Isosilybin B

CAS# 142796-22-3

Isosilybin B

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Chemical structure

Isosilybin B

3D structure

Chemical Properties of Isosilybin B

Cas No. 142796-22-3 SDF Download SDF
PubChem ID 10885340 Appearance White powder
Formula C25H22O10 M.Wt 482.4
Type of Compound Flavonoids Storage Desiccate at -20°C
Synonyms Silybin a2
Solubility Soluble in acetone, ethanol, ethyl acetate and methanol; insoluble in water
Chemical Name (2~{R},3~{R})-3,5,7-trihydroxy-2-[(2~{S},3~{S})-2-(4-hydroxy-3-methoxyphenyl)-3-(hydroxymethyl)-2,3-dihydro-1,4-benzodioxin-6-yl]-2,3-dihydrochromen-4-one
SMILES COC1=C(C=CC(=C1)C2C(OC3=C(O2)C=CC(=C3)C4C(C(=O)C5=C(C=C(C=C5O4)O)O)O)CO)O
Standard InChIKey FDQAOULAVFHKBX-WAABAYLZSA-N
Standard InChI InChI=1S/C25H22O10/c1-32-17-6-11(2-4-14(17)28)24-20(10-26)33-18-7-12(3-5-16(18)34-24)25-23(31)22(30)21-15(29)8-13(27)9-19(21)35-25/h2-9,20,23-29,31H,10H2,1H3/t20-,23-,24-,25+/m0/s1
General tips For obtaining a higher solubility , please warm the tube at 37 ℃ and shake it in the ultrasonic bath for a while.Stock solution can be stored below -20℃ for several months.
We recommend that you prepare and use the solution on the same day. However, if the test schedule requires, the stock solutions can be prepared in advance, and the stock solution must be sealed and stored below -20℃. In general, the stock solution can be kept for several months.
Before use, we recommend that you leave the vial at room temperature for at least an hour before opening it.
About Packaging 1. The packaging of the product may be reversed during transportation, cause the high purity compounds to adhere to the neck or cap of the vial.Take the vail out of its packaging and shake gently until the compounds fall to the bottom of the vial.
2. For liquid products, please centrifuge at 500xg to gather the liquid to the bottom of the vial.
3. Try to avoid loss or contamination during the experiment.
Shipping Condition Packaging according to customer requirements(5mg, 10mg, 20mg and more). Ship via FedEx, DHL, UPS, EMS or other couriers with RT, or blue ice upon request.

Source of Isosilybin B

The herbs of Silybum marianum

Biological Activity of Isosilybin B

DescriptionIsosilybin B causes androgen receptor degradation in human prostate carcinoma cells via PI3K-Akt-Mdm2-mediated pathway, it has anti-prostate cancer (PCA) activity that is mediated via cell cycle arrest and apoptosis induction. Isosilybin B showed inhibitory effect on CYP2C8 activity. It inhibited both monophenolase (IC50 = 1.7-7.6 µM) and diphenolase (IC50 = 12.1-44.9 µM) of tyrosinase.
TargetsPI3K | Akt | Mdm2 | CYP2C8 | Tyrosinase
In vitro

Angiopreventive efficacy of pure flavonolignans from milk thistle extract against prostate cancer: targeting VEGF-VEGFR signaling.[Pubmed: 22514647 ]

PLoS One. 2012;7(4):e34630.

The role of neo-angiogenesis in prostate cancer (PCA) growth and metastasis is well established, but the development of effective and non-toxic pharmacological inhibitors of angiogenesis remains an unaccomplished goal. In this regard, targeting aberrant angiogenesis through non-toxic phytochemicals could be an attractive angiopreventive strategy against PCA.
METHODS AND RESULTS:
The rationale of the present study was to compare the anti-angiogenic potential of four pure diastereoisomeric flavonolignans, namely silybin A, silybin B, isosilybin A and Isosilybin B, which we established previously as biologically active constituents in Milk Thistle extract. Results showed that oral feeding of these flavonolignans (50 and 100 mg/kg body weight) effectively inhibit the growth of advanced human PCA DU145 xenografts. Immunohistochemical analyses revealed that these flavonolignans inhibit tumor angiogenesis biomarkers (CD31 and nestin) and signaling molecules regulating angiogenesis (VEGF, VEGFR1, VEGFR2, phospho-Akt and HIF-1α) without adversely affecting the vessel-count in normal tissues (liver, lung, and kidney) of tumor bearing mice. These flavonolignans also inhibited the microvessel sprouting from mouse dorsal aortas ex vivo, and the VEGF-induced cell proliferation, capillary-like tube formation and invasiveness of human umbilical vein endothelial cells (HUVEC) in vitro. Further studies in HUVEC showed that these diastereoisomers target cell cycle, apoptosis and VEGF-induced signaling cascade. Three dimensional growth assay as well as co-culture invasion and in vitro angiogenesis studies (with HUVEC and DU145 cells) suggested the differential effectiveness of the diastereoisomers toward PCA and endothelial cells.
CONCLUSIONS:
Overall, these studies elucidated the comparative anti-angiogenic efficacy of pure flavonolignans from Milk Thistle and suggest their usefulness in PCA angioprevention.

Isosilybin B causes androgen receptor degradation in human prostate carcinoma cells via PI3K-Akt-Mdm2-mediated pathway.[Pubmed: 18332867 ]

Oncogene. 2008 Jun 26;27(28):3986-98.

The identification and development of novel nontoxic phytochemicals that target androgen and androgen receptor (AR) signaling remains a priority for prostate cancer (PCA) control.
METHODS AND RESULTS:
In the present study, we assessed the antiandrogenic efficacy of Isosilybin B employing human PCA LNCaP (mutated AR), 22Rv1 (mutated AR) and LAPC4 (wild-type AR) cells. Isosilybin B (10-90 microM) treatment decreased the AR and prostate specific antigen (PSA) levels in LNCaP, 22Rv1 and LAPC4 cells, but not in non-neoplastic human prostate epithelial PWR-1E cells. Isosilybin B treatment also inhibited synthetic androgen R1881-induced nuclear localization of AR, PSA expression and cell growth, and caused G(1) arrest. In mechanistic studies identifying AR degradation, Isosilybin B caused increased phosphorylation of Akt (Ser-473 and Thr-308) and Mdm2 (Ser-166), which was linked with AR degradation as pretreatment with PI3K inhibitor (LY294002)-restored AR level. Further, overexpression of kinase-dead Akt largely reversed Isosilybin B mediated-AR degradation suggesting a critical role of Akt in AR degradation. Antibody pull-down results also indicated that Isosilybin B treatment enhances the formation of complex between Akt, Mdm2 and AR, which promotes phosphorylation-dependent AR ubiquitination and its degradation by proteasome.
CONCLUSIONS:
Together, present findings identify a novel mechanism for Isosilybin B-mediated anticancer effects in human PCA cells.

Isosilybin B and isosilybin A inhibit growth, induce G1 arrest and cause apoptosis in human prostate cancer LNCaP and 22Rv1 cells.[Pubmed: 17389612]

Carcinogenesis. 2007 Jul;28(7):1533-42.

Silymarin and, one of its constituents, silibinin exert strong efficacy against prostate cancer (PCA); however, anticancer efficacy and associated mechanisms of other components of silymarin, which is a mixture of flavonolignans, are largely unknown.
METHODS AND RESULTS:
Here we have assessed the anticancer efficacy of two pure compounds Isosilybin B and isosilybin A, isolated from silymarin, in human prostate carcinoma LNCaP and 22Rv1 cells. Isosilybin B and isosilybin A treatment resulted in growth inhibition and cell death together with a strong G(1) arrest and apoptosis in both the cell lines. In the studies examining changes in cell cycle and apoptosis regulators, Isosilybin B and isosilybin A resulted in a decrease in the levels of both cyclins (D1, D3, E and A) and cyclin-dependent kinases (Cdk2, Cdk4 and cell division cycle 25A), but caused an increase in p21, p27 and p53 levels, except in 22Rv1 cells where Isosilybin B caused a decrease in p21 protein level. Isosilybin B- and isosilybin A-induced apoptosis was accompanied with an increase in the cleavage of poly (ADP-ribose) polymerase, caspase-9 and caspase-3 and a decrease in survivin levels. Compared with LNCaP and 22Rv1 cells, the antiproliferative and cytotoxic potentials of Isosilybin B and isosilybin A were of much lesser magnitude in non-neoplastic human prostate epithelial PWR-1E cells suggesting the transformation-selective effect of these compounds.
CONCLUSIONS:
Together, this study for the first time identified that Isosilybin B and isosilybin A, two diastereoisomers isolated from silymarin, have anti-PCA activity that is mediated via cell cycle arrest and apoptosis induction.

Protocol of Isosilybin B

Kinase Assay

The effect of milk thistle (Silybum marianum) and its main flavonolignans on CYP2C8 enzyme activity in human liver microsomes.[Pubmed: 28457856 ]

Tyrosinase inhibitory study of flavonolignans from the seeds of Silybum marianum (Milk thistle).[Pubmed: 30871862 ]

Bioorg Med Chem. 2019 Jun 15;27(12):2499-2507.

Anti-melanogenesis effects of silymarin from milk thistle have been reported recently, but detailed tyrosinase inhibition properties of individual components have not been investigated. This study purported to substantiate tyrosinase inhibition and its mechanism based on a single metabolite.
METHODS AND RESULTS:
The responsible components for tyrosinase inhibition of target source were found out as flavonolignans which consist of isosilybin A (1), Isosilybin B (2), silydianin (3), 2,3-dihydrosilychristin (4), silychristin A (5), silychristin B (6) and silybin (7), respectively. The isolated flavonolignans (1-7) inhibited both monophenolase (IC50 = 1.7-7.6 µM) and diphenolase (IC50 = 12.1-44.9 µM) of tyrosinase significantly. Their inhibitions were 10-fold effective in comparison with their mother skeletons (8-10). Inhibitory functions were also proved by HPLC analysis using N-acetyl-l-tyrosine as substrate. The predominant formation of Emet·I was confirmed from a long prolongation of lag time and a decrease of the static state activity of the enzyme.
CONCLUSIONS:
All tested compounds had a significant binding affinity to tyrosinase with KSV values of 0.06-0.27 × 104 L·mol-1, which are well correlated with IC50s. In kinetic study, all flavonolignan (1-7) were mixed type I (KI < KIS) inhibitors, whereas their mother skeletons (8-10) were competitive ones. The UPLC-ESI-TOF/MS analysis showed that the isolated inhibitors are the most abundant metabolites in the target plant.

Chem Biol Interact. 2017 Jun 1;271:24-29.

Milk thistle is a widely-consumed botanical used for an array of purported health benefits. The primary extract of milk thistle is termed silymarin, a complex mixture that contains a number of structurally-related flavonolignans, the flavonoid, taxifolin, and a number of other constituents. The major flavonolignans present in most extracts are silybin A, silybin B, isosilybin A and Isosilybin B, silydianin, silychristin and isosilychristin. Silymarin itself has been reported to inhibit CYP2C8 activity in vitro, but the effect of the individual flavonolignans on this enzyme has not been studied.
METHODS AND RESULTS:
To investigate the effects of milk thistle extract and its main flavonolignans (silybin A, silybin B, isosilybin A and Isosilybin B) on CYP2C8 activity at relevant concentrations, the effect of milk thistle extract and the flavonolignans on CYP2C8 enzyme activity was studied in vitro using human liver microsomes (HLM) incorporating an enzyme-selective substrate for CYP2C8, amodiaquine. Metabolite formation was analyzed using liquid chromatography-tandem mass spectrometry (LC/MS-MS). The concentration causing 50% inhibition of enzyme activity (IC50) was used to express the degree of inhibition. Isosilibinin, a mixture of the diastereoisomers isosilybin A and Isosilybin B, was found to be the most potent inhibitor, followed by Isosilybin B with IC50 values (mean ± SE) of 1.64 ± 0.66 μg/mL and 2.67 ± 1.18 μg/mL, respectively. The rank order of observed inhibitory potency after isosilibinin was silibinin > isosilybin A > silybin A > milk thistle extract > and silybin B.
CONCLUSIONS:
These in vitro results suggest a potentially significant inhibitory effect of isosilibinin and Isosilybin B on CYP2C8 activity. However, the observed IC50 values are unlikely to be achieved in humans supplemented with orally administered milk thistle extracts due to the poor bioavailability of flavonolignans documented with most commercially available formulations.

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Preparing Stock Solutions of Isosilybin B

1 mg 5 mg 10 mg 20 mg 25 mg
1 mM 2.073 mL 10.3648 mL 20.7297 mL 41.4594 mL 51.8242 mL
5 mM 0.4146 mL 2.073 mL 4.1459 mL 8.2919 mL 10.3648 mL
10 mM 0.2073 mL 1.0365 mL 2.073 mL 4.1459 mL 5.1824 mL
50 mM 0.0415 mL 0.2073 mL 0.4146 mL 0.8292 mL 1.0365 mL
100 mM 0.0207 mL 0.1036 mL 0.2073 mL 0.4146 mL 0.5182 mL
* Note: If you are in the process of experiment, it's necessary to make the dilution ratios of the samples. The dilution data above is only for reference. Normally, it's can get a better solubility within lower of Concentrations.

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References on Isosilybin B

Tyrosinase inhibitory study of flavonolignans from the seeds of Silybum marianum (Milk thistle).[Pubmed:30871862]

Bioorg Med Chem. 2019 Mar 7. pii: S0968-0896(19)30173-7.

Anti-melanogenesis effects of silymarin from milk thistle have been reported recently, but detailed tyrosinase inhibition properties of individual components have not been investigated. This study purported to substantiate tyrosinase inhibition and its mechanism based on a single metabolite. The responsible components for tyrosinase inhibition of target source were found out as flavonolignans which consist of isosilybin A (1), Isosilybin B (2), silydianin (3), 2,3-dihydrosilychristin (4), silychristin A (5), silychristin B (6) and silybin (7), respectively. The isolated flavonolignans (1-7) inhibited both monophenolase (IC50=1.7-7.6microM) and diphenolase (IC50=12.1-44.9microM) of tyrosinase significantly. Their inhibitions were 10-fold effective in comparison with their mother skeletons (8-10). Inhibitory functions were also proved by HPLC analysis using N-acetyl-l-tyrosine as substrate. The predominant formation of Emet.I was confirmed from a long prolongation of lag time and a decrease of the static state activity of the enzyme. All tested compounds had a significant binding affinity to tyrosinase with KSV values of 0.06-0.27x10(4)L.mol(-1), which are well correlated with IC50s. In kinetic study, all flavonolignan (1-7) were mixed type I (KI

Two new norneolignans from Callicarpa kwangtungensis.[Pubmed:30856343]

Nat Prod Res. 2019 Mar 11:1-7.

Two new norneolignans, (7S,8R)-3-methoxy-3',4,9-trihydroxy-4',7-epoxy-8,3'-neolignane-1'-carboxylic acid (1) and (7R,8R)-3-methoxyl-4,9-dihydroxy-3':7,4':8-diepoxyneolignan-1'-carboxylic acid methyl ester (2) were isolated from Callicarpa kwangtungensis, together with ten known compounds, genistin (3), daidzin (4), silybin A (5), isosilybin A (6), Isosilybin B (7), p-hydroxybenzaldehyde (8), syringic acid (9), lanceolatin A (10), icariside C5 (11), and (3S,6E,10R)-10-beta-D-glucopyranosyloxy-3,11-dihydroxy-3,7,11-trimethyldodeca-1,6 -diene (12). Compounds 1 and 2 were evaluated for their effects on the inhibition of nitric oxide (NO) production in lipopolysaccharide induced RAW264.7 cells. Compounds 1 and 2 exhibited inhibitory activity with IC50 values of 31.45 +/- 0.38 and 40.72 +/- 0.54 muM, respectively.

Differential accumulation of silymarin induced by exposure of Silybum marianum L. callus cultures to several spectres of monochromatic lights.[Pubmed:29803074]

J Photochem Photobiol B. 2018 Jul;184:61-70.

Silybum marianum L. (Milk thistle) is one of the most extensively studied medicinal herbs with well-known hepatoprotective activity. Light is considered as a key abiotic elicitor influencing several physiological processes in plants, including the biosynthesis of secondary metabolites. In this study, we investigated the influence of light quality on morphological and biochemical aspects in in vitro grown leaf-derived callus cultures of S. marianum. Combination of 6-benzylaminopurine (BAP 2.5mg/L) and alpha-naphthalene acetic acid (NAA 1.0mg/L) resulted in optimum callogenic response (97%) when placed under cool-white light with 16h light and 8h dark. Red light significantly increased the total phenolic content (TPC), total flavonoid content (TFC), antioxidant and superoxide dismutase (SOD) activities while highest peroxidase (POD) activity was recorded for the dark grown cultures, followed by green light grown cultures. HPLC analysis revealed enhanced total silymarin content under red light (18.67mg/g DW), which was almost double than control (9.17mg/g DW). Individually, the level of silychristin, isosilychristin, silydianin, silybin A and silybin B were found greatest under red light, whereas green spectrum resulted in highest accumulation of isosilybin A and Isosilybin B. Conversely, the amount of taxifolin was found maximum under continuous white light (0.480mg/g DW) which was almost 8-fold greater than control (0.063mg/g DW). A positive correlation was found between the TPC, TFC and antioxidant activities. This study will assist in comprehending the influence of light quality on production of valuable secondary metabolites in in vitro cultures of S. marianum L.

Metabolism of flavonolignans in human hepatocytes.[Pubmed:29414024]

J Pharm Biomed Anal. 2018 Apr 15;152:94-101.

This study examined the in vitro biotransformation of eight structurally related flavonolignans, namely silybin, 2,3-dehydrosilybin, silychristin, 2,3-dehydrosilychristin, silydianin, 2,3-dehydrosilydianin, isosilybin A and Isosilybin B. The metabolic transformations were performed using primary cultures of human hepatocytes and recombinant human cytochromes P450 (CYPs 1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1 and 3A4). The metabolites produced were analyzed by ultra-performance liquid chromatography coupled with tandem mass spectrometry. We found that each of the tested compounds was metabolized in vitro by one or more CYP enzymes, which catalyzed O-demethylation, hydroxylation, hydrogenation and dehydrogenation reactions. In human hepatocytes, silybin, 2,3-dehydrosilybin, silychristin, 2,3-dehydrosilychristin, and isosilybins A and B were directly conjugated by sulfation or glucuronidation. Moreover, isosilybin A was also converted to a methyl derivative, while Isosilybin B was hydroxylated and methylated. Silydianin and 2,3-dehydrosilydianin were found to undergo hydrogenation and/or glucuronidation. In addition, 2,3-dehydrosilydianin was found to be metabolically the least stable flavonolignan in human hepatocytes, and its main metabolite was a cleavage product corresponding to a loss of CO. We conclude that the hepatic biotransformation of flavonolignans primarily involves the phase II conjugation reactions, however in some cases the phase I reactions may also occur. These results are highly relevant for research focused on flavonolignan metabolism and pharmacology.

The study of flavonolignan association patterns in fruits of diverging Silybum marianum (L.) Gaertn. chemotypes provides new insights into the silymarin biosynthetic pathway.[Pubmed:28863306]

Phytochemistry. 2017 Dec;144:9-18.

Silymarin is the phytochemical with medicinal properties extracted from Silybum marianum (L.) Gaertn. fruits. Yet, little information is available about silymarin biosynthesis. Moreover, the generally accepted pathway, formulated thus far, is not in agreement with actual experimental measurements on flavonolignan contents. The present work analyses flavonolignan and taxifolin content in 201 S. marianum samples taking into consideration a wide phenotypic variability. Two stable chemotypes were identified: one characterized by both high silychristin and silybin content (chemotype A) and another by a high silydianin content (chemotype B). Through the correlation analysis of samples divided according to chemotype, it was possible to construct a simplified silymarin biosynthetic pathway that is sufficiently versatile in explaining experimental results responding to the actually unresolved questions about this process. The proposed pathway highlights that three separate and equally sized metabolite pools exist, namely: diastereoisomers A (silybin A plus isosilybin A), diastereoisomers B (silybin B plus Isosilybin B) and silychristin. In both A and B diastereoisomers pools, isosilybin A and Isosilybin B always represent a given amount of the metabolite flux through the specific metabolite pool suggesting the possible involvement of dirigent protein-like enzymes. We suggest that chemotype B possesses a complete silymarin biosynthetic pathway in which silydianin biosynthesis is enzymatically controlled. On the contrary, chemotype A is probably a natural mutant unable to biosynthesize silydianin. The present simplified pathway for silymarin biosynthesis will constitute an important tool for the further understanding of the reactions that drive flavonolignan biosynthesis in S. marianum.

The effect of milk thistle (Silybum marianum) and its main flavonolignans on CYP2C8 enzyme activity in human liver microsomes.[Pubmed:28457856]

Chem Biol Interact. 2017 Jun 1;271:24-29.

Milk thistle is a widely-consumed botanical used for an array of purported health benefits. The primary extract of milk thistle is termed silymarin, a complex mixture that contains a number of structurally-related flavonolignans, the flavonoid, taxifolin, and a number of other constituents. The major flavonolignans present in most extracts are silybin A, silybin B, isosilybin A and Isosilybin B, silydianin, silychristin and isosilychristin. Silymarin itself has been reported to inhibit CYP2C8 activity in vitro, but the effect of the individual flavonolignans on this enzyme has not been studied. To investigate the effects of milk thistle extract and its main flavonolignans (silybin A, silybin B, isosilybin A and Isosilybin B) on CYP2C8 activity at relevant concentrations, the effect of milk thistle extract and the flavonolignans on CYP2C8 enzyme activity was studied in vitro using human liver microsomes (HLM) incorporating an enzyme-selective substrate for CYP2C8, amodiaquine. Metabolite formation was analyzed using liquid chromatography-tandem mass spectrometry (LC/MS-MS). The concentration causing 50% inhibition of enzyme activity (IC50) was used to express the degree of inhibition. Isosilibinin, a mixture of the diastereoisomers isosilybin A and Isosilybin B, was found to be the most potent inhibitor, followed by Isosilybin B with IC50 values (mean +/- SE) of 1.64 +/- 0.66 mug/mL and 2.67 +/- 1.18 mug/mL, respectively. The rank order of observed inhibitory potency after isosilibinin was silibinin > isosilybin A > silybin A > milk thistle extract > and silybin B. These in vitro results suggest a potentially significant inhibitory effect of isosilibinin and Isosilybin B on CYP2C8 activity. However, the observed IC50 values are unlikely to be achieved in humans supplemented with orally administered milk thistle extracts due to the poor bioavailability of flavonolignans documented with most commercially available formulations.

Chemotaxonomic and biosynthetic relationships between flavonolignans produced by Silybum marianum populations.[Pubmed:28392269]

Fitoterapia. 2017 Jun;119:175-184.

Flavonolignans constitute an important class of plant secondary metabolites formed by oxidative coupling of one flavonoid and one phenylpropanoid moiety. The standardized flavonolignan-rich extract prepared from the fruits of Silybum marianum is known as silymarin and has long been used medicinally, prominently as an antihepatotoxic and as a chemopreventive agent. Principal component analysis of the variation in flavonolignan content in S. marianum samples collected from different locations in Egypt revealed biosynthetic relationships between the flavonolignans. Silybin A, silybin B, and silychristin are positively correlated as are silydianin, isosilychristin, and Isosilybin B. The detection of silyamandin in the extracts of S. marianum correlates with isosilychristin and silydianin content. The positive correlation between silydianin, isosilychristin, and silyamandin was demonstrated using quantitative (1)H nuclear magnetic resonance spectroscopy (qHNMR). These correlations can be interpreted as evidence for the involvement of a flavonoid radical in the biosynthesis of the flavonolignans in S. marianum. The predominance of silybins A & B over isosilybin A & B in the silybin-rich samples is discussed in light of the relative stabilities of their respective radical flavonoid biosynthetic intermediates.

A new approach to the rapid separation of isomeric compounds in a Silybum marianum extract using UHPLC core-shell column with F5 stationary phase.[Pubmed:27915198]

J Pharm Biomed Anal. 2017 Feb 5;134:203-213.

In this paper, a new ultra-high performance liquid chromatography (UHPLC) method using a core-shell column with a pentafluorophenyl stationary phase for separation of seven active compounds of a Silybum marianum extract was developed and validated. Silymarin, an extract of Silybum marianum, is known for its abilities to protect the liver from toxic substances, hepatitis therapy, and anti-tumour activity. Silymarin is currently being widely used in commercial preparations and herbal teas. Separation of seven compounds contained in the Silybum marianum extract (taxifolin, silychristin, silydianin, silybin A, silybin B, isosilybin A, Isosilybin B) and other substances occurring in real samples was performed on the Kinetex 1.7mu F5 100A (150x2.1mm), 1.7mum particle size core-shell column, with a mobile phase methanol/100mM phosphate buffer pH 2.0 according to the gradient program. A mobile phase 0.35mLmin(-1) flow rate and 50 degrees C temperature was used for the separation. The detection wavelength was set at 288nm. Under optimal chromatographic conditions, good linearity with a correlation coefficient of R(2) >0.999 for all compounds was achieved. The available commercial samples of herbal teas and food supplements were extracted with methanol using an ultrasonic bath. After dilution with water and centrifugation, a 2muL sample of the filtered supernatant was directly injected into the UHPLC system. The use of a pentafluorophenyl stationary phase with methanol as the organic component of the mobile phase showed new ways to effectively separate isomeric compounds in herbal extracts, which could not be done with the conventional C18 stationary phase.

Silymarin content in Silybum marianum populations growing in Egypt.[Pubmed:27182123]

Ind Crops Prod. 2016 May;83:729-737.

Chemical variation of Silybum marianum growing in the north, middle, and south of Egypt was investigated. Variation was assessed according to the content of the individual silymarin components in the fruits of the plant. The fruits were distinguished according to location, plant variety, and fruit color (maturity). Accelerated solvent extraction was used to standardize the silymarin extraction. Quantitative analysis of the content of silymarin components was carried out using HPLC with qNMR-controlled reference standards of taxifolin and seven major flavonolignans including silybin A, silybin B, isosilybin A, Isosilybin B, silychristin, isosilychristin, and silydianin. The quantification method was validated in accordance with ICH guidelines. Principal component analysis and hierarchical clustering were carried out to create homogeneous clusters of samples based on the content of the silymarin components. Taxifolin had the lowest correlation relative to other silymarin components, whereas silybin A was positively correlated with silybin B. The samples clustered into three classes: silydianin-rich samples, samples with an average silymarin content of <18.8 mg/g, and one class enriched in silymarin (>18.8 mg/g). S. marianum growing in the Nile delta showed the highest silymarin content. No correlation was found between fruit color and silymarin content, indicating that the fruit maturity stage has no significance.

Fatty acids, essential oil and phenolics composition of Silybum marianum seeds and their antioxidant activities.[Pubmed:27166539]

Pak J Pharm Sci. 2016 May;29(3):953-9.

The presentstudydescribes the biochemical evaluation of Silybum marianum seed. The analysis of essential oil composition of Silybum marianum seed by Gas Chromatography-Mass Spectrometry GC-MS showed the presence of14 volatile components with the predominance of gamma-cadinene (49.8%) and alpha-pinene (24.5%). Whereas, the analysis of fatty acids composition, showed the predominance of linoleic (50.5%) and oleic (30.2%) acids. Silybum marainum presented also an important polyphenol contents with 29mgGAE/g DW, a good antiradical activity (CI(50)=39mug/ml) but a lower reducing power ability. Flavonoid and condensed tannin contents were about 3.39mg EC/g DW and 1.8mg EC/gDW, respectively. The main phenolic compounds identified by RP-HPLC, were silybin A (12.2%), silybin B (17.67%), isosilybin A (21.9%), Isosilybin B (12.8%), silychristin (7.9%) andsilydianin (7.5%).

Head-to-Head Comparison of Ultra-High-Performance Liquid Chromatography with Diode Array Detection versus Quantitative Nuclear Magnetic Resonance for the Quantitative Analysis of the Silymarin Complex in Silybum marianum Fruit Extracts.[Pubmed:26806429]

J Agric Food Chem. 2016 Feb 24;64(7):1618-26.

Quantitative nuclear magnetic resonance (qNMR) spectroscopy is known as an excellent alternative to chromatography-based mixture analysis. NMR spectroscopy is a non-destructive method, needs only limited sample preparation, and can be readily automated. A head-to-head comparison of qNMR to an ultra-high-performance liquid chromatography with diode array detection (uHPLC-DAD)-based quantitative analysis of six flavonolignan congeners (silychristin, silydianin, silybin A, silybin B, isosilybin A, and Isosilybin B) of the Silybum marianum silymarin complex is presented. Both assays showed similar performance characteristics (linear range, accuracy, precision, and limits of quantitation) with analysis times below 30 min/sample. The assays were applied to industrial S. marianum extracts (AC samples) and to extracts locally prepared from S. marianum fruits (PL samples). An assay comparison by Bland-Altman plots (relative method bias AC samples, -0.1%; 2SD range, +/-5.1%; relative method bias PL samples, -0.3%; 2SD range, +/-7.8%) and Passing-Bablok regression analysis (slope and intercept for AC and PL samples not significantly different from 1.00 and 0.00, respectively; Spearman's coefficient of rank correlation, >0.99) did show that qNMR and uHPLC-DAD can be used interchangeably to quantitate flavonolignans in the silymarin complex.

Silymarin Constituents Enhance ABCA1 Expression in THP-1 Macrophages.[Pubmed:26729088]

Molecules. 2015 Dec 31;21(1):E55.

Silymarin is a hepatoprotective mixture of flavonolignans and flavonoids extracted from the seeds of milk thistle (Silybum marianum L. Gaertn). This study investigates the effect of major bioactive constituents from silymarin, silybin A, silybin B, isosilybin A, Isosilybin B, silydianin, silychristin, isosilychristin, and taxifolin, on the expression of ABCA1, an important cholesterol efflux transporter, in THP-1-derived macrophages. Four of the studied compounds, isosilybin A, silybin B, silychristin and isosilychristin, were found to significantly induce ABCA1 protein expression without affecting cell viability. Moreover, isosilybin A, a partial PPARgamma agonist, was found to promote cholesterol efflux from THP-1 macrophages in a concentration-dependent manner. These findings first show ABCA1 protein up-regulating activity of active constituents of silymarin and provide new avenues for their further study in the context of cardiovascular disease.

Chemoenzymatic Synthesis, Characterization, and Scale-Up of Milk Thistle Flavonolignan Glucuronides.[Pubmed:26316643]

Drug Metab Dispos. 2015 Nov;43(11):1734-43.

Plant-based therapeutics, including herbal products, continue to represent a growing facet of the contemporary health care market. Mechanistic descriptions of the pharmacokinetics and pharmacodynamics of constituents composing these products remain nascent, particularly for metabolites produced following herbal product ingestion. Generation and characterization of authentic metabolite standards are essential to improve the quantitative mechanistic understanding of herbal product disposition in both in vitro and in vivo systems. Using the model herbal product, milk thistle, the objective of this work was to biosynthesize multimilligram quantities of glucuronides of select constituents (flavonolignans) to fill multiple knowledge gaps in the understanding of herbal product disposition and action. A partnership between clinical pharmacology and natural products chemistry expertise was leveraged to optimize reaction conditions for efficient glucuronide formation and evaluate alternate enzyme and reagent sources to improve cost effectiveness. Optimized reaction conditions used at least one-fourth the amount of microsomal protein (from bovine liver) and cofactor (UDP glucuronic acid) compared with typical conditions using human-derived subcellular fractions, providing substantial cost savings. Glucuronidation was flavonolignan-dependent. Silybin A, silybin B, isosilybin A, and Isosilybin B generated five, four, four, and three monoglucuronides, respectively. Large-scale synthesis (40 mg of starting material) generated three glucuronides of silybin A: silybin A-7-O-beta-D-glucuronide (15.7 mg), silybin A-5-O-beta-D-glucuronide (1.6 mg), and silybin A-4 -O-beta-D-glucuronide (11.1 mg). This optimized, cost-efficient method lays the foundation for a systematic approach to synthesize and characterize herbal product constituent glucuronides, enabling an improved understanding of mechanisms underlying herbal product disposition and action.

Description

Isosilybin B, a flavonolignan isolated from silymarin, has anti-prostate cancer (PCA) activity via inhibiting proliferation and inducing G1 phase arrest and apoptosis. Isosilybin B causes androgen receptor (AR) degradation.

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