Traditionally, milk thistle extract was made from these seeds (which contain ~4-6% silymarin) — resulting in an extract consisting of around 65–80% silymarin (a flavonolignan complex) plus 20–35% various fatty acids (linoleic acid, etc).
Silymarin is a complex mixture of polyphenolic molecules, including seven closely related flavonolignans (silybin A, silybin B, isosilybin A, isosilybin B, silychristin, isosilychristin, silydianin) and one flavonoid (taxifolin). Silibinin, a semipurified fraction of silymarin, is primarily a mixture of 2 diastereoisomers, silybin A and silybin B, in a roughly 1: 1 ratio.
Pre-treatment of male mice with silymarin modulated the alteration of oxidative stress, cell cycle, cytoskeletal network, cell–cell adhesion, extra-cellular matrix, inflammation, apoptosis, cell-signaling and intermediary metabolism that was induced by pyrogallol. These effects leaded to the differential expression of 79 genes/transcripts (27 up-regulated and 52 down-regulated) in comparison to the pyrogallol treated group. The results showed that, effects of silymarin could be due to its multiple functions as well as its antioxidant activity ().
Fibrosis development is the major outcome of chronic liver infections that commonly occurs in immunecompetents (). Polyak et al (2007) showed that silymarin inhibits the replication of an infectious HCV genotype 2a strain (JFH1) in hepatoma cell culture (). These effects are the result of silymarin compounds being able to inhibit HCV RNA-dependent RNA polymerase activity (). Two phase II trials are being performed by the National Center for Complementary and Alternative Medicine (NCCAM) which investigates using silymarin as a treatment in hepatitis C ().