Anti-herpes virus activity of silibinin, the primary active component of Silybum marianum

Mechanistic Insights into the Pharmacological Significance of Silymarin

Medicinal plants are considered the reservoir of diverse therapeutic agents and have been traditionally employed worldwide to heal various ailments for several decades. Silymarin is a plant-derived mixture of polyphenolic flavonoids originating from the fruits and akenes of Silybum marianum and contains three flavonolignans, silibinins (silybins), silychristin and silydianin, along with taxifolin. Silybins are the major constituents in silymarin with almost 70–80% abundance and are accountable for most of the observed therapeutic activity. Silymarin has also been acknowledged from the ancient period and is utilized in European and Asian systems of traditional medicine for treating various liver disorders. The contemporary literature reveals that silymarin is employed significantly as a neuroprotective, hepatoprotective, cardioprotective, antioxidant, anti-cancer, anti-diabetic, anti-viral, anti-hypertensive, immunomodulator, anti-inflammatory, photoprotective and detoxification agent by targeting various cellular and molecular pathways, including MAPK, mTOR, β-catenin and Akt, different receptors and growth factors, as well as inhibiting numerous enzymes and the gene expression of several apoptotic proteins and inflammatory cytokines. Therefore, the current review aims to recapitulate and update the existing knowledge regarding the pharmacological potential of silymarin as evidenced by vast cellular, animal, and clinical studies, with a particular emphasis on its mechanisms of action.

The food plant Silybum marianum (L.) Gaertn.: Phytochemistry, Ethnopharmacology and clinical evidence

ETHNOPHARMACOLOGICAL RELEVANCE

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. 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.

AIM OF STUDY

The aim of our study is to draw a more comprehensive overview of the traditional heritage, pharmacological benefits and chemical fingerprint of S. marianum extracts and metabolites; as well as their metabolism and bioavailability.

MATERIALS AND METHODS

An extensive literature search has been conducted using relavant keywords and papers with rationale methodology and robust data were selected and discussed. Studies involving S. marianum or its main active ingredients with regards to hepatoprotective, antidiabetic, cardiovascular protection, anticancer and antimicrobial activities as well as the clinical trials performed on the plant, were discussed here.

RESULTS

S. marianum was subjected to thousands of ethnopharmacological, experimental and clinical investigations. Although, the plant is available for use as a dietary supplement, the FDA did not yet approve its use for cancer therapy. Nowadays, clinical investigations are in progress where a global evidence of its real efficiency is needed.

CONCLUSION

S. marianum is a worldwide used herb with unlimited number of investigations focusing on its benefits and properties, however, little is known about its clinical efficiency. Moreover, few studies have discussed its metabolism, pharmacokinetics and bioavailability, so that all future studies on S. marianum should focus on such areas.

Repression of Acetaminophen-Induced Hepatotoxicity in HepG2 Cells by Polyphenolic Compounds from Lauridia tetragona (L.f.) R.H. Archer

Lauridia tetragona (L.f) R.H. Archer is routinely used in traditional medicine; however, its hepatoprotective property is yet to be scientifically proven. To this effect, the hepatoprotective activity of the polyphenolic-rich fractions (PPRFs) was investigated against acetaminophen (APAP) injured HepG2 cells. The ability of the PPRF to scavenge free radicals was tested against 2,2-diphenyl-1-picrylhydrazyl (DPPH), and [2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonicacid)] (ABTS). The ferric ion reducing power (FRAP) was also evaluated as a cell-free antioxidant assay. The hepatoprotective activity was then investigated by observing the effect of PPRFs against APAP-induced reduction in cell viability of HepG2 cells. The concentrations of alanine aminotransferase (AST), aspartate aminotransferase (ALT) and lactate dehydrogenase (LDH) released into the medium were evaluated while the underlying mechanism was further explored through western blot analysis. Thereafter, the isolated PPRFs were identified using UHPLC-QToF-MS. All six fractions of the PPRFs isolated showed significant antioxidant properties that were evident by the effective scavenging of DPPH, ABTS, and higher FRAP. The results indicated that PPRF pretreatments ameliorated APAP-induced hepatocellular injury by significantly inhibiting the leakage of AST, ALT, and LDH into the medium. The most active fractions for hepatoprotection were PPRF4 and PPRF6 with IC₅₀ of 50.243 ± 8.03 and 154.59 ± 1.9 μg/mL, respectively. PPRFs markedly increased activities of liver superoxide dismutase, total antioxidant capacity, and liver glutathione concentration. Both PPRF4 and PPRF6 significantly increased the expression of Nrf2 and translocation. The LC-MS analysis revealed the presence of a wide variety of polyphenolics such as coumarin, ferulic acid, and caffeine among the dominant constituents. In conclusion, this study demonstrates that the isolated PPRFs have potential hepatoprotective activity that may be due to the increased expression of antioxidative genes dependent on Nrf2.

Antiviral and Immunomodulatory Effects of Norantea brasiliensis Choisy on Dengue Virus-2

BACKGROUND/AIMS

Severe dengue fever is a result of exacerbated immune responses and no specific treatments are available. We evaluated the antiviral and immunomodulatory effects of Norantea brasiliensis Choisy.

METHODS

Human adherent monocytes infected in vitro with dengue virus (DENV)-2 were incubated with the crude ethanol extract from leaves (NB1) or 3 derived fractions: dichloromethane (NB3), ethyl acetate (NB5), and butanolic (NB6) partitions. The antiviral and immunomodulatory activities were determined by intracellular detection of DENV antigen within monocytes and by secreted NS1 viral protein and cytokines.

RESULTS

The crude extract alone exhibited both antiviral activities (intracellular and secreted antigens) and all fractions derived from this extract modulated NS1 production. Regarding the immunomodulatory effect, among the secreted factors, TNF-α was inhibited by NB3 and NB6; IL-6 was inhibited by NB1, NB3, and NB6; IL-10 by NB1 and NB3; and IFN-α by NB6. The crude extract (NB1) presented the best antiviral effect, whereas the dichloromethane fraction (NB3) presented an immunomodulatory effect in the inflammatory and anti-inflammatory cytokines.

CONCLUSION

During in vitro DENV infection, N. brasiliensis Choisy exerts both antiviral and immunomodulatory effects that are likely associated, considering that less viral load may lead to less immunostimulation.

In vitro assessment of hepatoprotective agents against damage induced by acetaminophen and CCl4

BACKGROUND

In vitro bioassays are important in the evaluation of plants with possible hepatoprotective effects. The aims of this study were to evaluate the pretreatment of HepG2 cells with hepatoprotective agents against the damage induced by carbon tetrachloride (CCl₄) and paracetamol (APAP).

METHODS

Antioxidative activity was measured using an assay to measure 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging. The in vitro hepatotoxicity of CCl₄ and APAP, and the cytotoxic and hepatoprotective properties of silymarin (SLM), silybinin (SLB), and silyphos (SLP) were evaluated by measuring cell viability; activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH); total antioxidant capacity (TAOxC); and reduced glutathione (GSH), superoxide dismutase (SOD), and lipid peroxidation (malondialdehyde (MDA) levels).

RESULTS

Only SLB and SLM showed strong antioxidative activity in the DPPH assay (39.71 ± 0.85 μg/mL and 14.14 ± 0.65 μg/mL, respectively). CCl₄ induced time- and concentration-dependent changes. CCl₄ had significant effects on cell viability, enzyme activities, lipid peroxidation, TAOxC, and SOD and GSH levels. These differences remained significant up to an exposure time of 3 h. APAP induced a variety of dose- and time-dependent responses up to 72 h of exposure. SLM, SLB, and SLP were not cytotoxic. Only SLB at a concentration of 100 μg/mL or 150 μg/mL significantly decreased the enzyme activities and MDA level, and prevented depletion of total antioxidants compared with CCl₄.

CONCLUSIONS

CCl₄ was more consistent than APAP in inducing cell injury. Only SLB provided hepatoprotection. AST, LDH, and MDA levels were good markers of liver damage.