Chemoprotective effect of plant phenolics against anthracycline-induced toxicity on rat cardiomyocytes. Part I. Silymarin and its flavonolignans

Facilitated on-line supercritical fluid extraction - supercritical fluid chromatography for nonpolar and polar compounds from milk thistle seeds

Plant seeds, as those from milk thistle (Silybum marianum), are a valuable source of nonpolar and polar compounds with potentially interesting biological activity. The main nonpolar compounds are triglycerides, which are also the main components of all vegetable oils. In addition, specific polar compounds - flavonolignans, called silymarin, have been found in large amounts in milk thistle seeds extract. These flavonoids derivatives have different biological activity, for instance hepatoprotective effects. In order to extract and analyze both nonpolar (triglycerides) and polar compounds (flavonolignans) from milk thistle seeds through a sequential methodology, an on-line supercritical fluid extraction - supercritical fluid chromatography (SFE-SFC) method was developed. Different ways of transferring the extracts from SFE to SFC (i.e. direct on-column transfer and loop transfer) were compared, and particularly for their effect on chromatographic quality. In this respect, nonpolar and polar compounds caused different issues, especially as polar compounds required a significant portion of co-solvent in the extraction step, favoring early elution in the chromatographic column. First, on-line SFE-SFC was used for triglycerides analysis and allowed the comparison of transfer modes. Then, on-line kinetics were performed to measure defatting time before polar molecules extraction. Finally, the eventual benefit of loop transfer was also investigated for the analysis of flavonolignans, polar molecules whose analysis can be difficult by on-line SFE-SFC. The aim of this paper is to discuss the versatility of on-line SFE-SFC and how challenging the coupling can be, especially when both non-polar and polar molecules must be analyzed independently in a single sample.

A systematic review of the protective effects of silymarin/silibinin against doxorubicin-induced cardiotoxicity

PURPOSE

Although doxorubicin chemotherapy is commonly applied for treating different malignant tumors, cardiotoxicity induced by this chemotherapeutic agent restricts its clinical use. The use of silymarin/silibinin may mitigate the doxorubicin-induced cardiac adverse effects. For this aim, the potential cardioprotective effects of silymarin/silibinin against the doxorubicin-induced cardiotoxicity were systematically reviewed.

METHODS

In this study, we performed a systematic search in accordance with PRISMA guideline for identifying all relevant studies on "the role of silymarin/silibinin against doxorubicin-induced cardiotoxicity" in different electronic databases up to June 2022. Sixty-one articles were obtained and screened based on the predefined inclusion and exclusion criteria. Thirteen eligible papers were finally included in this review.

RESULTS

According to the echocardiographic and electrocardiographic findings, the doxorubicin-treated groups presented a significant reduction in ejection fraction, tissue Doppler peak mitral annulus systolic velocity, and fractional shortening as well as bradycardia, prolongation of QT and QRS interval. However, these echocardiographic abnormalities were obviously improved in the silymarin plus doxorubicin groups. As well, the doxorubicin administration led to induce histopathological and biochemical changes in the cardiac cells/tissue; in contrast, the silymarin/silibinin co-administration could mitigate these induced alterations (for most of the cases).

CONCLUSION

According to the findings, it was found that the co-administration of silymarin/silibinin alleviates the doxorubicin-induced cardiac adverse effects. Silymarin/silibinin exerts its cardioprotective effects via antioxidant, anti-inflammatory, anti-apoptotic activities, and other mechanisms.

The interplay of arsenic, silymarin, and NF-ĸB pathway in male reproductive toxicity: A review

Arsenic toxicity is one of the most trending reasons for several malfunctions, particularly reproductive toxicity. The exact mechanism of arsenic poisoning is a big question mark. Exposure to arsenic reduces sperm count, impairs fertilization, and causes inflammation and genotoxicity through interfering with autophagy, epigenetics, ROS generation, downregulation of essential protein expression, metabolite changes, and hampering several signaling cascades, particularly by the alteration of NF-ĸB pathway. This work tries to give a clear idea about the different aspects of arsenic resulting in male reproductive complications, often leading to infertility. The first part of this article explains the implications of arsenic poisoning and the crosstalk of the NF-ĸB pathway in male reproductive toxicity. Silymarin is a bioactive compound that exerts anti-cancer and anti-inflammatory properties and has demonstrated hopeful outcomes in several cancers, including colon cancer, breast cancer, and skin cancer, by downregulating the hyperactive NF-ĸB pathway. The next half of this article thus sheds light on silymarin's therapeutic potential in inhibiting the NF-ĸB signaling cascade, thus offering protection against arsenic-induced male reproductive toxicity.

Silymarin as a preventive or therapeutic measure for chemotherapy and radiotherapy-induced adverse reactions: a comprehensive review of preclinical and clinical data

PURPOSE

Thus far, silymarin has been examined in several studies for prevention or treatment of various chemotherapy or radiotherapy-induced adverse reactions. In this review, we try to collect all available human, animal, and pre-clinical data in this field.

METHODS

The search was done in Scopus, PubMed, Medline, and systematic reviews in the Cochrane database, using the following keywords: "Cancer," "Chemotherapy," "Radiotherapy," "Mucositis," "Nephrotoxicity," "Dermatitis," "Ototoxicity," "Cardiotoxicity," "Nephrotoxicity," "Hepatotoxicity," "Reproductive system," "Silybum marianum," "Milk thistle," and "Silymarin" and "Silybin." We included all relevant in vitro, in vivo, and human studies up to the date of publication.

RESULTS

Based on 64 included studies in this review, silymarin is considered a safe and well-tolerated compound, with no known clinical drug interaction. Notably, multiple adverse reactions of chemotherapeutic agents are effectively managed by its antioxidant, anti-apoptotic, anti-inflammatory, and anti-immunomodulatory properties. Clinical trials suggest that oral silymarin may be a promising adjuvant with cancer treatments, particularly against hepatotoxicity (n = 10), nephrotoxicity (n = 3), diarrhea (n = 1), and mucositis (n = 3), whereas its topical formulation can be particularly effective against radiodermatitis (n = 2) and hand-foot syndrome (HFS) (n = 1).

CONCLUSION

Further studies are required to determine the optimal dose, duration, and the best formulation of silymarin to prevent and/or manage chemotherapy and radiotherapy-induced complications.

Silibinin eliminates mitochondrial ROS and restores autophagy through IL6ST/JAK2/STAT3 signaling pathway to protect cardiomyocytes from doxorubicin-induced injury

Growing evidence indicates that silibinin (SLB), a main component extracted from Chinese herb Silybum marianum, can effectively antagonize doxorubicin (DOX) induced myocardial injury (DIMI), but the specific molecular mechanism is still unelucidated. Herein, DOX induced human AC16 cardiomyocyte injury model and Network Pharmacology are used to predict and verify the potential mechanism. The analysis results of the core PPI network of SLB against DIMI show that JAK/STAT signaling pathway and autophagy are significantly enriched. Molecular docking results indicate that SLB has stronger binding ability to signaling key proteins IL6ST, JAK2 and STAT3 (affinity ≤ -7.0 kcal/mol). The detection results of pathway activation and autophagy level demonstrate that SLB significantly alleviates DOX induced IL6ST/JAK2/STAT3 signaling pathway inhibition and autophagy inhibition, reduces the death rate of cardiomyocytes. This protective effect of SLB is eliminated when key pathway proteins (IL6ST, JAK2, STAT3) are knocked down or autophagy is inhibited (3-MA or Beclin1 knockdown). These results suggest that the regulation of IL6ST/JAK2/STAT3 signaling pathway and autophagy may be important mechanism for SLB's protective effect on DOX injured cardiomyocytes. Further experimental results prove that knockdown of IL6ST, JAK2 and STAT3 eliminate the mitochondrial ROS scavenging effect and autophagy promoting effect of SLB. In sum, SLB can decrease the mitochondrial ROS and restore autophagy to antagonize DOX-induced cardiomyocyte injury by activating IL6ST/JAK2/STAT3 signaling pathway.

Angiogenic and Osteogenic Effects of Flavonoids in Bone Regeneration

Bone is a highly vascularised tissue that relies on a close spatial and temporal interaction between blood vessels and bone cells. As a result, angiogenesis is critical for bone formation and healing. The vascular system supports bone regeneration by delivering oxygen, nutrients, and growth factors, as well as facilitating efficient cell-cell contact. Most clinical applications of engineered bone grafts are hampered by insufficient vascularization after implantation. Over the last decade, a number of flavonoids have been reported to have osteogenic-angiogenic potential in bone regeneration because of their excellent bioactivity, low cost, availability, and minimal in vivo toxicity. During new bone formation, the osteoinductive nature of certain flavonoids is involved in regulating multiple signaling pathways contributing toward the osteogenic-angiogenic coupling. This review briefly outlines the osteogenic-angiogenic potential of those flavonoids and the mechanisms of their action in promoting bone regeneration. However, further studies are needed to investigate their delivery strategies and establish their clinical efficacy. This article is protected by copyright. All rights reserved.

A Comprehensive Review of the Cardiovascular Protective Properties of Silibinin/Silymarin: A New Kid on the Block

Silibinin/silymarin has been used in herbal medicine for thousands of years and it is well-known for its hepato-protective properties. The present comprehensive literature review aimed to critically summarize the pharmacological properties of silymarin extract and its main ingredient silibinin in relation to classical cardiovascular risk factors (e.g., diabetes mellitus, etc.). We also assessed their potential protective and/or therapeutic application in cardiovascular diseases (CVDs), based on experimental and clinical studies. Pre-clinical studies including in vitro tests or animal models have predominantly implicated the following effects of silymarin and its constituents: (1) antioxidant, (2) hypolipidemic, (3) hypoglycemic, (4) anti-hypertensive and (5) cardioprotective. On the other hand, a direct amelioration of atherosclerosis and endothelial dysfunction after silymarin administration seems weak based on scarce data. In clinical trials, the most important findings are improved (1) glycemic and (2) lipid profiles in patients with type 2 diabetes mellitus and/or hyperlipidemia, while (3) the anti-hypertensive effects of silibinin/silymarin seem very modest. Finally, the changes in clinical endpoints are not robust enough to draw a firm conclusion. There are significant limitations in clinical trial design, including the great variety in doses and cohorts, the underlying conditions, the small sample sizes, the short duration and the absence of pharmacokinetic/pharmacodynamic tests prior to study commitment. More data from well-designed and high-quality pre-clinical and clinical studies are required to firmly establish the clinical efficacy of silibinin/silymarin and its possible therapeutic application in cardiovascular diseases.

Effect of lactic acid bacteria isolated from some fermented dairy products on carbon tetrachloride-induced hepatotoxicity and nephrotoxicity of albino rats

The current research was performed to evaluate the potential protective effect of Lactobacillus paracasei ssp. paracasei, Pediococcus acidilactici, Lactococcus lactis ssp. lactis, and silymarin in the alleviation of health (hepatic and renal) complications caused by carbon tetrachloride (CCl₄) in rats. Healthy sixty albino rats were divided into six groups, the first group was control (negative), the second group (control positive) was injected CCl₄ (1 ml/kg, 1:1 v/v paraffin oil mixture, i.p. every third day for 8 weeks), the third group (CCl₄ + silymarin group) receiving both CCl₄ and daily silymarin therapy (50 mg/kg, oral), and the fourth group: CCl₄ + Lactobacillus paracasei (1 ml orally). The fifth group (CCl₄ + Pediococcus acidilactici 1 ml orally) and the sixth group (CCl₄ + Lactococcus lactis 1 ml orally) for 8 weeks per day. Biochemical markers were tested for blood, liver, and kidney tissue. Histopathological examination of the liver and kidney tissues was performed. The findings obtained have shown that Lactobacillus paracasei ssp. paracasei, Pediococcus acidilactici, and Lactococcus lactis ssp. lactis improved the disrupted biochemical parameters caused by CCl₄ therapy. Besides, the findings of the histopathology are in consistent with biochemical parameters and the protective ability of lactic acid bacteria suggesting that the best lactic acid bacteria were Pediococcus acidilactici that helped strengthen liver fibrosis caused by CCl₄ therapy, while the best bacterium for improving renal damage was Lactococcus lactis.

Health Benefits of Silybum marianum: Phytochemistry, Pharmacology, and Applications

Silybum marianum (SM), a well-known plant used as both a medicine and a food, has been widely used to treat various diseases, especially hepatic diseases. The seeds and fruits of SM contain a flavonolignan complex called silymarin, the active compounds of which include silybin, isosilybin, silychristin, dihydrosilybin, silydianin, and so on. In this review, we thoroughly summarize high-quality publications related to the pharmacological effects and underlying mechanisms of SM. SM has antimicrobial, anticancer, hepatoprotective, cardiovascular-protective, neuroprotective, skin-protective, antidiabetic, and other effects. Importantly, SM also counteracts the toxicities of antibiotics, metals, and pesticides. The diverse pharmacological activities of SM provide scientific evidence supporting its use in both humans and animals. Multiple signaling pathways associated with oxidative stress and inflammation are the common molecular targets of SM. Moreover, the flavonolignans of SM are potential agonists of PPARγ and ABCA1, PTP1B inhibitors, and metal chelators. At the end of the review, the potential and perspectives of SM are discussed, and these insights are expected to facilitate the application of SM and the discovery and development of new drugs. We conclude that SM is an interesting dietary medicine for health enhancement and drug discovery and warrants further investigation.

Milk thistle (Silybum Marianum) as an antidote or a protective agent against natural or chemical toxicities: a review

Biological and chemical agents cause dangerous effects on human health via different exposing ways. Recently, herbal medicine is considered as a biological and safe treatment for toxicities. Silybum marianum (milk thistle), belongs to the Asteraceae family, possesses different effects such as hepatoprotective, cardioprotective, neuroprotective, anti-inflammatory and anti-carcinogenic activities. Several studies have demonstrated that this plant has protective properties against toxic agents. Herein, the protective effects of S. marianum and its main component, silymarin, which is the mixture of flavonolignans including silibinin, silydianin and silychristin acts against different biological (mycotoxins, snake venoms, and bacterial toxins) and chemical (metals, fluoride, pesticides, cardiotoxic, neurotoxic, hepatotoxic, and nephrotoxic agents) poisons have been summarized. This review reveals that main protective effects of milk thistle and its components are attributed to radical scavenging, anti-oxidative, chelating, anti-apoptotic properties, and regulating the inflammatory responses.

Silymarin and Cancer: A Dual Strategy in Both in Chemoprevention and Chemosensitivity

Silymarin extracted from milk thistle consisting of flavonolignan silybin has shown chemopreventive and chemosensitizing activity against various cancers. The present review summarizes the current knowledge on the potential targets of silymarin against various cancers. Silymarin may play on the system of xenobiotics, metabolizing enzymes (phase I and phase II) to protect normal cells against various toxic molecules or to protect against deleterious effects of chemotherapeutic agents on normal cells. Furthermore, silymarin and its main bioactive compounds inhibit organic anion transporters (OAT) and ATP-binding cassettes (ABC) transporters, thus contributing to counteracting potential chemoresistance. Silymarin and its derivatives play a double role, namely, limiting the progression of cancer cells through different phases of the cycle-thus forcing them to evolve towards a process of cell death-and accumulating cancer cells in a phase of the cell cycle-thus making it possible to target a greater number of tumor cells with a specific anticancer agent. Silymarin exerts a chemopreventive effect by inducing intrinsic and extrinsic pathways and reactivating cell death pathways by modulation of the ratio of proapoptotic/antiapoptotic proteins and synergizing with agonists of death domains receptors. In summary, we highlight how silymarin may act as a chemopreventive agent and a chemosensitizer through multiple pathways.

Protective Effects of Silymarin and Silibinin against DNA Damage in Human Blood Cells

Silymarin (SM), a standardized extract derived from Silybum marianum (L.) Gaertn, is primarily composed of flavonolignans, with silibinin (SB) as its major active constituent. The present study aimed to evaluate the antigenotoxic activities of SM and SB using the alkaline comet assay in whole blood cells and to assess their effects on the expression of genes associated with carcinogenesis and chemopreventive processes. Different concentrations of SM or SB (1.0, 2.5, 5.0, and 7.5 mg/ml) were used in combination with the DNA damage-inducing agent methyl methanesulfonate (MMS, 800 μM) to evaluate their genoprotective potential. To investigate the role of SM and SB in modulating gene expression, we performed quantitative real-time PCR (qRT-PCR) analysis of five genes that are known to be involved in DNA damage, carcinogenesis, and/or chemopreventive mechanisms. Treatment with SM or SB was found to significantly reduce the genotoxicity of MMS, upregulate the expression of PTEN and BCL2, and downregulate the expression of BAX and ABL1. We observed no significant changes in ETV6 expression levels following treatment with SM or SB. In conclusion, both SM and SB exerted antigenotoxic activities and modulated the expression of genes related to cell protection against DNA damage.

Cardioprotective mechanisms of phytochemicals against doxorubicin-induced cardiotoxicity

Doxorubicin (DOX) is an anthracycline antibiotic, which is effectively used in the treatment of different malignancies, such as leukemias and lymphomas. Its most serious side effect is dose-dependent cardiotoxicity, which occurs through inducing oxidative stress apoptosis. Due to the myelosuppressive effect of dexrazoxane, a commonly-used drug to alleviate DOX-induced cardiotoxicity, researchers investigated the potential of phytochemicals for prophylaxis and treatment of this condition. Phytochemicals are plant chemicals that have protective or disease preventive properties. Preclinical trials have shown antioxidant properties for several plant extracts, such as those of Aerva lanata, Aronia melanocarpa, Astragalus polysaccharide, and Bombyx mori plants. Other plant extracts showed an ability to inhibit apoptosis, such as those of Astragalus polysaccharide, Azadirachta indica, Bombyx mori, and Allium stavium plants. Unlike synthetic agents, phytochemicals do not impair the clinical activity of DOX and they are particularly safe for long-term use. In this review, we summarized the results of preclinical trials that investigated the cardioprotective effects of phytochemicals against DOX-induced cardiotoxicity. Future human trials are required to translate these cardioprotective mechanisms into practical clinical implications.

Anti‑proliferative activity of epigallocatechin‑3‑gallate and silibinin on soft tissue sarcoma cells

Disseminated soft tissue sarcomas (STS) present a therapeutic dilemma. The first-line cytostatic doxorubicin demonstrates a response rate of 30% and is not suitable for elderly patients with underlying cardiac disease, due to its cardiotoxicity. Well‑tolerated alternative treatment options, particularly in palliative situations, are rare. Therefore, the present study assessed the anti‑proliferative effects of the natural compounds epigallocatechin-3-gallate (EGCG), silibinin and noscapine on STS cells. A total of eight different human STS cell lines were used in the study: Fibrosarcoma (HT1080), liposarcoma (SW872, T778 and MLS‑402), synovial sarcoma (SW982, SYO1 and 1273) and pleomorphic sarcoma (U2197). Cell proliferation and viability were analysed by 5‑bromo-2'-deoxyuridine and MTT assays and real‑time cell analysis (RTCA). RTCA indicated that noscapine did not exhibit any inhibitory effects. By contrast, EGCG decreased proliferation and viability of all cell lines except for the 1273 synovial sarcoma cell line. Silibinin exhibited anti‑proliferative effects on all synovial sarcoma, liposarcoma and fibrosarcoma cell lines. Liposarcoma cell lines responded particularly well to EGCG while synovial sarcoma cell lines were more sensitive to silibinin. In conclusion, the green tea polyphenol EGCG and the natural flavonoid silibinin from milk thistle suppressed the proliferation and viability of liposarcoma, synovial sarcoma and fibrosarcoma cells. These compounds are therefore potential candidates as mild therapeutic options for patients that are not suitable for doxorubicin‑based chemotherapy and require palliative treatment. The findings from the present study provide evidence to support in vivo trials assessing the effect of these natural compounds on solid sarcomas.

Antimutagenic, Antigenotoxic, and Anticytotoxic Activities of Silybum Marianum [L.] Gaertn Assessed by the Salmonella Mutagenicity Assay (Ames Test) and the Micronucleus Test in Mice Bone Marrow

Silymarin (SM), a standardized extract from Silybum marianum (L.) Gaertn., is composed mainly of flavonolignans, and silibinin (SB) is its major active constituent. The present study aimed to evaluate the antimutagenic activities of SM and SB using the Ames mutagenicity test in Salmonella Typhimurium, as well as their anticytotoxic and antigenotoxic activities using the mouse bone marrow micronucleus test. To assess antimutagenicity, Salmonella Typhimurium strains were treated with different concentrations of SM or SB and the appropriate positive control for each strain. To assess antigenotoxicity and anticytotoxicity, Swiss mice were treated with different concentrations of SM or SB and mitomycin C (MMC). The results showed that SM was not significantly effective in reducing the number of frameshift mutations in strain TA98, while SB demonstrated significant protection at higher doses (P < 0.05). Regarding strain TA 100, SM and SB significantly decreased mutagenicity (point mutations) (P < 0.05). The results of the antigenotoxic evaluation demonstrated that SM and SB significantly reduced the frequency of micronucleated polychromatic erythrocytes (MNPCE) (P < 0.05). The results also indicated that SM and SB significantly attenuated MMC-induced cytotoxicity (P < 0.05). Based on these results, both SM and SB presented antimutagenic, antigenotoxic, and anticytotoxic actions.

The Protective Role of Phenolic Compounds Against Doxorubicin-induced Cardiotoxicity: A Comprehensive Review

Although doxorubicin (DOX) is among the most widely used anticancer agents, its clinical application is hampered owing to its cardiotoxicity. Adjuvant therapy with an antioxidant has been suggested as a promising strategy to reduce DOX-induced adverse effects. In this context, many phenolic compounds have been reported to protect against DOX-induced cardiotoxicity. The cardioprotective effects of phenolic compounds are exerted via multiple mechanisms including inhibition of reactive oxygen species generation, apoptosis, NF-κB, p53, mitochondrial dysfunction, and DNA damage. In this review, we present a summary of the in vitro, in vivo, and clinical findings on the protective mechanisms of phenolic compounds against DOX-induced cardiotoxicity.

Silymarin and Its Role in Chronic Diseases

Silymarin is the active constituent of Silybum marianum (milk thistle) which is a C-25 containing flavonolignan. Milk thistle has a lot of traditional values, being used as a vegetable, as salad, as bitter tonic, and as galactogogue in nursing mothers and in various ailments such as liver complications, depression, dyspepsia, spleenic congestions, varicose veins, diabetes, amenorrhea, uterine hemorrhage, and menstrual problems. In this present chapter, a comprehensive attempt has been made to discuss the potential of silymarin in chronic disorders. An insight into modulation of cellular signaling by silymarin and its implication in various disorders such as liver disorders, inflammatory disorders, cancer, neurological disorders, skin diseases, and hypercholesterolemia is being provided.

Silymarin Constituent 2,3-Dehydrosilybin Triggers Reserpine-Sensitive Positive Inotropic Effect in Perfused Rat Heart

2,3-dehydrosilybin (DHS) is a minor flavonolignan component of Silybum marianum seed extract known for its hepatoprotective activity. Recently we identified DHS as a potentially cardioprotective substance during hypoxia/reoxygenation in isolated neonatal rat cardiomyocytes. This is the first report of positive inotropic effect of DHS on perfused adult rat heart. When applied to perfused adult rat heart, DHS caused a dose-dependent inotropic effect resembling that of catecholamines. The effect was apparent with DHS concentration as low as 10 nM. Suspecting direct interaction with β-adrenergic receptors, we tested whether DHS can trigger β agonist-dependent gene transcription in a model cell line. While DHS alone was unable to trigger β agonist-dependent gene transcription, it enhanced the effect of isoproterenol, a known unspecific β agonist. Further tests confirmed that DHS could not induce cAMP accumulation in isolated neonatal rat cardiomyocytes even though high concentrations (≥ 10 μM) of DHS were capable of decreasing phosphodiesterase activity. Pre-treatment of rats with reserpine, an indole alkaloid which depletes catecholamines from peripheral sympathetic nerve endings, abolished the DHS inotropic effect in perfused hearts. Our data suggest that DHS causes the inotropic effect without acting as a β agonist. Hence we identify DHS as a novel inotropic agent.

Ultrasonic-assisted enzymatic extraction of silymarin from the Silybum marianum seed shell and evaluation of its antioxidant activity in vitro

This study revealed the optimal conditions for the Ultrasonic-Assisted Enzymatic Extraction (UAEE) of silymarin, and include: the concentration of ethanol, 50 %; enzyme concentration, 30 U/mg; liquid-solid ratio, 6:1; an extraction time of 120 min; and the ultrasonic power at 180 W. The extraction rate was 7.86 %, which is higher, by 74.67 %, than that of the silymarin extract from the Silybum marianum meal prepared by a distinct approach. SEM micrographs of the inner and outer surfaces of the Silybum marianum shell obtained by variant extractions demonstrated that the extraction of silymarin required the destruction of cell walls. The results suggest that UAEE is a promising alternative for the extraction of silymarin. The antioxidant activities of the silymarin were evaluated in vitro by its capabilities to scavenger the DPPH, hydroxyl and superoxide free radicals, as well as by its tyrosinase inhibitory activity. The results showed that silymarin has significant antioxidant activity, thus it can be used as a functional food material against oxidative stress. We believe that the knowledge gained from this study should contribute to the further development and application of this resource.

Cytotoxicity of monensin, narasin and salinomycin and their interaction with silybin in HepG2, LMH and L6 cell cultures

The cytotoxic effect of monensin, narasin and salinomycin followed by their co-action with silybin in the cell line cultures of human hepatoma (HepG2), chicken hepatoma (LMH) or rat myoblasts (L6) have been investigated. The effective concentration of the studied ionophoric polyethers has been assessed within two biochemical endpoints: mitochondrial activity (MTT assay) and membrane integrity (LDH assay) after 24h incubation of each compound and farther, the cytotoxicity influenced in course of their interaction with silybin was determined. The most affected endpoints were found for inhibition of mitochondrial activity of the hepatoma cell lines and their viability depended on concentration of the ionophoric polyether, as well as on the cell line tested. The rat myoblasts were more sensitive target for cellular membrane damage when compared to inhibition of mitochondrial activity. An interaction between the ionophoric polyethers and silybin resulted a considerable cytotoxicity decrease within all studied cell lines; the combination index (CI) showed differences of interaction mode and dependence on cell culture, concentration of silybin, as well as the assay used. The obtained results are of interest in respect to recent findings on applicability of salinomycin and monensin for human therapy.

Modulation of cutaneous wound healing by silymarin in rats

OBJECTIVE

To investigate the effect of topical application of silymarin on full-thickness cutaneous wounds in rats.

METHOD

A full-thickness cutaneous defect (2×2cm) was induced on the back of 85 male and female Wister rats. The animals were randomly divided into four groups (n=20 in each group), treated with 1ml basal cream (placebo group), low-dose (6mg/ml/rat) and high-dose (12mg/ml/rat) silymarin, and untreated (control). Five rats remained uninjured to serve as comparisons for biomechanical analysis. Wounds were evaluated 10, 20 and 30 days after injury, through histopathologic, biochemical and biomechanical analyses.

RESULTS

There was a significant (p < 0.05) increase observed in the amount of glycosaminoglycans and collagen present on days 10, 20 and 30 for both low-dose and high-dose silymarin groups. Low-dose silymarin reduced the number of lymphocytes and enhanced the number of fibrocytes at the earlier stages of wound healing; however, high-dose silymarin reduced both lymphocytes and macrophages, and increased number of fibrocytes at the later stages of wound healing. Silymarin significantly improved alignment of the healing tissue, enhanced maturity of the collagen fibres and fibroblasts (p < 0,05), and increased the ultimate tensile strength and stress of the healing tissue.

CONCLUSION

The results suggest that topical application of silymarin improved the morphological, biochemical and biomechanical properties of experimentally-induced wound defects in rats.

DECLARATION OF INTEREST

There were no external sources of funding for this study. The authors have no conflicts of interest to declare.

Treated effect of silymarin on vascular function of aged rats: Dependant on nitric oxide pathway

Abstract Context: Aging leads to endothelial dysfunction and vascular stiffness which are the main causes of many cardiovascular diseases. Previous reports have shown that the cell protective effect of silymarin (SM) is dependent on its antioxidant properties. Objectives: We investigated the effect of SM on vascular functions of aged rats and the involvement of nitric oxide or cyclooxygenase (COX) activity in this effect. Materials and methods: Isolated rat aortas were obtained from 22-month old rats. Each ring was incubated with SM (50 mg/L), SM/l-nitro-arginine methyl ester (100 μM, l-NAME) or SM/indomethacin (10 μM, INDO) in tissue bath. Three- to four-month-old rats were used as young controls. Endothelium-intact rings were precontracted with α-receptor agonist phenylephrine (0.001-30 µM) or voltage-dependent high potassium (40 mM), endothelium dependent/independent relaxant responses were obtained using acetylcholine (0.001-30 µM) and sodium nitroprusside (0.0001-3 µM), respectively. Results: Aging increased phenylephrine sensitivity (6.45 ± 0.08; 6.88 ± 0.09) and decreased KCl contraction (882 ± 118.4; 499 ± 80.4). SM treatment decreased the Emax of both agents (548 ± 109; 223 ± 48.9). Aging deteriorated acetylcholine relaxation (93.9 ± 2.09; 72.0 ± 2.56) and SM improved the response (86.3 ± 1.90). l-NAME prevented the SM effect whereas INDO was ineffective. Discussion and Conclusion: Immediate SM treatment partially restored endothelial dysfunction and vascular tone in aging. The possible mechanism might not be mediated by prostacyclin or the COX pathway in acute administration; the nitric oxide pathway and calcium antagonistic features of SM relate to its action on the vessel.

Silymarin improves vascular function of aged ovariectomized rats

Both aging and estrogen depletion lead to endothelial dysfunction, which is the main reason of many cardiovascular diseases. Previous reports have shown that cell protective effect of silymarin (SM) depends on its antioxidant and phytoestrogenic properties. We investigated the effect of SM on vascular stiffness of aged menopausal rats and the involvement of estrogenic activity in this effect. Isolated rat aortas were obtained from 22-month-old rats, after 18 months of ovariectomy (OVX) follow-up. Each ring was incubated in tissue bath either with SM (50 mg/L) and 17β-estradiol (10 μM, E2) or in the presence of SM/fulvestrant (50 mg/L, 10 μM). Endothelium-intact rings were precontracted with phenylephrine (0.001-30 μM) or high potassium (40 mM); endothelium-dependent/independent relaxant responses were obtained using acetylcholine (0.001-30 μM) and sodium nitroprusside (0.0001-3 μM), respectively. While phenylephrine sensitivity was significantly increased in OVX rats, relaxations were significantly less in aged OVX rats compared with young rats. In spite of the presence of estrogen antagonist, immediate SM treatment restored the endothelial function and vascular tone better than estrogen replacement. Additionally, as a complementary and alternative medicine, it does not cause estrogenic side effects when taken acutely.

The protective effect of silybin against lasalocid cytotoxic exposure on chicken and rat cell lines

Lasalocid, an ionophore coccidiostat, extensive use implies a risk of toxicological impacts. Protective effects of silybin, a herbal compound of Silybum marianum, are reported elsewhere. The aim of this study was to compare effects of the combined use of lasalocid and silybin in chicken hepatoma cells (LMH) and rat myoblasts (L6) cell lines cultures. The cytoprotective effect resulting from an interaction of both pharmaceuticals was measured with the help of MTT reduction and, coomassie brilliant blue binding (CBB) and LDH release assays. Isobolography and the combination index (CI) estimated the nature and scale of interaction. In all performed tests, the lowest lasalocid EC₅₀-values were obtained for chicken hepatocytes. In the rat myoblasts cultures, the lowest lasalocid EC₅₀-values were found with LDH test. Simultaneously, a lack of silybin cytotoxic effect was proven for the studied cell lines. An interaction between both substances led to a considerable decrease of lasalocid cytotoxicity. The isobolograms and combination index showed a significant antagonistic nature of silybin effect in the course of lasalocid cytotoxicity. It is concluded that the mechanism of cytoprotection results from complex reaction at biochemical and biophysical endpoints during chicken hepatocytes and rat myoblasts cell lines exposure to silybin and lasalocid co-action.

Strategies for quality control of Chinese medicines

Chinese medicines (CM) have been attracting interest and acceptance in many countries. Quality control is vital for ensuring the safety and efficacy of CM. Usually, CM are used as whole plant and/or combination of several herbs, and multiple constituents are responsible for the therapeutic effects. Therefore, quality control of CM is very difficult. To date, the valid method for quantitatively evaluating the quality of CM is poor. In this article, the strategies for quantification, related to the markers, reference compounds and approaches, in quality control of CM were reviewed and discussed.

Inhibitory effect of silibinin on tumour necrosis factor-alpha and hydrogen peroxide production by human monocytes

Silibinin is a chemically defined flavonoid and the main active component of silymarin, a polyphenolic complex from Silybum marianum, which has anti-inflammatory, hepatoprotective and anticarcinogenic properties. Monocytes obtained from healthy individuals were incubated with silibinin to evaluate cell viability, hydrogen peroxide (H(2)O(2)) release and tumour necrosis factor-alpha (TNF-α) production by these cells. The duration of treatment and different silibinin concentrations had no significant effect on cell viability. Monocytes showed a dose-dependent inhibitory effect on H(2)O(2) release by phorbol myristate acetate-stimulated monocytes in silibinin concentrations ranging from 6.25 to 50 µg mL(-1). Significant inhibition of TNF-α production by lipopolysaccharide-stimulated monocytes was observed at concentrations of 12.5, 50 and 100 µg mL(-1) of silibinin. These results suggest that silibinin exerts antioxidant and anti-inflammatory properties on human monocytes through an inhibitory effect on H(2)O(2) release and on TNF-α production, respectively.

Antioxidant and hepatoprotective activities of Egyptian moraceous plants against carbon tetrachloride-induced oxidative stress and liver damage in rats

CONTEXT

In the absence of reliable liver-protective drugs in modern medicine, a large number of medicinal preparations are recommended for treatment of liver disorders.

OBJECTIVE

The antioxidant, hepatoprotective and kidney protective activities of methanol extracts of Ficus carica Linn. (Moraceae) leaves and fruits and Morus alba Linn. root barks (Moraceae) are evaluated here.

MATERIALS AND METHODS

Liver and kidney damage were induced in rats by carbon tetrachloride in a subcutaneous dose of 1 mL (40% v/v in corn oil)/kg. The extract was given intraperitoneally at doses of 50 mg/kg (F. carica leaf and M. alba root bark) and 150 mg/kg (F. carica fruit). The activity of the extracts was comparable to that of silymarin, a known hepatoprotective agent. Antioxidant activity was evaluated by measuring blood glutathione (GSH) content, superoxide dismutase (SOD), catalase (CAT) activities, and malondialdehyde equivalent (MDA). Hepatoprotective activity was evaluated by measuring serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), total bilirubin, and total protein. These biochemical observations were supported by histopathological examination of liver sections. Kidney function was evaluated by measuring plasma urea and creatinine.

RESULTS

Methanol extracts of Ficus carica and Morus alba showed potent antioxidant and hepatoprotective activities; in-depth chromatographic investigation of the most active extract (Ficus carica leaf extract) resulted in identification of umbelliferone, caffeic acid, quercetin-3-O-β-d-glucopyranoside, quercetin-3-O-α-l-rhamnopyranoside, and kaempferol-3-O-α-l-rhamnopyranoside.

DISCUSSION AND CONCLUSION

These findings demonstrate that the phenolic constituents of Ficus carica leaf and Morus alba root bark are responsible at least in part for the observed protective effects.

Cisplatin-induced cardiotoxicity: Mechanisms and cardioprotective strategies

Increased oxidative stress and apoptosis have been implicated in the cardiotoxicity that limits the clinical use of cisplatin as an anti-tumoral drug. Our study was conducted to evaluate the protective potential of acetyl-l-carnitine, DL-α-lipoic acid and silymarin against cisplatin-induced myocardial injury. Eighty male albino rats were divided into eight groups. The first four groups were treated with normal saline, acetyl-l-carnitine (500mg/kg, i.p.), DL-α-lipoic acid (100mg/kg, p.o.) and silymarin (100mg/kg, p.o.) respectively, for 10 successive days. The remaining groups were treated with the same doses of normal saline, acetyl-l-carnitine, DL-α-lipoic acid and silymarin, respectively, for 5 successive days before and after a single dose of cisplatin (10mg/kg, i.p.). Serum activities of lactate dehydrogenase (LDH), creatine kinase (CK), creatine kinase isoenzyme MB (CK-MB) and plasma cardiac troponin I (cTnI) concentration were estimated. Malondialdehyde (MDA), reduced glutathione (GSH) contents, superoxide dismutase activity (SOD) and protein content in cardiac tissues were measured. Moreover, integrity of both mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) was also examined. Cisplatin-treated rats experienced a significant elevation of serum activities of LDH, CK, CK-MB and cTnI plasma concentration. These effects were accompanied by a significant increase in MDA level. On the other hand, a significant decrease in GSH content, SOD activity and total protein content was observed. In addition, both mtDNA and nDNA were heavily damaged. However, acetyl-l-carnitine, DL-α-lipoic acid and silymarin significantly attenuated the cisplatin-evoked disturbances in the above-mentioned parameters. In conclusion, the former drugs were proven to be potential candidates to ameliorate cisplatin-induced cardiotoxicity.

Dietary supplements commonly used for prevention

The use of complimentary and alternative medicine is on the rise. This article reviews some of the commonly used herbal supplements and others focusing mainly on disease prevention. A summary table of medical conditions is provided, and when possible, a summary of efficacy and safety is provided to facilitate decision making.

Naringenin-7-O-glucoside protects against doxorubicin-induced toxicity in H9c2 cardiomyocytes by induction of endogenous antioxidant enzymes

Doxorubicin, a widely used chemotherapeutic agent, can give rise to severe cardiotoxicity that limits its clinical use by generation of reactive oxygen species (ROS) and apoptosis. Protection or alleviation of doxorubicin cardiotoxicity can be achieved by administration of natural phenolic compounds via activating endogenous defense systems and antiapoptosis. Naringenin-7-O-glucoside (NARG), isolated from Dracocephalum rupestre Hance, has been demonstrated to protect against cardiomyocyte apoptosis. In the present study, we investigated the effects of NARG on endogenous antioxidant enzymes against doxorubicin toxicity and the potential role of extracellular signal-regulated kinase (ERK) in regulation of NARG-induced Nrf2-dependent gene expression in H9c2 cardiomyocytes. The mRNA expression of glutamate-cysteine ligase modifier subunit (GCLM) and glutamate-cysteine ligase catalytic subunit (GCLC) was upregulated by NARG as detected by RT-PCR. NARG (10, 20, and 40microM) pretreatment increased NAD (P) H: quinone oxidoreductase (NQO1), ERK, and Nrf2 protein levels in cardiomyocytes as detected by Western blotting. These results suggest that NARG could prevent cardiomyocytes from doxorubicin-induced toxicity by induction of endogenous antioxidant enzymes via phosphorylation of ERK1/2 and nuclear translocation of Nrf2.

Flavonolignans from Silybum marianum moderate UVA-induced oxidative damage to HaCaT keratinocytes

BACKGROUND

UV radiation from sunlight is a very potent environmental risk factor in the pathogenesis of skin cancer. Exposure to UV light, especially the UVA part, provokes the generation of reactive oxygen species (ROS), which induce oxidative stress in exposed cells. Topical application of antioxidants is a successful strategy for protecting the skin against UV-caused oxidative damage.

OBJECTIVE

In this study, silybin (SB) and 2,3-dehydrosilybin (DS) (1-50 micromol/l), flavonolignan components of Silybum marianum, were tested for their ability to moderate UVA-induced damage.

METHODS

Human keratinocytes HaCaT were used as an appropriate experimental in vitro model, to monitor the effects of SB and DS on cell viability, proliferation, intracellular ATP and GSH level, ROS generation, membrane lipid peroxidation, caspase-3 activation and DNA damage.

RESULTS

Application of the flavonolignans (1-50 micromol/l) led to an increase in cell viability of irradiated (20 J/cm(2)) HaCaT keratinocytes. SB and DS also suppressed intracellular ATP and GSH depletion, ROS production and peroxidation of membrane lipids. UVA-induced caspases-3 activity/activation was suppressed by treatment with SB and DS. Lower concentrations of both compounds (10 micromol/l) significantly reduced cellular DNA single strand break formation.

CONCLUSION

Taken together, the results suggest that these flavonolignans suppress UVA-caused oxidative stress and may be useful in the treatment of UVA-induced skin damage.

An updated systematic review of the pharmacology of silymarin

BACKGROUND

Recent years have seen an explosion of scientific papers that deal with drugs from the fruits of milk thistle and its active substances silymarin (standardized mixture of flavonolignanes), thus justifying an updated systematic review.

METHODS

Electronic databases identified silymarin, silibinin, silicristin or milk thistle as descriptors in >700 papers (34% published in last 5 years; 92% dealt with animal pharmacological). Only papers adequately reporting on experimental conditions, dosing, variables tested and statistics were analysed.

RESULTS

Silymarin was found to modify specifically the functions related to various transporters and receptors located in the cell membranes; that is, organic anion uptake transporter peptides (OATP), ABC transporters (P-gp), bile salt export pump, as well as TNF-alpha-dependent and possibly selectin-dependent phenomena. In the cytoplasm, some antioxidant properties and the inhibition of the lipoxygenase pathway seem quite selective and could concur to the antitoxic effects. Some effects like the inhibition of inducible nitric-oxide synthase, of nuclear factor kappa B, and reduction of collagen synthesis are indicative of DNA/RNA-mediated effects. Several studies using 'in vitro' and 'in vivo' cancer models suggest a potential of silymarin in such diseases. Topical and systemic silymarin has skin protective properties against UV-induced damage in epidermis and causes an up-regulation of tumour-suppressor genes p53- and p21CIP1. There were no data on hepatic viral replication, viremia or spontaneous tumours in the data examined.

CONCLUSIONS

Data presented here do not solve the question about the complex mechanism(s) of action of the medicinal herbal drug silymarin. Silymarin may be a natural multi-functional and multi-target drug.

Attenuation of UVA-induced damage to human keratinocytes by silymarin

BACKGROUND

UV radiation from sunlight is a potent environmental risk factor in skin cancer pathogenesis. UVA is the major portion of UV light reaching the earth surface ( approximately 95%) and it is reported to lead to benign and malignant tumor formation. UVA-mediated cellular damage occurs primarily through the release of reactive oxygen species (ROS) and it is responsible for inflammation, immunosuppression, photoaging and photocarcinogenesis.

OBJECTIVE

The aim of our study was to investigate the potency of silymarin, the polyphenol fraction from the seeds of Silybum marianum, to modulate UVA-induced oxidative damage to human keratinocytes.

METHODS

Skin epidermal cell line HaCaT, extensively used for studying the influence of UV radiation, was chosen as an experimental model. Silymarin's effect on UVA-disrupted cell viability, proliferation, mitochondrial function, and intracellular ATP and GSH level was measured. Furthermore, silymarin's potency to reduce UVA-induced ROS generation, membrane lipid peroxidation, caspase-3 activation and DNA damage was monitored.

RESULTS

Treatment of irradiated HaCaT (20 J/cm(2)) with silymarin (0.7-34 mg/l; 4h) resulted in concentration-dependent diminution of UVA-caused oxidative stress on all studied parameters. Silymarin application extensively reduced GSH depletion and ROS production as well as lipid peroxidation in irradiated cells. Formation of UVA-induced DNA single strand breaks and caspase-3 activity was also significantly decreased by silymarin.

CONCLUSION

The results suggest that silymarin may be beneficial in the treatment of UVA-induced skin oxidative injury and inflammation. However, further studies especially whose using human systems are needed to determine efficacy of silymarin in vivo.

Silymarin and epithelial cancer chemoprevention: how close we are to bedside?

Failure and high systemic toxicity of conventional cancer therapies have accelerated the focus on the search for newer agents, which could prevent and/or slow-down cancer growth and have more human acceptability by being less or non-toxic. Silymarin is one such agent, which has been extensively used since ages for the treatment of liver conditions, and thus has possibly the greatest patient acceptability. In recent years, increasing body of evidence has underscored the cancer preventive efficacy of silymarin in both in vitro and in vivo animal models of various epithelial cancers. Apart from chemopreventive effects, other noteworthy aspects of silymarin and its active constituent silibinin in cancer treatment include their capability to potentiate the efficacy of known chemotherapeutic drugs, as an inhibitor of multidrug resistance-associated proteins and as an adjunct to the cancer therapeutic drugs due to their organ-protective efficacy specifically liver, and immunostimulatory effects. Widespread use of silymarin for liver health in humans and commercial availability of its formulations with increased bioavailability, further underscore the necessity of carrying out controlled clinical trials with these agents in cancer patients. In this review, we will briefly discuss the outcomes of clinical trials being conducted by us and others in cancer patients to provide insight into the clinical relevance of the observed chemopreventive effects of these agents in various epithelial cancer models.

A phase I and pharmacokinetic study of silybin-phytosome in prostate cancer patients

Silibinin is a polyphenolic flavonoid isolated from milk thistle with anti-neoplastic activity in several in vitro and in vivo models of cancer, including prostate cancer. Silybin-phytosome is a commercially available formulation containing silibinin. This trial was designed to assess the toxicity of high-dose silybin-phytosome and recommend a phase II dose. Silybin-phytosome was administered orally to prostate cancer patients, giving 2.5-20 g daily, in three divided doses. Each course was 4 weeks in duration. Thirteen patients received a total of 91 courses of silybin-phytosome. Baseline patient characteristics included: median age of 70 years, median baseline prostate specific antigen (PSA) of 4.3 ng/ml, and a median ECOG performance status of 0. The most prominent adverse event was hyperbilirubinemia, with grade 1-2 bilirubin elevations in 9 of the 13 patients. The only grade 3 toxicity observed was elevation of alanine aminotransferase (ALT) in one patient; no grade 4 toxicity was noted. No objective PSA responses were observed. We conclude that 13 g of oral silybin-phytosome daily, in 3 divided doses, appears to be well tolerated in patients with advanced prostate cancer and is the recommended phase II dose. Asymptomatic liver toxicity is the most commonly seen adverse event.

Analysis and comparison of active constituents in commercial standardized silymarin extracts by liquid chromatography-electrospray ionization mass spectrometry

A sensitive method for the simultaneous quantitation of six active constituents in commercial silymarin standardized extracts was developed based on liquid chromatography (LC) in combination with mass spectrometry (MS). The six main active constituents, namely, silydianin, silychristin, diastereoisomers of silybin (silybin A and B), and diastereoisomers of isosilybin (isosilybin A and B) were completely separated and quantified by LC/MS. Silymarin obtained from Sigma-Aldrich Co. was evaluated and used as standard reference material for the six individual constituents in comparing the relative content of silymarin and the relative ratio of each constituent in commercial standardized silymarin extracts, respectively. Significant variation was found between different commercial silymarin sources. As a result, this method has proven useful in evaluating and quantifying the six active constituents in commercial milk thistle extracts. The calibration curves were over the range from 0.25 to 100 microg/mL for silychristin and silydianin, and from 0.10 to 100 microg/mL for silybin A, silybin B, isosilybin A and isosilybin B, respectively (r(2)> or =0.9958). For all six active constituents, the overall intra-day precision values, based on the relative standard deviation replicate for four QC levels, ranged from 1.18% to 12.4% and accuracy ranged from 89.4% to 112%. This methodology could easily be incorporated into standardized testing to assess content uniformity including lot-to-lot variation as part of routine process controls as well as a means to describe cross-product variation among the exiting marketed formulations.

Effect of silibinin on the growth and progression of primary lung tumors in mice

BACKGROUND

Silibinin, a flavanone from milk thistle, inhibits the growth of tumors in several rodent models. We examined the effects of dietary silibinin on the growth, progression, and angiogenesis of urethane-induced lung tumors in mice.

METHODS

A/J mice (15 per group) were injected with urethane (1 mg/g body weight) or saline alone and fed normal diets for 2 weeks, after which they were fed diets containing different doses of silibinin (0%-1% [wt/wt] silibinin) for 18 or 27 weeks. Immunohistochemistry and Western blot analysis were used to examine angiogenesis and enzymatic markers of inflammation, proliferation, and apoptosis. All statistical tests were two-sided.

RESULTS

Urethane-injected mice exposed to silibinin had statistically significantly lower lung tumor multiplicities than urethane-injected mice fed the control diet lacking silibinin (i.e., control mice). Mice that received urethane and 1% (wt/wt) dietary silibinin for 18 weeks had 93% fewer large (i.e., 1.5-2.5-mm-diameter) lung tumors than control mice (mean number of tumors/mouse: 27 in the urethane group versus 2 in the urethane + 1% silibinin group, difference = 25 tumors/mouse, 95% confidence interval [CI] = 13 to 37 tumors/mouse, P = .005). Lung tumors of silibinin-fed mice had 41%-74% fewer cells positive for the cell proliferation markers proliferating cell nuclear antigen and cyclin D1 than lung tumors of control mice. Tumor microvessel density was reduced by up to 89% with silibinin treatment (e.g., 56 microvessels/400x field in tumors from control mice versus 6 microvessels/400x field in tumors from urethane + 1% silibinin-treated mice [difference = 50 microvessels/400x field, 95% CI = 46 to 54 microvessels/400x field; P<.001]). Silibinin decreased lung tumor expression of vascular endothelial growth factor (VEGF) and of inducible nitric oxide synthase and cyclooxygenase-2, two enzymes that promote lung tumor growth and progression by inducing VEGF expression.

CONCLUSIONS

Silibinin inhibits lung tumor angiogenesis in an animal model and merits investigation as a chemopreventive agent for suppressing lung cancer progression.

Dietary agents in the chemoprevention of prostate cancer

Nutritional factors have been estimated to contribute 20-60% of cancers around the globe, and almost one-third of deaths are being reported in Western countries. According to estimates by the American Cancer Society, during the year 2005 about 232,090 new cases of prostate cancer will be diagnosed alone in the United States and 30,350 men will die of this disease. The high incidence and long latency period of prostate cancer offer plenty of time to pursue strategies toward prevention and/or treatment to suppress or revert this disease. Epidemiological evidence suggests that plant-based dietary agents decrease the risk of some types of human cancer, including prostate cancer. Intake of 400-600 g/day of fruits and vegetables is associated with reduced risk of several cancers. The use of micronutrients and/or other phenolic agents in the diet or synthetic exogenous supplements to prevent neoplastic transformation of normal cells or to slow the progression of established malignant changes in cancer cells is termed "chemoprevention." Considerable attention has been devoted to identify plant-based dietary agents that may serve as natural inhibitors of prostate carcinogenesis. Much progress has been made in the last decade in this area of investigation through identification of pathways that play important roles in prostate tumorigenesis. This article summarizes epidemiological, clinical, and mechanistic studies and the significance of plant-derived dietary agents such as flavonoids, indoles, isothiocyanates, phenolics, monoterpenes, and complementary and alternative agents in the management of prostate cancer with recommendations for future studies to advance this area of research.

Separation and characterization of silybin, isosilybin, silydianin and silychristin in milk thistle extract by liquid chromatography-electrospray tandem mass spectrometry

A selective and sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method has been developed for the characterization of silymarin in commercially available milk thistle extract. In this study, six main active constituents, including silydianin, silychristin, diastereomers of silybin (silybin A and B) and diastereomers of isosilybin (isosilybin A and B) in silymarin, were completely separated on a YMC ODS-AQ HPLC column using a gradient mobile phase system comprised of ammonium acetate and methanol/water/formic acid. Identification and characterization of the major constituents were based not only on the product ion scan, which provided unique fragmentation information of a selected molecular ion, but also on the specific fragmentation of multiple reaction monitoring (MRM) data, which confirmed the retention times of LC chromatographic peaks. The method was applied in the analysis of human plasma samples in the presence of silymarin and appeared to be suitable for the pharmacokinetic studies in which the discrimination of silymarin constituents is essential.

Dietary flavonoids: effects on xenobiotic and carcinogen metabolism

Flavonoids are present in fruits, vegetables and beverages derived from plants (tea, red wine), and in many dietary supplements or herbal remedies including Ginkgo Biloba, Soy Isoflavones, and Milk Thistle. Flavonoids have been described as health-promoting, disease-preventing dietary supplements, and have activity as cancer preventive agents. Additionally, they are extremely safe and associated with low toxicity, making them excellent candidates for chemopreventive agents. The cancer protective effects of flavonoids have been attributed to a wide variety of mechanisms, including modulating enzyme activities resulting in the decreased carcinogenicity of xenobiotics. This review focuses on the flavonoid effects on cytochrome P450 (CYP) enzymes involved in the activation of procarcinogens and phase II enzymes, largely responsible for the detoxification of carcinogens. A number of naturally occurring flavonoids have been shown to modulate the CYP450 system, including the induction of specific CYP isozymes, and the activation or inhibition of these enzymes. Some flavonoids alter CYPs through binding to the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor, acting as either AhR agonists or antagonists. Inhibition of CYP enzymes, including CYP 1A1, 1A2, 2E1 and 3A4 by competitive or mechanism-based mechanisms also occurs. Flavones (chrysin, baicalein, and galangin), flavanones (naringenin) and isoflavones (genistein, biochanin A) inhibit the activity of aromatase (CYP19), thus decreasing estrogen biosynthesis and producing antiestrogenic effects, important in breast and prostate cancers. Activation of phase II detoxifying enzymes, such as UDP-glucuronyl transferase, glutathione S-transferase, and quinone reductase by flavonoids results in the detoxification of carcinogens and represents one mechanism of their anticarcinogenic effects. A number of flavonoids including fisetin, galangin, quercetin, kaempferol, and genistein represent potent non-competitive inhibitors of sulfotransferase 1A1 (or P-PST); this may represent an important mechanism for the chemoprevention of sulfation-induced carcinogenesis. Importantly, the effects of flavonoids on enzymes are generally dependent on the concentrations of flavonoids present, and the different flavonoids ingested. Due to the low oral bioavailability of many flavonoids, the concentrations achieved in vivo following dietary administration tend to be low, and may not reflect the concentrations tested under in vitro conditions; however, this may not be true following the ingestion of herbal preparations when much higher plasma concentrations may be obtained. Effects will also vary with the tissue distribution of enzymes, and with the species used in testing since differences between species in enzyme activities also can be substantial. Additionally, in humans, marked interindividual variability in drug-metabolizing enzymes occurs as a result of genetic and environmental factors. This variability in xenobiotic metabolizing enzymes and the effect of flavonoid ingestion on enzyme expression and activity can contribute to the varying susceptibility different individuals have to diseases such as cancer. As well, flavonoids may also interact with chemotherapeutic drugs used in cancer treatment through the induction or inhibition of their metabolism.

Chemosensitization and radiosensitization of tumors by plant polyphenols

The treatment of cancer with chemotherapeutic agents and radiation has two major problems: time-dependent development of tumor resistance to therapy (chemoresistance and radioresistance) and nonspecific toxicity toward normal cells. Many plant-derived polyphenols have been studied intently for their potential chemopreventive properties and are pharmacologically safe. These compounds include genistein, curcumin, resveratrol, silymarin, caffeic acid phenethyl ester, flavopiridol, emodin, green tea polyphenols, piperine, oleandrin, ursolic acid, and betulinic acid. Recent research has suggested that these plant polyphenols might be used to sensitize tumor cells to chemotherapeutic agents and radiation therapy by inhibiting pathways that lead to treatment resistance. These agents have also been found to be protective from therapy-associated toxicities. How these polyphenols protect normal cells and sensitize tumor cells to treatment is discussed in this review.

Silybin and silymarin--new effects and applications

This article aims to review critically literature published mainly within this millennium on the new and emerging applications of silymarin, the polyphenolic fraction from the seeds of Silybum marianum and its main component silybin. Silymarin and silybin used so far mostly as hepatoprotectants were shown to have other interesting activities as e.g., anticancer and canceroprotective. These activities were demonstrated in a large variety of illnesses of different organs as e.g., prostate, lungs, CNS, kidneys, pancreas and others. Besides the cytoprotective activity of silybin mediated by its antioxidative and radical-scavenging properties also new activities based on the specific receptor interaction were discovered--e.g., inhibition and modulation of drug transporters, P-glycoproteins, estrogenic receptors, nuclear receptors and some others. New derivatives of silybin open new ways to its therapeutic applications. Pharmacology dealing with optically pure silybin diastereomers may suggest new mechanisms of its action.

Antioxidative and Cardioprotective Effects of Phyllanthus urinaria L. on Doxorubicin-Induced Cardiotoxicity

Cardiac toxicity is a major adverse effect caused by doxorubicin (DOX) therapy. Many recent studies have shown that DOX toxicity involves generation of reactive oxygen species (ROS). Although protection or alleviation of DOX toxicity can be achieved by administration of antioxidant vitamins such as ascorbic acid and vitamin E, their cardioprotective effect remains controversial. Thus alternative naturally occurring antioxidants may potentially be candidates for antioxidant therapy. In this study, we investigated the antioxidative and cytoprotective effects of Phyllanthus urinaria (PU) against DOX toxicity using H9c2 cardiac myoblasts. The total antioxidant capacity of PU (1 mg/ml) was 5306.75+/-461.62 FRAP value (microM). DOX IC50 values were used to evaluate the cytoprotective effects of PU ethanolic extract (1 or 10 microg/ml) in comparison with those of ascorbic acid (VIT C, 100 microM) and N-acetylcysteine (NAC, 100 microM). PU treatments (1 or 10 microg/ml) dose dependently caused rightward DOX IC50 shifts of 2.8- and 8.5-fold, respectively while treatments with VIT C and NAC increased DOX IC50 by 3.3- and 4.2-fold, respectively. Additionally, lipid peroxidation and caspase-3 activity were parameters used to evaluate cytoprotective effect. All antioxidants completely inhibited cellular lipid peroxidation and caspase-3 activation induced by DOX (1 microM). Endogenous antioxidant defense such as total glutathione (tGSH), catalase and superoxide dismutase (SOD) activity was also modulated by the antioxidants. PU treatment alone dose dependently increased tGSH, and this effect was retained in the presence of DOX. Similar effect was observed in the assessment of catalase and SOD enzyme activity. The nuclear factor kappaB (NFkappaB) transcription factor assay demonstrated that all antioxidants significantly inhibited DOX-induced NFkappaB activation. Our results suggest that PU protection against DOX cardiotoxicity was mediated through multiple pathways and this plant may serve as an alternative source of antioxidants for prevention of DOX cardiotoxicity.

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.