Isosilybin is one of the major flavonolignan constituents of silymarin, the active extract of Silybum marianum (milk thistle). Silymarin and its components, including isosilybin, have been traditionally used for various liver ailments, including cirrhosis. Scientific research has primarily focused on silymarin as a whole, with some studies investigating individual isomers like isosilybin. The proposed mechanisms of action for silymarin and isosilybin include antioxidant effects, inhibition of lipid peroxidation, antifibrotic properties, and stimulation of hepatocyte regeneration.

Preclinical studies (in vitro and animal models) suggest that isosilybin may help protect hepatocytes from toxin-induced damage and reduce fibrosis, which is relevant in cirrhosis. However, most clinical studies evaluating silymarin in cirrhosis patients have not specifically isolated isosilybin’s effects. The clinical evidence for silymarin in cirrhosis is mixed, with some trials showing modest improvement in liver function tests and possible reduction in mortality, while others show minimal or no benefit. Systematic reviews and meta-analyses generally conclude that evidence is insufficient or of low quality to definitively recommend silymarin or its individual components for cirrhosis treatment.

In summary, while preclinical data suggest biologically plausible mechanisms for isosilybin, direct high-quality clinical evidence supporting its use for cirrhosis is limited, and the overall rating of evidence remains low.