Presence of Mycotoxins in Milk Thistle (Silybum marianum) Food Supplements: A Review

The consumption of herbal-based supplements, which are believed to have beneficial effects on human health with no side effects, has become popular around the world and this trend is still increasing. Silybum marianum (L.) Gaertn, commonly known as milk thistle (MT), is the most commonly studied herb associated with the treatment of liver diseases. The hepatoprotective effects of active substances in silymarin, with silybin being the main compound, have been demonstrated in many studies. However, MT can be affected by toxigenic micro-fungi and contaminated by mycotoxins with adverse effects. The beneficial effect of silymarin can thus be reduced or totally antagonized by mycotoxins. MT has proven to be affected by micro-fungi of the Fusarium and Alternaria genera, in particular, and their mycotoxins. Alternariol-methyl-ether (AME), alternariol (AOH), beauvericin (BEA), deoxynivalenol (DON), enniatin A (ENNA), enniatin A1 (ENNA1), enniatin B (ENNB), enniatin B1 (ENNB1), HT-2 toxin (HT-2), T-2 toxin (T-2), tentoxin (TEN), and zearalenone (ZEA) seem to be most significant in MT-based dietary supplements. This review focuses on summarizing cases of mycotoxins in MT to emphasize the need for strict monitoring and regulation, as mycotoxins in relation with MT-based dietary supplements are not covered by European Union legislation.

Safety and toxicity of silymarin, the major constituent of milk thistle extract: An updated review

Milk thistle (Silybum marianum) is a medicinal plant from the Asteraceae family. Silymarin is the major constituent of milk thistle extract and is a mixture of some flavonolignans such as silybin, which is the most active component of silymarin. It is most commonly known for its hepatoprotective effect. Also, studies have shown other therapeutic effects such as anticancer, anti-Alzheimer, anti-Parkinson, and anti-diabetic, so its safety is very important. It has no major toxicity in animals. Silymarin was mutagen in Salmonella typhimurium strains in the presence of metabolic enzymes. Silybin, silydianin, and silychristin were not cytotoxic and genotoxic at concentration of 100 μM. Silymarin is safe in humans at therapeutic doses and is well tolerated even at a high dose of 700 mg three times a day for 24 weeks. Some gastrointestinal discomforts occurred like nausea and diarrhea. One clinical trial showed silymarin is safe in pregnancy, and there were no anomalies. Consequently, caution should be exercised during pregnancy, and more studies are needed especially in humans. Silymarin has low-drug interactions, and it does not have major effects on cytochromes P-450. Some studies demonstrated that the use of silymarin must be with caution when co-administered with narrow therapeutic window drugs.

Pharmacokinetic Interactions between Drugs and Botanical Dietary Supplements

The use of botanical dietary supplements has grown steadily over the last 20 years despite incomplete information regarding active constituents, mechanisms of action, efficacy, and safety. An important but underinvestigated safety concern is the potential for popular botanical dietary supplements to interfere with the absorption, transport, and/or metabolism of pharmaceutical agents. Clinical trials of drug-botanical interactions are the gold standard and are usually carried out only when indicated by unexpected consumer side effects or, preferably, by predictive preclinical studies. For example, phase 1 clinical trials have confirmed preclinical studies and clinical case reports that St. John's wort (Hypericum perforatum) induces CYP3A4/CYP3A5. However, clinical studies of most botanicals that were predicted to interact with drugs have shown no clinically significant effects. For example, clinical trials did not substantiate preclinical predictions that milk thistle (Silybum marianum) would inhibit CYP1A2, CYP2C9, CYP2D6, CYP2E1, and/or CYP3A4. Here, we highlight discrepancies between preclinical and clinical data concerning drug-botanical interactions and critically evaluate why some preclinical models perform better than others in predicting the potential for drug-botanical interactions. Gaps in knowledge are also highlighted for the potential of some popular botanical dietary supplements to interact with therapeutic agents with respect to absorption, transport, and metabolism.

The therapeutic potential of milk thistle in diabetes

Milk thistle has been known for more than 2.000 years as a herbal remedy for a variety of disorders. It has mainly been used to treat liver and gallbladder diseases. Silibum marianum, the Latin term for the plant, and its seeds contain a whole family of natural compounds, called flavonolignans. Silimarin is a dry mixture of these compounds; it is extracted after processing with ethanol, methanol, and acetone. Silimarin contains mainly silibin A, silibin B, taxifolin, isosilibin A, isosilibin B, silichristin A, silidianin, and other compounds in smaller concentrations. Apart from its use in liver and gallbladder disorders, milk thistle has recently gained attention due to its hypoglycemic and hypolipidemic properties. Recently, a substance from milk thistle has been shown to possess peroxisome proliferator-activated receptor γ (PPARγ) agonist properties. PPARγ is the molecular target of thiazolidinediones, which are used clinically as insulin sensitizers to lower blood glucose levels in diabetes type 2 patients. The thiazolidinedione type of PPARγ ligands is an agonist with a very high binding affinity. However, this ligand type demonstrates a range of undesirable side effects, thus necessitating the search for new effective PPARγ agonists. Interestingly, studies indicate that partial agonism of PPARγ induces promising activity patterns by retaining the positive effects attributed to the full agonists, with reduced side effects. In this review, the therapeutic potential of milk thistle in the management of diabetes and its complications are discussed.

A phase I dose-finding study of silybin phosphatidylcholine (milk thistle) in patients with advanced hepatocellular carcinoma

PURPOSE

To determine the maximum tolerated dose per day of silybin phosphatidylcholine (Siliphos) in patients with advanced hepatocellular carcinoma (HCC) and hepatic dysfunction.

EXPERIMENTAL DESIGN

Patients with advanced HCC not eligible for other therapies based on poor hepatic function were enrolled in a phase I study of silybin phosphatidylcholine. A standard phase I design was used with 4 planned cohorts, dose escalating from 2, 4, 8, to 12 g per day in divided doses for 12 weeks.

RESULTS

Three participants enrolled in this single institution trial. All enrolled subjects consumed 2 g per day of study agent in divided doses. Serum concentrations of silibinin and silibinin glucuronide increased within 1 to 3 weeks. In all 3 patients, liver function abnormalities and tumor marker α-fetoprotein progressed, but after day 56 the third patient showed some improvement in liver function abnormalities and inflammatory biomarkers. All 3 participants died within 23 to 69 days of enrolling into the trial, likely from hepatic failure, but it could not be ruled out that deaths were possibly due to the study drug.

CONCLUSION

Short-term administration of silybin phosphatidylcholine in patients with advanced HCC resulted in detectable increases in silibinin and its metabolite, silibinin glucuronide. The maximum tolerated dose could not be established. Since patients died soon after enrollment, this patient population may have been too ill to benefit from an intervention designed to improve liver function tests.

Complementary and alternative medicine in epistaxis: a point worth considering during the patient's history

A large number of patients take complementary and alternative medicine (CAM) for a variety of reasons, but most do not inform their physicians. This has implications for safety, as many forms of herbal CAM are thought to have a variety of side-effects and may interact with conventional medicines with potentially adverse consequences. We present the case of an otherwise healthy 25-year-old man with difficult-to-control epistaxis. On further questioning, we learnt that he had recently started self-medicating with a combination of aspirin, garlic tablets and milk thistle. Garlic increases bleeding time and milk thistle alters the function of liver enzymes, both of which may have contributed to the difficulty in his management of epistaxis. This case highlights the importance of asking about CAM use when taking a patient's history, as it may have implications for management.

A randomized, controlled, double-blind, pilot study of milk thistle for the treatment of hepatotoxicity in childhood acute lymphoblastic leukemia (ALL)

BACKGROUND

Despite limited preclinical and clinical investigations, milk thistle (MT) is often used for the treatment of chemotherapy-associated hepatotoxicity. Limited treatment options exist for chemotherapy-related hepatoxicity. Given the wide use of MT, the authors investigated MT in both the laboratory and a clinical setting.

METHODS

In a double-blind study, children with acute lymphoblastic leukemia (ALL) and hepatic toxicity were randomized to MT or placebo orally for 28 days. Liver function tests were evaluated during the study period. To assess MT in vitro, the authors evaluated supratherapeutic concentrations in an ALL cell line.

RESULTS

Fifty children were enrolled. No significant differences in frequency of side effects, incidence and severity of toxicities, or infections were observed between groups. There were no significant changes in mean amino alanine transferase (ALT), aspartate amino transferase (AST), or total bilirubin (TB) at Day 28. At Day 56, the MT group had a significantly lower AST (P = .05) and a trend toward a significantly lower ALT (P = .07). Although not significantly different, chemotherapy doses were reduced in 61% of the MT group compared with 72% of the placebo group. In vitro experiments revealed no antagonistic interactions between MT and vincristine or L-asparaginase in CCRF-CEM cells. A modest synergistic effect with vincristine was observed.

CONCLUSIONS

In children with ALL and liver toxicity, MT was associated with a trend toward significant reductions in liver toxicity. MT did not antagonize the effects of chemotherapy agents used for the treatment of ALL. Future study is needed to determine the most effective dose and duration of MT and its effect on hepatotoxicity and leukemia-free survival.

Advances in the use of milk thistle (Silybum marianum)

Milk thistle (Silybum marianum) is an herbal supplement used to treat liver and biliary disorders. Silymarin, a mixture of flavanoid complexes, is the active component that protects liver and kidney cells from toxic effects of drugs, including chemotherapy. Although milk thistle has not significantly altered the course of chronic liver disease, it has reduced liver enzyme levels and demonstrated anti-inflammatory and T cell-modulating effects. There is strong preclinical evidence for silymarin's hepatoprotective and anticarcinogenic effects, including inhibition of cancer cell growth in human prostate, skin, breast, and cervical cells. Milk thistle is considered safe and well-tolerated, with gastrointestinal upset, a mild laxative effect, and rare allergic reaction being the only adverse events reported when taken within the recommended dose range. More clinical trials of rigorous methodology, using standardized and well-defined products and dosages, are needed to evaluate the potential of silymarin against liver toxicity, chronic liver disease, and human cancers.

Future directions for research on Silybum marianum for cancer patients

Silymarin (Silybum marianum [L.] Gaertn. [Asteraceae]) is a promising agent for cancer prevention, adjuvant cancer treatment, and reduction of iatrogenic toxicity. Although it is safe and free of serious adverse side effects, few studies have evaluated its use alongside conventional cytotoxic therapies, and adverse events associated with long-term administration are uncertain. Although it may prevent some types of cancer, its promotion of tissue regeneration and its potential estrogen activity could promote the growth of some tumors. Further clinical trials using authenticated fractions of silymarin as simple and complex derivatives are required prior to any general recommendations. Future research should focus on authentication of active chemicals, pharmacokinetics, adverse interactions and quality control, prevention of cancer initiation and progression, adjuvant therapy for specific cancers, and prevention of toxicity from anticancer therapies.

Clinical applications of Silybum marianum in oncology

Milk thistle (Silybum marianum) is an herb that is increasingly used in oncology research and treatment settings. Historically, it has been used to treat liver and biliary disorders and has been used in detoxification and cleansing protocols. However, milk thistle is increasingly being investigated for its use in adult and pediatric populations for oncology indications. Possible indications during cancer treatment include cleansing and detoxification after chemotherapy, preventing hepatotoxicity during chemotherapy, treating hepatotoxicity after chemotherapy, and potentiating chemotherapy and radiation therapy as an adjunctive treatment. Milk thistle may also have applications in ameliorating long-term hepatic and cardiovascular effects of cancer treatment. Preliminary studies are investigating its use as a chemopreventive agent and possibly to treat cancer directly. Much of milk thistle's current clinical use grows out of historical uses but is informed by an increasing number of clinical trials and animal studies. This article provides an overview of the current clinical applications of milk thistle in the oncology setting, including guidelines on commonly used forms and doses.

Immunostimulatory effect of Silybum Marianum (milk thistle) extract

BACKGROUND

Herbal products are increasingly used for their effects on the immune system. Milk Thistle, a commonly used herbal product is known to inhibit growth of certain tumors, although the mechanism of this effect remains unknown. Previously we have shown that Milk Thistle extracts stimulate neurons in culture. Since other drugs that affect the neuronal; system also affect the immune system, we investigated the effects of Milk Thistle on the immune system.

MATERIAL/METHODS

Standardized Milk Thistle extract was studied in murine lymphocyte proliferation tests using Concanavalin A (ConA) as mitogen for non-specific stimulation and mixed lymphocyte culture (MLC) as allospecific stimulation. Th1 and Th2 cytokine levels in MLC were assayed by two antibody capture ELISA technique. All tests were performed in triplicate and repeated twice.

RESULTS

We found that Milk Thistle is immunostimulatory in vitro. It increased lymphocyte proliferation in both mitogen and MLC assays. These effects of Milk Thistle were associated with an increase in interferon gamma, interleukin (IL)-4 and IL-10 cytokines in the MLC (table). This immunostimulatory effect increased in response to increasing doses of Milk Thistle.

CONCLUSIONS

Our study has uncovered a novel effect of milk thistle on the immune system. This immunostimulatory effect may be of benefit in increasing the immunity to infectious diseases.

Milk thistle for the treatment of liver disease: a systematic review and meta-analysis

PURPOSE

Milk thistle, an herbal compound, is the dietary supplement taken most frequently by patients with chronic liver disease. We performed a systematic review of the literature to determine the efficacy and safety of this herb for the treatment of liver disease.

METHODS

We searched English and non-English reports through July 1999 using thirteen databases and reference lists, and contacting manufacturers and technical experts. Reviewers independently screened all reports to identify randomized placebo-controlled trials that evaluated milk thistle for the treatment of liver disease. Outcomes of primary interest included mortality, histological findings on liver biopsy specimens, serum aminotransferase and albumin levels, and prothrombin times.

RESULTS

Fourteen trials met inclusion criteria. Four trials reported outcomes for mortality among 433 participants. The overall summary odds ratio for mortality in the milk thistle group compared with placebo was 0.8 (95% confidence interval [CI]: 0.5 to 1.5; P = 0.6). Three trials assessed histology on liver biopsy; study quality was inversely associated with the likelihood of histological benefit for milk thistle compared with placebo. There were no differences in serum alanine aminotransferase, aspartate aminotransferase, or albumin levels, or prothrombin times, among participants assigned to milk thistle compared with those assigned to placebo. The only statistically significant difference was a greater reduction in alanine aminotransferase levels among patients with chronic liver disease assigned to milk thistle (-9 IU/L, 95% CI: -18 to -1 IU/L; P = 0.05), but this reduction was of negligible clinical importance and no longer statistically significant after limiting analyses to studies of longer duration or of higher quality. The frequency of adverse effects was low and, in clinical trials, indistinguishable from placebo.

CONCLUSION

Treatment with milk thistle appears to be safe and well tolerated. We found no reduction in mortality, in improvements in histology at liver biopsy, or in biochemical markers of liver function among patients with chronic liver disease. Data are too limited to exclude a substantial benefit or harm of milk thistle on mortality, and also to support recommending this herbal compound for the treatment of liver disease.

Effect of milk thistle on the pharmacokinetics of indinavir in healthy volunteers

STUDY OBJECTIVE

To characterize the pharmacokinetics of indinavir in the presence and absence of milk thistle and to determine the offset of any effect of milk thistle on indinavir disposition.

DESIGN

Prospective open-label drug interaction study.

SETTING

Outpatient clinic.

SUBJECTS

Ten healthy volunteers. Intervention. Blood samples were collected over 8 hours after the volunteers took four doses of indinavir 800 mg every 8 hours on an empty stomach for baseline pharmacokinetics. This dosing and sampling were repeated after the subjects took milk thistle 175 mg (confirmed to contain silymarin 153 mg, the active ingredient) 3 times/day for 3 weeks. After an 11-day washout, indinavir dosing and blood sampling were repeated to evaluate the offset of any potential interaction.

MEASUREMENTS AND MAIN RESULTS

Indinavir concentrations were measured by using a validated high-performance liquid chromatography method. The following pharmacokinetic parameters were determined: highest concentration (Cmax), hour-0 concentration, hour-8 concentration (C8), time to reach Cmax, and area under the plasma concentration-time curve over the 8-hour dosing interval (AUC8). Milk thistle did not alter significantly the overall exposure of indinavir, as evidenced by a 9% reduction in the indinavir AUC8 after 3 weeks of dosing with milk thistle, although the least squares mean trough level (C8) was significantly decreased by 25%.

CONCLUSION

Milk thistle in commonly administered dosages should not interfere with indinavir therapy in patients infected with the human immunodeficiency virus.

Milk thistle and the treatment of hepatitis

Gastroenterology nurses and associates will find it helpful to be informed about milk thistle (silybum marianum), a popular, safe and promising herb used by patients with liver disease. Silymarin is a derivative from the milk thistle plant with few side effects that has been safely used for centuries to treat liver ailments. Since the 1970s, there has been a reemergence of the marketing and use of silymarin. Research results of some small studies suggest silymarin has hepatoprotective, antiinflammatory, and regenerative properties producing a beneficial effect for some types of hepatitis. It is unclear, however, whether silymarin might interfere with the effect of interferon or ribavirin. A well-designed, placebo-controlled study of a larger population is needed. It is certainly encouraging that a large collaborative study is currently underway for milk thistle therapy in hepatitis C. This study is funded by NCCAM, the National Institute of Allergy and Infectious Diseases (NIAID), and the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Research updates are available online at www.nccam.nih.gov and through the NCCAM Clearinghouse at 1-888-644-6226.