Silymarin as Supportive Treatment in Liver Diseases: A Narrative Review

Silymarin, an extract from milk thistle seeds, has been used for centuries to treat hepatic conditions. Preclinical data indicate that silymarin can reduce oxidative stress and consequent cytotoxicity, thereby protecting intact liver cells or cells not yet irreversibly damaged. Eurosil 85® is a proprietary formulation developed to maximize the oral bioavailability of silymarin. Most of the clinical research on silymarin has used this formulation. Silymarin acts as a free radical scavenger and modulates enzymes associated with the development of cellular damage, fibrosis and cirrhosis. These hepatoprotective effects were observed in clinical studies in patients with alcoholic or non-alcoholic fatty liver disease, including patients with cirrhosis. In a pooled analysis of trials in patients with cirrhosis, silymarin treatment was associated with a significant reduction in liver-related deaths. Moreover, in patients with diabetes and alcoholic cirrhosis, silymarin was also able to improve glycemic parameters. Patients with drug-induced liver injuries were also successfully treated with silymarin. Silymarin is generally very well tolerated, with a low incidence of adverse events and no treatment-related serious adverse events or deaths reported in clinical trials. For maximum benefit, treatment with silymarin should be initiated as early as possible in patients with fatty liver disease and other distinct liver disease manifestations such as acute liver failure, when the regenerative potential of the liver is still high and when removal of oxidative stress, the cause of cytotoxicity, can achieve the best results.

Silybin, a Major Bioactive Component of Milk Thistle (Silybum marianum L. Gaernt.)-Chemistry, Bioavailability, and Metabolism

Milk thistle (Silybum marianum) is a medicinal plant that has been used for thousands of years as a remedy for a variety of ailments. The main component of S. marianum fruit extract (silymarin) is a flavonolignan called silybin, which is not only the major silymarin element but is also the most active ingredient of this extract, which has been confirmed in various studies. This compound belongs to the flavonoid group known as flavonolignans. Silybin's structure consists in two main units. The first is based on a taxifolin, the second a phenyllpropanoid unit, which in this case is conyferil alcohol. These two units are linked together into one structure by an oxeran ring. Since the 1970s, silybin has been regarded in official medicine as a substance with hepatoprotective properties. There is a large body of research that demonstrates silybin's many other healthy properties, but there are still a lack of papers focused on its molecular structure, chemistry, metabolism, and novel form of administration. Therefore, the aim of this paper is a literature review presenting and systematizing our knowledge of the silybin molecule, with particular emphasis on its structure, chemistry, bioavailability, and metabolism.

Enhanced bioavailability of silymarin by self-microemulsifying drug delivery system

The main purpose of this study was to prepare lipid-based self-microemulsifying drug delivery system (SMEDDS) to improve peroral bioavailability of silymarin. SMEDDS was a system consisting of silymarin, Tween 80, ethyl alcohol, and ethyl linoleate. Particle size change of the microemulsion was evaluated upon dilution with aqueous media and loading with incremental amount of silymarin. In vitro release was investigated by a dialysis or an ultrafiltration method. Results showed that release of silymarin from SMEDDS was limited, incomplete, and typical of sustained characteristics. Pharmacokinetics and bioavailability of silymarin suspension, solution, and SMEDDS were evaluated and compared in rabbits. Plasma silybin, which was treated as the representing component of silymarin, was determined by high-performance liquid chromatography. After gavage administration of silymarin suspension, plasma silybin level was very low and fell below limit of detection 4h after. As for silymarin solution and SMEDDS, double peak of maximum concentrations were observed, which was characteristic of enterohepatic circulation. Relative bioavailability of SMEDDS was dramatically enhanced in an average of 1.88- and 48.82-fold that of silymarin PEG 400 solution and suspension, respectively. It was concluded that bioavailability of silymarin was enhanced greatly by SMEDDS. Alternative mechanisms, such as improved lymphatic transport pathway, other than improved release may contribute to enhancement of bioavailability of silymarin.

Silybin combined with phosphatidylcholine and vitamin E in patients with nonalcoholic fatty liver disease: a randomized controlled trial

The only currently recommended treatment for nonalcoholic fatty liver disease (NAFLD) is lifestyle modification. Preliminary studies of silybin showed beneficial effects on liver function. Realsil (RA) comprises the silybin phytosome complex (silybin plus phosphatidylcholine) coformulated with vitamin E. We report on a multicenter, phase III, double-blind clinical trial to assess RA in patients with histologically documented NAFLD. Patients were randomized 1:1 to RA or placebo (P) orally twice daily for 12 months. Prespecified primary outcomes were improvement over time in clinical condition, normalization of liver enzyme plasma levels, and improvement of ultrasonographic liver steatosis, homeostatic model assessment (HOMA), and quality of life. Secondary outcomes were improvement in liver histologic score and/or decrease in NAFLD score without worsening of fibrosis and plasma changes in cytokines, ferritin, and liver fibrosis markers. We treated 179 patients with NAFLD; 36 were also HCV positive. Forty-one patients were prematurely withdrawn and 138 patients analyzed per protocol (69 per group). Baseline patient characteristics were generally well balanced between groups, except for steatosis, portal infiltration, and fibrosis. Adverse events (AEs) were generally transient and included diarrhea, dysgeusia, and pruritus; no serious AEs were recorded. Patients receiving RA but not P showed significant improvements in liver enzyme plasma levels, HOMA, and liver histology. Body mass index normalized in 15% of RA patients (2.1% with P). HCV-positive patients in the RA but not the P group showed improvements in fibrogenesis markers. This is the first study to systematically assess silybin in NAFLD patients. Treatment with RA but not P for 12 months was associated with improvement in liver enzymes, insulin resistance, and liver histology, without increases in body weight. These findings warrant further investigation.

Silibinin is a potent antiviral agent in patients with chronic hepatitis C not responding to pegylated interferon/ribavirin therapy

BACKGROUND & AIMS

Oral Silibinin (SIL) is widely used for treatment of hepatitis C, but its efficacy is unclear. Substantially higher doses can be administered intravenously (IV).

METHODS

Pedigreed nonresponders to full-dose pegylated (Peg)-interferon/ribavirin (PegIFN/RBV) were studied. First, 16 patients received 10 mg/kg/day SIL IV (Legalon Sil; Madaus, Köln, Germany) for 7 days. In a subsequent dose-finding study, 20 patients received 5, 10, 15, or 20 mg/kg/day SIL for 14 days. In both protocols, PegIFN alpha-2a/RBV were started on day 8. Viral load was determined daily.

RESULTS

Unexpectedly, in the first study, HCV-RNA declined on IV SIL by 1.32 +/- 0.55 log (mean +/- SD), P < .001 but increased again in spite of PegIFN/RBV after the infusion period. The viral load decrease was dose dependent (log drop after 7 days SIL: 0.55 +/- 0.5 [5 mg/kg, n = 3], 1.41 +/- 0.59 [10 mg/kg, n = 19], 2.11 +/- 1.34 [15 mg/kg, n = 5], and 3.02 +/- 1.01 [20 mg/kg, n = 9]; P < .001), decreased further after 7 days combined SIL/PegIFN/RBV (1.63 +/- 0.78 [5 mg/kg, n = 3], 4.16 +/- 1.28 [10 mg/kg, n = 3], 3.69 +/- 1.29 [15 mg/kg, n = 5], and 4.85 +/- 0.89 [20 mg/kg, n = 9]; P < .001), and became undetectable in 7 patients on 15 or 20 mg/kg SIL, at week 12. Beside mild gastrointestinal symptoms, IV SIL monotherapy was well tolerated.

CONCLUSIONS

IV SIL is well tolerated and shows a substantial antiviral effect against HCV in nonresponders.

Protective effect of silymarin on oxidative stress in rat brain

Brain is susceptible to oxidative stress and it is associated with age-related brain dysfunction. Previously, we have pointed out a dramatic decrease of glutathione levels in the rat brain after acetaminophen (APAP) oral administration overdose. Silymarin (SM) is a mixture of bioactive flavonolignans isolated from Silybum marianum (L.) Gaertn., employed usually in the treatment of alcoholic liver disease and as anti-hepatotoxic agent in humans. In this study, we have evaluated the effect of SM on enzymatic and non enzymatic antioxidant defensive systems in rat brain after APAP-induced damage. Male albino Wistar rats were treated with SM (200 mg/kg/die orally) for three days, or with APAP single oral administration (3 g/kg) or with SM (200 mg/kg/die orally) for 3 days and APAP single oral administration (3 g/kg) at third day. Successively the following parameters were measured: reduced and oxidized glutathione (GSH and GSSG), ascorbic acid (AA), enzymatic activity variations of superoxide dismutase (SOD) and malondialdehyde levels (MDA). Our results showed a significant decrease of GSH levels, AA levels and SOD activity and an increase of MDA and GSSG levels after APAP administration. After SM administration GSH and AA significantly increase and SOD activity was significantly enhanced. In the SM+APAP group, GSH values significantly increase and the others parameters remained unchanged respect to control values. These results suggest that SM may to protect the SNC by oxidative damage for its ability to prevent lipid peroxidation and replenishing the GSH levels.

Analysis of silibinin in rat plasma and bile for hepatobiliary excretion and oral bioavailability application

Silibinin is an herbal ingredient isolated from milk thistle. The aim of this study was to develop a simple liquid chromatographic system to assay silibinin in plasma and bile for pharmacokinetic study. Silibinin was given oral and intravenously. The plasma sample (25 microL) was vortex-mixed with 50 microL of internal standard solution (naringenin 10 microg/mL in acetonitrile) to achieve protein precipitation. Silibinin in the rat plasma and bile was separated using a reversed-phase C18 column (250 mm x 4.6 mm, 5 microm) with a mobile phase of acetonitrile -10 mM monosodium phosphate (pH 5.45 adjusted with orthophosphoric acid) (50:50, v/v) and the flow-rate of 1 mL/min. The UV detection wavelength was 288 nm. The concentration-response relationship from the present method indicated linearity over a concentration range of 0.5-100 microg/mL. Intra- and inter-assay precision and accuracy of silibinin fell well within the predefined limits of acceptability (<15%). An ultrafiltration method was used in this experiment and the protein binding of silibinin was 70.3+/-4.6%. After silibinin administration in rats, the disposition of silibinin in the plasma and bile fluid was due to rapid distribution and equilibration between the blood and hepatobiliary system, and the bile levels of unconjugated silibinin and total silibinin were greater than those in the plasma. The oral bioavailability of silibinin in rats was estimated to be 0.73%.

Amelioration of lead toxicity on rat liver with Vitamin C and silymarin supplements

The aim of the present study was to investigate the impact of the combined administration of Vitamin C and silymarin on lead toxicity. Male albino rats were subdivided into three groups: the first was a control group, the second received lead acetate in diet as 500 mg/kg diet daily, the third received the same lead acetate dose and supplemented with Vitamin C (1 mg/100g body weight) and silymarin (1 mg/100g body weight) by gastric tube three times per week. Blood samples were taken after 2, 4 and 6 weeks of treatment. Significant lead-induced elevations in serum ALT, AST, GGT and ALP activities were observed after different periods of treatment. However, serum LDLc was decreased. The intensities of RNA and apoptotic fragments of DNA were measured as optical density by Gel-pro program. Lead acetate decreased the intensity of DNA at 6 weeks and induced apoptotic DNA fragments reversibly with time. After 2 weeks of lead administration dilation and congestion of terminal hepatic veins and portal vein branches were observed. Lead also induced hepatocyte proliferation without any localized distribution among zones 1-3. Portal inflammatory infiltrate with disruption of the limiting plates (interface hepatitis), steatosis, apoptosis and mild fibrosis were detected especially by sixth week of lead administration. Combined treatment of lead-exposed animals with Vitamin C and silymarin showed marked improvement of the biochemical, molecular and histopathological findings. These experimental results strongly indicate the protective effect of Vitamin C and silymarin against toxic effects of lead on liver tissue.

Pharmacokinetic studies on IdB 1016, a silybin- phosphatidylcholine complex, in healthy human subjects

IdB 1016 is a complex of silybin (the main active component of silymarin) and phosphatidylcholine, which in animal models shows greater oral bioavailability and therefore greater pharmacological activity compared with pure silybin and silymarin. In order to assess its pharmacokinetic profile in man, plasma silybin levels were determined after administration of single oral doses of IdB 1016 and silymarin (equivalent to 360 mg silybin) to 9 healthy volunteers. Although absorption was rapid with both preparations, the bioavailability of IdB 1016 was much greater than that of silymarin, as indicated by higher plasma silybin levels at all sampling times after intake of the complex. Regardless of the preparation used, the terminal half-life was relatively short (generally less than 4 h). In a subsequent study, 9 healthy volunteers received IdB 1016 (120 mg b.i.d., expressed as silybin equivalents) for 8 consecutive days. The plasma silybin level profiles and kinetic parameters on day 1 were similar to those determined on day 8. Most of the silybin present in the systemic circulation was in conjugated form. Less than 3% of the administered dose was accounted for by urinary recovery of free plus conjugated silybin, a significant proportion of the dose probably being excreted in the bile. It is concluded that complexation with phosphatidylcholine in IdB 1016 greatly increases the oral bioavailability of silybin, probably by facilitating its passage across the gastrointestinal mucosa.

Pilot study of oral silibinin, a putative chemopreventive agent, in colorectal cancer patients: silibinin levels in plasma, colorectum, and liver and their pharmacodynamic consequences

Silibinin, a flavonolignan from milk thistle, has intestinal cancer chemopreventive efficacy in rodents. It is a strong antioxidant and modulates the insulin-like growth factor (IGF) system by increasing circulating levels of IGF-binding protein 3 (IGFBP-3) and decreasing levels of IGF-I. Here, the hypothesis was tested that administration of oral silibinin generates agent levels in human blood and colorectal and hepatic tissues consistent with pharmacologic activity. Patients with confirmed colorectal adenocarcinoma received silibinin formulated with phosphatidylcholine (silipide) at dosages of 360, 720, or 1,440 mg silibinin daily for 7 days. Blood and biopsy samples of normal and malignant colorectum or liver were obtained before dosing, and blood and colorectal or hepatic tissues were collected at resection surgery after the final silipide dose. Levels of silibinin were quantified by high-pressure liquid chromatography-UV, and plasma metabolites were identified by liquid chromatography-mass spectrometry. Blood levels of IGFBP-3, IGF-I, and the oxidative DNA damage pyrimidopurinone adduct of deoxyguanosine (M1dG) were determined. Repeated administration of silipide was safe and achieved levels of silibinin of 0.3 to 4 micromol/L in the plasma, 0.3 to 2.5 nmol/g tissue in the liver, and 20 to 141 nmol/g tissue in colorectal tissue. Silibinin monoglucuronide, silibinin diglucuronide, silibinin monosulfate, and silibinin glucuronide sulfate were identified in the plasma. Intervention with silipide did not affect circulating levels of IGFBP-3, IGF-I, or M1dG. The high silibinin levels achieved in the human colorectal mucosa after consumption of safe silibinin doses support its further exploration as a potential human colorectal cancer chemopreventive agent.

Effect of silymarin (milk thistle) on liver disease in patients with chronic hepatitis C unsuccessfully treated with interferon therapy: a randomized controlled trial

CONTEXT

The botanical product silymarin, an extract of milk thistle, is commonly used by patients to treat chronic liver disease, despite scant and conflicting evidence of its efficacy.

OBJECTIVE

To determine the effect of silymarin on liver disease activity in patients with chronic hepatitis C virus (HCV) infection unsuccessfully treated with interferon-based therapy.

DESIGN, SETTING, AND PARTICIPANTS

Multicenter, double-blind, placebo-controlled trial conducted at 4 medical centers in the United States. Participants included 154 persons with chronic HCV infection and serum alanine aminotransferase (ALT) levels of 65 U/L or greater who were previously unsuccessfully treated with interferon-based therapy. Enrollment began in May 2008 and was completed in May 2010, with the last follow-up visit completed in March 2011.

INTERVENTION

Participants were randomly assigned to receive 420-mg silymarin, 700-mg silymarin, or matching placebo administered 3 times per day for 24 weeks.

MAIN OUTCOME MEASURES

The primary outcome measure was serum ALT level of 45 U/L or less (considered within the normal range) or less than 65 U/L, provided this was at least a 50% decline from baseline values. Secondary outcomes included changes in ALT levels, HCV RNA levels, and quality-of-life measures.

RESULTS

After 24 weeks of treatment, only 2 participants in each treatment group (P ≥ .99) met the primary outcome measure (3.8% [95% CI, 0.5% to 13.2%] for placebo, 4.0% [95% CI, 0.5% to 13.7%] for 420-mg silymarin, and 3.8% [95% CI, 0.5% to 13.2%] for 700-mg silymarin). The mean decline in serum ALT activity at the end of treatment did not differ significantly (P = .75) across the 3 treatment groups (mean decline, -4.3 [95% CI, -17.3 to 8.7] U/L for placebo, -14.4 [95% CI, -41.6 to 12.7] U/L for 420-mg silymarin, -11.3 [95% CI, -27.9 to 5.4] U/L for 700-mg silymarin); there likewise were no significant differences in HCV RNA levels (mean change, 0.07 [95% CI, -0.05 to 0.18] log10 IU/mL for placebo, -0.03 [95% CI, -0.18 to 0.12] log10 IU/mL for 420-mg silymarin, 0.04 [95% CI, -0.08 to 0.16] log10 IU/mL for 700-mg silymarin; P = .54) or quality-of-life measures. The adverse event profile of silymarin was comparable with that of placebo.

CONCLUSION

Higher than customary doses of silymarin did not significantly reduce serum ALT levels more than placebo in participants with chronic HCV infection unsuccessfully treated with interferon-based therapy.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00680342.

Hepatoprotective effects of rubiadin, a major constituent of Rubia cordifolia Linn

The hepatoprotective effects of rubiadin, a major constituent isolated from Rubia cordifolia Linn., were evaluated against carbon tetrachloride (CCl4)-induced hepatic damage in rats. Rubiadin at a dose of 50, 100 and 200 mg/kg was administered orally once daily for 14 days. The substantially elevated serum enzymatic activities of serum glutamic oxaloacetic transaminase (SGOT), serum glutamate pyruvate transaminase (SGPT), serum alkaline phosphatase (SALP) and gamma-glutamyltransferase (gamma-GT) due to carbon tetrachloride treatment were dose dependently restored towards normalization. Meanwhile, the decreased activities of glutathione S-transferase and glutathione reductase were also restored towards normalization. In addition, rubiadin also significantly prevented the elevation of hepatic malondialdehyde formation and depletion of reduced glutathione content in the liver of CCl4 intoxicated rats in a dose dependent manner. Silymarin used as standard reference also exhibited significant hepatoprotective activity on post treatment against carbon tetrachloride induced hepatotoxicity in rats. The biochemical observations were supplemented with histopathological examination of rat liver sections. The results of this study strongly indicate that rubiadin has a potent hepatoprotective action against carbon tetrachloride induced hepatic damage in rats.

Anti-oxidant activities of fucosterol from the marine algae Pelvetia siliquosa

The anti-oxidant activities of fucosterol isolated from the marine algae Pelvetia siliquosa were investigated. Fucosterol exhibited a significant decrease in serum transaminase activities elevated by hepatic damage induced by CCl4-intoxication in rats. Fucosterol inhibited the sGOT and sGPT activities by 25.57 and 63.16%, respectively. Fucosterol showed the increase in the anti-oxidant enzymes such as hepatic cytosolic superoxide dismutase (SOD), catalase and glutathione peroxidase (GSH-px) activities by 33.89, 21.56 and 39.24%, respectively, in CCl4-intoxicated rats. These results suggest that fucosterol possess not only the anti-oxidant, but also the hepatoprotective activities in rats.

Hepatitis C virus and natural compounds: a new antiviral approach?

Hepatitis C is a major global health burden with an estimated 160 million infected individuals worldwide. This long-term disease evolves slowly, often leading to chronicity and potentially to liver failure. There is no anti-HCV vaccine, and, until recently, the only treatment available, based on pegylated interferon and ribavirin, was partially effective, and had considerable side effects. With recent advances in the understanding of the HCV life cycle, the development of promising direct acting antivirals (DAAs) has been achieved. Their use in combination with the current treatment has led to encouraging results for HCV genotype 1 patients. However, this therapy is quite expensive and will probably not be accessible for all patients worldwide. For this reason, constant efforts are being made to identify new antiviral molecules. Recent reports about natural compounds highlight their antiviral activity against HCV. Here, we aim to review the natural molecules that interfere with the HCV life cycle and discuss their potential use in HCV therapy.

Silibinin protects against photocarcinogenesis via modulation of cell cycle regulators, mitogen-activated protein kinases, and Akt signaling

Here, we assessed the protective effect of silibinin on UVB-induced skin carcinogenesis in SKH-1 hairless mice. Topical application of silibinin before or immediately after UVB exposure or its dietary feeding resulted in a strong protection against photocarcinogenesis, in terms of tumor multiplicity (60-66%; P < 0.001), tumor volume per mouse (93-97%; P < 0.001) and tumor volume per tumor (80-91%; P < 0.001). Silibinin also moderately inhibited tumor incidence (5-15%; P < 0.01) and delayed tumor latency period (up to 4 weeks; P < 0.01-0.001). To investigate in vivo molecular mechanisms of silibinin efficacy, tumors and uninvolved skin from tumor-bearing mice were examined immunohistochemically for proliferation, p53, apoptosis, and activated caspase-3. Silibinin treatment showed a strong decrease (P < 0.001) in proliferating cell nuclear antigen-positive cells and an increase in p53-positive (P < 0.005-0.001), terminal deoxynucleotidyltransferase-mediated nick end labeling-positive (P < 0.005-0.001), and cleaved caspase-3-positive cells (P < 0.001). Western blot analysis of normal skin and tumor lysates showed that silibinin decreases the levels of cyclin-dependent kinase 2 and cyclin-dependent kinase 4 and associated cyclins A, E, and D1, together with an up-regulation of Cip1/p21, Kip1/p27, and p53. Silibinin also showed a strong phosphorylation of extracellular signal-regulated protein kinase 1/2, stress-activated protein kinase/c-JUN NH2-terminal kinase 1/2, and p38 mitogen-activated protein kinases but inhibited Akt phosphorylation and decreased survivin levels with an increase in cleaved caspase-3. Together, these results show a strong preventive efficacy of silibinin against photocarcinogenesis, which involves the inhibition of DNA synthesis, cell proliferation, and cell cycle progression and an induction of apoptosis. Furthermore, these results also identify in vivo molecular mechanisms of silibinin efficacy against photocarcinogenesis.

Effect of addition of silymarin to renin-angiotensin system inhibitors on proteinuria in type 2 diabetic patients with overt nephropathy: a randomized, double-blind, placebo-controlled trial

BACKGROUND

A large proportion of patients with type 2 diabetes mellitus have diabetic nephropathy. Despite current therapies including renin-angiotensin system inhibitors, diabetic nephropathy progresses to end-stage renal disease in most of these patients. Therefore, there is an urgent need to find new treatments for such patients. The aim of this study was to evaluate the efficacy of silymarin, an herbal drug with antioxidant and anti-inflammatory properties, in preventing the progression of diabetic nephropathy.

STUDY DESIGN

Randomized, double-blind, placebo-controlled, 2-arm parallel trial.

SETTING & PARTICIPANTS

60 patients with type 2 diabetes with macroalbuminuria (urinary albumin excretion >300 mg/24 h) despite treatment with the maximum dose of a renin-angiotensin system inhibitor for more than 6 months and estimated glomerular filtration rate >30 mL/min/1.73 m(2).

INTERVENTION

Patients were randomly assigned to 2 equal groups to receive three 140-mg tablets of silymarin or 3 tablets of placebo daily for 3 months.

OUTCOMES

The primary outcome was absolute change in urinary albumin-creatinine ratio (UACR) from baseline to the end of the treatment phase.

MEASUREMENTS

UACR and urinary and serum levels of TNF-α (tumor necrosis factor α; an inflammatory marker), malondialdehyde (MDA; an oxidative stress marker), and TGFβ (transforming growth factor β; a marker of fibrosis) at baseline and the end of the treatment phase.

RESULTS

Although UACR decreased in both groups, this decrement was significantly higher in the silymarin compared with the placebo group; mean difference in change in UACR between the 2 groups was -347 (95% CI, -690 to -4) mg/g. Urinary levels of TNF-α and urinary and serum levels of MDA also decreased significantly in the silymarin compared with the placebo group.

LIMITATIONS

Small sample size and short duration of the treatment phase.

CONCLUSIONS

Silymarin reduces urinary excretion of albumin, TNF-α, and MDA in patients with diabetic nephropathy and may be considered as a novel addition to the anti-diabetic nephropathy armamentarium.

Oral silibinin inhibits lung tumor growth in athymic nude mice and forms a novel chemocombination with doxorubicin targeting nuclear factor kappaB-mediated inducible chemoresistance

The acute and cumulative dose-related toxicity and drug resistance, mediated via nuclear factor kappaB (NFkappaB), of anthracycline anticancer drugs pose a major problem in cancer chemotherapy. Here, we report that oral silibinin (a flavanone) suppresses human non-small-cell lung carcinoma A549 xenograft growth (P = 0.003) and enhances the therapeutic response (P < 0.05) of doxorubicin in athymic BALB/c nu/nu mice together with a strong prevention of doxorubicin-caused adverse health effects. Immunohistochemical analyses of tumors showed that silibinin and doxorubicin decrease (P < 0.001) proliferation index and vasculature and increase (P < 0.001) apoptosis; these effects were further enhanced (P < 0.001) in combination treatment. Pharmacologic dose of silibinin (60 mumol/L) achieved in animal study was biologically effective (P < 0.01 to 0.001, growth inhibition and apoptosis) in vitro in A549 cell culture together with an increased efficacy (P < 0.05 to 0.001) in doxorubicin (25 nmol/L) combination. Furthermore, doxorubicin increased NFkappaB DNA binding activity as one of the possible mechanisms for chemoresistance in A549 cells, which was inhibited by silibinin in combination treatment. Consistent with this, silibinin inhibited doxorubicin-caused increased translocation of p65 and p50 from cytosol to nucleus. Silibinin also inhibited cyclooxygenase-2, an NFkappaB target, in doxorubicin combination. These findings suggest that silibinin inhibits in vivo lung tumor growth and reduces systemic toxicity of doxorubicin with an enhanced therapeutic efficacy most likely via an inhibition of doxorubicin-induced chemoresistance involving NFkappaB signaling.

Enhancement of oral bioavailability of the poorly water-soluble drug silybin by sodium cholate/phospholipid-mixed micelles

AIM

To evaluate a mixed micellar drug delivery system composed of sodium cholate and phospholipid for oral administration of silybin, a promising hepatoprotectants.

METHODS

The optimum formulation of sodium cholate/phospholipid-mixed micelles containing silybin was obtained based on the study of pseudo-ternary phase diagram. The dissolution of silybin-mixed micelles was investigated. The pharmacokinetic characteristics and bioavailability after oral administration of silybin-mixed micelles and silybin-N-methylglucamine were compared in dogs.

RESULTS

The mean particle size of prepared mixed micelles was 75.9+/-4.2 nm. The largest solubility of silybin was found to be 10.0+/-1.1 mg/mL in the optimum formulation of mixed micelles. The silybin-sodium cholate/phospholipid-mixed micelles showed a very slow release of silybin 17.5% (w/w) within 72 h in phosphate buffer (pH 7.4) and 15.6% (w/w) in HCl solution (pH 1.2). After oral administration to dogs, the relative bioavailability of mixed micelles versus silybin-N-methylglucamine in dogs was 252.0%.

CONCLUSION

Sodium cholate/phospholipid-mixed micelles are promising carriers in orally delivery of silybin, considering their capability of enhancing bioavailability and large-scale production.

Preparation of silymarin proliposome: a new way to increase oral bioavailability of silymarin in beagle dogs

The aim of the present study was to find a method to increase oral bioavailability of silymarin, that is to say, by the preparation of silymarin proliposome and to compare the pharmacokinetic characteristics and bioavailability after oral administration of silymarin proliposome and silymarin in beagle dogs. Silymarin proliposome was prepared by the film-deposition on carriers. After the proliposome was contacted with water, the silymarin liposome suspensions formed automatically. The tests of physicochemical properties including SEM, TEM, encapsulation efficiency, dissolution studies, particle size of the reconstituted liposome and stability of the silymarin proliposome were determined by laser-particle-sizer, HPLC, etc. The concentrations of silymarin in plasma of beagle dogs and its pharmacokinetic behaviors after oral administration of silymarin liposome suspensions and silymarin were studied by RP-HPLC. The pharmacokinetic parameters were computed by software program 3p97. The encapsulation efficiency of silymarin liposome could be more than 90%, with an average particle size of about 196.4 nm and the proliposome appeared a very stability at 40 degrees C during 3 months. It was found that mean plasma concentration-time curves of silymarin after oral administration of liposome suspensions and silymarin in beagle dogs were both in accordance with open two-compartments model and first-order absorption. Pharmacokinetic parameters of silymarin proliposome and silymarin in beagle dogs were Tmax both 30 min; Cmax 472.62 and 89.78 ng mL(-1); and AUC0-infinity 2606.21 and 697 ng mL(-1)h, respectively. The high bioavailability of silymarin proliposome could be obtained by oral administration. Silymarin proliposome was stable and did enchance the gastrointestinal absorption of silymarin.

Efficacy of silymarin-phospholipid complex in reducing the toxicity of aflatoxin B1 in broiler chicks

Silymarin, the standardized extract of Silybum marianum, is used as a hepatoprotector in man, and is a potent antihepatotoxic agent. This study focused on the effects of a silymarin-phospholipid complex in reducing the toxic effects of aflatoxin B1 (AFB1) in broiler chickens. Twenty-one 14-d-old male commercial broilers were randomly allotted to 3 groups and treated as follows: basal diet alone [Group C (Control)]; AFB1 at 0.8 mg/kg of feed [Group B1]; AFB1 at 0.8 mg/kg of feed plus silymarin phytosome, a silymarin complexed form with phospholipids from soy, at 600 mg/kg of BW [Group B1+Sil]. Considering the whole growth cycle, BW gain and feed intake were lower in AFB1-treated birds with respect to controls (P < 0.05). In the B1+Sil group, BW gain and feed intake were higher with respect to birds receiving AFB1 alone (P < 0.05), and not different from the control birds. Serum biochemistry showed no difference among groups, except for a decrease of alanine amino transferase (ALT) in chicks treated only with AFB1. Alanine amino transferase activity in AFB1 plus silymarin phytosome treated birds was not different from the controls. No treatment differences were noted on liver weight. In conclusion, our results suggest that silymarin phytosome can provide protection against the negative effects of AFB1 on performance of broiler chicks.

Effect of silybin and its congeners on human liver microsomal cytochrome P450 activities

Silybin and related flavonolignans form a major part of the Silybum marianum extract, silymarin, which has been used to treat liver diseases for hundreds of years. Although regarded as safe, many of the extract constituents remain thus far untested for their possible effects on liver biotransformation enzymes. Cytochromes P450 (CYP) are very important in this regard. We tested the effect of four flavonolignans: silybin, its hemisynthetic derivative dehydrosilybin, silydianin, and silycristin on three specific CYP activities: bufuralol 1'-hydroxylation (CYP2D6), p-nitrophenol hydroxylation (CYP2E1), and nifedipine oxidation (CYP3A4). All flavonolignans displayed dose-dependent inhibition of these activities with IC(50) values in the micromolar range. The inhibition was competitive or mixed as revealed by double reciprocal plots of kinetic experiments. However, the inhibition is not considered to be relevant for therapy because physiological concentrations of the individual flavonolignans do not exceed 0.5 microM. The data support the use of the extract as a dietary supplement.

Formulation and biopharmaceutical evaluation of silymarin using SMEDDS

Silymarin has been used to treat hepatobiliary diseases. However, it has a low bioavailability after being administered orally on account of its low solubility in water. In order to improve the dissolution rate, silymarin was formulated in the form of a self-microemulsifying drug delivery system (SMEDDS). The optimum formulation of SMEDDS containing silymarin was obtained based on the study of pseudo-ternary phase diagram. The SMEDDS consisted of 15% silymarin, 10% glyceryl monooleate as the oil phase, a mixture of polysorbate 20 and HCO-50 (1:1) as the surfactant, Transcutol as the cosurfactant with a surfactant/cosurfactant ratio of 1. The mean droplet size of the oil phase in the microemulsion formed from the SMEDDS was 67 nm. The % release of silybin from the SMEDDS after 6 hours was 2.5 times higher than that from the reference capsule. After its oral administration to rats, the bioavailability of the drug from the SMEDDS was 3.6 times higher than the reference capsule.

Silibinin suppresses PMA-induced MMP-9 expression by blocking the AP-1 activation via MAPK signaling pathways in MCF-7 human breast carcinoma cells

Matrix metalloproteinase-9 (MMP-9) plays an important role in the invasion and metastasis of cancer cells. In this study, we examined the inhibitory effect of silibinin, a flavonoid antioxidant from milk thistle (Silybum marianum L.) on PMA-induced MMP-9 expression in MCF-7 human breast carcinoma cells. Silibinin significantly and selectively suppressed PMA-induced MMP-9 expression in MCF-7. Silibinin has been found to inhibit PMA-induced MMP-9 gene transcriptional activity by blocking the activation of AP-1 via MAPK signaling pathways. Moreover, the Matrigel invasion assay showed that silibinin reduces PMA-induced invasion of MCF-7 cells. These results suggest that silibinin represents a potential anti-metastatic agent suppressing PMA-induced cancer cell invasion through the specific inhibition of AP-1-dependent MMP-9 gene expression.

Silymarin in non-cirrhotics with non-alcoholic steatohepatitis: A randomized, double-blind, placebo controlled trial

The botanical product silymarin, an extract of milk thistle, is commonly used by patients to treat chronic liver disease and may be a treatment for NASH due to its antioxidant properties. We aimed to assess the safety and efficacy of higher than customary doses of silymarin in non-cirrhotic patients with NASH. This exploratory randomized double-blind placebo controlled multicenter Phase II trial tested a proprietary standardized silymarin preparation (Legalon^®, Rottapharm|Madaus, Mylan) and was conducted at 5 medical centers in the United States. Eligible adult patients had liver biopsy within 12 months showing NASH without cirrhosis with NAFLD Activity Score (NAS) ≥4 per site pathologist’s assessment. Participants were randomized to Legalon^® 420 mg, 700 mg, or placebo t.i.d. for 48 weeks. The primary endpoint was histological improvement ≥2 points in NAS. Of 116 patients screened, 78 were randomized. There were no significant differences in adverse events among the treatment groups. After 48–50 weeks, 4/27 (15%) in the 700 mg dose, 5/26 (19%) participants randomized to 420 mg, and 3/25 (12%) of placebo recipients reached the primary endpoint (p = 0.79) among all randomized participants, indicating no benefit from silymarin in the intention to treat analysis Review by a central pathologist demonstrated that a substantial number of participants (49, 63%) did not meet histological entry criteria and that fibrosis stage improved most in the placebo treated group, although not significantly different from other groups. Silymarin (Legalon^®) at the higher than customary doses tested in this study is safe and well tolerated. The effect of silymarin in patients with NASH remains inconclusive due to the substantial number of patients who entered the study but did not meet entry histological criteria, the lack of a statistically significant improvement in NAS of silymarin treated patients, and the unanticipated effect of placebo on fibrosis indicate the need for additional clinical trials.

Trial Registration: clinicaltrials.gov, Identifier: NCT00680407.

Lipid peroxidation and irreversible damage in the rat hepatocyte model. Protection by the silybin-phospholipid complex IdB 1016

IdB 1016 is a new silybin-phospholipid complex which is more bioavailable than the flavonoid silybin itself and displays free radical scavenging and antioxidant properties in liver microsomes. We report here that the addition of increasing concentrations of IdB 1016 to isolated rat hepatocytes caused a dose-dependent inhibition of lipid peroxidation induced by ADP-Fe3+ or cumene hydroperoxide. Moreover, IdB 1016 at the concentration which completely prevented MDA formation also protected isolated hepatocytes against the toxicity of pro-oxidant agents such as allyl alcohol, cumene hydroperoxide and bromotrichloromethane, without interfering with the activation mechanism of these xenobiotics. Similar protection was also obtained in hepatocytes prepared from animals pretreated in vivo with IdB 1016 while rat supplementation with pure silybin was totally inefficient. These results indicate IdB 1016 as being a potentially useful protective agent against free radical-mediated toxic liver injury.