Silibinin (also known as "Silybin") is the major active flavolignan constituent of silymarin, which is a combination of flavonolignans extracted from Silybum marianum (milk thistle). Other flavolignans found in silymarin are isosibilinin A and B, silicristin, and silidianin. In vitro and animal in vivo demonstrations both consistently suggest that silibinin has hepatoprotective/antihepatotoxicity properties Silibinin has also demonstrated cancer-fighting effects against human prostate adenocarcinoma cells, estrogen-dependent and estrogen-independent breast carcinoma cells, human ectocervical carcinoma cells, human colon cancer cells, and both types of human lung carcinoma cells. Chemically modified silibinin, silibinin dihydrogen disuccinate disodium, is injected in treatment of severe intoxications with hepatotoxic substances.
A complex of silymarin and phosphatidylcholine (lecithin), is about ten times more bioavailable than silymarin. Silymarin complexed with beta-cyclodextrin is much more soluble than silymarin by itself.
Wagoner et al demonstrate and report silibinin's profound effects on Hepatitis C:
Silymarin, an extract from milk thistle (Silybum marianum), and its purified flavonolignans have been recently shown to inhibit hepatitis C virus (HCV) infection, both in vitro and in vivo. In the current study, we further characterized silymarin's antiviral actions. Silymarin had antiviral effects against hepatitis C virus cell culture (HCVcc) infection that included inhibition of virus entry, RNA and protein expression, and infectious virus production...Although inhibition of in vitro NS5B polymerase activity is demonstrable, the mechanisms of silymarin's antiviral action appear to include blocking of virus entry and transmission, possibly by targeting the host cell.
Amazingly, Neumann et al achieved successful prevention of Hepatitis C reinfection-via-liver-graft with silibin mono-therapy.
Polyak et al comment that silibinin and related flavolignans are so effective in hepatitis C treatment and intervention, more research to establish therapeutic modalities is "urgently needed":
Silymarin, also known as milk thistle extract, inhibits hepatitis C virus (HCV) infection and also displays antioxidant, anti-inflammatory, and immunomodulatory actions that contribute to its hepatoprotective effects. In the current study, we evaluated the hepatoprotective actions of the seven major flavonolignans and one flavonoid that comprise silymarin.The most potent compounds across multiple assays were taxifolin, isosilybin A, silybin A, silybin B, and silibinin, a mixture of silybin A and silybin B. The data suggest that silymarin- and silymarin-derived compounds may influence HCV disease course in some patients. Studies where standardized silymarin is dosed to identify specific clinical endpoints are urgently needed.
Tamoxifen is absorbed more effectively when coadministerered with silibinin and silibinin-containing compounds:
The enhanced bioavailability of tamoxifen by silybinin might be due to the promotion of intestinal absorption in the small intestine and the reduction of first-pass metabolism of tamoxifen in the small intestine and in the liver. If these results are confirmed in clinical trials, the tamoxifen dosage should be adjusted when tamoxifen is administered with silybinin or silybinin-containing dietary supplements.
Cheung et al describe silibinin as a promising adjunct therapy for, potentially, many forms of cancer:
Silymarin and its major constituent, Silibinin, are extracts from the medicinal plant Silybum marianum (milk thistle) and have traditionally been used for the treatment of liver diseases. Recently, these orally active, flavonoid agents have also been shown to exert significant anti-neoplastic effects in a variety of in vitro and in vivo cancer models, including skin, breast, lung, colon, bladder, prostate and kidney carcinomas. The aim of the present review is to examine the pharmacokinetics, mechanisms, effectiveness and adverse effects of silibinin's anti-cancer actions reported to date in pre-clinical and clinical trials. The review will also discuss the results of current research efforts seeking to determine the extent to which the effectiveness of silibinin as an adjunct cancer treatment is influenced by such factors as histologic subtype, hormonal status, stromal interactions and drug metabolising gene polymorphisms. The results of these studies may help to more precisely target and dose silibinin therapy to optimise clinical outcomes for oncology patients.
Wang et al observed protective superoxide generation in human breast cancer cells via silibinin administration:
The pharmacological activity of polyphenolic silibinin from milk thistle (Silybum marianum) is primarily due to its antioxidant property. However, this study found that silibinin promoted sustained superoxide (O(2)(.-)) production that was specifically scavenged by exogenous superoxide dismutase (SOD) in MCF-7 cells, while the activity of endogenous SOD was not changed by silibinin. Previous work proved that silibinin induced MCF-7 cell apoptosis through mitochondrial pathway and this study further proved that O(2)(.-) generation induced by silibinin was also related to mitochondria. It was found that respiratory chain complexes I, II and III were all involved in silibinin-induced O(2)(.-) generation. Moreover, it was found that silibinin-induced O(2)(.-) had protective effect, as exogenous SOD markedly enhanced silibinin-induced apoptosis.
Haddad et al extol the therapeutic potential of silibinin in treating nonalcoholic steatohepatitis (NASH):
Nonalcoholic steatohepatitis (NASH) is a progressive liver disease related to the metabolic syndrome, obesity and diabetes. The rising prevalence of NASH and the lack of efficient treatments have led to the exploration of different therapeutic approaches. Milk thistle (Silibum marianum) is a medicinal plant used for its hepatoprotective properties in chronic liver disease since the 4th century BC...Silibinin also decreased O(2)(*-) release and returned the relative liver weight as well as GSH back to normal. Our results suggest that milk thistle's extract, silibinin, possesses antioxidant, hypoinsulinemic and hepatoprotective properties that act against NASH-induced liver damage. This medicinal herb thus shows promising therapeutic potential for the treatment of NASH.
Lu et al found dramatic reversals in methamphetamine-induced cognitive impairment in mice treated first with methamphetamine, then with silibinin:
Cognitive deficits are a core feature of patients with methamphetamine (METH) abuse....Silibinin dose-dependently ameliorated the impairment of recognition memory caused by METH treatment in mice. Silibinin significantly attenuated the decreases in the dopamine content of the prefrontal cortex and serotonin content of the hippocampus caused by METH treatment. We also found a correlation between the recognition values and dopamine and serotonin contents of the prefrontal cortex and hippocampus. The effect of silibinin on cognitive impairment may be associated with an amelioration of decreases in dopamine and serotonin levels in the prefrontal cortex and hippocampus, respectively. These results suggest that silibinin may be useful as a pharmacological tool to investigate the mechanisms of METH-induced cognitive impairments. 
Silymarin may help patients with type II diabetes by assisting in blood sugar control similarly to the way therapeutic insulin is used in insulin-dependent type II diabetics.
Al-Anati L, Essid E, Reinehr R, Petzinger E. Silibinin protects OTA-mediated TNF-alpha release from perfused rat livers and isolated rat Kupffer cells. Mol Nutr Food Res 53 (4): 460–6.
Jayaraj R, Deb U, Bhaskar AS, Prasad GB, Rao PV. Hepatoprotective efficacy of certain flavonoids against microcystin induced toxicity in mice. Environ. Toxicol. 22 (5): 472–9. 2007.
Mokhtari MJ, Motamed N, Shokrgozar MA. Evaluation of silibinin on the viability, migration and adhesion of the human prostate adenocarcinoma (PC-3) cell line. Cell Biol. Int. 32 (8): 888–92. 2008.
Bhatia N, Zhao J, Wolf DM, Agarwal R. Inhibition of human carcinoma cell growth and DNA synthesis by silibinin, an active constituent of milk thistle: comparison with silymarin. Cancer Lett. 147 (1-2): 77–84. 1999.
Hogan FS, Krishnegowda NK, Mikhailova M, Kahlenberg MS. Flavonoid, silibinin, inhibits proliferation and promotes cell-cycle arrest of human colon cancer. J. Surg. Res. 143 (1): 58–65. 2007. Sharma G, Singh RP, Chan DC, Agarwal R. Silibinin induces growth inhibition and apoptotic cell death in human lung carcinoma cells. Anticancer Res. 23 (3B): 2649–55. 2003.
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Neumann UP, Biermer M, Eurich D, Neuhaus P, Berg T. Successful prevention of hepatitis C virus (HCV) liver graft reinfection by silibinin mono-therapy. J Hepatol. 2010 Jun;52(6):951-2.
Polyak SJ, Morishima C, Lohmann V, Pal S, Lee DY, Liu Y, Graf TN, Oberlies NH. Identification of hepatoprotective flavonolignans from silymarin. Proc Natl Acad Sci U S A. 2010 Mar 30;107(13):5995-9.
Kim CS, Choi SJ, Park CY, Li C, Choi JS. Effects of silybinin on the pharmacokinetics of tamoxifen and its active metabolite, 4-hydroxytamoxifen in rats. Anticancer Res. 2010 Jan;30(1):79-85.
Cheung CW, Gibbons N, Johnson DW, Nicol DL. Silibinin--a promising new treatment for cancer. Anticancer Agents Med Chem. 2010 Mar;10(3):186-95.
Wang HJ, Jiang YY, Wei XF, Huang H, Tashiro S, Onodera S, Ikejima T. Silibinin induces protective superoxide generation in human breast cancer MCF-7 cells. Free Radic Res. 2010 Jan;44(1):90-100.
Haddad Y, Vallerand D, Brault A, Haddad PS. Antioxidant and Hepatoprotective Effects of Silibinin in a Rat Model of Nonalcoholic Steatohepatitis. Evid Based Complement Alternat Med. 2009 Nov 1.
Lu P, Mamiya T, Lu L, Mouri A, Niwa M, Kim HC, Zou LB, Nagai T, Yamada K, Ikejima T, Nabeshima T. Silibinin attenuates cognitive deficits and decreases of dopamine and serotonin induced by repeated methamphetamine treatment. Behav Brain Res. 2010 Mar 5;207(2):387-93.
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*The latter article is intended for educational / informational purposes only. THIS PRODUCT IS INTENDED AS A RESEARCH CHEMICAL ONLY. This designation allows the use of research chemicals strictly for in vitro testing and laboratory experimentation only. Bodily introduction of any kind into humans or animals is strictly forbidden by law.