What is Milk Thistle?

Stew Eckard and Mike Darnofall

Thanks to the University of North Carolina School of Pharmacy
for the use of this article!

Michelle Giesler and Kimberly Jones

General Description

• Other names: Marian thistle, St. Mary's thistle, Our Lady's thistle
• Family: Asteraceae
• Distribution: Native to the Mediterranean region of Europe, but naturalized in California and the eastern US

Description of plant:

• tall herb with prickly leaves and a milky sap
• Small, hard fruits (achenes), a feathery tuft or pappus is removed
• Milk white veins in the leaves (originated in the milk of the Virgin Mary which once fell upon the plant)

Parts used:

• ripe fruit (not seeds), root, leaves, hull

Chemical composition

• Silymarin- chemical mixture of antihepatotoxic principles; 1-4% conc. in fruit
• Shown to consist of a large number of flavonolignans, including principally silybin accompanied by isosilybin, dehydrosilybin, silydianin, silychristin, etc.

History and folk use

• Formerly frequently cultivated in gardens
• The stalks may be eaten and are palatable and nutritious
• Young leaves may be eaten as a salad, and were sometimes baked in pies
• The heads were formerly boiled and eaten, treated like those of an Artichoke
• Thought to be a great breeder of milk and proper diet for nursing women
• Thought to have a healing property in those with snake bites
• If worn around the neck it would protect you from snake bites
• Fruit formerly thought to cure hydrophobia
• Applied externally, said to have been proven beneficial in cases of cancer
• The young, tender plant be boiled and eaten in the spring as a blood cleanser
• Fruits have been used for many years for a variety of conditions, especially liver complaints. However, medicinal use of the plant, except as a simple bitter, was practically discontinued early in the twentieth century.

Primary effects in the body

• Acts on cell membranes of liver cells to prevent the entry of toxic substances
• Stimulates protein synthesis, accelerating regeneration process & production of liver cells
• Acts as an antioxidant, with far greater free radical damage control than vitamin E
• It may offer some protection against toxic side effects from acetaminophen

Clinical applications

• Early treatment for chronic liver problems
• Rehabilitation from alcohol, solvent or IV recreational abuse
• Protects hepatocytes from heavy metal, chemical and alcohol injury
• Limits fatty degeneration and speeds up hepatitis recovery, slowing or reversing cirrhosis
• Supportive treatment for inflammatory liver conditions and cirrhosis

Toxicity

• None reported

Drug and disease interactions

• None reported

Dosage

• Fruit (seeds): 2-3 capsules up to 3 x day
• Tincture: 1:5, 60% alcohol, ½ to 1 teaspoon up to 4 x day (equal parts of root & seed with hull attached)
• Silymarin is very poorly soluble in water so is not effective as a tea (< 10% plant activity)
• Poor solubility and poor absorption from GI tract (20-50%) make active principles best administered parenterally
• Oral use requires a concentrated product
• Capsules containing 200mg of a concentrated extract representing 140mg of silymarin

Primary and Tertiary literature

Protection from Amanita phalloides intoxication Tox Appl Pharm 73 (1984)

• Severe poisoning with mortality rate of 30%
• Study in beagles
• 50 gm/kg silibinin 5 and 24 hrs post-intoxication
• 4 deaths in control group / 0 deaths with silibinin
• Reduction in elevations of GPT, GOT, AP and bilirubin with silibinin; less decrease in PT
• Mechanism of Action?
  • Modification or occupance of cell membrane receptor sites
  • Decrease phospholipid metabolism
  • Prevention of inhibition of RNA Polymerase and RNA synthesis by toxin

Increase of Glutathione Content in the Liver Planta Medica 55 (1989)

• 200 mg/kg silymarin single dose
• Over 50% increase GSH in liver and intestine
• Selectivity
  • accumulation principally in liver
  • entero-hepatic recirculation
• An increase in GSH can increase conjugation/elimination of toxins and decrease lipid peroxidation
• Mechanism of action?
  • Increase in membrane permeability of amino acids involved in GSH synthesis

Stimulation of DNA synthesis in malignant cell lines? Biochem Pharm 35(1986)

• 27 mg/kg silibinin prior to injection of radioactive thymidine
• Silibinin increases ribosomal RNA synthesis
• No influence on DNA synthesis in normal livers
• Large increase in DNA synthesis in hepatectomized rats / 23-35% increase in thymidine incorporation
• No influence on DNA synthesis in fast growing hepatoma cell cultures
• Mechanism of action?
  • Hepatectomized rats
    • If the regulatory signal for replication initiation is given, increase in rRNA and protein synthesis also accelerates DNA synthesis
  • Hepatoma cells
    • The rate of proliferation is already maximal and cannot be further intensified

Effect of silibinin on biliary lipid composition Journal of Hepatology 12(1991)

• The rats
  • 100mg/kg or 50mg/kg silymarin for 7 days
  • measured biliary cholesterol, biliary phospholipid, total bile salt and bile flow
  • decrease in biliary cholesterol and phosolipid
  • no change in bile flow and total bile salts

• The Humans
  • 400mg/day silymarin in cholecystectomized and gallstone patients for 1 month
  • significant decrease in biliary cholesterol for both groups

• Mechanism of Action?
  • Found a dose dependent decrease in HMG-CoA reductase in the liver with increasing silymarin concentration
  • A decrease in HMG-CoA reductase leads to a decrease in synthesis of cholesterol

Thanks to the University of North Carolina School of Pharmacy for the use of this article!

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