Deoxypodophyllotoxin Induces ROS-Mediated Apoptosis by Modulating the PI3K/AKT and p38 MAPK-Dependent Signaling in Oral Squamous Cell Carcinoma.

Deoxypodophyllotoxin (DPT), a naturally occurring flavonolignan, possesses several pharmacological properties, including anticancer property. However, the mechanisms underlying DPT mode of action in oral squamous cell carcinoma (OSCC) remain unknown. This study aimed to investigate the anticancer effects of DPT on OSCC and the underlying mechanisms. Results of the MTT assay revealed that DPT significantly reduced the cell viability in a time- and dose-dependent manner. Flow cytometry analysis revealed that DPT induces apoptosis in OSCC cells in a dose-dependent manner. Moreover, DPT enhanced the production of mitochondrial reactive oxygen species (ROS) in OSCC cells. Mechanistically, DPT induced apoptosis in OSCC cells by suppressing the PI3K/AKT signaling pathway while activating the p38 MAPK signaling to regulate the expression of apoptotic proteins. Treatment with SC79, an AKT activator, reversed the effects of DPT on AKT signaling in OSCC cells. Taken together, these results provide the basis for the use of DPT in combination with conventional chemotherapy for the treatment of oral cancer.

Natural flavonolignans as potential therapeutic agents against common diseases.

OBJECTIVES: Plant-derived flavonolignans had been demonstrated to have various biological functions. They are an important class of natural products combined by a flavonoid unit and a phenylpropanoid unit. KEY FINDINGS: From the literature survey, 88 constituents from natural resources were identified. Different derivatives of flavonolignans were listed, fused phenylpropanoid unit with dioxane ring, or cyclic ether, or simple ether side chain, or lactone, and so on. Besides, the pharmacological effects of flavonolignans were summarized as well. It has a wide range of anti-tumour, antioxidant, anti-microorganic and anti-inflammatory effects. SUMMARY: This review had provided a full-scale profile of flavonolignans on its plant sources, phytochemistry and pharmacology, and also proposed some issues and perspectives which may be of concern in the future. It was greatly anticipated that the commercialization of the flavonolignans would lead to uplift the financial abilities of communities attending the growing of the flavonolignans and the relevant and potential production becoming an international herbal and pharmaceutical commodity.

Structurally Diverse Flavonolignans with Immunosuppressive and Neuroprotective Activities from the Fruits of Hippophae rhamnoides L.

The fruit of Hippophae rhamnoides L. has been used for centuries in Europe and Asia as a food with high nutritional and medicinal values. In this study, a bioactivity-guided phytochemical investigation of H. rhamnoides L. has resulted in four new dimethylallylated flavonolignans (1-4), four new isopropylpentenone-flavonolignan heterodimers (5-8), two new geranylated flavonolignans (9 and 10), and 14 known flavonolignan derivatives (11-24); they were elucidated by their spectrometric and spectroscopic methods, including HR-ESI-MS, NMR, IR, and UV from the fruit of H. rhamnoides L. for the first time. Among them, compounds 2, 5, 6, 20, and 21 showed potent immunosuppressive activities with IC50 values from 19.42 ± 3.91 to 48.05 ± 12.56 µM. Meanwhile, compounds 1, 4, 11, 12, and 13 showed moderate neuroprotective activities, which increased the cell survival rate from 50.30 ± 4.24% for the model group to 71.63 ± 3.04%, 70.02 ± 4.13%, 61.53 ± 5.93%, 61.08 ± 3.58%, and 65.68 ± 4.88% at 10 µM, respectively. The hypothetical biogenetic pathway and preliminary structure-activity relationship were found and discussed scientifically.

Anti-Alzheimer's flavanolignans from Ceiba pentandra aerial parts.

Four flavanolignans, ceibapentains A (1) and B (2) and cinchonains Ia (3) and Ib (4), were isolated for the first time from an ethyl acetate extract of Ceiba pentandra (L) (Bombacaceae) aerial parts. The ceibapentains A (1) and B (2) are new compounds and their structures, including the absolute configurations, were determined by HRESIMS, 1D and 2D NMR, and electronic circular dichroism analyses, then compared with reported data. Compounds 1-4 were tested for their anti-Alzheimer's activity via an assessment of their inhibitory effect on amyloid ß42 aggregation using a thioflavin T assay. The results revealed that cinchonain Ia (3) showed a higher inhibitory effect (91%) than the standard curcumin (70%). Compounds 1, 2, and 4 exhibited moderate activity, with inhibition ratios of 43%, 47%, and 58%, respectively. A molecular docking study on the binding mode of 3 and curcumin with an amyloid ß1-40 peptide fibril structure indicated a high affinity of cinchonain 1a (3) towards amyloid ß1-40 peptide, in agreement with the experimental results.

The protective effects of vernicilignan A, a new flavonolignan isolated from Toxicodendron vernicifluum on SH-SY5Y cells against oxidative stress-induced injury.

In this study, a new flavonolignan vernicilignan A was isolated from Toxicodendron vernicifluum. The neuroprotective effects of this compound against H2O2 induced cell injury in SH-SY5Y cells were evaluated by MTT assay and LDH release assay. Vernicilignan A dose-dependently attenuated the cell injury and LDH release induced by H2O2 in SH-SY5Y cells. Further study indicated that vernicilignan A reduced cell apoptosis caused by H2O2 treatment via regulation of some apoptotic related proteins including Bax, Bcl-2, caspase 3 and caspase 9. Also, vernicilignan A increase the cell viability of H2O2 treated cells via the activation of Akt and GSK3ß. Base on the findings, vernicilignan A exhibited neuroprotective effects through the activation of PI3K/Akt signaling and inhibition of mitochondria apoptosis pathway. Vernicilignan A might be a promising therapeutic agent for oxidative stress induced neurodegenerative diseases.

Silibinin to improve cancer therapeutic, as an apoptotic inducer, autophagy modulator, cell cycle inhibitor, and microRNAs regulator.

Silibinin is a natural plant polyphenol with high antioxidant and anticancer properties, which causes broad-spectrum efficacy against cancer, including cell cycle arrest and apoptosis in most cancer cell types. Silibinin, by modulating the apoptosis, cell cycle progression and autophagic pathways in various cellular and molecular routs might be used to design more effective anticancer strategies. Silibinin also regulates aberrant miRNAs expression linked to many aspects of cell biology in cancer. Maybe the most interesting aspect of silibinin is its ability to trigger multiple cellular signaling pathways to induce a particular biologic effect in various cell types. This review discusses investigations supporting the ability of silibinin to be as a natural modulator of involved cellular biological events in cancer progression. In this review, we introduce the salient features of silibinin therapy to optimize clinical outcomes for oncology patients. The goal of the treatments is to make it possible to eliminate the tumor with the minimum side effects and cure the patient in the early stage cancer. Therefore, plant extracts such as silibinin can be included in the treatments.

Evaluation of the Cytotoxicity and Genotoxicity of Flavonolignans in Different Cellular Models.

Flavonolignans are the main components of silymarin, which represents 1.5-3% of the dry fruit weight of Milk thistle (Silybum marianum L. Gaernt.). In ancient Greece and Romania, physicians and herbalists used the Silybum marianum to treat a range of liver diseases. Besides their hepatoprotective action, silymarin flavonolignans have many other healthy properties, such as anti-platelet and anti-inflammatory actions. The aim of this study was to evaluate the toxic effect of flavonolignans on blood platelets, peripheral blood mononuclear cells (PBMCs) and human lung cancer cell line-A549-using different molecular techniques. We established that three major flavonolignans: silybin, silychristin and silydianin, in concentrations of up to 100 µM, have neither a cytotoxic nor genotoxic effect on blood platelets, PMBCs and A549. We also saw that silybin and silychristin have a protective effect on cellular mitochondria, observed as a reduction of spontaneous mitochondrial DNA (mtDNA) damage in A549, measured as mtDNA copies, and mtDNA lesions in ND1 and ND5 genes. Additionally, we observed that flavonolignans increase the blood platelets' mitochondrial membrane potential and reduce the generation of reactive oxygen species in blood platelets. Our current findings show for the first time that the three major flavonolignans, silybin, silychristin and silydianin, do not have any cytotoxicity and genotoxicity in various cellular models, and that they actually protect cellular mitochondria. This proves that the antiplatelet and anti-inflammatory effect of these compounds is part of our molecular health mechanisms.

Flavonolignans inhibit the arachidonic acid pathway in blood platelets.

BACKGROUND: Arachidonic acid metabolism by cyclooxygenase (COX) is a major pathway for blood platelets' activation, which is associated with pro-thrombotic platelet activity and the production of pro-inflammatory mediators. Inhibition of COX activity is one of the major means of anti-platelet pharmacotherapy preventing arterial thrombosis and reducing the incidence of cardiovascular events. Recent studies have presented that a silymarin (standardized extract of Milk thistle (Silybum marianum)) can inhibit the COX pathway. Accordingly, the aim of our study was to determine the effects of three major flavonolignans (silybin, silychristin and silydianin) on COX pathway activity in blood platelets. METHODS: We determined the effect of flavonolignans on arachidonic acid induced blood platelet aggregation, COX pathway metabolites formation, as well as COX activity in platelets. Additionally, we analysed the potential mechanism of this interaction using the bioinformatic ligand docking method. RESULTS: We observed that tested compounds decrease the platelet aggregation level, both thromboxane A2 and malondialdehyde formation, as well as inhibit the COX activity. The strongest effect was observed for silychristin and silybin. In our in silico study we showed that silychristin and silybin have conformations which interact with the active COX site as competitive inhibitors, blocking the possibility of substrate binding. CONCLUSIONS: The results obtained from this study clearly present the potential of flavonolignans as novel antiplatelet and anti-inflammatory agents.

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

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

[Flavonolignans - compounds not only for liver treatment]. / Flawonolignany ­ zwiazki nie tylko leczace watrobe.

Flavonolignans are the major bioactive components presented in the Milk thistle (Silybum marianum) standarized extract - silymarin. S. marianum is a medicinal plant, which has been using for thousands of years as a remedy for a variety of ailments. Since the 70s of the last century flavonolignans presented in silymarin have been regarded to the official medicine as substances having an hepatoprotective properties. Structurally, flavonolignans are composed of a flavonoid unit (taxifolin) and a phenylpropane unit (coniferyl alcohol), linked together by an oxeran ring. Many studies which have been conducted in recent years demonstrated that flavonolignans posses a various healthy properties. Flavonolignans modulate of a variety cell-signaling pathways as well as inhibit arachidonic acid metabolism, resulting in the reduction of pro-inflammatory mediators formation. The researches performed in last year's demonstrated that the major flavonolignan - silybin is able to inhibit two blood coagulation factors: thrombin and FXa. Flavonolignans have been also studied as a potential anticancer agents. This review article presents flavonolignans health benefits effects not only for the liver.

"Non-Taxifolin" Derived Flavonolignans: Phytochemistry and Biology.

Flavonolignans are plant natural products, composed of a flavonoid moiety and a lignan (phenylpropanoid) part. Current literature focuses on flavonolignans formed from taxifolin and coniferyl alcohol as e.g. silybin and its congeners from fruit extract from the purple variety of the milk thistle (Silybum marianum) denoted as "silymarin". This review describes chemistry and biological activity of so far neglected "non-taxifolin" based flavonolignans, derived from apigenin, luteolin, tricin, chrysoeriol, naringenin and eriodictyol, as the flavonoid part. Up-to-date knowledge on hydnocarpin, hydnocarpin-D, pseudotsuganol, hydnowightin, neohydnocarpin, palstatin, salcolins A and B, anastatins A and B, sinaiticin, silyamandin and silandrin is summarized in the present paper. Most of non-taxifolin derived flavonolignans have been shown to exhibit in vitro and/or in vivo anti-hepatotoxic, anti-oxidant, free radical scavenging, anti-inflammatory, anti-proliferative, anti-cancer, chemotherapy potentiating, anti-melanogenic, anti-bacterial, vasorelaxing, anti-platelet aggregation and/or hypotriglyceridemic activity, often stronger than silybin. Many of these compounds inhibited Staphylococcus aureus multidrug resistance pump NorA and sensitized multidrug resistant cancer cell lines showing a potential as adjuvants. Non-taxifolin derived flavonolignans are a relatively unexplored group of compounds with interesting biological activity and great application potential. Their detailed study could provide a new insight into the biomimetic synthesis in order to obtain new compounds with greater activity and identify new lead structures for the biomedicinal research.

Flavonolignans and other constituents from Lepidium meyenii with activities in anti-inflammation and human cancer cell lines.

From the roots of Lepidium meyenii Walpers (Brassicaceae) have been isolated and identified 2 flavonolignans, tricin 4'-O-[threo-ß-guaiacyl-(7″-O-methyl)-glyceryl] ether (1) and tricin 4'-O-(erythro-ß-guaiacyl-glyceryl) ether (2), along with 11 other known compounds, tricin (3), pinoresinol (4), 4-hydroxycinnamic acid (5), guanosine (6), glucotropaeolin (7), desulfoglucotropaeolin (8), 3-hydroxybenzylisothiocyanate (9), malic acid benzoate (10), 5-(hydroxymethyl)-2-furfural (11), d-phenylalanine (12), and vanillic acid 4-O-ß-d-glucoside (13). Structures were elucidated on the basis of NMR and MS data. Some isolates and previously isolated lepidiline B (14) were tested for cytotoxicity in a small panel of human cancer cell lines (Hep G2, COLO 205, and HL-60) and for anti-inflammatory activities in LPS-treated RAW 264.7 macrophage. Among them, compounds 1 and 14 were modestly active for inhibiting nitrite production in macrophage. Compounds 1, 14, and 3 were demonstrated to be selectively active against HL-60 cells with IC50 values of 40.4, 52.0, and 52.1 µM, respectively.

Tricin derivatives as anti-inflammatory and anti-allergic constituents from the aerial part of Zizania latifolia.

Methanol extract of Zizania latifolia was partitioned with EtOAc, n-BuOH, and H2O. From the EtOAc layers, a new flavonolignan along with a known flavone and three known flavonolignans, tricin (1), salcolin A (2), salcolin B (3), and salcolin C (4), were isolated through repeated silica gel and ODS column chromatography. The chemical structure of the new flavonolignan was determined to be tricin-4'-O-[erythro-ß-guaiacyl-(7″-O-methyl)-glyceryl] ether and was named salcolin D (5) based on physicochemical and spectroscopic data, including FT-NMR and ESI-MS. All compounds were isolated for the first time from this plant. Compounds 2-5, tricin derivatives, all exhibited higher anti-inflammatory and anti-allergy activities than tricin. In particular, salcolin D (5) was shown to have the strongest inhibitory activity against LPS-induced NO production in RAW 264.7 cells as well as ß-hexosaminidase release in IgE-sensitized RBL-2H3 cells. These results suggest that the presence of tricin derivatives conveys allergy and inflammation treatment ability to Z. latifolia.

Biotransformation on the flavonolignan constituents of Silybi Fructus by an intestinal bacterial strain Eubacterium limosum ZL-II.

Eubacterium limosum ZL-II is an anaerobic bacterium with demethylated activity, which was isolated from human intestinal bacteria in our previous work. In this study, the flavonolignan constituents of Silybi Fructus were biotransformed by E. limosum(1) ZL-II, producing four new transformation products - demethylisosilybin B (T1), demethylisosilybin A (T2), demethylsilybin B (T3) and demethylsilybin A (T4), among which T1 and T2 were new compounds. Their chemical structures were identified by ESI-TOF/MS, (1)H NMR, (13)C NMR, HMBC and CD spectroscopic data. The bioassay results showed that the transformation products T1-T4 exhibited significant inhibitory activities on Alzheimer's amyloid-ß 42 (Aß42(2)) aggregation with IC50 values at 7.49 µM-10.46 µM, which were comparable with that of the positive control (epigallocatechin gallate, EGCG(3), at 9.01 µM) and much lower than those of their parent compounds (at not less than 145.10 µM). The method of biotransformation by E. limosum ZL-II explored a way to develop the new and active lead compounds in Alzheimer's disease from Silybi Fructus. However, the transformation products T1-T4 exhibited decreased inhibitory activities against human tumor cell lines comparing with their parent compounds.

Potentiating effect of the flavonolignan (-)-hydnocarpin in combination with vincristine in a sensitive and P-gp-expressing acute lymphoblastic leukemia cell line.

The potentiating action of the flavonolignan, (-)-hydnocarpin, in combination with vincristine was evaluated in the 697 acute lymphoblastic leukemia cell line and a P-gp-expressing variant, 697-R. Vincristine at 3 nM caused nearly complete growth inhibition in 697 cells versus a 17% growth inhibition in 697-R cells. When combined with (-)-hydnocarpin at concentrations of 10 and 5 µM, vincristine-mediated growth inhibition in the 697-R cells increased significantly over the sum of the individual agents to 72% (p ≤ 0.0001) and 41% (p = 0.0256), respectively. Vincristine at 1.5 nM (66% growth inhibition) and 0.75 nM (39% growth inhibition) combined with (-)-hydnocarpin at 10 µM (42% growth inhibition) in the 697 cells caused a significant increase in growth inhibition to 83% (p = 0.03) and to 61% (p < 0.0001), respectively, when compared to vincristine treatment as a single agent. To investigate the mechanism for the vincristine re-sensitization caused by (-)-hydnocarpin, the P-gp inhibitory effect of (-)-hydnocarpin was evaluated.

Isolation, characterization and quantification of tricin and flavonolignans in the medicinal rice Njavara (Oryza sativa L.), as compared to staple varieties.

Njavara is an important medicinal rice variety of Kerala, India, widely used in Ayurveda as a 'health food' and in the treatment of rheumatoid arthritis, paralysis, neurodegenerative diseases and in rejuvenation therapy. Phytochemical investigations and spectroscopic studies of the diethyl ether fraction of methanolic extract of Njavara Black (NB) rice bran gave three important compounds namely, tricin and two rare flavonolignans- tricin 4'-O-(erythro-ß-guaiacylglyceryl) ether and tricin 4'-O-(threo-ß-guaiacylglyceryl) ether. The EC(50) values of these compounds in DPPH system were 90.39, 352.04 and 208.1 µg/ml, respectively. Quantification of the compounds by HPLC in NB and staple, non-medicinal rice varieties Sujatha (SJ) and Palakkadan Matta (PM) showed that tricin is present 39.64 and 16.12 fold higher in NB, compared to SJ and PM, respectively. This is the first report on the occurrence of tricin at significantly higher levels in Njavara and occurrence of the two flavonolignans in Oryza sativa species. Of the three compounds, tricin and the threo- form of flavonolignan showed anti-inflammatory effect of >65% after 5 h, at 2 mg/kg, in carrageenan-induced, paw edema experiments in rats. The results of the study corroborate with the preferential use of Njavara in indigenous medicine, over staple varieties.

Investigating the potential for toxicity from long-term use of the herbal products, goldenseal and milk thistle.

Two-year toxicity studies were conducted on the widely used herbal products, goldenseal and milk thistle, in male and female F344/N rats and B6C3F1 mice. With goldenseal root powder, the primary finding was an increase in liver tumors in rats and mice, and with milk thistle extract, a decrease in spontaneous background tumors including mammary gland tumors in female rats and liver tumors in male mice. Increased tumorigenicity in rodents exposed to goldenseal root powder may be due in part to the topoisomerase inhibition properties of berberine, a major alkaloid constituent in goldenseal, or its metabolite, berberrubine. In the clinic, use of topoisomerase-inhibiting agents has been associated with secondary tumor formation and inhibition in DNA repair processes. In contrast, the radical-scavenging and antioxidant properties of silibinin and other flavonolignans in milk thistle extract may have contributed to the decrease in background tumors in rodents in the present studies. The fate of the active constituents of goldenseal and milk thistle is similar in humans and rodents; therefore, the modes of action may translate across species. Further studies are needed to extrapolate the findings to humans.

Anti-inflammatory flavonolignans from Hydnocarpus anthelminthica seeds.

A new flavonolignan, anthelminthicol A (1), together with four known compounds, was isolated from the EtOAc extracts of the seeds of Hydnocarpus anthelminthica. Their structures were elucidated using extensive spectroscopic techniques. Bioassay showed that compounds 3-5 could inhibit nitric oxide production in LPS-stimulated RAW 264.7 macrophage cell lines, with IC(50) values of 7.81, 9.38, and 10.55 µM, respectively.

NF-kappaB inhibitors from Brucea javanica exhibiting intracellular effects on reactive oxygen species.

AIM: Brucea javanica was studied to identify nuclear factor kappaB (NF-κB) inhibitors exhibiting reactive oxygen species (ROS) intracellular amplification. MATERIAL AND METHODS: Eight compounds were evaluated for selective cytotoxicity using HT-29, HeLa, and HL-60 cells, and in a NF-κB assay. Active compounds were then tested using ROS and mitochondria transmembrane potential (MTP) assays. NF-κB and nuclear factor activated T-cell (NFAT) translocation were also assessed using their respective whole cell assays. RESULTS: Bruceajavanone B, bruceantin, bruceine A, (-)-hydnocarpin, and chrysoeriol exhibited cytotoxic potential and NF-κB p65 inhibition. Chrysoeriol exhibited selective cytotoxicity against leukemia cells with greater potency and also showed an ability to up-regulate NFAT transcriptional pathways through the amplification of intracellular ROS, in the presence of H2O2, to a greater degree than bruceantin and bruceine. CONCLUSION: Chrysoeriol selectively kills leukemic cells and potentiates the amplification of ROS levels. Therefore, chrysoeriol could serve as a potential chemotherapeutic modifier for leukemia chemotherapy since leukemia cells have a higher susceptibility to elevated ROS levels.

Identification of hepatoprotective flavonolignans from silymarin.

Silymarin, also known as milk thistle extract, inhibits hepatitis C virus (HCV) infection and also displays antioxidant, anti-inflammatory, and immunomodulatory actions that contribute to its hepatoprotective effects. In the current study, we evaluated the hepatoprotective actions of the seven major flavonolignans and one flavonoid that comprise silymarin. Activities tested included inhibition of: HCV cell culture infection, NS5B polymerase activity, TNF-alpha-induced NF-kappaB transcription, virus-induced oxidative stress, and T-cell proliferation. All compounds were well tolerated by Huh7 human hepatoma cells up to 80 muM, except for isosilybin B, which was toxic to cells above 10 muM. Select compounds had stronger hepatoprotective functions than silymarin in all assays tested except in T cell proliferation. Pure compounds inhibited JFH-1 NS5B polymerase but only at concentrations above 300 muM. Silymarin suppressed TNF-alpha activation of NF-kappaB dependent transcription, which involved partial inhibition of IkappaB and RelA/p65 serine phosphorylation, and p50 and p65 nuclear translocation, without affecting binding of p50 and p65 to DNA. All compounds blocked JFH-1 virus-induced oxidative stress, including compounds that lacked antiviral activity. The most potent compounds across multiple assays were taxifolin, isosilybin A, silybin A, silybin B, and silibinin, a mixture of silybin A and silybin B. The data suggest that silymarin- and silymarin-derived compounds may influence HCV disease course in some patients. Studies where standardized silymarin is dosed to identify specific clinical endpoints are urgently needed.