Formulation design and characterization of silymarin liposomes for enhanced antitumor activity.

Liposomes, a nanoscale carrier, plays an important role in the delivery of drug, affects the in vivo efficacy of drugs. In this paper, silymarin(SM)-loaded liposomes was optimized using the response surface method (RSM), with entrapment efficiency (EE%) as an index. The formulation was optimized as follow: lecithin (7.8mg/mL), SM/lecithin (1/26) and lecithin/cholesterol (10/1). The optimized SM liposomes had a high EE (96.58 ±3.06%), with a particle size of 290.3 ±10.5nm and a zeta potential of +22.98 ±1.73mV. In vitro release tests revealed that SM was released in a sustained-release manner, primarily via diffusion mechanism. In vitro cytotoxicity studies demonstrated that the prepared SM liposomes had stronger inhibitory effects than the model drug. Overall, these results indicate that this liposome system is suitable for intravenous delivery to enhance the antitumor effects of SM.

Silibinin solubilization: combined effect of co-solvency and inclusion complex formation.

OBJECTIVE: Belonging to the class II drugs according to the biopharmaceutics classification system, silibinin (SLB) benefits from high permeability but suffers poor solubility that negatively affects the development of any delivery system. This research aimed to improve SLB solubility by combined use of co-solvency and complexation phenomena. METHODS: Solubility studies were performed using the phase solubility analysis according to the shake-flask method in the presence of ethanol and 2-hydroxypropyl-ß-cyclodextrin (HP-ß-CD) as a co-solvent and inclusion complexing agent, respectively. SLB release studies from chitosan nanoparticles were carried out in double-wall, diffusion cells using the optimized drug release medium. RESULTS: SLB solubility was mathematically optimized constraining to using the lowest concentrations of ethanol and HP-ß-CD. SLB solubility increased linearly with the increase of HP-ß-CD concentration. The solubility in PBS-ethanol mixtures followed a log-linear model. SLB solubility in the presence of the ethanol co-solvent and HP-ß-CD complexing agent was optimized by adopting a genetic algorithm suggesting the phosphate buffer saline solution supplemented by 6%v/v ethanol and 8 mM HP-ß-CD as an optimized medium. The optimized solution was examined to study SLB release from chitosan nanoparticles (4.5 ± 0.2% drug loading) at 37 °C under static conditions. The sigmoidal release profile of SLB from the particles indicated a combination of erosion and diffusion mechanisms governing drug release from the nanoparticles. CONCLUSION: SLB solubility in a buffered solution supplemented by ethanol co-solvent and HP-ß-CD complexing agent is a function of free drug present in the semi-aqueous media, the drug-ligand binary complex, and the drug/ligand/co-solvent ternary complex.

Synthesis, physiochemical characterization, molecular docking study, and anti-breast cancer activity of silymarin loaded zein nanoparticles.

Breast cancer is a major cause of death in women worldwide leading to requirement of new therapeutic strategies. Silymarin demonstrated the anti-cancer activity however, due to low bioavailability its use is restricted. This study aimed to improve the solubility of silymarin by developing a silymarin loaded zein nanoparticles (SLNPs) which was stabilized by beta cyclodextrin. Comprehensive physiochemical characterization studies based on DLS, FTIR, UV-Vis Spectroscopy, FE-SEM, TEM, XRD, DSC, NMR and TGA confirmed the successful synthesis of SLNPs via an anti-solvent precipitation method. FE-SEM and TEM images demonstrated the uniform size and spherical shape of nanoparticles with encapsulation and loading efficiencies of 84.32 ± 1.9 % and 15.25 ± 2.4 % respectively. The zein protein interaction with silymarin, and ß-cyclodextrin was shown to be beneficial via the use of molecular simulations and binding energy calculations. Cellular studies demonstrated dose and time dependent cytotoxicity of SLNPs on MCF-7 breast cancer cell. FACS, qRT-PCR and Western blotting showed Bax (pro-apoptotic) upregulation while Bcl-2 (anti-apoptotic) downregulation. Our findings suggest that these loaded nanoparticles are more efficient than pure drug, enhancing its bioavailability and paving the path for developing it as a promising nutraceutical to treat breast cancer.

Preparation and in vitro evaluation of protective effects of Silibinin-loaded polymeric micelles on human hair against UV-B radiation.

BACKGROUND: The purpose of this study was to investigate the protective effect of Silibinin-loaded polymeric micelles from human hair against UV-B radiation. METHODS: Eight formulations with different concentrations of Silibinin, Pluronic F-127, and Labrasol-Labrafil were made by a solvent evaporation method, and the selected formulation was chosen by examining their properties like particle size and loading efficiency. Six groups of human hair, including a group that received the selected formulation, were exposed to UV-B radiation and by calculating its factors such as peak-to-valley roughness, RMS roughness, FTIR, and the amount of protein loss, the protective effect of the selected formulation was judged. RESULTS: According to the results, the loading efficiency and particle size of the selected formulation were 45.34% and 43.19 nm. The Silibinin release profile had two parts, fast and slow, which were suitable for creating a drug depot on hair. Its zeta potential also confirmed the minimum electrostatic interference between the formulation and hair surface. The zeta potential of selected formulation was -5.9 mv. Examination of AFM images showed that the selected formulation was able to prevent the increase in peak-to-valley roughness and RMS roughness caused by UV-B radiation. RMS roughness after 600 h of UV radiation in Groups 5 and 6 was significantly lower than the negative control group and the amount of this factor did not differ significantly between 0 and 600, so it can be concluded that the selected formulation containing Silibinin and the positive control group was able to prevent the increase of RMS roughness and hair destruction. In other hands, the two positive control groups and the selected formulation containing Silibinin were able to effectively reduce hair protein loss. CONCLUSION: Silibinin-loaded polymeric micelles were able to effectively protect hair from structural and chemical changes caused by UV-B radiation.

Effect of Field Trial on Silymarin Complex Composition and Antioxidant Assessment of Milk Thistle (Silybum marianum L. Gaertner).

Plant foods are receiving increasing attention as a valuable source of health beneficial compounds. Understanding the impact of growing conditions on the quality of milk thistle is critical for determining appropriate agro-ecological and agro-economic parameters for its production and, subsequently, food products rich in health-beneficial compounds. For this purpose, a randomized milk thistle cultivation trial was established in the experimental field of Agritec Plant Research Plc. in Sumperk, Czech Republic, and carried out for two subsequent growing seasons in 2020 and 2021. The milk thistle achenes, variety Mirel, were sown in the row width of 12.5, 25 and 37 cm; and the qualitative parameters of each field trial such as achenes yields, silymarin complex determination and also antioxidant assessment (total phenolic content, total flavonoids content, DPPH and ABTS radical scavenging activity) were evaluated. The environmental impact of the extraction process was reduced by using pressurized liquid extraction with 60% EtOH (v/v). The weather conditions during the trial as well as the row spacing of milk thistle sowing were revealed to have a significant influence on the evaluated parameters (p ≤ 0.05). The highest yields of evaluated parameters were obtained for the growing season 2021 and the row spacing of 37 cm.

A Descriptive Review of the Action Mechanisms of Berberine, Quercetin and Silymarin on Insulin Resistance/Hyperinsulinemia and Cardiovascular Prevention.

Insulin resistance (IR) and the associated hyperinsulinemia are early pathophysiological changes which, if not well treated, can lead to type 2 diabetes, endothelial dysfunction and cardiovascular disease. While diabetes care is fairly well standardized, the prevention and treatment of IR lacks a single pharmaceutical approach and many lifestyle and dietary interventions have been proposed, including a wide range of food supplements. Among the most interesting and well-known natural remedies, alkaloid berberine and the flavonol quercetin have particular relevance in the literature, while silymarin-the active principle of the Silybum marianum thistle-was traditionally used for lipid metabolism disorders and to sustain liver function. This review describes the major defects of insulin signaling leading to IR and the main properties of the three mentioned natural substances, their molecular targets and synergistic action mechanisms. The actions of berberine, quercetin and silymarin are partially superimposable as remedies against reactive oxygen intermediates generated by a high-lipid diet and by NADPH oxidase, which is triggered by phagocyte activation. Furthermore, these compounds inhibit the secretion of a battery of pro-inflammatory cytokines, modulate intestinal microbiota and are especially able to control the various disorders of the insulin receptor and post-receptor signaling systems. Although most of the evidence on the effects of berberine, quercetin and silymarin in modulating insulin resistance and preventing cardiovascular disease derive from experimental studies on animals, the amount of pre-clinical knowledge strongly suggests the need to investigate the therapeutic potential of these substances in human pathology.

The Protective Effects of Silymarin on the Reproductive Toxicity: A Comprehensive Review.

The reproductive system is extremely vulnerable to chemotherapy drugs, ionizing radiation, toxic heavy metals, chemicals, and so on. These harmful stimuli are able to induce oxidative damage, apoptosis, inflammation, and other mechanisms in the reproductive organs, leading to different adverse reproductive effects. It was shown that using medicinal plants (medicinal herbs) can be an effective medication for the prevention and treatment of multiple health conditions. Silymarin is a medicinal herb extract, obtained from the seeds of Silybum marianum. This herbal agent is a nontoxic agent even at relatively high physiological dose values, which suggests that it is safe for use in the treatment of different diseases. The hepato-, neuro-, cardio- and nephro-protective effects of silymarin have been assessed previously. The protective activities of silymarin can point to anti-oxidant, anti-apoptotic, anti-inflammatory, anti-fibrotic, immunomodulatory, and membrane-stabilizing properties. In this review, we aim to summarize current studies on the protective potentials of silymarin against reproductive toxicity. The molecular mechanisms of silymarin protection against cellular toxicity are also studied. Moreover, the findings obtained from improved formulations and delivery systems of silymarin have been addressed.

Structural basis of Nrf2 activation by flavonolignans from silymarin.

Several properties of silymarin (SM) extract have been attributed to their three major flavonolignans (silybin, silychristin, and silydianin) and their 2,3-dehydro derivatives (2,3-dehydrosilybin, 2,3-dehydrosilychristin, and 2,3-dehydrosilydianin). Experimental findings have suggested that the antioxidative and protective activities of these compounds could be due to their ability to activate nuclear factor erythroid 2-related factor 2 (Nrf2). The mechanism by which SM compounds exert their effect has been suggested to be by disrupting the complex between Nrf2 and Kelch-like ECH-associated protein 1 (Keap1). However, information about the structural and energetic basis of the inhibitory mechanism of SM compounds on the Nrf2-Keap1 pathway is lacking. We evaluated the binding properties of SM compounds because experimental findings have pointed to them as potential activators of Nrf2. Our study combined docking and molecular dynamics (MD) simulations with the Poisson-Boltzmann and generalized Born and surface area (MMPBSA and MMGBSA) methods and quantum mechanics-molecular mechanics (QMMM) calculations to investigate Keap1-ligand interactions. Our results predicted that silybinA and 2,3-dehydrosilybin bind to Keap1, forming interactions with the same pockets as those observed for the cocrystallized Keap1-Cpd16 complex but with more favorable binding free energies. These findings indicate that both natural compounds are potential activators of Nrf2.

A computational approach to discover antioxidant and anti-inflammatory attributes of silymarin derived from Silybum marianum by comparison with hydroxytyrosol.

Medicinal plants possess therapeutic potential for reducing reactive oxygen species (ROS)-mediated cellular damage. Hydroxytyrosol is one of the most potent antioxidants that served as control in the current study, including other synthetic antioxidants to computationally identify the antioxidant properties of Silymarin. The sequences of the receptors IκB kinase (IKK), Kelch-like ECH-associated protein 1 (Keap-1) and mitochondrial transcription factor A (Tfam) were retrieved from UniProtKB and homology modeling was performed using Swiss-Model server. Thereof the molecular docking and dynamic simulation studies were performed using Schrödinger's software version 11.5. From the current study, it was reported that on comparison of the binding energy of silymarin, hydroxytyrosol, α-tocopherol, ascorbic acid, butylated hydroxy anisole (BHA) and butylated hydroxytoluene (BHT), Silymarin exhibited better affinities with IKK receptor followed by Hydroxytyrosol suggesting it as the best or comparable of all other known antioxidants that could potentially suppress inflammation and other diseases. Also, Silymarin exhibited poorest binding affinity with Tfam promoting mitochondrial biogenesis, thereby scavenging ROS. However, with Keap-1, Silymarin is ranked 4th in the list, whereas hydroxytyrosol exhibited highest binding affinity to release oxidative stress. The stability of docked complexes made us conclude that Silymarin has comparable antioxidant properties to hydroxytyrosol, better anti-inflammatory potential and mitochondrial biogenesis enhancing properties to ultimately reduce oxidative stress. Now it can be tested further for in vitro or in vivo studies as potential drug against oxidative insult.Communicated by Ramaswamy H. Sarma.

Neural Network-based Optimization of Silybum Marianum Extract-loaded Chitosan Particles: Modeling, Preparation and Antioxidant Evaluation.

BACKGROUND: Silymarin is a flavonolignan extracted from Silybum marianum with various therapeutic applications. Many studies have focused on improving the bioavailability of silymarin due to its wide range of efficacy and low bioavailability. Chitosan, a naturally occurring polymeric substance, has a strong reputation for increasing the solubility of poorly soluble compounds. OBJECTIVE: This study used artificial neural networks (ANNs) to measure the effects of pH, chitosan to silymarin ratio, chitosan to tripolyphosphate ratio, and stirring time on the loading efficiency of silymarin into chitosan particles. METHODS: A model was developed to investigate the interactions between input factors and silymarin loading efficiency. The DPPH method was utilized to determine the antioxidant activity of an optimized formula and pure raw materials. RESULTS: According to the outcome of the ANN model, pH and the chitosan to silymarin ratio demonstrated significant effects on loading efficiency. In addition, increased stirring time decreased silymarin loading, whereas the chitosan-to-tripolyphosphate ratio showed a negligible effect on loading efficiency. CONCLUSION: Maximum loading efficiency occurred at a pH of approximately~5. Moreover, silymarin- loaded chitosan particles with a lower IC50 value (36.17 ± 0.02 ppm) than pure silymarin (165.04 ± 0.07 ppm) demonstrated greater antioxidant activity.

Silibinin Schiff Base Derivatives Counteract CCl4-Induced Acute Liver Injury by Enhancing Anti-Inflammatory and Antiapoptotic Bioactivities.

Background: Silibinin (Sil), a flavonoid lignan-like natural compound derived from milk thistle seeds, has been used to treat hepatic diseases, including early-phase hepatocirrhosis and fatty liver, for many years. However, its poor water solubility limits its gastrointestinal absorption and bioavailability. It clinical use has been limited due to its slow onset of action. Faced with this problem, research on the derivatives of silibinin has been receiving much attention. Purpose: A series of silibinin derivatives with good biosafety and higher hepatoprotective activity were obtained by a safe, efficient and green chemical synthesis method. Patients and Methods: First, the carbonyl group in the structure of silibinin was used to obtain silibinin Schiff base derivatives by dehydration condensation with the carboxyl group in the sulfur-containing amino acid. Next, relevant experiments were performed to characterize the structure, physical form and solubility of the derivatives. Then, toxicity tests of the derivatives were performed in LO-2 cells and SD rats to evaluate their biosafety. Finally, the anti-inflammatory and antiapoptotic activities were observed using a carbon tetrachloride (CCl4)-induced acute liver injury model in C57BL/6J mice using silibinin as a control. Results: The studies showed that SS and ST behaved as amorphous substances and showed a significant increase in solubility compared to silibinin. These two derivatives showed low toxicity in biosafety tests and higher bioactivity (anti-inflammatory and anti-apoptotic) than silibinin against acute liver injury induced by CCl4. Conclusion: Two silibinin derivatives (SS and ST) obtained by the Schiff base reaction improved the solubility of the silibinin parent nucleus in biological media with the help of the hydrophilic and amorphous morphology of the ligand. The low toxicity in vivo and in vitro ensures the biosafety of the derivatives. The hepatoprotective activity (anti-inflammatory and anti-apoptotic) was significantly improved compared to silibinin.

Silybin and its congeners: from traditional medicine to molecular effects.

Covering: 2015 up to 2022 (Feb)Silymarin, an extract of milk thistle (Silybum marianum) fruits, has been used in various medicinal applications since ancient times. A major component of silymarin is the flavonolignan silybin and its relatives isosilybin, silychristin, silydianin, 2,3-dehydrosilybin, and some others. Except for silydianin, they occur in nature as two stereomers. This review focuses on recent developments in chemistry, biosynthesis, modern advanced analytical methods, and transformations of flavonolignans specifically reflecting their chirality. Recently described chemotypes of S. marianum, but also the newest findings regarding the pharmacokinetics, hepatoprotective, antiviral, neuroprotective, and cardioprotective activity, modulation of endocrine functions, modulation of multidrug resistance, and safety of flavonolignans are discussed. A growing number of studies show that the respective diastereomers of flavonolignans have significantly different activities in anisotropic biological systems. Moreover, it is now clear that flavonolignans do not act as antioxidants in vivo, but as specific ligands of biological targets and therefore their chirality is crucial. Many controversies often arise, mainly due to the non-standard composition of this phytopreparation, the use of various undefined mixtures, the misattribution of silymarin vs. silybin, and also the failure to consider the chemistry of the respective components of silymarin.

Design and optimization of silymarin loaded in lyophilized fast melt tablets to attenuate lung toxicity induced via HgCl2 in rats.

The present study aimed to develop fast melting tablets (FMTs) using silymarin (SM) owing to FMTs rapid disintegration and dissolution. FMTs represent a pathway to help patients to increase their compliance level of treatment via facile administration without water or chewing beside reduction cost. One of the methods for FMTs formulation is lyophilization. Optimization of SM-FMTs was developed via a 32 factorial design. All prepared SM-FMTs were evaluated for weight variation, thickness, breaking force, friability, content uniformity, disintegration time (DT), and % SM released. The optimized FMT formula was selected based on the criteria of scoring the fastest DT and highest % SM released after 10 min (Q10). Optimized FMT was subjected to Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), and scanning electron microscopy (SEM) besides investigating its lung-protective efficacy. All SM-FMT tablets showed acceptable properties within the pharmacopeial standards. Optimized FMT (F7) scored a DT of 12.5 ± 0.64 Sec and % SM released at Q10 of 82.69 ± 2.88%. No incompatibilities were found between SM and excipients, it showed a porous structure under SEM. The optimized formula decreased cytokines, up-regulated miRNA133a, and down-regulated miRNA-155 and COX-2 involved in the protection against lung toxicity prompted by HgCl2 in a manner comparable to free SM at the same dosage.

Phosphodiester Silybin Dimers Powerful Radical Scavengers: A Antiproliferative Activity on Different Cancer Cell Lines.

Silibinin is the main biologically active component of silymarin extract and consists of a mixture 1:1 of two diastereoisomeric flavonolignans, namely silybin A (1a) and silybin B (1b), which we call here silybins. Despite the high interest in the activity of this flavonolignan, there are still few studies that give due attention to the role of its stereochemistry and, there is still today a strong need to investigate in this area. In this regard, here we report a study concerning the radical scavenger ability and the antiproliferative activity on different cell lines, both of silybins and phosphodiester-linked silybin dimers. An efficient synthetic strategy to obtain silybin dimers in an optical pure form (6aa, 6ab and 6bb) starting from a suitable building block of silybin A and silybin B, obtained by us from natural extract silibinin, was proposed. New dimers show strong antioxidant properties, determined through hydroxyl radical (HO●) scavenging ability, comparable to the value reported for known potent antioxidants such as quercetin. A preliminary screening was performed by treating cells with 10 and 50 µM concentrations for 48 h to identify the most sensitive cell lines. The results show that silibinin compounds were active on Jurkat, A375, WM266, and HeLa, but at the tested concentrations, they did not interfere with the growth of PANC, MCF-7, HDF or U87. In particular, both monomers (1a and 1b) and dimers (6aa, 6ab and 6bb) present selective anti-proliferative activity towards leukemia cells in the mid-micromolar range and are poorly active on normal cells. They exhibit different mechanisms of action in fact all the cells treated with the 1a and 1b go completely into apoptosis, whereas only part of the cells treated with 6aa and 6ab were found to be in apoptosis.

Flavonolignans from silymarin modulate antibiotic resistance and virulence in Staphylococcus aureus.

Antibiotic resistance is currently a serious health problem. Since the discovery of new antibiotics no longer seems to be a sufficient tool in the fight against multidrug-resistant infections, adjuvant (combination) therapy is gaining in importance as well as reducing bacterial virulence. Silymarin is a complex of flavonoids and flavonolignans known for its broad spectrum of biological activities, including its ability to modulate drug resistance in cancer. This work aimed to test eleven, optically pure silymarin flavonolignans for their ability to reverse the multidrug resistance phenotype of Staphylococcus aureus and reduce its virulence. Silybin A, 2,3-dehydrosilybin B, and 2,3-dehydrosilybin AB completely reversed antibiotic resistance at concentrations of 20 µM or less. Both 2,3-dehydrosilybin B and AB decreased the antibiotic-induced gene expression of representative efflux pumps belonging to the major facilitator (MFS), multidrug and toxic compound extrusion (MATE), and ATP-binding cassette (ABC) families. 2,3-Dehydrosilybin B also inhibited ethidium bromide accumulation and efflux in a clinical isolate whose NorA and MdeA overproduction was induced by antibiotics. Most of the tested flavonolignans reduced cell-to-cell communication on a tetrahydrofuran-borate (autoinducer-2) basis, with isosilychristin leading the way followed by 2,3-dehydrosilybin A and AB, which halved communication at 10 µM. Anhydrosilychristin was the only compound that reduced communication based on acyl-homoserine lactone (autoinducer 1), with an IC50 of 4.8 µM. Except for isosilychristin and anhydrosilychristin, all of the flavonolignans inhibited S. aureus surface colonization, with 2,3-dehydrosilybin A being the most active (IC50 10.6 µM). In conclusion, the selected flavonolignans, particularly derivatives of 2,3-dehydrosilybin B, 2,3-dehydrosilybin AB, and silybin A are non-toxic modulators of S. aureus multidrug resistance and can decrease the virulence of the bacterium, which deserves further detailed research.

System biology-based investigation of Silymarin to trace hepatoprotective effect.

Silymarin is used as a hepatoprotective agent since ancient times which could be via its potent anti-oxidant effect. However, the mode of silymarin for the hepatoprotective effect has not been established with the targets involved in hepatic cirrhosis. The present study investigated the multiple interactions of the flavonolignans from Silybum marianum with targets involved in hepatic cirrhosis using a series of system biology approaches. Chemo-informative tools and databases i.e. DIGEP-Pred and DisGeNET were used to predict the targets of flavonolignans and proteins involved in liver cirrhosis respectively. Further, STRING was used to enrich the protein-protein interaction for the flavonolignans-modulated targets. Similarly, molecular docking was performed using AutoDock Vina. Additionally, molecular dynamics simulation and MM-PBSA calculations were carried out for the lead-hit complexes by GROMACS. Thirteen flavonolignans were identified from S. marianum, in which silymonin exhibited the highest drug-likeness score i.e. 1.09. Similarly, CTNNB1 was found to be regulated by the 12 different flavonolignans and was majorly expressed within the compound(s)-protein(s)-pathway(s) network. Further, silymonin had the highest binding affinity; binding energy -9.2 kcal/mol with the CTNNB1 and formed very stable hydrogen bond interactions with Arg332, Ser336, Lys371, and Arg475 throughout 100 ns molecular dynamic production run. The binding free energy of CTNNB1-silymonin complex was found to be -15.83 ± 2.71 kcal/mol. The hepatoprotective property of S. marianum may be due to the presence of silymonin and silychristin; this could majorly modulate CTNNB1, HMOX1, and CASP8 in combination with other flavonolignans. Our findings further suggest designing the in-vitro and in-vivo studies to validate the interaction of flavonolignans with identified targets to strengthen present findings of S. marianum as a hepatoprotective..

Functional Insights into Silymarin as an Antiviral Agent against Enterovirus A71 (EV-A71).

Enterovirus A71 (EV-A71) is a major neurovirulent agent capable of causing severe hand, foot and mouth disease (HFMD) associated with neurological complications and death. Currently, no FDA-approved antiviral is available for the treatment of EV-A71 infections. The flavonoid silymarin was shown to exert virucidal effects, but the binding site on the capsid was unknown. In this study, the ligand interacting site of silymarin was determined in silico and validated in vitro. Moreover, the potential of EV-A71 to develop resistance against silymarin was further evaluated. Molecular docking of silymarin with the capsid of EV-A71 indicated that silymarin binds to viral protein 1 (VP1) of EV-A71, specifically at the GH loop of VP1. The in vitro binding of silymarin with VP1 of EV-A71 was validated using recombinant VP1 through ELISA competitive binding assay. Continuous passaging of EV-A71 in the presence of silymarin resulted in the emergence of a mutant carrying a substitution of isoleucine by threonine (I97T) at position 97 of the BC loop of EV-A71. The mutation was speculated to overcome the inhibitory effects of silymarin. This study provides functional insights into the underlying mechanism of EV-A71 inhibition by silymarin, but warrants further in vivo evaluation before being developed as a potential therapeutic agent.

SARS-CoV-2 Main Protease Active Site Ligands in the Human Metabolome.

In late 2019, a global pandemic occurred. The causative agent was identified as a member of the Coronaviridae family, called severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this study, we present an analysis on the substances identified in the human metabolome capable of binding the active site of the SARS-CoV-2 main protease (Mpro). The substances present in the human metabolome have both endogenous and exogenous origins. The aim of this research was to find molecules whose biochemical and toxicological profile was known that could be the starting point for the development of antiviral therapies. Our analysis revealed numerous metabolites-including xenobiotics-that bind this protease, which are essential to the lifecycle of the virus. Among these substances, silybin, a flavolignan compound and the main active component of silymarin, is particularly noteworthy. Silymarin is a standardized extract of milk thistle, Silybum marianum, and has been shown to exhibit antioxidant, hepatoprotective, antineoplastic, and antiviral activities. Our results-obtained in silico and in vitro-prove that silybin and silymarin, respectively, are able to inhibit Mpro, representing a possible food-derived natural compound that is useful as a therapeutic strategy against COVID-19.

The hepatoprotective effect of silibinin after hepatic ischemia/reperfusion in a rat model is confirmed by immunohistochemistry and qRT-PCR.

OBJECTIVES: We investigated the positive effect of silibinin after IV administration as silibinin-hydroxypropyl-ß-cyclodextrin lyophilized product, by measuring gene expression and liver tissue protein levels of tumor necrosis factor-α, interleukin-6, monocyte chemoattractant protein-1, matrix metalloproteinases matrix metalloproteinases and tissue inhibitor of matrix metalloproteinases-2. METHODS: 63 Wistar rats of age 13.24±4.40 weeks underwent ischemia/reperfusion (I/R) injury of the liver. The animals were randomized into three groups: Sham (S; n = 7); Control (C; n-28); silibinin (Si; n-28). The C and Si groups underwent 45 min ischemia. Si received silibinin-hydroxypropyl-ß-cyclodextrin intravenously immediately before reperfusion at a dose of 5 mg/kg. Both groups were further divided into 4 subgroups, based on euthanasia time (i.e., 60, 120, 180 and 240 min). KEY FINDINGS: qRT-PCR results confirmed the statistically significant reduction of the expression of the pro-inflammatory factors at 240 min after I/R injury (tumor necrosis factor-α: P < 0.05; MCR1: P < 0.05) and matrix metalloproteinases (matrix metalloproteinases 2: P < 0.05; matrix metalloproteinases 3: P < 0.05) and the increase of tissue inhibitor of matrix metalloproteinases-2 in liver tissue in the Si group. Moreover, results of immunohistochemistry levels confirmed that at 240 min pro-inflammatory factors (tumor necrosis factor-α: P < 0.05; MCR1: P < 0.05) and matrix metalloproteinases ( matrix metalloproteinases 2: P < 0.05; matrix metalloproteinases 3: P < 0.05) had a statistically significantly lower expression in the Si group while tissue inhibitor of matrix metalloproteinases-2 had a higher expression. CONCLUSIONS: Silibinin may have a beneficial effect on the protection of the liver.

Interaction of silymarin components and their sulfate metabolites with human serum albumin and cytochrome P450 (2C9, 2C19, 2D6, and 3A4) enzymes.

Silymarin is a mixture of flavonolignans isolated from the fruit of milk thistle (Silybum marianum (L.) Gaertner). Milk thistle extract is the active ingredient of several medications and dietary supplements to treat liver injury/diseases. After the oral administration, flavonolignans are extensively biotransformed, resulting in the formation of sulfate and/or glucuronide metabolites. Previous studies demonstrated that silymarin components form stable complexes with serum albumin and can inhibit certain cytochrome P450 (CYP) enzymes. Nevertheless, in most of these investigations, silybin was tested; while no or only limited information is available regarding other silymarin components and metabolites. In this study, the interactions of five silymarin components (silybin A, silybin B, isosilybin A, silychristin, and 2,3-dehydrosilychristin) and their sulfate metabolites were examined with human serum albumin and CYP (2C9, 2C19, 2D6, and 3A4) enzymes. Our results demonstrate that each compound tested forms stable complexes with albumin, and certain silymarin components/metabolites can inhibit CYP enzymes. Most of the sulfate conjugates were less potent inhibitors of CYP enzymes, but 2,3-dehydrosilychristin-19-O-sulfate showed the strongest inhibitory effect on CYP3A4. Based on these observations, the simultaneous administration of high dose silymarin with medications should be carefully considered, because milk thistle flavonolignans and/or their sulfate metabolites may interfere with drug therapy.