BACKGROUND: Over the past two decades, the global incidence of gout has markedly increased, affecting people worldwide. Considering the side effects of xanthine oxidase (XO) inhibitor drugs (e.g. allopurinol and febuxostat) used in the treatment of hyperuricemia and gout, the potential application of phytochemicals has been widely studied. In addition, XO also takes part in the elimination of certain drugs, including 6-mercaptopurine. In the current explorative study, we aimed to examine the potential effects of tea catechins, resveratrol, silymarin flavonolignans and some of their conjugated metabolites on XO-catalyzed xanthine and 6-mercaptopurine oxidation, applying in vitro assays and modeling studies. RESULTS: Catechins, resveratrol and resveratrol conjugates exerted no or only weak inhibitory effects on XO. Silybin A, silybin B and isosilybin A were weak, silychristin was a moderate, while 2,3-dehydrosilychristin was a potent inhibitor of the enzyme. Sulfate metabolites of silybin A, silybin B and isosilybin A were considerably stronger inhibitors compared to the parent flavonolignans, and the sulfation of 2,3-dehydrosilychristin slightly increased its inhibitory potency. Silychristin was the sole flavonolignan tested, where sulfate conjugation decreased its inhibitory effect. CONCLUSION: 2,3-Dehydrosilychristin seems to be a promising candidate for examining its in vivo antihyperuricemic effects, because both the parent compound and its sulfate conjugate are highly potent inhibitors of XO. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

• Keywords
• catechins, enzyme inhibition, resveratrol, silymarin, sulfate conjugates, xanthine oxidase,
• MeSH
• Enzyme Inhibitors chemistry   MeSH
• Catalysis MeSH
• Catechin * chemistry   MeSH
• Humans MeSH
• Mercaptopurine * chemistry   metabolism   MeSH
• Oxidation-Reduction MeSH
• Resveratrol * chemistry   MeSH
• Silybin chemistry   MeSH
• Silymarin * chemistry   MeSH
• Xanthine * chemistry   metabolism   MeSH
• Xanthine Oxidase * chemistry   metabolism   antagonists & inhibitors   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Enzyme Inhibitors MeSH
• Catechin * MeSH
• Mercaptopurine * MeSH
• Resveratrol * MeSH
• Silybin MeSH
• Silymarin * MeSH
• Xanthine * MeSH
• Xanthine Oxidase * MeSH

Silymarin is an extract obtained from the seeds of milk thistle (Sylibum marianum L., Asteraceae) and contains several structurally related flavonolignans and a small family of flavonoids. Mouse spleen cells represent highly sensitive primary cells suitable for studying the pharmacological potential and biofunctional properties of natural substances. Cultivation of splenocytes for 24 h under standard culture conditions (humidity, 37 °C, 5% CO2, atmospheric oxygen) resulted in decreased viability of splenocytes compared to intact cells. A cytoprotective effect of silybin (SB), silychristin (SCH) and 2,3-dehydrosilybin (DHSB) was observed at concentrations as low as 5 µmol/ml. At 50 µmol/ml, these substances restored and/or stimulated viability and mitochondrial membrane potential and had anti-apoptotic effect in the order SB > DHSB > SCH. The substances demonstrated a concentration-dependent activity in restoring the redox balance based on the changes in the concentration of reactive oxygen species (ROS), hydrogen peroxide (H2O2) and nitric oxide. This was in the order DHSB > SCH > SB, which correlated with the suppressed expression of nuclear factor erythroid 2-related factor 2 (Nrf2), catalase and glutathione peroxidase. The strong stimulation of the superoxide dismutase 1 gene converting ROS to H2O2 points to its dominant role in the maintaining redox homeostasis in splenocytes, which was disrupted by oxidative stress due to non-physiological culture conditions. Our study showed significant differences in the cytoprotective, antioxidant and anti-apoptotic activities of SB, SCH, and DHSB on splenocytes exposed to mild and AAPH-induced oxidative stress.

• Keywords
• 2,3-dehydrosilybin, Apoptosis, Mouse splenocytes, Redox balance, Silybin, Silychristin, Viability,
• MeSH
• Antioxidants * pharmacology   MeSH
• Apoptosis * drug effects   MeSH
• Cytoprotection * drug effects   MeSH
• NF-E2-Related Factor 2 metabolism   MeSH
• Membrane Potential, Mitochondrial drug effects   MeSH
• Mice, Inbred BALB C MeSH
• Mice MeSH
• Nitric Oxide metabolism   MeSH
• Oxidative Stress drug effects   MeSH
• Hydrogen Peroxide metabolism   MeSH
• Reactive Oxygen Species metabolism   MeSH
• Silybin MeSH
• Silymarin * pharmacology   analogs & derivatives   MeSH
• Spleen * cytology   drug effects   metabolism   MeSH
• Cell Survival drug effects   MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Antioxidants * MeSH
• dehydrosilybin MeSH Browser
• NF-E2-Related Factor 2 MeSH
• Nitric Oxide MeSH
• Hydrogen Peroxide MeSH
• Reactive Oxygen Species MeSH
• Silybin MeSH
• silychristin MeSH Browser
• Silymarin * MeSH

Flavonoids are naturally occurring compounds found in fruits, vegetables, and other plant-based foods, and they are known for their health benefits, such as UV protection, antioxidant, anti-inflammatory, and antiproliferative properties. This study investigates whether flavonoids, such as quercetin and 2,3-dehydrosilybin, can act as photoactivatable carbon monoxide (CO)-releasing molecules under physiological conditions. CO has been recently recognized as an important signaling molecule. Here, we show that upon direct irradiation, CO was released from both flavonoids in PBS with chemical yields of up to 0.23 equiv, which increased to almost unity by sensitized photooxygenation involving singlet oxygen. Photoreleased CO reduced cellular toxicity caused by high flavonol concentrations, partially restored mitochondrial respiration, reduced superoxide production induced by rotenone and high flavonol levels, and influenced the G0/G1 and G2/M phases of the cell cycle, showing antiproliferative effects. The findings highlight the potential of quercetin and 2,3-dehydrosilybin as CO-photoreleasing molecules with chemopreventive and therapeutic implications in human pathology and suggest their possible roles in plant biology.

• Keywords
• 2,3-dehydrosilybin, carbon monoxide, cell cycle, mitochondrial respiration, oxidative stress, photoCORM, photoinduced release, quercetin,
• MeSH
• Cell Cycle drug effects   MeSH
• Flavonoids * chemistry   pharmacology   MeSH
• Humans MeSH
• Mitochondria metabolism   drug effects   MeSH
• Carbon Monoxide * chemistry   metabolism   MeSH
• Cell Proliferation drug effects   MeSH
• Quercetin chemistry   pharmacology   MeSH
• Plant Extracts * chemistry   pharmacology   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Flavonoids * MeSH
• Carbon Monoxide * MeSH
• Quercetin MeSH
• Plant Extracts * MeSH

A library of previously unknown halogenated derivatives of flavonolignans (silybins A and B, 2,3-dehydrosilybin, silychristin A, and 2,3-dehydrosilychristin A) was prepared. The effect of halogenation on the biological activity of flavonolignans was investigated. Halogenated derivatives had a significant effect on bacteria. All prepared derivatives inhibited the AI-2 type of bacterial communication (quorum sensing) at concentrations below 10 µM. All prepared compounds also inhibited the adhesion of bacteria (Staphyloccocus aureus and Pseudomonas aeruginosa) to the surface, preventing biofilm formation. These two effects indicate that the halogenated derivatives are promising antibacterial agents. Moreover, these derivatives acted synergistically with antibiotics and reduced the viability of antibiotic-resistant S. aureus. Some flavonolignans were able to reverse the resistant phenotype to a sensitive one, implying that they modulate antibiotic resistance.

• Keywords
• bacteria, biological activity, flavonoids, flavonolignans, halogenation, multidrug resistance,
• MeSH
• Anti-Bacterial Agents pharmacology   MeSH
• Bacteria MeSH
• Biofilms MeSH
• Methicillin-Resistant Staphylococcus aureus * MeSH
• Pseudomonas aeruginosa MeSH
• Quorum Sensing MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Anti-Bacterial Agents MeSH

Silymarin is known for its hepatoprotective effects. Although there is solid evidence for its protective effects against Amanita phalloides intoxication, only inconclusive data are available for alcoholic liver damage. Since silymarin flavonolignans have metal-chelating activity, we hypothesized that silymarin may influence alcoholic liver damage by inhibiting zinc-containing alcohol dehydrogenase (ADH). Therefore, we tested the zinc-chelating activity of pure silymarin flavonolignans and their effect on yeast and equine ADH. The most active compounds were also tested on bovine glutamate dehydrogenase, an enzyme blocked by zinc ions. Of the six flavonolignans tested, only 2,3-dehydroderivatives (2,3-dehydrosilybin and 2,3-dehydrosilychristin) significantly chelated zinc ions. Their effect on yeast ADH was modest but stronger than that of the clinically used ADH inhibitor fomepizole. In contrast, fomepizole strongly blocked mammalian (equine) ADH. 2,3-Dehydrosilybin at low micromolar concentrations also partially inhibited this enzyme. These results were confirmed by in silico docking of active dehydroflavonolignans with equine ADH. Glutamate dehydrogenase activity was decreased by zinc ions in a concentration-dependent manner, and this inhibition was abolished by a standard zinc chelating agent. In contrast, 2,3-dehydroflavonolignans blocked the enzyme both in the absence and presence of zinc ions. Therefore, 2,3-dehydrosilybin might have a biologically relevant inhibitory effect on ADH and glutamate dehydrogenase.

• Keywords
• alcohol dehydrogenase, chelation, dehydrosilybin, docking, flavonolignans, glutamate dehydrogenase, silybin, zinc,
• MeSH
• Alcohol Dehydrogenase antagonists & inhibitors   MeSH
• Chelating Agents pharmacology   MeSH
• Flavonolignans pharmacology   MeSH
• Glutamate Dehydrogenase antagonists & inhibitors   MeSH
• Horses MeSH
• Yeasts drug effects   MeSH
• Silybin pharmacology   MeSH
• Silymarin pharmacology   MeSH
• Zinc isolation & purification   metabolism   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Alcohol Dehydrogenase MeSH
• Chelating Agents MeSH
• Flavonolignans MeSH
• Glutamate Dehydrogenase MeSH
• Silybin MeSH
• Silymarin MeSH
• Zinc MeSH

Milk thistle-based dietary supplements have become increasingly popular. The extract from milk thistle (Silybum marianum) is often used for the treatment of liver diseases because of the presence of its active component, silymarin. However, the co-occurrence of toxic mycotoxins in these preparations is quite frequent as well. The objective of this study was to investigate the changes in composition of liver lipidome and other clinical characteristics of experimental mice fed by a high-fat methionine-choline deficient diet inducing non-alcoholic fatty liver disease. The mice were exposed to (i) silymarin, (ii) mycotoxins (trichothecenes, enniatins, beauvericin, and altertoxins) and (iii) both silymarin and mycotoxins, and results were compared to the controls. The liver tissue extracts were analyzed by ultra-high performance liquid chromatography coupled with high-resolution tandem mass spectrometry. Using tools of univariate and multivariate statistical analysis, we were able to identify 48 lipid species from the classes of diacylglycerols, triacylglycerols, free fatty acids, fatty acid esters of hydroxy fatty acids and phospholipids clearly reflecting the dysregulation of lipid metabolism upon exposure to mycotoxin and/or silymarin.

• Keywords
• lipidome, mass spectrometry, metabolome, mice liver, mycotoxins, silymarin,
• MeSH
• Liver * metabolism   drug effects   MeSH
• Lipidomics * MeSH
• Lipid Metabolism drug effects   MeSH
• Mycotoxins * toxicity   MeSH
• Mice, Inbred C57BL MeSH
• Mice MeSH
• Non-alcoholic Fatty Liver Disease * metabolism   drug therapy   chemically induced   MeSH
• Silymarin * pharmacology   MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Mycotoxins * MeSH
• Silymarin * MeSH

This review focuses on the specific biological effects of optically pure silymarin flavo-nolignans, mainly silybins A and B, isosilybins A and B, silychristins A and B, and their 2,3-dehydro derivatives. The chirality of these flavonolignans is also discussed in terms of their analysis, preparative separation and chemical reactions. We demonstrated the specific activities of the respective diastereomers of flavonolignans and also the enantiomers of their 2,3-dehydro derivatives in the 3D anisotropic systems typically represented by biological systems. In vivo, silymarin flavonolignans do not act as redox antioxidants, but they play a role as specific ligands of biological targets, according to the "lock-and-key" concept. Estrogenic, antidiabetic, anticancer, antiviral, and antiparasitic effects have been demonstrated in optically pure flavonolignans. Potential application of pure flavonolignans has also been shown in cardiovascular and neurological diseases. Inhibition of drug-metabolizing enzymes and modulation of multidrug resistance activity by these compounds are discussed in detail. The future of "silymarin applications" lies in the use of optically pure components that can be applied directly or used as valuable lead structures, and in the exploration of their true molecular effects.

• Keywords
• Silybum marianum, chirality, dehydroflavonolignan, diastereomer, flavonoid, flavonolignan, isosilybin, milk thistle, silibinin, silybin, silychristin, silydianin, silymarin,
• MeSH
• Anti-Infective Agents chemistry   pharmacology   MeSH
• Antioxidants chemistry   pharmacology   MeSH
• Antineoplastic Agents, Phytogenic chemistry   pharmacology   MeSH
• Humans MeSH
• Silybin chemistry   pharmacology   MeSH
• Stereoisomerism MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Anti-Infective Agents MeSH
• Antioxidants MeSH
• Antineoplastic Agents, Phytogenic MeSH
• Silybin MeSH

2,3-Dehydrosilybin A and 2,3-dehydrosilybin B are a pair of enantiomers formed by the oxidation of the natural flavonolignans silybin A and silybin B, respectively. However, the antioxidant activity of 2,3-dehydrosilybin molecules is much stronger than that of their precursors. Here, we investigated the biotransformation of pure 2,3-dehydrosilybin A and 2,3-dehydrosilybin B in isolated human hepatocytes, and we also aimed to identify human UDP-glucuronosyltransferases (UGTs) and sulfotransferases (SULTs) with activity toward their respective enantiomers. After incubation with hepatocytes, both 2,3-dehydrosilybin A and 2,3-dehydrosilybin B were converted to hydroxyl derivatives, methylated hydroxyl derivatives, methyl derivatives, sulfates, and glucuronides. The products of direct conjugations predominated over those of oxidative metabolism, and glucuronides were the most abundant metabolites. Furthermore, we found that recombinant human UGTs 1A1, 1A3, 1A7, 1A8, 1A9, and 1A10 were capable of catalyzing the glucuronidation of both 2,3-dehydrosilybin A and 2,3-dehydrosilybin B. UGTs 1A1 and 1A7 showed the highest activity toward 2,3-dehydrosilybin A, and UGT1A9 showed the highest activity toward 2,3-dehydrosilybin B. The sulfation of 2,3-dehydrosilybin A and B was catalyzed by SULTs 1A1*1, 1A1*2, 1A2, 1A3, 1B1, 1C2, 1C4, and 1E1, of which SULT1A3 exhibited the highest activity toward both enantiomers. We conclude that 2,3-dehydrosilybin A and B are preferentially metabolized by conjugation reactions, and that several human UGT and SULT enzymes may play a role in these conjugations.

• Keywords
• UDP-glucuronosyltransferase, dehydrosilybin, glucuronidation, metabolism, silybin, sulfation, sulfotransferase,
• Publication type
• Journal Article MeSH

Veterinarians can recommend milk thistle for the treatment of equine liver disease and laminitis. Milk thistle seed cakes were fed in the range of normal feed doses in this study. The milk thistle seed cakes were fed (twice a day) to the experimental group of the horses (n = 5) and biochemical blood markers (TP, Albumin, ALT (alanine transaminase), AST (aspartate transaminase), ALP (alkaline phosphatase), GGT (gamma-glutamyltransferase), Bilirubin, Cholesterol, HDL (high-density lipoprotein), LDL (low-density lipoprotein), TAG (triacylglycerol), BHB (beta-hydroxybutyric acid), NEFA (non-esterified fatty acids), creatine kinase, creatinine, Urea, GSH-Px (glutathione peroxidase), TAS (total antioxidant status), lactate, glucose, cortisol, Ca, Pi) were monitored. The control group of horses (n = 5), bred and trained in the same conditions, was used for comparison. The control group received the entire feed dose as accepted by the horses in the experimental group before the beginning of the experiment. The aim was to find out whether the preparation of milk thistle seed cakes could have positive effects on the health of the horses. All ten horses received one feeding form before the beginning of the experimental monitoring. All horses were exposed to heavy physical exercise (regular combined driving training) after 56 days of milk thistle seed cakes feeding (up to 400 g/day). Three blood samples were taken (before physical exercise; about 15 min and 60 min after physical exercise). Significant differences (p < 0.05) were detected in the values of AST, NEFA, cortisol and Pi in the experimental group. The exercise effect was detected in the values of albumin, lactate, cortisol, NEFA, and calcium. Our results suggest that the feeding of milk thistle seed cakes could have a positive effect on the health of the horses.

• Keywords
• biochemical parameters, horse nutrition, physical exercise, phytogenics, silymarin,
• Publication type
• Journal Article MeSH

Some aromatic polyketides such as dietary flavonoids have gained reputation as miraculous molecules with preeminent beneficial effects on human health, for example, as antioxidants. However, there is little conclusive evidence that dietary flavonoids provide significant leads for developing more effective drugs, as the majority appears to be of negligible medicinal importance. Some aromatic polyketides of limited distribution have shown more interesting medicinal properties and additional research should be focused on them. Combretastatins, analogues of phenoxodiol, hepatoactive kavalactones, and silymarin are showing a considerable promise in the advanced phases of clinical trials for the treatment of various pathologies. If their limitations such as adverse side effects, poor water solubility, and oral inactivity are successfully eliminated, they might be prime candidates for the development of more effective and in some case safer drugs. This review highlights some of the newer compounds, where they are in the new drug pipeline and how researchers are searching for additional likely candidates.

• Keywords
• anticancer, antioxidants, clinical significance, dietary supplements, flavonoids, nutrition, polyketides,
• MeSH
• Antioxidants * chemistry   therapeutic use   MeSH
• Flavonoids * chemistry   therapeutic use   MeSH
• Clinical Trials as Topic MeSH
• Humans MeSH
• Polyketides * chemistry   therapeutic use   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Antioxidants * MeSH
• Flavonoids * MeSH
• Polyketides * MeSH