Astilbin selectively induces dysfunction of liver-infiltrating cells--novel protection from liver damage

The natural source, physicochemical properties, biological activities and metabolism of astilbin

Astilbin is a dihydroflavanol found in many plants and processed foods. Astilbin possesses multiple health-beneficial bioactivities and has received great attention. Hence, the natural source, physicochemical properties, biological activities and metabolism of astilbin are summarized in the present article. Engelhardia roxburghiana Wall. and Smilax glabra Roxb. are the main resource for astilbin purification because of high content. Because of chemical instability, astilbin amount in foods is dependent on the processing and storage conditions. The degradation of astilbin includes isomerization and decomposition. The interconversion of astilbin and its isomers occurs through a chalcone intermediates, which significantly affects the taste of wine during storage. Many factors such as temperature, pH, metal ions and food additives could affect the chemical stability of astilbin. Astilbin exhibits very novel selective immunosuppressive activity, which is not found in other compounds. The rhamnose moiety of astilbin is essential for this bioactivity. After digestion, astilbin was mainly absorbed and transported in circulatory blood in its intact form, and only one metabolite, 3'-O-methylastilbin, was found. Although having many bioactivities, astilbin faces the challenge of poor bioavailability. Some promising strategies were developed for improving its bioavailability, particularly through fabrication the zein nanoparticles.

Astilbin Protects Against Carbon Tetrachloride-Induced Liver Fibrosis in Rats

BACKGROUND

Hepatic fibrosis is an inflammatory liver disease, and there is no effective therapy at present. Astilbin is a bioactive ingredient found in many medicinal and food plants, with antioxidative, anti-inflammatory, and antitumor properties.

OBJECTIVES

This study aimed to investigate the protective effect and related molecular mechanism of astilbin against carbon tetrachloride (CCl4)-induced liver fibrosis in rats.

METHODS

Liver fibrosis was induced by injection of CCl4 in male Sprague-Dawley rats, and those rats were then treated with astilbin at different concentrations. Pathological changes, collagen production, inflammatory cytokine, and oxidative stress were evaluated to evaluate the effects of astilbin on CCl4-induced hepatic fibrosis. Real-time PCR and western blot were performed to detect the mRNA and protein expression of indicated genes.

RESULTS

We discovered that CCl4 caused significant fibrosis damage in rat liver, and astilbin dose-dependently improved the liver functions and fibrosis degree. Astilbin treatment significantly decreased collagen production, inflammatory response, and oxidative stress in vivo. Mechanically, administration of astilbin obviously elevated the hepatic levels of Nrf2 and its downstream components, including NAD(P)H:quinone oxidoreductase 1 (Nqo1), heme oxygenase (HO-1), glutamate-cysteine ligase catalytic subunit, and glutamate cysteine ligase modifier.

CONCLUSIONS

Taken together, these findings demonstrate that astilbin could protect against CCL4 induced-liver fibrosis in rats.

Inhibitory effects of astilbin, neoastilbin and isoastilbin on human cytochrome CYP3A4 and 2D6 activities

Astilbin, neoastilbin and isoastilbin are three flavonoid isomers from Smilacis glabrae Roxb. (S. glabrae). Several studies have shown that consumption of flavonoids can increase the risk of food/drug-drug interaction by affecting the activities of human cytochrome CYP3A4 and 2D6. In the present study, an ultrahigh-performance liquid chromatography and triple quadrupole mass spectrometry method was developed for the determination of the interaction between three flavonoid isomers and two CYPs. Under the optimized reaction conditions, the K_m values were 18.9 and 36.4 μM and the V_max values were 0.02 and 0.20 μM/min for CYP3A4 and 2D6 in vitro, respectively. Astilbin showed the strongest inhibition on CYP3A4, followed by isoastilbin and neoastilbin with IC₅₀ values of 2.63, 3.03 and 6.51 μM. Neoastilbin showed the strongest inhibition on CYP2D6, followed by isoastilbin and astilbin, with IC₅₀ values of 1.48, 11.87 and 14.16 μM, respectively. The three isomers showed reversible inhibition on both enzymes. Neoastilbin and astilbin were noncompetitive type for CYP3A4 and 2D6, isoastilbin was a mixture and noncompetitive type for CYP3A4 and 2D6, respectively. Our study suggests that the three isomers may increase the risk of food/drug-drug interactions by affecting the activities of CYP3A4 and 2D6.

ASTILBIN: A PROMISING UNEXPLORED COMPOUND WITH MULTIDIMENSIONAL MEDICINAL AND HEALTH BENEFITS

BACKGROUND

Many flavonoids have various beneficial actions like anti-inflammatory, anti-carcinogenic properties and many other clinical conditions. Astilbin is one such flavanoid compound having many physiological as well as pharmacological actions.

PURPOSE

To summarize the important findings from the research conducted using astilbin having significance to its physiological and pharmacological activities as well as the patents filed using astilbin.

STUDY DESIGN

Systematic review and compilation of the collected literature.

METHOD

An extensive investigation of literature was done using several worldwide electronic scientific databases like PUBMED, SCOPUS, Science Direct and Google Scholar etc. All the article available in the English language that used our compound of interest i.e. astilbin, on the basis of inclusion criteria decided were retrieved from these databases, thoroughly reviewed and were summarized.

RESULT

It has been established that astilbin can play a vital in the management of diseases associated with immune system. It also possesses antibacterial, anti-oxidative and hepatoprotective activity.

CONCLUSION

These researches provide evidence that astilbin possesses great potential and thus can be utilized in the management of various disorders, thus establishing itself as a potential candidate for novel drug development. Also, there is still room for research on astilbin like it can be evaluated for anticancer potential, protective effect in various diabetic complications and many more. Overall observations from data suggested that astilbin is a promising compound and proved its efficacy in every preclinical study which is conducted till date. Some of the pharmacological activity is still unexplored. After successful preclinical trials, astilbin can go for further clinical trials.

Pharmacokinetic, bioavailability and tissue distribution study of astilbin in rats

OBJECTIVE

The purpose of this study is to reveal the pharmacokinetic profiles of astilbin with various doses in rats and investigate the oral absolute bioavailability and tissue distribution of astilbin after oral administration.

METHODS

Wistar rats were orally administered astilbin 12, 24 mg/kg and intravenous administered astilbin 6 mg/kg randomly. The concentration of astilbin in rat plasma and various tissue samples was determined by LC-MS/MS method. Noncompartmental pharmacokinetic parameters including AUC and t_1/2 were calculated from plasma concentration-time data of astilbin with the DAS 3.0.

KEY FINDINGS

After oral administration of astilbin 12 and 24 mg/kg to rats, the oral absolute bioavailability of astilbin were 1.16 ± 0.695% and 1.27 ± 0.379%; the plasma elimination half-lives (t_1/2 ) were 101 ± 35.8 and 109 ± 25.3 min, respectively. Astilbin had a rapid absorption and a wide distribution throughout the whole body except liver and fat following oral administration. Astilbin could penetrate the blood-brain barrier of rat.

CONCLUSIONS

The oral absolute bioavailability of astilbin is poor because of the low permeability and solubility. Both oral absorption and clearance of astilbin in rats are rapid after oral administration.

Study of pro-angiogenic activity of astilbin on human umbilical vein endothelial cells in vitro and zebrafish in vivo

Astilbin is a dihydroflavonol natural product isolated from a variety of food and medicinal herbs (e.g. Smilax glabra Roxb.), and its mechanism of action in vascular pharmacology remains unclear. The aim of this study was to investigate the pro-angiogenic effects of astilbin and its putative mechanism of action. Briefly, our in vitro studies showed a dose-dependent ability of astilbin to increase the ability of HUVECs to proliferate and migrate, and undergo cell invasion and tube formation. Moreover, astilbin significantly increased the expression levels of several major proteins involved in the angiogenesis pathway, e.g. PI3K, Akt, p38 and ERK1/2. Our in vivo studies demonstrated the ability of astilbin to significantly restore the blood vessel loss induced by VRI in a VRI-induced vascular insufficiency zebrafish model. In conclusion, in this study we first demonstrate that astilbin exhibits pro-angiogenic activity in HUVECs and VRI-induced vascular insufficient zebrafish, possibly through the activation of the PI3K/Akt and MAPK/ERK dependent signaling pathways. These findings suggest that astilbin could be further developed as a potential agent in the prevention or treatment of insufficient angiogenesis related diseases in the future.

Pro-angiogenic activity of astilbin on endothelial cells in vitro and zebrafish in vivo.

Screening the Best Compatibility of Selaginella moellendorffii Prescription on Hyperuricemia and Gouty Arthritis and Its Mechanism

Objectives

The Selaginella moellendorffii prescription (SMP) consists of S. moellendorffii Herba (SM), Smilacis glabrae Rhizoma (SGR), and Plantaginis Semen (PS). It has been commonly used to treat hyperuricemia and acute gouty arthritis as a hospital preparation. This study was aimed at investigating the best compatibility ratio of SMP on hyperuricemia and gouty arthritis and getting better insight of the possible mechanism. Methods. In vitro, anti-inflammatory activity of SMP was evaluated by lipopolysaccharide (LPS) induced RAW264.7 cells. The release of nitric oxide (NO) was screened by Griess assay, and NF-κB p65 and NLRP3 proteins expression was examined by immunofluorescence assay. Then, the levels of creatinine (Cr), blood urea nitrogen (BUN), and uric acid (UA) were detected in mice induced by potassium oxonate, and the paw oedema, inflammatory mediators, and histological examination were analyzed in rats induced by monosodium urate (MSU). HPLC method was employed to investigate the chemical profile of this preparation. Results. In vitro, SMP-3 (the ratio of SMP:SGR:PS was 3:1:1) exhibited the most potent anti-NO production activity without obvious toxicity. This anti-inflammatory effect was associated with suppression of NF-κB p65 nuclear translocation and NLRP3 protein expression. In animal experiments, the levels of BUN and Cr in SMP-3 group were lower than other extract groups, and the level of UA was also remarkably decreased by SMP-3 in hyperuricemic mice (P<0.01). Besides, SMP-3 extract was able to prevent the paw edema, reduce gouty joint inflammatory features, and decrease the levels IL-1β, PGE-2, IL-8, and NO in gouty arthritis rats. Furthermore, 6-C-β-D-xylopyranosyl-8-C-β-D-glucopyranosyl, apigenin, and astilbin were identified from SMP-3 extract.

Conclusions

In summary, SMP-3 may be a potential therapeutic agent for the prevention of hyperuricemic and gout.

Bioavailability Enhancement of Astilbin in Rats through Zein-Caseinate Nanoparticles

Astilbin-encapsulated zein-caseinate nanoparticles were fabricated through the antisolvent method. The encapsulation and loading efficiency of astilbin in the nanoparticles were determined by high-performance liquid chromatography. The nanoparticles were characterized by particle size, ζ potential, redispersibility, scanning electron microscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy, and differential scanning calorimetry (DSC). Under the optimal formulation of astilbin, zein, and sodium caseinate with a mass ratio of 1:1:2, the size and ζ potential of the nanoparticles were 152.9 nm and -40.43 mV, respectively, while the encapsulation and loading efficiency of astilbin were 80.1 and 21.8%, respectively. The nanoparticles had good redispersibility in water without a particle size change after freeze drying. The nanoparticles showed a spherical shape with a smooth surface. XRD and DSC analyses showed that astilbin existed in amorphous form in the nanoparticles. The interactions between astilbin and the protein were found, and astilbin was encapsulated in nanoparticles rather than adsorbed. The diffusion of astilbin from nanoparticles was significantly faster than that of astilbin suspensions in both simulated gastric and intestinal fluids. Astilbin was relatively stable in simulated intestinal fluids, and the encapsulation in the nanoparticles showed a slight stability improvement effect. A pharmacokinetic study showed that the absolute bioavailability of astilbin was improved from 0.32 to 4.40% in rats through nanoparticle fabrication.

Ethnomedicine, Phytochemistry and Pharmacology of Smilax glabra: An Important Traditional Chinese Medicine

Smilax glabra (SG) Roxb., a well-known traditional Chinese medicine, has been extensively used worldwide for its marked pharmacological activities for treating syphilitic poisoned sores, limb hypertonicity, morbid leucorrhea, eczema pruritus, strangury due to heat, carbuncle toxin, and many other human ailments. Approximately 200 chemical compounds have been isolated from SG Roxb., and the major components have been determined to be flavonoids and flavonoid glycosides, phenolic acids, and steroids. Among these active compounds, the effects of astilbin, which is used as a quality control marker to determine the quality of SG Roxb., have been widely investigated. Based on in vivo and in vitro studies, the primary active components of SG Roxb. possess various pharmacological activities, such as cytotoxic, anti-inflammatory and immune-modulatory effects, anti-oxidant, hepatoprotective, antiviral, antibacterial, and cardiovascular system protective activities. However, an extensive study to determine the relationship between the chemical compositions and pharmacological effects of SG Roxb. has not been conducted and is worth of our study. Improving the means of utilizing the effects of SG is crucial. The present paper reviews the ethnopharmacology, phytochemistry, and pharmacology of SG Roxb. and assesses its ethnopharmacological use in order to explore its therapeutic potential for future research.

Astilbin from Smilax glabra Roxb. Attenuates Inflammatory Responses in Complete Freund's Adjuvant-Induced Arthritis Rats

Astilbin, a flavonoid compound, was isolated from the rhizome of Smilax glabra Roxb. (with red cross-section) grown in Guizhou Province, China. We accessed its effect and potential mechanism on attenuation of the inflammatory response in CFA-induced AA rats. Our results showed that daily oral administration of astilbin at 5.3 mg/kg reduced joint damage in the hind paw of AA rats. Accordingly, astilbin exhibited remarkable inhibitory effects on TNF-α, IL-1β, and IL-6 mRNA expression. Significant decrease of serum cytokine levels of TNF-α, IL-1β, and IL-6 was also observed in astilbin-treated AA rats compared to the vehicle-treated AA rats. The reduced expression of these cytokines was associated with protein activity suppression of three key molecular targets in the pathogenesis of RA, including IKKβ, NF-κB p65 subunit, and TLR adaptor MyD88. Furthermore, the therapeutic effects of astilbin on the inhibition of cytokines production as well as the reduction of inflammatory response in AA rats are close to a commonly used antirheumatic drug, leflunomide. Collectively, our data suggest that the action mechanism of astilbin, as an anti-inflammatory agent for RA treatment, is associated with modulating the production of proinflammatory cytokines and inhibiting the expression of key elements in NF-κB signaling pathway mediated by TLR.

Astilbin ameliorates experimental autoimmune myasthenia gravis by decreased Th17 cytokines and up-regulated T regulatory cells

Astilbin, a major bioactive compound extracted from Rhizoma smilacis glabrae (RSG), has been reported to possess immunosuppressive properties. Our study first evaluated the effect of astilbin on experimental autoimmune myasthenia gravis (EAMG) in Lewis rats. The results showed that astilbin could attenuate the severity of EAMG by decreasing antigen-specific autoantibodies with up-regulation of regulatory T cells and down-regulation of Th17 cells. In addition to, astilbin also reduced the efficiency of the antigen presenting cells on which the expression of MHC class II decreased. These results suggest that astilbin might be a candidate drug for immunoregulation of EAMG, and provide us new treatment ideas for human myasthenia gravis (MG).

Decrease of Functional Activated T and B Cells and Treatment of Glomerulonephitis in Lupus-Prone Mice Using a Natural Flavonoid Astilbin

Treatment of systemic lupus erythematosus (SLE), a chronic inflammatory disease, involves the long-term use of immunosuppressive agents with significant side effects. New therapeutic approaches are being explored to find better treatment possibilities. In this study, age-matched female MRL/lpr mice were treated orally with a natural flavonoid astilbin. Astilbin administration started either at week 8 or week 12 of age though week 20. In the early treatment regimen, the treatment with astilbin reduced splenomegaly / lymphomegaly, autoantibody production and ameliorated lupus nephitis. Several serum cytokines were significantly decreased upon treatment including IFN-g, IL-17A, IL-1b, TNF-a and IL-6. Both spleen CD44^hiCD62L^lo activated T cells and CD138⁺B220^- plasma cells greatly declined. Furthermore, astilbin treatment resulted in decreased mitochondrial membrane potential in activated T cells and downregulated expression of the co-stimulatory molecules CD80 and CD86 on LPS stimulated B cells. Similar but less profound effectiveness was observed in the mice with established disease in the late treatment regimen. These results indicate that the natural product astilbin can mitigate disease development in lupus-prone mice by decreasing functional activated T and B cells.

Sarsaparilla (Smilax Glabra Rhizome) extract inhibits migration and invasion of cancer cells by suppressing TGF-β1 pathway

Sarsaparilla, also known as Smilax Glabra Rhizome (SGR), was shown to modulate immunity, protect against liver injury, lower blood glucose and suppress cancer. However, its effects on cancer cell adhesion, migration and invasion were unclear. In the present study, we found that the supernatant of water-soluble extract from SGR (SW) could promote adhesion, inhibit migration and invasion of HepG2, MDA-MB-231 and T24 cells in vitro, as well as suppress metastasis of MDA-MB-231 cells in vivo. Results of F-actin and vinculin dual staining showed the enhanced focal adhesion in SW-treated cells. Microarray analysis indicated a repression of TGF-β1 signaling by SW treatment, which was verified by real-time RT-PCR of TGF-β1-related genes and immunoblotting of TGFBR1 protein. SW was also shown to antagonize TGF-β1-promoted cell migration. Collectively, our study revealed a new antitumor function of Sarsaparilla in counteracting invasiveness of a subset of cancer cells by inhibiting TGF-β1 signaling.

Aqueous stability of astilbin: effects of pH, temperature, and solvent

The influence of temperature, pH value, and solvent on the degradation behavior of astilbin was studied by HPLC. Results showed that the degradation of astilbin was pH and temperature dependent, and the isomerization of astilbin to its three stereoisomers was found. The degradation process followed the first-order kinetics model, and the degradation rate k values increased, whereas half-life (t1/2) values declined with the rise of pH and temperature. The stability of astilbin was related to its B-ring substitution. Engeletin with a 4'-hydroxy-substituted B-ring was more stable than astilbin with a 3',4'-dihydroxy-substituted B-ring. The stability of astilbin differed depending on the solvent and followed the order 50% ethanol > ethanol > methanol > 50% methanol > water. In cultural media, astilbin was less stable than in water, which may be related to the presence of metal ions. The stability results of astilbin were confirmed in the extraction of dihydroflavonols from Rhizoma Smilacis Glabrae and may have a guiding function in turtle jelly production.

PVP and surfactant combined carrier as an effective absorption enhancer of poorly soluble astilbin in vitro and in vivo

CONTEXT

Astilbin is considered to be a new and promising immunosuppressant for immune related diseases, but limited in clinical application due to its poor water solubility, difficult oral absorption and low bioavailability.

OBJECTIVE

The present work studied the effect of PVP and surfactant combined carrier on its capability to improve drug absorption.

MATERIALS AND METHODS

PVP K30-Tween 80 combined carries was applied into the astilbin solid dispersions, tested both in vivo in beagle dogs and in vitro in transport experiments across Caco-2 cell monolayers.

RESULTS AND DISCUSSION

In the animal studies a many fold increase in plasma AUC was observed for the solid dispersions of drug in PVP K30-Tween 80 combined carries compared to active pharmaceutical ingredient (API). The applicability of Caco-2 monolayers as a tool for predicting the in vivo transport behavior of Astilbin in combination with a solubility enhancing carries was shown. In vitro transport studies confirmed the effect of combined carries on the absorption behavior of the astilbin. MTT studies showed the cell viability gradually decreased with the increase of the drug concentration in a dose dependent manner for astilbin and that in solid dispersions. The permeability and apparent permeability coefficients (Papp) increased with drug in the Caco-2 cell.

CONCLUSION

In this study, it was found that PVP K30 and Tween 80 promoted the permeability of drugs best within a certain amount. For astilbin PVP K30 and surfactant combined carrier had a strong potential to improve oral bioavailability.

Aqueous solubility and stability enhancement of astilbin through complexation with cyclodextrins

The complexation of astilbin with α-, β-, and γ-cyclodextrin (CD) was studied by phase solubility test and UV-vis spectral titration. Complexation with CDs gradually decreased the absorbance of astilbin at 291 nm and obviously increased its water solubility. The formation constant (K(a)) between astilbin and the three CDs was calculated. The stability of astilbin complexes increased in the order α-CD < γ-CD < β-CD, attributed to the CDs' cavity size. Temperature studies showed that the K(a) value decreased along with the rise of temperature. The negative values of enthalpy and entropy during complexation indicated that the complexation process was enthalpy-controlled. In alkaline medium isomerization and decomposition of astilbin were found; however, the addition of CDs significantly improved its stability through complexation. The solubility of astilbin in β-CD microcapsules prepared by the freeze-drying method was enhanced by 122.1-fold, and its dissolution profile was improved.

Ruscogenin glycoside (Lm-3) isolated from Liriope muscari improves liver injury by dysfunctioning liver-infiltrating lymphocytes

The effects of ruscogenin 1-O-[β-d-glucopyranosyl(1 → 2)] [β-d-xylopyranosyl(1 → 3)]-β-d-fucopyranoside (Lm-3) and its aglycone, ruscogenin, on liver injury induced in mice by delayed-type hypersensitivity to picryl chloride have been investigated. Lm-3 and ruscogenin significantly decreased liver injury when given during the effector phase of the delayed-type hypersensitivity reaction. The pretreatment of nonparenchymal cells, but not hepatocytes, with Lm-3 or ruscogenin in-vitro caused a concentration- and time-dependent inhibition against the damage. Lm-3 showed a stronger inhibition against the damage than ruscogenin (IC50: Lm-3 6.3 times 10−10  m, ruscogenin 3.9 times 10−7  m). However, neither Lm-3 nor ruscogenin blocked the hepatotoxic potential of CCl4, when used to pretreat hepatocytes. Moreover, Lm-3 and ruscogenin inhibited concanavalin A-induced lymphocyte proliferation only at high concentrations. These results suggested that Lm-3 and ruscogenin improved the immunological liver injury by selectively causing dysfunction of the liver-infiltrating cells rather than by protecting hepatocyte membranes. Such characteristics would be significant for treating immunologically related liver diseases as well as for developing new drugs.

Astilbin prevents concanavalin A-induced liver injury by reducing TNF-α production and T lymphocyte adhesion

The aim of this study was to evaluate the effect of astilbin on concanavalin A (Con A)-induced hepatitis, a T cell-dependent model of liver injury. Con A administration resulted in a severe liver injury in mice, with a strong increment in spleen cell adhesion and liver infiltration of T cells, as well as in tumour necrosis factor (TNF)-α production. Against this liver injury, astilbin significantly inhibited the elevation in transaminase activity, reduced the TNF-α production, and improved the histological changes, including inflammatory infiltration, hepatocyte necrosis and degeneration and Kupffer cell hyperplasia. In addition, astilbin inhibited the adhesion of spleen cells and purified T lymphocytes isolated from the liver-injured mice to fibronectin, laminin and type IV collagen. Moreover, the adhesion of human Jurkat T cells to endothelial cell line ECV-304 was also inhibited by astilbin. These results suggest that the improvement of the T cell-mediated liver injury by astilbin may be related to the reduction in TNF-α production and in T cell adhesion to extracellular matrices and endothelial cells.

Dregea volubilis Ameliorates Concanavalin A-Induced Liver Injury by Facilitating Apoptosis of Activated T Cells

Activation of T cells is a critical event in the pathogenesis of concanavalin A (Con A)-induced liver injury, and facilitating apoptosis of activated T cells may provide a strategy for the treatment. Here, we found that the ethanol extract from the stem parts of Dregea volubilis (DVE) inhibited cell proliferation and induced apoptosis, which was selective for Con A-activated, rather than nonactivated, lymph node cells. Administration of DVE prevented mice from Con A-induced elevation of serum transaminases, liver necrosis and increased TNF-α, IFN-γ, IL-2 and IL-4 in mice sera. DVE also caused apoptosis of in vivo activated T cells. In addition, increased active fragments of caspase-3 were found in the DVE-treated cells. But DVE-induced apoptosis was Fas-independent, as it was still observed in T cells from Fas ligand-mutated gld/gld mice. These results suggest that DVE may have great potential to treat T cell-mediated diseases through facilitating apoptosis of activated T cells.

Identification of a New Metabolite of Astilbin, 3′-O-Methylastilbin, and Its Immunosuppressive Activity against Contact Dermatitis

Background: Astilbin is a flavonoid isolated from the rhizome of Smilax glabra. In a previous study, we revealed its unique immunosuppressive activity, a selective inhibition against activated T lymphocytes. This characteristic of astilbin is beneficial for the treatment of human immune diseases.

Methods: We incubated astilbin with rat liver microsomal/cytosolic fractions and isolated the metabolite of astilbin, which was fully characterized by mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy. We administered astilbin orally via a gastric tube to rats at 0.22 mmol/kg and collected whole blood samples after 30 min and urine samples after 0 to 12 h. We applied HPLC and liquid chromatography/MS to measure the metabolite in the samples, and we assayed cytokine expression by reverse-transcription PCR.

Results: After incubation of astilbin with rat liver microsomal/cytosolic fractions, we detected a new metabolite of astilbin and isolated it from the culture solution. We characterized this metabolite by MS and NMR techniques as 3′-O-methylated astilbin. We detected the metabolite in both blood and urine samples after oral administration of astilbin, and the metabolite inhibited picryl chloride–induced ear swelling in mice and suppressed the expression of tumor necrosis factor-α and interferon-γ, similarly to astilbin.

Conclusion: This is the first identification of 3′-O-methylastilbin as a new flavonoid, as well as an active metabolite of astilbin in vivo, and is helpful for studying the kinetics of astilbin and its clinical applications.

Simultaneous quantification of five major bioactive flavonoids in Rhizoma smilacis glabrae by high-performance liquid chromatography

A high-performance liquid chromatographic (HPLC) method was developed for the simultaneous determination of five flavonoids, taxifolin, neoastilbin, astilbin, neoisoastilbin and isoastilbin, contained in rhizoma smilacis glabrae. The optimal conditions of separation and detection were achieved on a Lichrospher C18 column (250 mm x 4.6 mm, 5 microm), with a gradient elution program, detected at 291 nm. The correlation coefficients of all the calibration curves showed good linearity (r>0.999) within test ranges. The relative deviation of this method was less than 3% for intra- and inter-day assays, and the average recoveries (n=3) were between 96.2 and 103.1%. The extraction process was also optimized as 2 h immersion and 30 min sonication in 60% ethanol. Eight samples of rhizoma smilacis glabrae from different locations in China were analyzed. The results indicate that the assay is reproducible and precise and could be readily utilized for the quality control of rhizoma smilacis glabrae.

Synthesis and immunosuppressive activity of l-rhamnopyranosyl flavonoids

Astilbin, a flavonoid isolated from different plants, shows diverse biological activities. This paper reports the synthesis and immunosuppressive activity of seven analogues of astilbin, which may shed light on the structure-activity relationship of the compounds. The following glycosyl flavonoids, 6-alpha-L-rhamnopyranosyloxyflavanone (20), 3-alpha-L-rhamnopyranosyloxyflavone (22), 3-alpha-L-rhamnopyranosyloxyflavanone (24), 3-alpha-L-rhamnopyranosyloxychromanone (26), 4-alpha-L-rhamnopyranosyloxychromanol (27), 7-hydroxy-3-alpha-L-rhamnopyranosyloxyflavanone (30) and 4'-hydroxy-3-alpha-L-rhamnopyranosyloxyflavanone (32) were prepared respectively by glycosylation of 6-hydroxyflavanone (1), 3-hydroxyflavone (2), 3-hydroxyflavanone (5), 3-hydroxychromanone (8), 4-chromanol (9), 7-benzyloxy-3-hydroxyflavanone (12), 4'-benzyloxy-3-hydroxyflavanone (15). Among them, compounds 5, 8, 12 and 15 were synthesized from flavanone (3), 4-chromanone (6), 7-hydroxyflavanone (10) and 4'-hydroxyflavanone (13) respectively. Similar to astilbin (4), compounds 22, 24, 26, 30 and 32 significantly inhibited the single mixed lymphocytes reaction (sMLR) and enhanced the apoptosis of spleen cells isolated from mice with sheep red blood cell-induced delayed-type hypersensitivity respectively. However, compound 20 only showed a slight tendency to inhibit sMLR at higher concentration. Both compounds 20 and 27 did not influence the cell apoptosis. These data suggest that the following factors play essential roles in determining the biological activity of the flavonoids: the position at which the sugar is linked to the flavone, the presence of carbonyl on C-4 and phenol hydroxyl group in A or B ring. However, the presence of a B ring is unfavorable for the biological activity and the double bond at C2-C3 in C-ring shows little effect on the activity.

Quantitative determination of astilbin in rabbit plasma by liquid chromatography

A simple method for determining the concentration of astilbin, a flavanone, in rabbit plasma has been developed. After liquid-liquid extraction, the flavanone was detected by HPLC on a 4.6-microm octadecylsilica column (Nova-Pak C-18) at 291 nm. Linear calibration graphs for astilbin were constructed from 0.44 to 22.17 microM. The limit of quantitation was 0.44 microM in plasma. The method has been applied to pharmacokinetic studies after a single i.v. and an oral administration of the compound to rabbits.

Astilbin suppresses delayed-type hypersensitivity by inhibiting lymphocyte migration

This study examined the effects of astilbin, a flavanone, on delayed-type hypersensitivity reactions and its mechanisms of action on cell migration. Astilbin significantly inhibited the sheep-red-blood-cell-induced footpad reaction and picryl-chloride-induced ear dermatitis without affecting the organ weights, when administered during the effector phase but not the induction phase. The flavanone also significantly inhibited the migration to gelatin of spleen cells isolated from mice with ear dermatitis in a transwell system. Furthermore, the isolated spleen cells from normal mice were incubated with astilbin in the presence of concanavalin A, or those from mice with ear dermatitis were cultured with astilbin. In the supernatants collected, the activity of matrix metalloproteinases (MMPs) MMP-2 and MMP-9 was remarkably inhibited by astilbin. These results suggest that astilbin may inhibit delayed-type hypersensitivity reactions through selectively suppressing the lymphocyte functions, including cell migration, via down-regulating MMP activity.

Preparative isolation of polyphenolic compounds from Vitis vinifera by centrifugal partition chromatography

This study deals with a centrifugal partition chromatography developed for the separation of phenolic compounds from Vitis vinifera. EtOAc grape seed extracts were separated using the solvent system hexane-ethyl acetate-ethanol-water (1:8:2:7; v/v) in two fractions: one containing about 75% of flavanol monomers (catechin and epicatechin) corresponding to 18% of crude extract and another fraction B-type dimers (22% of crude extract). From the stalk extracts, we could separate stilbenoid compounds (resveratrol and its oligomers; 12% of crude extract) which were eluted in less than 30 min from flavanols (which required a few hours of additional elution). Using the same solvent system but in different ratios (4:5:3:3; v/v), we isolated the trans-resveratrol (7@1000; 90% purity).

Biological activity of astilbin from Dimorphandra mollis against Anticarsia gemmatalis and Spodoptera frugiperda

Astilbin was isolated in high yield from Dimorphandra mollis, and its insecticidal and growth inhibiting activity by stomach ingestion were evaluated against Anticarsia gemmatalis and Spodoptera frugiperda. The insecticidal activity of astilbin, the weight reduction of the larval phase and the prolongation of the larval and pupal phases were verified for both species. Astilbin was identified on the base of its NMR, MS and physical data.

Astilbin selectively facilitates the apoptosis of interleukin-2-dependent phytohemagglutinin-activated Jurkat cells

The present study examined the relationship between the activation of T cells and the apoptosis-facilitating effect of astilbin on them. By the stimulation of PHA, a remarkable IL-2 production was detected in the supernatant of Jurkat cells after 120 h among 72--144 h incubation. This kinetics was quite in accordance with that of astilbin-induced apoptosis of Jurkat cells, where 1 h-exposure of the PHA-activated cells to astilbin caused a significantly increased apoptosis in a dose-dependent manner. To the Jurkat cells that had been cultivated for 72--144 h without PHA, however, astilbin did not show any facilitation of the cell apoptosis. Pre-treatment by cyclosporine A simultaneously with PHA dose-dependently lowered the IL-2 production and susceptibility of the cells to astilbin, while the treatment after 120 h of PHA-activation did not. The exogenous IL-2 treatment after 72 h of PHA-activation significantly and dose-dependently raised the susceptibility of the Jurkat cells to astilbin. These results indicated the dependency of the apoptosis-facilitating effect of astilbin on appropriate status of activated T lymphocytes with a relation to IL-2 production. This characteristic of astilbin may be of great significance for the treatment of a variety of immunologically related diseases.