Silychristin

Otros Nombres

(2R,3R)-3,5,7-trihydroxy-2-[(2R,3S)-7-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-3-(hydroxymethyl)-2,3-dihydro-1-benzofuran-5-yl]-2,3-dihydrochromen-4-one(2R,3R)-3,5,7-Trihydroxy-2-[(2R,3S)-7-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-3-(hydroxymethyl)-2,3-dihydro-1-benzofuran-5-yl]chroman-4-one4H-1-Benzopyran-4-one, 2-[(2R,3S)-2,3-dihydro-7-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-3-(hydroxymethyl)-5-benzofuranyl]-2,3-dihydro-3,5,7-trihydroxy-, (2R,3R)-CHEBI:9143IsosilychristinSilichristinSilicristinSilicristin [INN]SilicristinaSilicristineSilicristinumSilychristin ASilychristin BSilycristinSilymarin II

Sinopsis

Silychristin: A Comprehensive Reference

1. Identity, Nomenclature, and Natural Source

1.1 Names and Synonyms

Silychristin (also known as silichristin) is a natural product and one of the constituents of silymarin, the standardized, active extract of the fruit of milk thistle, Silybum marianum. It is the second most abundant constituent in silymarin, after silybin. Silychristin is a flavonolignan, meaning it is composed of a flavonoid and a lignan. Its synonyms include silycristin, silicristin, silichristin, and Silymarin II.

Silychristin bears the CAS Registry Number 33889-69-9, has a molecular weight of 482.44, and carries the empirical formula C₂₅H₂₂O₁₀. Its full IUPAC name is (2R,3R)-3,5,7-trihydroxy-2-[(2R,3S)-7-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-3-(hydroxymethyl)-2,3-dihydro-1-benzofuran-5-yl]-2,3-dihydrochromen-4-one, and it is also known as Silymarin II and silichristin.

1.2 Natural Source and Botanical Context

The milk thistle Silybum marianum (L.) Gaernt., a member of the Asteraceae family, is an herb whose fruits have been used medicinally for over 2,000 years. Its properties are due to the presence of silymarin, an isomeric mixture of the flavonolignans silydianin, silychristin — present in two diastereoisomeric forms, A and B — silybin, and isosilybin, which also exist as two diastereoisomers.

Silybum marianum (L.) Gaertn., or milk thistle, is a medicinal plant native to Northern Africa, Southern Europe, Southern Russia and Anatolia. It also grows in South Australia, North and South America.

Silychristin is the second most abundant flavonolignan in the silymarin complex, which is usually produced by the acetone extraction of Silybum marianum (L.) Gaertn. (milk thistle) fruits. Natural silychristin is itself a mixture of two diastereomers (silychristin A and B) in approximately a 95:5 ratio. Isosilychristin is a silychristin isomer that occurs mainly in wild milk thistle.

1.3 Proportion Within the Silymarin Complex

Silymarin is a polyphenolic flavonoid and a mixture of silybin (silibinin), silychristin, isosilybin, and silydianin, which make up approximately 33.4%, 12.9%, 8.35%, and 3.5% of its structure, respectively. Another frequently cited estimate places silychristin at approximately 20% of the silymarin complex. Within the silymarin complex, silybin is present as two diastereomers (A and B) in approximately 1:1 proportion, with considerable amounts of other flavonolignans including silychristin (~20%), silydianin (~10%), isosilybin (~5%), dehydrosilybin, and a few flavonoids, mainly taxifolin.

The silymarin flavonolignans share the same molecular formula (C₂₅H₂₂O₁₀) and a common flavonolignan backbone, but differ in hydroxylation and stereochemistry, which may influence their solubility, absorption, and biological activity.

1.4 Common Forms and Preparations

In traditional knowledge, people have used S. marianum for liver disorders such as hepatitis, liver cirrhosis and gallbladder diseases. The main active compound of the plant seeds is silymarin, which is the most commonly used herbal supplement in the United States for liver problems. Nowadays, S. marianum products are available as capsules, powders, and extracts. Silychristin itself is not typically isolated as a standalone supplement but is encountered as an integral component of standardized silymarin extracts. Silymarin is extracted from the milk thistle seeds (technically the fruits) and available as a standardized extract.

Silymarin is poorly soluble in water, and its absorption from the gastrointestinal tract is 20–50% following oral administration; silymarin is administered in capsule form at a dosage of 240–800 mg/day in adult patients. Flavonolignans are, as a rule, insoluble or not very soluble in water. Because of this dissolving behaviour, the rate of liberation of these compounds and thus also the bioavailability and resorbability in the body of humans and mammals is unsatisfactory.

2. Historical and Traditional Use

2.1 Ancient Mediterranean Civilizations

The milk thistle Silybum marianum is an herb whose fruits have been used medicinally for over 2,000 years. It has a long history as a medicinal plant in folk medicine against liver disorders, kidney problems, rheumatism, gastronomic disturbances, cardiac disorders, and gall bladder-related disorders such as jaundice, hepatitis, and cirrhosis.

Roman physician Pliny the Elder in A.D. 23–79 had written about the use of this plant as a vegetable and juice mixed with honey to be good for "carrying off bile." In the 18th century, Culpepper mentioned that it is effective against liver and spleen obstructions, thereby being good for jaundice. During the 20th century, medicinal use of milk thistle was generalized for the treatment of hepatitis, jaundice, cirrhosis, liver poisoning and drug or alcohol abuse.

Written records show that as early as the first century, Romans were using the plant as a liver-protecting agent. The plant was also frequently used throughout the Middle Ages, and it is in the herbal literature of this period that the medicinal properties of milk thistle seeds are first noted.

2.2 European Folk and Monastic Medicine

Silybum marianum has a long history as a medicinal plant in folk medicine against liver disorders, kidney problems, rheumatism, gastronomic disturbances, cardiac disorders, and fever. In European folk medicine, S. marianum is used for the treatment of chronic hepatitis.

It is traditionally used in Europe as a vegetable in salads, and the seeds are used as a galactagogue for breastfeeding mothers.

Historically, milk thistle was used for liver disorders and to increase breast milk production.

2.3 Scientific Isolation of Silymarin and Its Constituents

Silymarin was first isolated by Wagner et al. in 1968. In 1968, Wagner et al. successfully isolated the active compound of milk thistle, which was designated as silymarin and later described as a mixture of chemicals known as flavonolignans. Further, constituents of silymarin were isolated and structurally characterized by Wagner and Seligmann, which include silybin (silibinin), silydianin and silychristin.

Silymarin is extracted from the seeds and fruit of Silybum marianum (Compositae) and in reality is a mixture of three structural components: silibinin, silydianine and silychristine. The structure of the constituents of silymarin was clarified in the 1960s.

2.4 Regulatory Recognition

In 2018, the European Medicines Agency (EMA) published an assessment report on the oral use of milk thistle fruit and its extracts in EU states. It finds that there is a "well-established use" of hepatoprotection approved by 11 countries and a "traditional use" of dyspeptic complaints in 4 countries. The EMA has also published a monograph on this herbal substance.

3. Biosynthesis and Chemistry

3.1 Biosynthetic Origin

Natural flavonolignans, which include silychristin, are biosynthesized by the oxidative coupling of a flavonoid and a phenylpropanoid moiety. The flavonoid moiety can be any number of flavonoids, including taxifolin, naringenin, luteolin, etc., while the phenylpropanoid moiety includes coniferyl alcohol, a monolignol, in most all flavonolignans. The two biosynthetic precursors specifically for silychristin are taxifolin and coniferyl alcohol, which are both biosynthesized via the phenylpropanoid pathway, a pathway which converts phenylalanine into 4-coumaroyl-CoA. Still much is not known today about the specific enzymes and mechanism of the biosynthesis of silychristin and its related flavonolignan counterparts in S. marianum.

The oxidative coupling reaction between taxifolin and coniferyl alcohol is mediated by free radical formation and catalyzed by peroxidase enzyme. Unfortunately, the enzyme catalyzing the oxidative coupling of flavonolignans has not yet been characterized. Mechanistically, the reaction proceeds by one-electron oxidation of the dihydroflavonol (+)-taxifolin to provide a phenoxy radical. This free radical couples with the quinone methide radical generated from coniferyl alcohol to produce an adduct in a reaction that is neither regio- nor enantioselective. Silychristin and silydianin are derived from a mesomer of the taxifolin-derived free radical.

The biosynthesis of these compounds is carried out by oxidative coupling catalysed by peroxidase enzymes between the flavonoid taxifolin and the phenylpropanoid coniferyl alcohol.

3.2 Structural Features and Diastereomerism

Silychristin belongs to a subclass of plant-based compounds called flavonolignans, which are part of the larger flavonoid family. These compounds are formed from a unique combination of flavonoids and lignans, two classes of naturally occurring molecules in plants.

Biogenetically, silymarin flavonolignans are generated by oxidatively combining taxifolin with coniferyl alcohol. The specificity of this method for stereochemical results is low. As a result, silybin is a two-diastereomer combination denoted as A and B. While it is technically possible to discriminate between these two diastereomers, preparatory separation is quite difficult. Similarly, silychristin itself occurs as two diastereomers. Natural silychristin is a mixture of two diastereomers (silychristin A and B) in an approximately 95:5 ratio.

The main chemical difference between silymarin and other flavonoids is that its isomers are substituted by a coniferyl alcohol group.

The silymarin content in fruits depends on the milk thistle variety and geographic and climatic conditions in which they grow; however, the relative proportions of individual components is a genetic characteristic associated with specific chemoraces.

4. Key Constituents of the Silymarin Complex and Relationship to Silychristin

Silymarin's primary constituents are the flavonolignan isomers silybins A and B, isosilybins A and B, silychristin (also known as silichristin), silydianin (also known as silidianin), and their flavonoid precursor, taxifolin. In the literature, the mixture of the silybins A and B is often referred to as silibinin.

In some descriptions, silymarin includes approximately 70–80 percent silymarin flavonolignans such as silybin A, silybin B, isosilybin A, isosilybin B, silydianin, silychristin A, silychristin B, 2,3-cis-silybin A, 2,3-cis-silybin B, 2,3-cis-isosilybin isomer; and flavonoids including taxifolin and quercetin, with the remaining 20–30 percent consisting of a chemically undefined fraction comprised of polymeric and oxidized polyphenolic compounds.

Silybin is the most abundant and pharmacologically active component, making it a key marker for evaluating silymarin bioavailability. Despite this, silychristin possesses distinct and in some respects superior properties relative to silybin, particularly in the domain of antioxidant activity, as detailed in Section 6 below.

5. Mechanisms of Action

5.1 Antioxidant Pathways

Mechanistic studies have clarified that silymarin's major bioactive constituents, including silibinin, silydianin, and silychristin, interact with redox-sensitive transcriptional pathways such as Nrf2/ARE and NF-κB, while also influencing metabolic regulators like AMPK and SIRT1. These mechanisms collectively work for their antioxidant, anti-inflammatory, and antifibrotic actions.

Silymarin is renowned for its hepatoprotective effects, and its antioxidant properties are equally significant. Silymarin's antioxidant mechanism involves the inhibition of ROS-producing enzymes, stabilization of mitochondrial membranes under oxidative stress, and activation of the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. This pathway enhances the expression of various antioxidant enzymes, improving the cellular redox balance. Furthermore, silymarin's ability to chelate metal ions prevents the formation of highly reactive hydroxyl radicals, a key contributor to oxidative stress.

The primary constituents of silymarin, including silybin, silydianin, and silychristin, each contribute to its multifaceted antioxidant mechanisms. These mechanisms include direct scavenging of ROS, inhibition of ROS-producing enzymes, maintenance of mitochondrial integrity, activation of antioxidant enzymes and transcription factors, and modulation of cellular redox homeostasis.

DPPH and ABTS radical scavenging assays revealed silychristin and its analogues to be powerful antioxidants, which were found to be more potent than silybin and 2,3-dehydrosilybin. Certain derivatives exhibited inhibition of microsomal lipoperoxidation with IC₅₀ values of 4–6 μM. On the basis of these results, silychristin-related compounds are likely responsible for most of the antioxidant properties of silymarin attributed traditionally to silybin (silibinin).

Silychristin's potential to scavenge the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical is nearly 14× higher than that of silybin (considered "the active component of silymarin") and approximately 1.5× lower than that of its oxidized derivative 2,3-dehydrosilybin. This compound exhibited a higher antioxidant capacity than "traditional" antioxidants.

5.2 Anti-inflammatory Mechanisms

It is generally accepted that silymarin exerts a membrane-stabilizing action preventing or inhibiting membrane peroxidation. Experiments with soybean lipoxygenase showed that the three components of silymarin brought about a concentration-dependent non-competitive inhibition of the lipoxygenase. The experiments also showed an analogous interaction with animal lipoxygenase, thus indicating that an inhibition of the peroxidation of fatty acids in vivo was plausible.

An inhibitory effect of silychristin (10–100 μM) on arachidonic acid metabolism by cyclooxygenase (COX) in blood platelets was discovered. This suggests silychristin can serve as an antiplatelet and anti-inflammatory agent.

Silychristin also inhibits LPS-induced production of nitric oxide (NO) in RAW 264.7 cells, with an IC₅₀ of 65 μM.

Silymarin was found to modify specifically the functions related to various transporters and receptors located in the cell membranes, including organic anion uptake transporter peptides (OATP), ABC transporters (P-gp), and bile salt export pump, as well as TNF-alpha-dependent phenomena. In the cytoplasm, some antioxidant properties and the inhibition of the lipoxygenase pathway seem quite selective and could contribute to 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.

5.3 Inhibition of P-Glycoprotein (Multidrug Resistance Modulation)

Silychristin (a component of silymarin) and silychristin derivatives have shown the particular ability to inhibit P-gp (P-glycoprotein) activity in a concentration-dependent manner.

Silychristin inhibits P-glycoprotein (P-gp) in P-gp-containing membranes with an IC₅₀ of 21 μM.

The inhibition of P-glycoprotein (P-gp) was determined in vitro, and the respective sensitization of doxorubicin-resistant ovarian carcinoma overproducing P-gp was detected. Despite the fact that inhibition of P-gp was demonstrated in a concentration-dependent manner for each tested compound, the sensitization of the resistant cell line was observed predominantly for silychristin A and 2,3-dehydrosilychristin A. Anhydrosilychristin and isosilychristin affected the expression of both the P-gp (ABCB1) and ABCG2 genes. This is the first report showing that silychristin A and its 2,3-dehydro-derivative modulate multidrug resistance by the direct inhibition of P-gp, in contrast to anhydrosilychristin and isosilychristin, which modulate multidrug resistance by downregulating the expression of the dominant transmembrane efflux pumps.

5.4 Inhibition of MCT8 (Monocarboxylate Transporter 8)

It is important to identify compounds with relevant environmental exposure and thyroid hormone transporter–modulating activity. Based on a non-radioactive TH uptake assay, a screening of 13 chemicals was performed. Silymarin, an extract of the milk thistle, was identified as a potent inhibitor of T3 uptake by MCT8. Individual silymarin components were further tested and silychristin was identified as the most effective one with an IC₅₀ of approximately 100 nM. The measured IC₅₀ value is at least 1 order of magnitude below those of other known thyroid hormone transporter inhibitors.

Monocarboxylate transporter 8 (MCT8) is a key player in thyroid hormone (TH) transport, known for its high specificity and affinity for THs and its direct association with Allan-Herndon-Dudley syndrome (AHDS) caused by pathogenic mutations. Cryo-EM structures of human MCT8 bound to the substrate T3 or the inhibitor silychristin, both in an outward-open conformation, have been resolved at resolutions of 3.0–3.2 Å. The carboxyl group of T3 is recognized by Arg371, while silychristin is also recognized by Arg371, competing with T3 for binding.

Silychristin already blocked MCT8 activity by approximately 40% at the lowest concentration tested (0.1 μM) and fully inhibited MCT8 activity at higher concentrations, whereas MCT10 activity was not inhibited at any concentration, confirming previous studies that identified silychristin as a potent and selective MCT8 inhibitor.

5.5 α-Glucosidase Inhibition

Silychristin was able to inhibit α-glucosidase, exhibiting a potential in the treatment of diabetes mellitus type II.

The hypoglycemic effect of silychristin A on streptozotocin (STZ)-induced type 1 diabetes in rats was evaluated. Silychristin A significantly lowered the glucose level, increased insulin secretion, and improved the structure of β cells in STZ-induced rats. Reactive oxygen species (ROS) production induced by STZ or high concentration of glucose (HG) was effectively suppressed by silychristin A in pancreatic INS-1 β cells. Western blot analysis demonstrated that silychristin A markedly suppressed STZ- or HG-induced cell apoptosis. It should be noted that this is animal and in vitro evidence; no human trials have specifically evaluated silychristin alone for diabetes.

Researchers demonstrated the α-amylase inhibitory activity of silymarin and investigated the components responsible for this effect. Two major flavonolignans, silibinin and silychristin, did not show inhibition against α-amylase, but two novel silychristin derivatives conjugated with dehydrodiconiferyl alcohol were isolated as the mildly inhibiting components of silymarin. Further analyses indicated the presence of various silychristin derivatives in silymarin that may act synergistically to show α-amylase inhibitory activity.

6. Scientific Evidence by Area of Use

Important methodological note: Silychristin has been studied almost entirely in the context of the full silymarin complex. There are very few clinical trials that examine silychristin as an isolated compound in humans. The bulk of human/clinical evidence described below pertains to silymarin (the full extract), and silychristin's contribution to those outcomes is inferred from its known chemical properties and in vitro or animal research. Where evidence applies specifically to silychristin as an isolated compound, this is noted explicitly.

6.1 Hepatoprotection (Liver Protection)

Silymarin protects liver cell membrane against hepatotoxic agents and improves liver function in experimental animals and humans. It is a mixture of three structural isomers: silybin, silydianin and silychristin, the former being the most active component. Silymarin protects liver cell membrane against hepatotoxic agents and improves liver function in experimental animals and humans. It is generally accepted that silymarin exerts a membrane-stabilizing action preventing or inhibiting membrane peroxidation.

Silychristin has been shown to be an antihepatotoxic flavonolignan and a flavonolignan isolated from Silybum marianum that has exhibited inhibitory activities against lipoxygenase and prostaglandin synthetase.

Silymarin has been used in the treatment of liver disease (alcoholic and non-alcoholic hepatitis), drug-induced liver damage, cirrhosis, mushroom poisoning, and viral hepatitis over the past 40 years.

Clinical evidence (silymarin complex): There isn't enough high-quality evidence to allow definite conclusions to be reached about the effects of milk thistle on health conditions in people. Results from clinical trials of milk thistle for liver diseases, such as alcohol-related liver disease, hepatitis B and C, non-alcoholic fatty liver disease, and liver problems caused by cancer chemotherapy, low oxygen levels, or toxins have been conflicting or too limited to support firm conclusions.

Drug-induced liver injury (anti-tuberculosis drugs): A meta-analysis of five randomized controlled trials (RCTs) totaling 1,198 patients (585 with silymarin, 613 with placebo) found that silymarin significantly reduced the occurrence of anti-TB drug-induced liver injury (DILI) at week 4 [RR: 0.33, 95% CI (0.15, 0.75)]. Silymarin also exerted a protective effect on liver function as measured by ALT, AST, and ALP. Adverse events were similar between silymarin and placebo groups.

6.2 Metabolic Effects and Diabetes

Human evidence (silymarin complex): Data indicate that silymarin treatment correlated with reduced insulin resistance and decreased fasting insulin levels significantly. Patients treated with 600 mg/day of silymarin for 12 months demonstrated lower fasting insulin levels. A separate clinical trial evaluated silymarin's effectiveness compared to metformin and pioglitazone in NAFLD patients.

Results from a small number of studies in people show that milk thistle extracts may help to control blood sugar in people with type 2 diabetes. Most of this research was done in Middle Eastern countries, and it is unclear whether the same results would be seen in other parts of the world.

Mechanistic evidence specific to silychristin (preclinical): Silychristin A, a major component with potent antioxidant capacity, recently gained more attention in control of diabetes. Research evaluated the hypoglycemic effect of silychristin A and investigated the underlying pharmacological mechanism. Data demonstrated that silychristin A attenuates type 1 diabetes via decreasing oxidative stress in pancreatic islet β cells and inhibiting intestinal α-glucosidase both in vitro and in STZ-induced type 1 diabetic rats. This evidence remains at the preclinical (animal and in vitro) stage. No human trials exist specifically evaluating isolated silychristin for diabetes.

6.3 Cancer-Related Research

Human clinical trials have investigated milk thistle or silymarin primarily in individuals with hepatitis or cirrhosis, although small studies have been reported about individuals with acute lymphoblastic leukemia, prostate cancer, breast cancer, and hepatocellular carcinoma.

A randomized clinical trial in children with acute lymphoblastic leukemia found that silymarin decreased the side effects of chemotherapy on the liver without harming the cancer treatment.

A randomized clinical trial in men with prostate cancer who had surgery to remove their prostate found that taking silymarin and selenium improved quality of life, lowered cholesterol, and increased the amount of selenium in the blood.

A randomized clinical trial of 30 patients with head and neck cancer who had radiation therapy found that those who took silymarin for 6 weeks had lower rates of radiation-related mucositis compared to those who did not.

Silychristin-specific mechanism in multidrug resistance: Both silychristin A and its derivatives inhibited P-gp in a concentration-dependent manner. 2,3-Dehydrosilychristin A and anhydrosilychristin exhibited the lowest IC₅₀ values. All the tested compounds acted as antioxidants within the cells, but 2,3-dehydro- and anhydro derivatives were almost twice as potent as the other tested compounds. Similar results were obtained in LPS-stimulated macrophages, where 2,3-dehydro- and anhydrosilychristin inhibited NO production nearly twice as efficiently as silychristin A.

The biochemical and molecular mechanisms of action of these substances in cancer are subjects of ongoing research. Paradoxically, many of its identified actions such as antioxidant, promoter of ribosomal synthesis, and mitochondrial membrane stabilization, may seem protumoral at first sight; however, silymarin compounds have clear anticancer effects. Evidence for silychristin's specific anticancer effects is limited to in vitro and animal models; human clinical data on isolated silychristin in oncology are absent.

6.4 Thyroid Hormone System

Silychristin inhibits MCT8-mediated thyroid hormone (TH) uptake, with an IC₅₀ of 110 nM. Despite its therapeutic use in liver disease, concerns have been raised about silychristin's potential adverse effects on the TH axis. Therefore, further structural insights are necessary to fully understand the mechanism.

Because silymarin is a frequently used adjuvant therapeutic for hepatitis C infection and chronic liver disease, these observations raise questions regarding its safety with respect to unwanted effects on the TH axis. This represents an area of emerging concern. The evidence is currently preclinical (cell-based and structural biology), and the clinical significance in humans taking standard silymarin doses is not yet established. In vivo effects of exposure to silychristin, as a potent in vitro inhibitor of MCT8, on several aspects of the thyroid hormone system were examined in a rat study. Adult female rats were daily gavaged with 0, 250, or 500 mg/kg/day (n = 10/group) of silychristin for 7 days.

6.5 Neurological Context

Silymarin has emerged as one of the most mechanistically characterized botanical agents in hepatoprotective and neuroprotective therapy. Silymarin has a rich history of use in traditional medicine, and its recognized hepatoprotective, neuroprotective and antioxidant effects are now understood in relation to its complex phytochemical composition and the downstream molecular pathways it modulates. Silychristin, as a constituent, participates in Nrf2/ARE and NF-κB pathway interactions. However, specific human clinical evidence for silychristin alone in neurological conditions is absent; the neuroprotective data are largely preclinical.

6.6 Antioxidant Activity: Comparison with Silybin

DPPH and ABTS radical scavenging assays revealed silychristin and its analogues to be powerful antioxidants, found to be more potent than silybin and 2,3-dehydrosilybin. Certain silychristin derivatives exhibited inhibition of microsomal lipoperoxidation (IC₅₀ 4–6 μM). Moreover, these compounds were found to be almost noncytotoxic for 10 human cell lines of different histogenetic origins. On the basis of these results, silychristin-related compounds are likely responsible for most of the antioxidant properties of silymarin attributed traditionally to silybin (silibinin).

7. Body Systems and Health Areas of Association

Hepatic (Liver) System: Silymarin manifests hepatoprotection by scavenging free radicals, raising the glutathione content, inhibiting lipid peroxidation, and restoring the function of enzymes, thereby generating membrane stabilization and preventing toxic metabolic liver injury.
Endocrine System (Thyroid): Silychristin was found to inhibit the thyroid hormone transporter (MCT8) with an IC₅₀ of approximately 100 nM in MDCK1 cells. This data indicate that silychristin could block the uptake of thyroid hormone.
Metabolic / Pancreatic System: Silychristin A shows potent α-glucosidase inhibitory activity and protects pancreatic β cell line INS-1 from ROS-induced apoptosis.
Immune and Inflammatory System: Silymarin constituents including silychristin act as antioxidant, anti-inflammatory, hepatoprotective, anti-cancer, immune response modulator, and anti-viral agents.
Oncology / Multidrug Resistance: Silychristin and silychristin derivatives have shown the particular ability to inhibit P-gp activity in a concentration-dependent manner.
Cardiovascular / Platelet System: An inhibitory effect of silychristin (10–100 μM) on the arachidonic acid metabolism by cyclooxygenase (COX) in blood platelets was discovered, suggesting silychristin can serve as an antiplatelet and anti-inflammatory agent.

8. Dosage Forms and Reported Dosages

Silychristin is not marketed as a standalone therapeutic agent. It is encountered as a constituent of standardized silymarin (milk thistle) preparations. The dosages reported below are for the silymarin complex in clinical studies and regulatory contexts, within which silychristin comprises approximately 12–20% by weight.

Silymarin is administered in capsule form at a dosage of 240–800 mg/day in adult patients.
A phase II clinical trial (ClinicalTrials.gov NCT00680407) enrolled patients with histologically confirmed NASH, randomizing them to placebo or one of two active silymarin (Legalon®) treatment groups: 420 mg three times daily or 700 mg three times daily, for 48–50 weeks.
A Phase II trial for chronic hepatitis C randomized eligible subjects to placebo or one of two dosages of Legalon®: 420 mg or 700 mg, administered orally thrice daily.
Data indicate that silymarin treatment at 600 mg/day for 12 months was associated with lower fasting insulin levels in one clinical trial.
In a rat in vivo study investigating silychristin's effects on the thyroid hormone system, adult female rats were gavaged with 0, 250, or 500 mg/kg/day of isolated silychristin for 7 days. This represents a preclinical dosing study; these doses are not applicable to humans and no equivalent human dose for isolated silychristin has been established.

9. Pharmacokinetics and Bioavailability Considerations

Flavonolignans are, as a rule, insoluble or not very soluble in water. Because of this dissolving behaviour, the rate of liberation of these compounds and thus also the bioavailability and resorbability in the body of humans and mammals is unsatisfactory.

Although hepatoprotective properties of silybin are well documented, the clinical therapeutic efficacy is limited by its low bioavailability due to absorption rates, extensive phase II metabolism, and biliary excretion. Similar bioavailability constraints apply to silychristin, given its shared molecular scaffold and physicochemical properties.

Silymarin, silybin, and milk thistle extract currently rank among the top-selling botanical supplements or phytomedicines. However, the clinical outcomes of the hepatoprotective effects are varied for silymarin, mainly caused by its low bioavailability.

In the liver, silymarin undergoes Phase I and Phase II metabolism. Silymarin metabolization in Phase I by cytochrome P450 family 2 subfamily C member 8 (CYP2C8) produces a major metabolite, o-demethylated silybin, and several minor metabolites.

Silymarin may be a natural multi-functional and multi-target drug. Various formulation strategies, including phospholipid complexes, nanoemulsions, and cyclodextrin inclusion, have been investigated to improve bioavailability of silymarin components. The quality of silymarin products is a documented concern: concerns have been raised about poor chemical and microbiological quality of milk thistle dietary supplements sold in the United States and other countries.

10. Safety Considerations and Drug Interactions

10.1 General Tolerability

The most common side effects are digestive symptoms such as bloating, nausea, and gas.

As with most herbal products, there is no definitive way to monitor blood levels of milk thistle or its compounds, and little data is available on the therapeutic index of the supplement.

10.2 Hepatotoxicity Signal in Cancer Patients

Asymptomatic liver toxicity in clinical trials performed on cancer patients has been reported; researchers observed an increase in ALT and bilirubin levels.

10.3 Cytochrome P450 and UGT Interactions

Silymarin has been shown to decrease the activity of cytochrome P-450 enzymes and UDP-glucuronosyltransferase (UGT) enzymes, prompting healthcare providers to caution patients against co-administration of milk thistle and specific pharmaceutical agents.

10.4 Thyroid Hormone Axis: A Specific Concern for Silychristin

Silychristin inhibits MCT8-mediated thyroid hormone uptake with an IC₅₀ of 110 nM. Despite its therapeutic use in liver disease, concerns have been raised about silychristin's potential adverse effects on the thyroid hormone axis. Because silymarin is a frequently used adjuvant therapeutic for hepatitis C infection and chronic liver disease, these observations raise questions regarding its safety with respect to unwanted effects on the thyroid hormone axis. This concern is based on in vitro and structural biology findings, and the clinical significance at human-relevant exposures from standard silymarin supplementation remains to be established.

10.5 Antiplatelet Effects

An inhibitory effect of silychristin (10–100 μM) on arachidonic acid metabolism by cyclooxygenase (COX) in blood platelets was discovered, suggesting silychristin can serve as an antiplatelet and anti-inflammatory agent. The clinical relevance of this effect in patients concurrently using anticoagulant or antiplatelet medications warrants attention, though specific human interaction data for isolated silychristin are not established.

10.6 Evidence Quality and Limitations

Electronic database searches have identified silymarin, silibinin, silicristin, or milk thistle as descriptors in over 700 papers (with 34% published in the last 5 years at time of review; 92% dealing with animal pharmacological data). Only papers adequately reporting on experimental conditions, dosing, variables tested and statistics were analyzed. Available data 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.

The future of milk thistle research is promising, and high-quality randomized clinical trials on milk thistle versus placebo may be needed to further demonstrate the safety and efficacy of this herb.

References

Condiciones de Salud

Condiciones de salud que Silychristin puede ayudar a apoyar.

Ojos Inyectados en SangreTradicional
Silychristin is a flavonolignan component of the silymarin complex from milk thistle (Silybum marianum). As part of the clinically studied silymarin complex it contributes to the hepatoprotective and choleretic effects used for liver and gallbladder disease, with evidence derived indirectly through the whole silymarin complex.
ConjuntivitisTradicional
A minor flavonolignan component of Milk Thistle's silymarin complex, silychristin contributes to the overall hepatoprotective and antioxidant activity of silymarin preparations used for post-illness liver recovery. Specific isolated studies are limited; its effects derive from the well-documented silymarin complex evidence base.
Digestión (deficiente)Tradicional
Silychristin is a flavonolignan component of silymarin (milk thistle extract) with antioxidant and hepatoprotective activity. As part of the silymarin complex used in traditional and scientific whole-body liver cleanse applications, silychristin contributes to the overall hepatoprotective and detoxification-supporting effects of standardized milk thistle.

Sistemas Corporales

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