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Silibinin

Description of silibinin: Silibinin (INN), also known as silybin, is the major active constituent of silymarin, standardized extract of the milk thistle seeds, containing mixture of flavonolignans consisting of among others of silibinin, isosilibinin, silicristin and silidianin. Silibinin itself is mixture of two diastereomers Silibinin A and Silybinin B in approximately equimolar ratio. Both in vitro and animal research suggest that silibinin has hepatoprotective (antihepatotoxic) properties that protect liver cells against toxins. Silibinin has also demonstrated anti-cancer effects against human prostate adenocarcinoma cells, estrogen-dependent and -independent human breast carcinoma cells, human ectocervical carcinoma cells, human colon cancer cells, and both small and nonsmall human lung carcinoma cells. (source: http://en.wikipedia.org/wiki/Silibinin).

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Silibinin (INN), also known as silybin, is the major active constituent of silymarin, the mixture of flavonolignans extracted from blessed milk thistle. Poor water solubility and bioavailability of silymarin led to the development of enhanced formulations. Silipide (trade name Siliphos), a complex of silymarin and phosphatidylcholine (lecithin), is about ten times more bioavailable than silymarin.  It has been also reported  that silymarin inclusion complex with β-cyclodextrin is much more soluble than silymarin itself. There have also been prepared glycosides of silybin, which show better water solubility and even stronger hepatoprotective effect. Silymarin, as other flavonoids, has been shown to inhibit P-glycoprotein-mediated cellular efflux.  The modulation of P-glycoprotein activity may result in altered absorption and bioavailability of drugs that are P-glycoprotein substrates. It has been reported that silymarin inhibit cytochrome P450 enzymes and an interaction with drugs primarily cleared by P450s cannot be excluded.  [source: http://en.wikipedia.org/wiki/Silibinin].

Toxicity: The acute toxicity of silymarin and silybin were investigated by oral and intravenous route in various animal species. No mortality or any signs of adverse effects were observed after silymarin at oral doses of 20 g/kg in mice and 1 g/kg in dogs. The 50% lethal dose (LD50) after intravenous infusion values are 400 mg/kg in mice, 385 mg/kg in rats and 140 mg/kg in rabbits and dogs. These data demonstrate that the acute toxicity of silymarin is very low [source: http://en.wikipedia.org/wiki/Silibinin].

1: Kaur M, Velmurugan B, Tyagi A, Agarwal C, Singh RP, Agarwal R. Silibinin suppresses growth of human colorectal carcinoma SW480 cells in culture and xenograft through down-regulation of beta-catenin-dependent signaling. Neoplasia. 2010 May;12(5):415-24. PubMed PMID: 20454513; PubMed Central PMCID: PMC2864479.

2: Duan W, Jin X, Li Q, Tashiro S, Onodera S, Ikejima T. Silibinin induced autophagic and apoptotic cell death in HT1080 cells through a reactive oxygen species pathway. J Pharmacol Sci. 2010;113(1):48-56. Epub 2010 Apr 22. PubMed PMID: 20431246.

3: Wu K, Zeng J, Li L, Fan J, Zhang D, Xue Y, Zhu G, Yang L, Wang X, He D. Silibinin reverses epithelial-to-mesenchymal transition in metastatic prostate cancer cells by targeting transcription factors. Oncol Rep. 2010 Jun;23(6):1545-52. PubMed PMID: 20428808.

4: Li L, Zeng J, Gao Y, He D. Targeting silibinin in the antiproliferative pathway. Expert Opin Investig Drugs. 2010 Feb;19(2):243-55. Review. PubMed PMID: 20047507.

5: Mateen S, Tyagi A, Agarwal C, Singh RP, Agarwal R. Silibinin inhibits human nonsmall cell lung cancer cell growth through cell-cycle arrest by modulating expression and function of key cell-cycle regulators. Mol Carcinog. 2010 Mar;49(3):247-58. PubMed PMID: 19908243.

6: Kidd PM. Bioavailability and activity of phytosome complexes from botanical polyphenols: the silymarin, curcumin, green tea, and grape seed extracts. Altern Med Rev. 2009 Sep;14(3):226-46. Review. PubMed PMID: 19803548.

7: Jung HJ, Park JW, Lee JS, Lee SR, Jang BC, Suh SI, Suh MH, Baek WK. Silibinin inhibits expression of HIF-1alpha through suppression of protein translation in prostate cancer cells. Biochem Biophys Res Commun. 2009 Dec 4;390(1):71-6. Epub 2009 Sep 22. PubMed PMID: 19778521.

8: Kaur M, Velmurugan B, Tyagi A, Deep G, Katiyar S, Agarwal C, Agarwal R. Silibinin suppresses growth and induces apoptotic death of human colorectal carcinoma LoVo cells in culture and tumor xenograft. Mol Cancer Ther. 2009 Aug;8(8):2366-74. Epub 2009 Jul 28. PubMed PMID: 19638451; PubMed Central PMCID: PMC2728169.

9: Lin CJ, Sukarieh R, Pelletier J. Silibinin inhibits translation initiation: implications for anticancer therapy. Mol Cancer Ther. 2009 Jun;8(6):1606-12. Epub 2009 Jun 9. PubMed PMID: 19509268.

10: Kim KW, Choi CH, Kim TH, Kwon CH, Woo JS, Kim YK. Silibinin inhibits glioma cell proliferation via Ca2+/ROS/MAPK-dependent mechanism in vitro and glioma tumor growth in vivo. Neurochem Res. 2009 Aug;34(8):1479-90. Epub 2009 Mar 5. PubMed PMID: 19263218.

11: Bhatt RS, Bubley GJ. The challenge of herbal therapies for prostate cancer. Clin Cancer Res. 2008 Dec 1;14(23):7581-2. Review. PubMed PMID: 19047081.

12: Thongphasuk P, Stremmel W, Chamulitrat W. 2,3-dehydrosilybin is a better DNA topoisomerase I inhibitor than its parental silybin. Chemotherapy. 2009;55(1):42-8. Epub 2008 Nov 21. PubMed PMID: 19023201.

13: García-Maceira P, Mateo J. Silibinin inhibits hypoxia-inducible factor-1alpha and mTOR/p70S6K/4E-BP1 signalling pathway in human cervical and hepatoma cancer cells: implications for anticancer therapy. Oncogene. 2009 Jan 22;28(3):313-24. Epub 2008 Nov 3. PubMed PMID: 18978810.

14: Wang HJ, Tashiro S, Onodera S, Ikejima T. Inhibition of insulin-like growth factor 1 receptor signaling enhanced silibinin-induced activation of death receptor and mitochondrial apoptotic pathways in human breast cancer MCF-7 cells. J Pharmacol Sci. 2008 Jul;107(3):260-9. PubMed PMID: 18635919.

15: Zhou L, Liu P, Chen B, Wang Y, Wang X, Chiriva Internati M, Wachtel MS, Frezza EE. Silibinin restores paclitaxel sensitivity to paclitaxel-resistant human ovarian carcinoma cells. Anticancer Res. 2008 Mar-Apr;28(2A):1119-27. PubMed PMID: 18507063.

16: Deep G, Oberlies NH, Kroll DJ, Agarwal R. Identifying the differential effects of silymarin constituents on cell growth and cell cycle regulatory molecules in human prostate cancer cells. Int J Cancer. 2008 Jul 1;123(1):41-50. PubMed PMID: 18435416.

17: Huber A, Thongphasuk P, Erben G, Lehmann WD, Tuma S, Stremmel W, Chamulitrat W. Significantly greater antioxidant anticancer activities of 2,3-dehydrosilybin than silybin. Biochim Biophys Acta. 2008 May;1780(5):837-47. Epub 2008 Jan 3. PubMed PMID: 18222181.

18: Thongphasuk P, Stremmel W, Chamulitrat W. Potent direct or TNF-alpha-promoted anticancer effects of 2,3-dehydrosilybin: comparison study with silybin. Chemotherapy. 2008;54(1):23-30. Epub 2007 Dec 7. PubMed PMID: 18063863.

19: Raina K, Agarwal R. Combinatorial strategies for cancer eradication by silibinin and cytotoxic agents: efficacy and mechanisms. Acta Pharmacol Sin. 2007 Sep;28(9):1466-75. Review. PubMed PMID: 17723180.

20: Jancová P, Anzenbacherová E, Papousková B, Lemr K, Luzná P, Veinlichová A, Anzenbacher P, Simánek V. Silybin is metabolized by cytochrome P450 2C8 in vitro. Drug Metab Dispos. 2007 Nov;35(11):2035-9. Epub 2007 Aug 1. PubMed PMID: 17670841.