 1995)

California (USA) ranchers claim milk thistle loosens hard compacted soil and make their own "clod-buster" from chopped plants soaked in 55 gallon drums of water. (JL Hudson Seedsman)

PRODUCTION

It is difficult to find simple "how to grow" instructions for Silybum marianum in English. There is major interest in developing methods of cultivation which will yield the highest silymarin content. Papers are listed which discuss different water regimes and nitrogen fertilization levels in order to obtain the highest silymarin content in the plant for its commercial production for pharmaceutical use. (Hammouda, 1993)

The genus Silybum contains two species: S. marianum (variegated white/green) and S. eburneum (completely green). From crossing experiments it appears that the two species are only variants. In European gardens Silybum has been cultivated as a vegetable for centuries.

In the Nile Valley of Egypt Silybum marianum occurs in two types, the most abundant has purple flowers while the least abundant has white flowers. The seeds of the plant are used for medicinal purposes.

Mean total mass of fruits, content and yield of silymarin were determined for Silybum marianum Gaertn. as follows: 1.2 - 21.4 g/pot, 2.9 - 4.2% and 91-700 mg/pot, respectively. The higher cropping of fruits as well as the content of silymarin were obtained in the case of mineral fertilization with double dose of phosphorus (NP2K), and those results were not the ground moisture dependent. The best yield of silymarin from Silybum marianum fruits (700 mg/pot) can be obtained on fertilization with double dose of phosphorus and at 60% of moisture in the ground. (Kozlowski, 1984)

In Egypt the plant was cultivated and subjected to different agricultural conditions including the effect of water regime 70%, 60% and 45% per field capacity and nitrogen fertilization levels 0, 50, 100, and 150 kg/feddan. The fruits grown under the seven treatments were collected separately and subjected to investigation in comparison with the two wild growing types of S. marianum. (Hammouda, 1993). Cultivated Silybum marianum yielded increased silymarin content when compared to wild Silybum. Higher results were obtained with 60% water regime per field capacity without fertilization. When soil was treated with different nitrogen fertilization levels, the 100 and 150 kg nitrogen per feddan gave the highest silymarin contents in the fruits (1.46%, 1.42% respectively) and relatively high contents in the ethyl acetate extract (52.2% and 52.8% respectively). (Hammouda, 1993)

In areas with mild winters, the best seed is obtained by direct seeding in midsummer and overwintering the rosettes. The following spring, the already established plants bolt quickly to flower and the seed has time to mature and darken during the summer. In areas with hard winters, sow seed directly as an annual in mid-spring. Sprouts in 1 to 3 weeks. (Horizon Herbs) Note: fresh seed will not germinate at warm temperatures, only sprouting at cool temperatures, but after 5 months of dry storage after ripening, seeds will germinate will at warm temperatures. (JL Hudson Seedsman)

Spines of plant are extremely sharp; rows should be spaced at least 5 feet apart and thin plants to 2 feet apart in the rows to allow for harvest of the capitulae -- which have more spines at the tip of the bract. (Horizon Herbs)

REFERENCES

Bailey, Liberty Hyde and Ethel Zoe Bailey. (1976) Hortus Third: A Concise Dictionary of Plants Cultivated in the United States and Canada. Rev. and exp. by The Staff of the Liberty Hyde Bailey Hortorium. New York. Macmillan Pub. Co.

Foster, Steven. (1991) Milk Thistle: Silybum marianum. Botanical Series No. 305. Austin, TX: American Botanical Council.

Foster, Steven and James A. Duke. (1990) A Field Guide to Medicinal Plants: Eastern and Central North America. Boston: Houghton Mifflin Co.

Hammouda, F. M., S. I. Ismail, N. M. Hassan [et al]. (1993) "Evaluation of the Silymarin Content in Silybum marianum (L.) Gaertn. Cultivated under Different Agricultural Conditions." Phytotherapy Research, 7(1):90-1.

Hetz, Erich, Reinhard Liersch and Otto Schieder. (1995) "Genetic Investigations on Silybum marianum and S. eburneum with respect to leaf colour, outcrossing ratio, and flavonolignan composition." Planta Medica, 61: pp.54-57.

Horizon Herbs Seed Catalog (1996). Williams, Oregon USA

JL Hudson, Seedsman Catalog (1996). La Honda, California USA

Kozlowski, J. and M. Holynska. (1984) "Changes in content and yield of Silymarin as well as the cropping of fruits of Silybum marianum Gaertn. under influence of different fertilization and moisture in a pot experiment." Herba Polonica, 30 (3-4):pp.191-198.

Morazzoni, Paolo and Ezio Bombardelli. (1995) "Silybum marianum (Carduus marianus)." Fitoterapia, 46(1):pp.3-42.

Weiss, R. F. (1988) Herbal Medicine (tr. from German by A.R. Meuss). Beaconsfield, England: Beaconsfield Publishers Ltd.