Date published: 2026-5-14

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Isosilybin A (CAS 142796-21-2)

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Alternate Names:
(2R,3R)-3,5,7-Trihydroxy-2-[(2R,3R)-2-(4-hydroxy-3-methoxyphenyl)-3-(hydroxymethyl)-2,3-dihydrobenzo[1,4]dioxin-6-yl]-4-chromanone
CAS Number:
142796-21-2
Molecular Weight:
482.44
Molecular Formula:
C25H22O10
For Research Use Only. Not Intended for Diagnostic or Therapeutic Use.
* Refer to Certificate of Analysis for lot specific data.

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Isosilybin A is a flavonolignan and one of the components available in silymarin, which is isolated from the milk thistle plant (Silybum marianum). It has hepatoprotective, antioxidant, anti-cancer, and anti-inflammatory properties. It inhibits lipid peroxidation in rat liver microsomes (IC50 = 32 μM) and reduces ADP/Fe3+-induced malondialdehyde (MDA) production and lactate dehydrogenase (LDH) release in rat hepatocytes. Isosilybin A inhibits the production of reactive oxygen species (ROS), MDA and LDH release, and reduction in total antioxidant capacity induced by amyloid-β (25-35) (Aβ25-35) in HT-22 hippocampal cells. It also increases protein and mRNA expression of heme oxygenase-1 (HO-1), glutathione S-transferase (GST), and the aldo-keto reductases (AKCR) 1C1 and AKCR1C2 in HT-22 cells. Isosilybin A reduces tumor volume and increases tumor cell apoptosis. It also reduces expression of the tumor angiogenesis markers CD31, nestin, VEGF, VEGFR1, VEGFR2, phospho-Akt, and HIF-1α in tumor tissue without reducing blood vessel count in non-cancerous liver, lung, and kidney tissue in DU145 tumor-bearing mice.


Isosilybin A (CAS 142796-21-2) References

  1. Molecular structure and stereochemistry of silybin A, silybin B, isosilybin A, and isosilybin B, Isolated from Silybum marianum (milk thistle).  |  Lee, DY. and Liu, Y. 2003. J Nat Prod. 66: 1171-4. PMID: 14510591
  2. Separation and characterization of silybin, isosilybin, silydianin and silychristin in milk thistle extract by liquid chromatography-electrospray tandem mass spectrometry.  |  Lee, JI., et al. 2006. J Chromatogr A. 1116: 57-68. PMID: 16631762
  3. Isosilybin A induces apoptosis in human prostate cancer cells via targeting Akt, NF-κB, and androgen receptor signaling.  |  Deep, G., et al. 2010. Mol Carcinog. 49: 902-12. PMID: 20721970
  4. HiFSA fingerprinting applied to isomers with near-identical NMR spectra: the silybin/isosilybin case.  |  Napolitano, JG., et al. 2013. J Org Chem. 78: 2827-39. PMID: 23461697
  5. An assessment of pharmacokinetics and antioxidant activity of free silymarin flavonolignans in healthy volunteers: a dose escalation study.  |  Zhu, HJ., et al. 2013. Drug Metab Dispos. 41: 1679-85. PMID: 23835761
  6. Flavonolignans from Aspergillus iizukae, a fungal endophyte of milk thistle (Silybum marianum).  |  El-Elimat, T., et al. 2014. J Nat Prod. 77: 193-9. PMID: 24456525
  7. Identification of isosilybin a from milk thistle seeds as an agonist of peroxisome proliferator-activated receptor gamma.  |  Pferschy-Wenzig, EM., et al. 2014. J Nat Prod. 77: 842-7. PMID: 24597776
  8. Silymarin Constituents Enhance ABCA1 Expression in THP-1 Macrophages.  |  Wang, L., et al. 2015. Molecules. 21: E55. PMID: 26729088
  9. The effect of milk thistle (Silybum marianum) and its main flavonolignans on CYP2C8 enzyme activity in human liver microsomes.  |  Albassam, AA., et al. 2017. Chem Biol Interact. 271: 24-29. PMID: 28457856
  10. Metabolism of flavonolignans in human hepatocytes.  |  Vrba, J., et al. 2018. J Pharm Biomed Anal. 152: 94-101. PMID: 29414024
  11. Immunomodulatory effects of two silymarin isomers in a Balb/c mouse model of allergic asthma.  |  Nasab, EM., et al. 2020. Allergol Immunopathol (Madr). 48: 646-653. PMID: 32284261
  12. Recapitulation of Evidence of Phytochemical, Pharmacokinetic and Biomedical Application of Silybin.  |  Islam, A., et al. 2021. Drug Res (Stuttg). 71: 489-503. PMID: 34318464
  13. Development of a capillary electrophoresis method for the separation of flavonolignans in silymarin complex.  |  Riasová, P., et al. 2022. Electrophoresis. 43: 930-938. PMID: 34751959

Ordering Information

Product NameCatalog #UNITPriceQtyFAVORITES

Isosilybin A, 5 mg

sc-506052
5 mg
$750.00