Milk Thistle Extract: Composition and Bioactivity

Milk thistle [Silybum marianum (L.) Gaernt., family Asteraceae/Compositaceae] is probably the oldest and the best-studied plant in the treatment of liver diseases. Milk thistle extracts have been used as traditional herbal remedies for almost 2000 years. The extracts are still widely used to protect the liver against toxins and to control chronic liver diseases. Recent experimental and clinical studies suggest that milk thistle extracts also have anticancer, antidiabetic, and cardioprotective effects[1].

Composition

Milk Thistle extract is a bioflavonoid complex consisting of at least seven flavonolignans. Silibinin is the major component of this complex extract (about 60-70%) and is biologically the most active constituent of silymarin, followed by silicristin (20%), silidianin (10%), and isosilybin (5%). Silibinin is a mixture of two stereoisomers, silibinin A and silibinin B in the equimolar ratio 1:1. Silymarin is found in the entire plant but it is concentrated in the fruit and seeds[2].

Treatment for Liver Disease

Silybum marianum or milk thistle (MT) is the most well-researched plant in the treatment of liver disease. Milk Thistle Extract is a lipophilic extract from the seeds of the plant and is composed of three isomer flavonolignans (silybin, silydianin, and silychristin) collectively known as silymarin. Silymarin acts as an antioxidant by reducing free radical production and lipid peroxidation, has antifibrotic activity and may act as a toxin blockade agent by inhibiting binding of toxins to the hepatocyte cell membrane receptors. In animals, silymarin reduces liver injury caused by acetaminophen, carbon tetrachloride, radiation, iron overload, phenylhydrazine, alcohol, cold ischaemia and Amanita phalloides. Silymarin has been used to treat alcoholic liver disease, acute and chronic viral hepatitis and toxin-induced liver diseases[3]. 

Bioactivity

The hepatoprotective effect of Milk Thistle extract has clinically been proved. Low toxicity, favorable pharmacokinetics, powerful antioxidant, detoxifying, preventive, protective and regenerative effects and side effects similar to placebo make silymarin extremely attractive and safe for therapeutic use. The medicinal properties of silymarin and its main component silibinin have been studied in the treatment of Alzheimer's disease, Parkinson's disease, sepsis, burns, osteoporosis, diabetes, cholestasis and hypercholesterolemia. Owing to its apoptotic effect, without cytotoxic effects, silymarin possesses potential applications in the treatment of various cancers. Silymarin is being examined as a neuro-, nephro- and cardio-protective in the damage of different etiologies due to its strong antioxidant potentials. Furthermore, it has fetoprotective (against the influence of alcohol) and prolactin effects and is safe to be used during pregnancy and lactation[2].

References

[1] Tamayo, C., & Diamond, S. (2007). Review of clinical trials evaluating safety and efficacy of milk thistle (Silybum marianum [L.] Gaertn.). Integrative Cancer Therapies, 6 2, 146–157. https://doi.org/10.1177/1534735407301942

[2] Milić, N., Milo\vsević, N., Suvajd\vzić, L., Zarkov, M., & Abenavoli, L. (2013). New Therapeutic Potentials of Milk Thistle (Silybum marianum). Natural Product Communications, 72 1. https://doi.org/10.1177/1934578X1300801236

[3] Abenavoli, L., Capasso, R., Milic, N., & Capasso, F. (2010). Milk thistle in liver diseases: past, present, future. Phytotherapy Research, 24 10, 1423–1432. https://doi.org/10.1002/ptr.3207