Silybin (Flavonolignan · Hepatoprotective · Liver Membrane Integrity)

Compound	Silybin (Silibinin)
Chemical class	Polyphenol — Flavonolignan
CAS	22888-70-6
Primary source	Silybum marianum (milk thistle seeds)
Key applications	Hepatoprotective, liver membrane integrity, antioxidant
Claim strength	High
Typical form	Silybin 30% extract; silymarin 80% (silybin-containing complex)

Name origin: From Silybum, the genus of milk thistle. Silybin (also called silibinin) is the primary active flavonolignan in the silymarin complex — constituting approximately 50–70% of silymarin by weight. Silymarin is the total flavonolignan extract from milk thistle seeds; silybin is its dominant and most pharmacologically active constituent. Traditional use: Milk thistle has been used in European phytomedicine for over 2,000 years for liver and gallbladder conditions, with Pliny the Elder documenting its use for bile complaints. Carduus marianus (historical name) preparations remained a central European liver tonic through to the 20th century when standardised silymarin extracts entered clinical medicine. Research trajectory: Silybin has one of the most robust hepatoprotective evidence bases of any botanical compound, with multiple human RCTs and systematic reviews. Intravenous silybin is used clinically for acute Amanita (death cap mushroom) poisoning. Commercial source: Herbuno supplies Silybin 30% extract and Milk Thistle Water Soluble Extract — directly applicable products.

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Evidence for Silybin Applications

Hepatoprotection and liver disease: Multiple RCTs demonstrate silybin (as silymarin) reduces ALT/AST liver enzymes in alcoholic liver disease, non-alcoholic fatty liver disease (NAFLD), and drug-induced liver injury. A Cochrane review concluded there is reasonable evidence for ALT reduction in chronic liver disease, though mortality endpoint data are insufficient. Silybin’s mechanism: stabilises hepatocyte membrane lipid bilayer, inhibits hepatotoxin transport (particularly Amanita phalloïdes amatoxin), and activates hepatocyte regeneration via RNA polymerase I stimulation. Claim strength: High.

Antioxidant and anti-inflammatory: Silybin is a potent antioxidant and iron chelator. It suppresses NF-κB, reduces hepatic oxidative stress, and inhibits Kupffer cell inflammatory activation. These mechanisms underpin its hepatoprotective activity and also support broader antioxidant formulation use. Claim strength: High.

Metabolic and insulin sensitising: Emerging human data show silymarin (silybin-dominant) improves insulin resistance markers in NAFLD and type 2 diabetes patients. Mechanisms include PPAR-γ activation and hepatic glucose output reduction. Claim strength: Moderate.

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Dosage & Formulator Specification

Clinical hepatoprotection dose: 140 mg silybin (as silymarin 70–80% extract) three times daily = 420 mg/day silybin equivalent. This is the dose used in the majority of clinical trials. For Herbuno’s Silybin 30% extract, equivalent dose: 1,400 mg/day extract (to deliver 420 mg silybin) — specify as a divided daily dose.

Bioavailability note: silybin has low oral bioavailability (~0.5–1% absolute) in standard formulations due to poor water solubility and limited GI absorption. Silybin-phosphatidylcholine complex (phytosome, 1:2 silybin:phospholipid) improves bioavailability 4–10-fold in human pharmacokinetic studies and is the preferred delivery format for premium liver health formulations. Specify silybin-phytosome for bioavailability-enhanced formulations.

Silymarin 80% extract (Herbuno): standard grade for liver support supplements. Silybin 30% extract: higher silybin enrichment for premium applications. For the highest silybin content, specify 98% silybin isolate from specialist suppliers, but note the phytosome requirement for adequate oral bioavailability.

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Frequently Asked Questions — Silybin

What is the difference between silybin and silymarin?
Silymarin is the total flavonolignan extract from milk thistle seeds, typically standardised to 70–80% total flavonolignans. Silybin (silibinin) is the principal flavonolignan within silymarin, constituting 50–70% of the silymarin complex. Silymarin also contains silychristin, silydianin, and isosilybin. Most clinical evidence uses silymarin as the tested material; silybin is the primary pharmacological driver of that evidence.

Is silybin effective for drug-induced liver injury from medications?
Silybin has demonstrated hepatoprotective effects in studies of liver injury from acetaminophen, alcohol, and various hepatotoxic medications. It is used clinically (IV form) for Amanita mushroom poisoning. For drug-induced liver injury in a supplement context, silybin may be relevant as a supportive co-ingredient; formulators should include appropriate advisory language and not position it as a treatment.

Does the phytosome form of silybin significantly improve outcomes over standard silymarin?
Human pharmacokinetic studies consistently show 4–10-fold higher silybin plasma AUC with the phytosome versus standard silymarin extract. Clinical outcome studies (liver enzymes, symptom scores) with silybin phytosome (SILIPHOS®) show efficacy at lower doses than standard silymarin. For premium liver health formulations targeting measurable outcomes, the phytosome form is justified by the bioavailability data.

Can silybin be used in combination with chemotherapy?
Silybin has been investigated as a hepatoprotectant during chemotherapy to reduce liver toxicity, with some supportive pilot data. However, there is also in vitro evidence of CYP enzyme inhibition by silybin, which could affect chemotherapy drug metabolism. Oncology use requires medical supervision; formulators should not make liver protection claims in the context of chemotherapy without clinical guidance.

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Claim-strength scale – High = multiple human RCTs; Moderate = limited trials or strong preclinical convergence; Emerging = early-stage lab or animal data.

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