The Sunlight Experiment

Compound Monograph

Silybin

Silybin — the principal and most biologically active flavonolignan within milk thistle's silymarin complex, responsible for much of its hepatoprotective, anti-fibrogenic, and anti-HCV activity.

Work in progress

Classification

Silybin is a flavonolignan, part of the phenolics class. Antioxidant compounds built around one or more phenol rings — the flavonoids, tannins, phenolic acids, coumarins, and pigments behind much of a plant's protective chemistry.

Phenolics Lignans

Where Does It Come From? (1)

Silybin is a naturally occurring flavonolignan, found in Milk Thistle. It is well tolerated orally (low toxicity).

Milk Thistle Silybum marianum

Research & Evidence

Silybin (also called silibinin) is the single most biologically significant flavonolignan within milk thistle’s silymarin complex; it occurs as two diastereomers, silybin A and silybin B 1Reference 1Powers J · 2014ReviewSilybum marianum Monograph. Where “silymarin” refers to the whole flavonolignan mixture (silybin, silydianin, silychristin, silymandin and the isosilybins), silybin is the dominant individual molecule driving much of that complex’s activity.

The milk thistle monograph in this database reports the following silybin-specific findings:

  • Hepatoprotective — silybin has been examined from basic research through to clinical practice as the key liver-protective constituent of the herb 3Reference 3Loguercio C · 2011Silybin and the liver: From basic research to clinical practice.
  • Anti-inflammatory and anti-fibrogenic — silybin, as a component of silymarin, exerts anti-inflammatory and anti-fibrogenic effects on human hepatic stellate cells 4Reference 4Trappoliere M et al. · 2009Silybin, a component of silymarin, exerts anti-inflammatory and anti-fibrogenic effects on human hepatic stellate cells, a central mechanism in limiting liver fibrosis. Inhibition of Kupffer cell function has been proposed as an explanation for silibinin’s hepatoprotective properties 5Reference 5Dehmlow C et al. · 1996Inhibition of Kupffer cell functions as an explanation for the hepatoprotective properties of silibinin.
  • Antiviral (hepatitis C) — silibinin and related compounds are direct inhibitors of the hepatitis C virus RNA-dependent RNA polymerase 6Reference 6Ahmed-Belkacem A et al. · 2009Silibinin and Related Compounds Are Direct Inhibitors of Hepatitis C Virus RNA-Dependent RNA Polymerase, and silibinin has been shown to act as a potent antiviral agent in patients with chronic hepatitis C who did not respond to pegylated interferon/ribavirin therapy 7Reference 7Ferenci P et al. · 2008Clinical trialSilibinin is a potent antiviral agent in patients with chronic hepatitis C not responding to pegylated interferon/ribavirin therapy.

These activities mirror those attributed to the silymarin complex as a whole, which is expected given that silybin is its principal active constituent 2Reference 2Bone K · 2013Principles and Practice of Phytotherapy.

Toxicity & Safety

The source monograph reports no contraindications for milk thistle and treats its silymarin/silybin content as well tolerated. As with the parent complex, the relevant caution is that up-regulation of liver detoxification can alter the metabolism of prodrugs and of drugs cleared by the liver, so care is advised alongside medications 2Reference 2Bone K · 2013Principles and Practice of Phytotherapy. No toxicity figures specific to isolated silybin are provided in the source.

References

  1. Powers J. (2014). Silybum marianum Monograph. JATMS, 20(1).
  2. Bone K, Mills S. (2013). Principles and Practice of Phytotherapy. Elsevier Health, China. (Pg. 861–882).
  3. Loguercio C, Feste D. (2011). Silybin and the liver: From basic research to clinical practice. World Journal of Gastroenterology, 17(18), 2288–2301.
  4. Trappoliere M, Caligiuri A, Schmid M, et al. (2009). Silybin, a component of silymarin, exerts anti-inflammatory and anti-fibrogenic effects on human hepatic stellate cells. J Hepatol, 50, 1102–1111.
  5. Dehmlow C, Erhard J, de Groot H. (1996). Inhibition of Kupffer cell functions as an explanation for the hepatoprotective properties of silibinin. Hepatology, 23, 749–754.
  6. Ahmed-Belkacem A, Ahnou N, Barbotte L. (2009). Silibinin and Related Compounds Are Direct Inhibitors of Hepatitis C Virus RNA-Dependent RNA Polymerase. Gastroenterology.
  7. Ferenci P, Scherzer TM, Kerschner H, et al. (2008). Silibinin is a potent antiviral agent in patients with chronic hepatitis C not responding to pegylated interferon/ribavirin therapy. Gastroenterology, 135, 1561–1567.