Liquiritigenin, an aglycone of liquiritin in Glycyrrhizae radix, prevents acute liver injuries in rats induced by acetaminophen with or without buthionine sulfoximine

Correlation analysis between the rate of respiration in the root and the active components in licorice (Glycyrrhiza uralensis)

The aim of this study was to investigate the correlation between root respiration and the percentage of active components in licorice (Glycyrrhiza uralensis Fisch.), in order to provide a foundation for the regulation and modulation of the quality of G. uralensis. Respiration efflux of annual and biennial G. uralensis was determined using a Li-7000 CO₂/H₂O analyzer. The root systems were scanned at a resolution of 3,000 dpi using an Epson Expression 10000XL scanner. Root growth was determined by analyzing the scanned images using WinRHIZO version Pro2007d software and the rate of respiration in the root was subsequently calculated. In addition, the percentages of the five major active components in licorice, glycyrrhizic acid, glycyrrhizin, isoliquiritin, liquiritigenin and isoliquiritigenin, were detected using high-performance liquid chromatography (HPLC). The correlation between the root respiration and the percentage of the active components was investigated. Significant seasonal changes were observed in the rates of respiration of first and zero-class roots. In annual and biennial G. uralensis, the maximum and minimum values for rate of respiration were present in July (P<0.05) and November (P<0.05), respectively. The correlation coefficients between the five major active components and the rate of respiration were −0.304 (glycyrrhizin), −0.129 (liquiritigenin), −0.441 (glycyrrhizic acid; P<0.05), −0.471 (isoliquiritin; P<0.05) and 0.148 (isoliquiritigenin). The percentages of glycyrrhizic acid and isoliquiritin were significantly negatively correlated with the rate of respiration in annual and biennial G. uralensis. Understanding the correlation between the root rate of respiration and the active components in G. uralensis may be beneficial to ensuring the quality of cultivated G. uralensis.

Inhibition of Acute Phase Inflammation by Laminaria japonica through Regulation of iNOS-NF- κ B Pathway

Laminaria japonica has been frequently used as food supplements in many of the Asian countries and as a drug in traditional oriental medicine. This research investigated the effects of Laminaria japonica extract (LJE) on acute phase inflammation in a carrageenan-induced paw edema model, as assessed by histomorphometric and immunohistochemical analyses. The effect of LJE was also evaluated in Raw264.7 cells stimulated with lipopolysaccharide (LPS) in the aspect of the inhibition of nitric oxide (NO), prostaglandin E₂ (PGE₂), and proinflammatory cytokines production. NO, PGE₂, tumor necrosis factor (TNF)-α, interleukin-1β, and interleukin-6 contents were assayed by ELISA, and inducible NO synthase (iNOS) and cyclooxygenase (COX)-2 expressions were determined by western blot analyses. In rats, LJE treatment inhibited carrageenan-induced paw edema formation and infiltration of inflammatory cells in H&E staining. LJE treatment prevented the ability of LPS to increase the levels of iNOS and COX-2 protein in a concentration-dependent manner. Consistently, LJE suppressed the production of TNF-α, interleukin-1β, and interleukin-6. Treatment of the cells with LJE caused inhibition of inhibitor of κBα phosphorylation induced by LPS, suggesting LJE repression of nuclear factor-κB activity by LPS. In conclusion, this study shown here may be of help to understand the action mechanism of LJE and the anti-inflammatory use of L. japonica.

Employing bifunctional enzymes for enhanced extraction of bioactives from plants: flavonoids as an example

A cost-effective and environmentally friendly approach was developed to improve the extraction of active ingredients from plants, in which a bifunctional enzyme was employed for not only facilitating cell wall degradation but also increasing the bioactivity of target compounds in the extract. In the aqueous extraction of flavonoids from Glycyrrhizae radix, Trichoderma viride cellulase, a commercial cell-wall-degrading enzyme, was found to efficiently deglycosylate liquiritin and isoliquiritin, which are of high content but low bioactivity, into their aglycones that have much higher physiological activities for dietary and medicinal uses. Under optimized conditions, the extraction yield of liquiritigenin and isoliquiritigenin aglycones reached 4.23 and 0.39 mg/g of dry weight (dw) with 6.51- and 3.55-fold increases, respectively. The same approach was expanded to the extraction of flavonoids from Scutellariae radix using Penicillium decumbens naringinase, where enhanced production of more bioactive bacalein and wogonin was achieved via enzymatic deglycosylation of bacalin and wogonoside.

Water extract of licorice had anti-viral activity against human respiratory syncytial virus in human respiratory tract cell lines

ETHNOPHARMACOLOGICAL RELEVANCE

Licorice (Glycyrrhiza uralensis Fisch., Leguminosae) has been used in herbal medicine and food supplement worldwide for centuries. Licorice is a common ingredient of several prescriptions of traditional Chinese medicine which have been proved to inhibit infection of human respiratory syncytial virus (HRSV). There are two preparations of licorice, Radix Glycyrrhizae and Radix Glycyrrhizae Preparata. However, it is unknown whether licorice or which preparation of licorice is effective against HRSV, nor is its active constituent.

AIM OF THE STUDY

We tested the hypothesis that Radix Glycyrrhizae can effectively decrease HRSV-induced plaque formation in respiratory mucosal cell lines. We also tried to find out the active constituent.

MATERIALS AND METHODS

Anti-HRSV activities of hot water extracts of preparations of licorice, glycyrrhizin and 18β-glycyrrhetinic acid (18β-GA), the active constituents of licorice, were examined by plaque reduction assay in both human upper (HEp-2) and low (A549) respiratory tract cell lines. Abilities of crude licorice to inhibit viral replication and to stimulate IFN-β were evaluated by reverse transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA), respectively.

RESULTS

Radix Glycyrrhizae and Radix Glycyrrhizae Preparata dose-dependently inhibited HRSV-induced plaque formation in both HEp-2 and A549 cell lines (p<0.0001). The effect of Radix Glycyrrhizae was better than that of Radix Glycyrrhizae Preparata on HEp-2 cells. However, there was no difference of their anti-HRSV effects on A549 cells. Besides, glycyrrhizin was ineffective at all. Nevertheless, 18β-GA showed a potent anti-HRSV activity. Radix Glycyrrhizae was more effective when given before viral inoculation (p<0.0001) which may be due to its inhibition of viral attachment on (p<0.0001) and penetration (p<0.0001) into the host cells. The anti-HRSV activity of Radix Glycyrrhizae was further confirmed by RT-PCR and qRT-PCR. 300 μg/ml Radix Glycyrrhizae markedly decreased the viral amounts within the cells and in the suspension. Radix Glycyrrhizae might further stimulate mucosal cells to secrete IFN-β to counteract viral infection.

CONCLUSIONS

Both Radix Glycyrrhizae and Radix Glycyrrhizae Preparata are effective against HRSV infection on airway epithelial cells. Radix Glycyrrhizae inhibited HRSV mainly by preventing viral attachment, internalization, and by stimulating IFN secretion. 18β-GA may be one of its active constituents.

Metiram-induced nephrotoxicity in albino mice: effect of licorice aqueous extract

The present study was designed to estimate the effect of aqueous extract of licorice on metiram toxicity in mice. Treating mice with metiram at a dose level of [1/2] LD(50) daily for 3 weeks induced many histological changes in the kidney cortex. The renal tubules lost their characteristic appearance and their lining epithelial cells were degenerated. The glomeruli were atrophied and the renal blood vessels were congested. The intertubular spaces infiltrated by inflammatory leukocytic cells. Metiram caused an increase in proliferating cell nuclear antigen (PCNA) expression in nuclei of tubular epithelial cells. Metiram also caused marked elevation in serum creatinine and blood urea nitrogen. Treating animals with metiram and licorice aqueous extract led to an improvement, in both biochemical and histopathological alterations. These results proved that licorice had an ameliorative effect against kidney injury induced by metiram and this effect may be attributed to its antioxidant activity.

Role of the Nrf2-ARE pathway in liver diseases

The liver is a central organ that performs a wide range of functions such as detoxification and metabolic homeostasis. Since it is a metabolically active organ, liver is particularly susceptible to oxidative stress. It is well documented that liver diseases including hepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma are highly associated with antioxidant capacity. NF-E2-related factor-2 (Nrf2) is an essential transcription factor that regulates an array of detoxifying and antioxidant defense genes expression in the liver. It is activated in response to electrophiles and induces its target genes by binding to the antioxidant response element (ARE). Therefore, the roles of the Nrf2-ARE pathway in liver diseases have been extensively investigated. Studies from several animal models suggest that the Nrf2-ARE pathway collectively exhibits diverse biological functions against viral hepatitis, alcoholic and nonalcoholic liver disease, fibrosis, and cancer via target gene expression. In this review, we will discuss the role of the Nrf2-ARE pathway in liver pathophysiology and the potential application of Nrf2 as a therapeutic target to prevent and treat liver diseases.

Liquiritigenin prevents Staphylococcus aureus-mediated lung cell injury via inhibiting the production of α-hemolysin

Staphylococcus aureus is a significant Gram-positive bacterium that is associated with a broad spectrum of diseases ranging from minor skin infections to lethal pneumonia, endocarditis, and toxinoses. α-Hemolysin is one of the most important exotoxins that contribute to the pathogenesis of S. aureus infections. Liquiritigenin is one of the most significant active components in licorice. In this study, hemolysis, western blot, and real-time reverse transcription-PCR assays were performed to investigate the impact of liquiritigenin on the production of S. aureus α-hemolysin. The results showed that low concentrations of liquiritigenin remarkably decreased S. aureus α-hemolysin production in a dose-dependent manner. Using live/dead cell staining and lactate dehydrogenase assays, we found that liquiritigenin could protect human lung cells (A549) from α-hemolysin-mediated injury. The data indicated that this compound could potentially be useful in developing drugs aiming at staphylococcal α-hemolysin.

Dynamic residual complexity of the isoliquiritigenin-liquiritigenin interconversion during bioassay

Bioactive components in food plants can undergo dynamic processes that involve multiple chemical species. For example, 2'-hydroxychalcones can readily isomerize into flavanones. Although chemically well documented, this reaction has barely been explored in the context of cell-based assays. The present time-resolved study fills this gap by investigating the isomerization of isoliquiritigenin (a 2'-hydroxychalcone) and liquiritigenin (a flavanone) in two culture media (Dulbecco's modified eagle medium and Roswell Park Memorial Institute medium) with and without MCF-7 cells, using high-performance liquid chromatography-diode array detector-electrospray ionization/atmospheric pressure chemical ionization-mass spectrometry for analysis. Both compounds were isomerized and epimerized under all investigated biological conditions, leading to mixtures of isoliquiritigenin and R/S-liquiritigenin, with 19.6% R enantiomeric excess. Consequently, all three species can potentially modulate the biological responses. This exemplifies dynamic residual complexity and demonstrates how both nonchiral reactions and enantiomeric discrimination can occur in bioassay media, with or without cells. The findings highlight the importance of controlling in situ chemical reactivity, influenced by biological systems when evaluating the mode of action of bioactives.

Bojesodok-eum, a Herbal Prescription, Ameliorates Acute Inflammation in Association with the Inhibition of NF-κB-Mediated Nitric Oxide and ProInflammatory Cytokine Production

Bojesodok-eum (BSE) is a herbal prescription consisting of Coptidis Rhizoma and Scutellariae Radix as main components. This paper investigated the effects of BSE on the induction of nitric oxide (NO), prostaglandin E(2) (PGE(2)), and proinflammatory cytokines that are caused by lipopolysaccharide (LPS) in murine macrophage cell line and on the paw edema formation in animals. Administration of BSE (0.3 g/kg and 1 g/kg) in rats significantly inhibited carrageenan-induced paw edema formation, as did dexamethasone, an anti-inflammatory positive control drug. In cell model, treatment of BSE decreased the production of NO and PGE(2) in RAW264.7 cells stimulated by LPS. BSE also inhibited the expression of iNOS and COX-2 protein as well as COX activity in a concentration-dependent manner. Consistently, BSE suppressed the ability of LPS to produce TNF-α, interleukin-1β, and interleukin-6. LPS treatment induced nuclear NF-κB level and I-κBα phosphorylation, which were inhibited subsequent treatment of BSE, suggesting its repression of LPS-inducible NF-κB activation. BSE abrogated the induction of NO, PGE(2), and proinflammatory cytokines, as well as iNOS and COX-2 protein expression in RAW264.7 cells stimulated by LPS as mediated with NF-κB inhibition.

Cytoprotective Activity of Glycyrrhizae radix Extract Against Arsenite-induced Cytotoxicity

Licorice, Glycyrrhizae radix, is one of the herbal medicines in East Asia that has been commonly used for treating various diseases, including stomach disorders. This study investigated the effect of licorice on arsenite (As)-induced cytotoxicity in H4IIE cells, a rat hepatocyte-derived cell line. Cell viability was significantly diminished in As-treated H4IIE cells in a time and concentration-dependent manner. Furthermore, results from flow cytometric assay and DNA laddering in H4IIE cells showed that As treatment induced apoptotic cell death by activating caspase-3. Licorice (0.1 and 1.0 mg ml(-1)) treatment significantly inhibited cell death and the activity of caspase-3 in response to As exposure. These results demonstrate that licorice induced a cytoprotective effect against As-induced cell death by inhibition of caspase-3.

Dioscin, a natural steroid saponin, shows remarkable protective effect against acetaminophen-induced liver damage in vitro and in vivo

The aim of the study was to investigate the protective effect of dioscin against APAP-induced hepatotoxicity. In the in vitro tests, HepG2 cells were given APAP pretreatment with or without dioscin. In the in vivo experiments, mice were orally administrated dioscin for five days and then given APAP. Some biochemical and morphology parameters were assayed and the possible mechanism was investigated. Dioscin improved AST release, mitochondrial dysfunction, apoptosis and necrosis of HepG2 cells induced by APAP. Following administration of dioscin, APAP-induced hepatotoxicity in mice was significantly attenuated. Furthermore, the liver cell apoptosis and necrosis, and hepatic mitochondrial edema were also prevented. Fifteen differentially expressed proteins were found by using proteomics, and six of them, Suox, Krt18, Rgn, Prdx1, MDH and PNP were validated. These proteins may be involved in the hepatoprotective effect of dioscin and might cooperate with the levels of Ca(2+) in mitochondria, decreased expression of ATP2A2, and decreased mitochondrial cardiolipin. In addition, dioscin inhibited APAP-induced activation and expression of CYP2E1, up-regulated the expression of Bcl-2 and Bid, and inhibited the expression of Bax, Bak and p53. Dioscin showed a remarkable protective effect against APAP-induced hepatotoxicity by adjusting mitochondrial function. These results indicated that dioscin has the capability on the treatment of liver injury.

Comparative evaluation of two structurally related flavonoids, isoliquiritigenin and liquiritigenin, for their oral infection therapeutic potential

Isoliquiritigenin (1) and liquiritigenin (2) are structurally related flavonoids found in a variety of plants. The purpose of this study was to perform a comparative analysis of biological properties of these compounds in regard to their therapeutic potential for oral infections. Compound 1 demonstrated significant antibacterial activity against three major periodontopathogens, Porphyromonas gingivalis, Fusobacterium nucleatum, and Prevotella intermedia. In contrast, 2 exerted less pronounced effects on the above bacterial species. Neither compound was effective against cariogenic bacteria (Streptococcus mutans and Streptococcus sobrinus). Furthermore, 1 exhibited a stronger inhibitory activity than 2 toward P. gingivalis collagenase and human matrix metalloproteinase 9. Finally, the capacity of 1 to attenuate the inflammatory response of macrophages induced by Aggregatibacter actinomycetemcomitans lipopolysaccharide (LPS) was much higher when compared to 2. The activation of transcriptional factors nuclear factor-κB (NF-κB) p65 and activator protein-1 (AP-1) associated with the LPS-induced inflammatory response in macrophages was inhibited strongly by 1, but less affected by 2.

Liquiritigenin attenuates the learning and memory deficits in an amyloid protein precursor transgenic mouse model and the underlying mechanisms

The present paper is to examine whether liquiritigenin is able to attenuate the Alzheimer's-like learning and memory deficits in a transgenic (Tg) mouse model that over-expresses amyloid protein precursor (APP), and explores the underlying mechanisms. Consistent with our previous observations, we found that treatment with liquiritigenin improved the behavioral performance of Tg mice and it attenuated the protein expression of oligomeric form of amyloid β-peptide (Aβ). Furthermore, treatment with liquiritigenin inhibited astrocytosis in the hippocampus, and it may through its inhibitory activities on Notch-2, an important molecular regulating neural proliferation and differentiation. These findings provide evidence for beneficial activity of liquiritigenin in a mouse model of Alzheimer's disease and support the continued investigation of Notch signaling pathway as a target for treatment of Alzheimer's disease.

Simultaneous determination of liquiritin, hesperidin, and glycyrrhizin by HPLC-photodiode array detection and the anti-inflammatory effect of Pyungwi-san

A high-performance liquid chromatographic method was developed and validated to determine liquiritin, hesperidin, and glycyrrhizin levels in a traditional Korean medicine, Pyungwi-san (PWS). Reverse-phase chromatography using a C18 column operating at 40oC, and photodiode array detection at 254 nm and 280 nm, were used for quantification of the three marker components of PWS. The mobile phase using gradient flow consisted of two solvent systems. Solvent A was 1.0% (v/v) aqueous acetic acid and solvent B was acetonitrile with 1.0% (v/v) acetic acid. Calibration curves were acquired with r (2) > 0.9999, and the relative standard deviation values (%) for intra- and inter-day precision were both less than 4.0%. The recovery of each compound was in the range 97.33-110.72%, with an relative standard deviation less than 6.0%. To provide information on the biological activity of PWS, anti-inflammatory action was evaluated. Production of nitric oxide and prostaglandin E(2) were measured using the Griess reagent and enzyme-linked immunosorbent assay, respectively. PWS showed inhibitory effect on prostaglandin E(2) production in LPS-treated RAW 264.7 cells.

Inhibition of LXRα-dependent steatosis and oxidative injury by liquiritigenin, a licorice flavonoid, as mediated with Nrf2 activation

Liver X receptor-α (LXRα) functions as a major regulator of lipid homeostasis through activation of sterol regulatory element binding protein-1c (SREBP-1c), which promotes hepatic steatosis and steatohepatitis. NF-E2-related factor 2 (Nrf2) is the crucial transcription factor that is necessary for the induction of antioxidant enzymes. This study investigated the potential of liquiritigenin (LQ), a hepatoprotective flavonoid in licorice, to inhibit LXRα-induced hepatic steatosis, and the underlying mechanism of the action. LQ treatment attenuated fat accumulation and lipogenic gene induction in the liver of mice fed a high fat diet. Also, LQ had the ability to inhibit oxidative liver injury, as shown by decreases in thiobarbituric acid reactive substances formation and nitrotyrosinylation. Moreover, LQ treatment antagonized LXRα agonist (T0901317)-mediated SREBP-1c activation, and transactivation of the lipogenic target genes. LQ was found to activate Nrf2, and the ability of LQ to inhibit LXRα-mediated SREBP-1c activation was reversed by Nrf2 deficiency, which supports the inhibitory role of Nrf2 in LXRα-dependent lipogenesis. Consistently, treatment with other Nrf2 activators or forced expression of Nrf2 also inhibited LXRα-mediated SREBP-1c activation. Our results demonstrate that LQ has an efficacy to activate Nrf2, which contributes to inhibiting the activity of LXRα that leads to SREBP-1c induction and hepatic steatosis.

Effects of acute renal failure induced by uranyl nitrate on the pharmacokinetics of liquiritigenin and its two glucuronides, M1 and M2, in rats

OBJECTIVES

Liver disease and acute renal failure (ARF) are closely associated. The pharmacokinetics of liquiritigenin (LQ), a candidate therapy for inflammatory liver disease, and its metabolites M1 and M2 were evaluated in rats with ARF induced by uranyl nitrate (U-ARF rats).

METHODS

LQ was administered intravenously (20 mg/kg) or orally (50 mg/kg) in U-ARF and control rats, and uridine diphosphate-glucuronosyltransferases (UGT) activity and uridine 5'-diphosphoglucuronic acid (UDPGA) concentrations were determined in the liver and intestine.

KEY FINDINGS

After intravenous LQ administration, U-ARF rats displayed significantly slower LQ renal clearance but no significant changes in the LQ area under the plasma concentration-time curve (AUC) compared with controls. This was because of similar hepatic UGT activity and UDPGA levels between two groups, which resulted in comparable non-renal clearance, as well as the limited contribution of LQ renal clearance to total LQ clearance. However, the AUC and AUC(M) /AUC(LQ) ratios of M1 and M2 were significantly increased in U-ARF rats because of decreased urinary excretion of M1 and M2. Similar results were observed following oral administration because of the comparable LQ intestinal metabolism in both groups and decreased urinary excretion of M1 and M2 in U-ARF rats.

CONCLUSIONS

U-ARF rats displayed decreased urinary excretion of LQ glucuronides, resulting in significantly greater AUC and metabolite ratios of M1 and M2 following LQ administration.

Liquiritigenin pharmacokinetics in a rat model of diabetes mellitus induced by streptozotocin: greater formation of glucuronides in the liver, especially M2, due to increased hepatic uridine 5'-diphosphoglucuronic acid level

Liquiritigenin (LQ) is a candidate for the treatment of inflammatory liver disease. Many studies have confirmed that hepatic disease and diabetes mellitus are closely associated. Thus, the pharmacokinetic changes of LQ and its 2 glucuronides, M1 and M2, in a rat model of diabetes mellitus induced by streptozotocin (DMIS rats) were evaluated. Liquiritigenin was administered intravenously (20 mg/kg) or orally (50 mg/kg) in DMIS and control rats. Changes in in vitro activity and in vivo uridine 5'-diphosphoglucuronic acid level in the liver and intestine of DMIS rats compared with controls were also studied. After intravenous administration of LQ in DMIS rats, no significant changes in the pharmacokinetic parameters of LQ were observed. However, the AUC(M2)/AUC(LQ) ratio was significantly greater (by 53.0%) than that of controls. After oral administration of LQ, the AUC of LQ and metabolite ratios of M1 and M2 were comparable to controls. The increase in the formation of glucuronides of LQ, especially M2, after intravenous administration of LQ was due to the increased in vivo hepatic uridine 5'-diphosphoglucuronic acid level in DMIS rats as a result of alteration in carbohydrate metabolism in diabetes. The comparable pharmacokinetics of LQ, M1, and M2 after oral administration of LQ were mainly due to the comparable intestinal metabolism of LQ between the control and DMIS rats.

Solid-phase extraction of liquiritin and glycyrrhizin from licorice using porous alkyl-pyridinium polymer sorbent

INTRODUCTION

Liquiritin and glycyrrhizin are valuable components of licorice. An effective separation and determination procedure is needed to separate the liquiritin and glycyrrhizin from the licorice extract.

METHODOLOGY

A polymer-confined, ionic liquid sorbent was developed using a process involving polymerisation and modification. The obtained porous particles were used as a sorbent in a solid-phase extraction process to isolate liquiritin and glycyrrhizin from licorice with different washing and elution solvents. The porous alkyl-pyridinium polymer sorbent was compared with the C(18) sorbent.

RESULTS

A simple and convenient method was established to the selectively separate and determinate of liquiritin and glycyrrhizin using a porous ionic liquid-based polymer coupled with HPLC. Additionally, this study evaluated the application of this sorbent for the detection of these two compounds in commercial medicines.

CONCLUSION

This method was a viable tool that was compatible with the existing HPLC methods and was used to separate and analyse the content of liquiritin and glycyrrhizin in licorice.

Liquiritigenin Derivatives and Their Hepatotoprotective Activity

Liquiritigenin (7,4’-dihydroxyflavanone), isolated from the roots of Glycyrrhiza Glabra, was derivatized to liquiritigenin 7, 4’-diacetate, liquiritigenin 4’-acetate, isoliquiritigenin, and liquiritigenin 7, 4’-dibenzoate. All these derivatives were evaluated for in vitro hepatoprotective activity against D-galactosamine–lipopolysaccharide(GalN/LPS) induced toxicity. In-vitro hepatotoxicity was manifested by a significant increase ( P < 0.05) in liver toxicity biomarkers (SGPT, SGOT, ALKP, triglyceride, LPO, NO and LDH). The level of biomarkers in the treatment groups was significantly decreased ( P< 0.05) when compared with the GalN/LPS group. The results revealed that isoliquiritigenin exhibited better hepatoprotective activity than liquiritigenin and its derivatives.

Inhibition of hepatoma 22 tumor by Liquiritigenin

The purpose of this study was to evaluate the in vivo antitumor effects of liquiritigenin (LQ) on H(22) Hepatocarcinoma. After mice were administrated liquiritigenin (10, 20 and 40 mg/kg) intragastrically for 15 days, tumor volume, indices of thymus and spleen, MDA level in serum, optical microscopy, electron microscopy were determined. We have found that LQ had inhibitory effects on transplanted tumors and that the middle dose of LQ was more effective than the others. All LQ groups could increase thymus weight but it had no obvious effect on the spleen. MDA content decreased with LQ treatment but there wasn't a significant difference. In the group treated with LQ, we observed that the nuclei changed markedly and had ultrastructural morphological changes to apoptosis. The study supports that LQ significantly inhibits the growth of H(22) in vivo, and might be a promising antihepatoma agent.

Solid-phase extraction of liquiritin and glycyrrhizic acid from licorice using ionic liquid-based silica sorbent

A new ionic liquid-based silica sorbent was developed by a process involving surface chemical modification of commercial silica using a synthesized ionic liquid. The obtained particles were successfully used as a special sorbent in a solid-phase extraction process to isolate liquiritin and glycyrrhizic acid from licorice. Different washing and elution solvents, such as water, methanol/water (v/v), and pure methanol were evaluated. Ionic liquid-based silica sorbent was compared with traditional C(18) sorbent and it exhibited higher selectivity. Quantitative analysis was carried out by using a C(18) column. Good linearities of two compounds were obtained from 5x10(-4) to 0.2 mg/mL (r(2)>0.99) with the relative standard deviations <1.0%. The target compounds in commercial herbal medicines containing licorice were determined, and the bound rates between the target compounds and protein were obtained by this sorbent.

Effects of liquiritigenin treatment on the learning and memory deficits induced by amyloid beta-peptide (25-35) in rats

Considerable evidence has emerged supporting the neuroprotective and cognition-preserving effects of estrogen, but these benefits are complicated by the evidence that estrogen increases the risk of certain cancers. Selective estrogen receptor modulators (SERMs) that specifically target the brain while avoiding peripheral organs offer a way to allow the application of estrogen treatment to neurodegenerative diseases with fewer undesirable effects. In an attempt to find such estrogen substitutes, liquiritigenin was discovered as a relatively selective estrogen receptor beta (ERbeta) agonist. In the present study, we extend our previous findings to investigate the effects of liquiritigenin on the learning and memory deficits and related neuropathology in Abeta(25-35) hippocampal-injected rats. Our results show that liquiritigenin treatment improves the behavioral performance of the model rats and attenuates neuronal loss in the brain. More importantly, liquiritigenin treatment decreases mRNA levels and protein expression of Notch-2, an effect that could promote the generation of new neurons. These findings provide evidence for the beneficial activity of liquiritigenin in a brain-injured rat model and support the continued investigation of SERMs such as liquiritigenin as an alternative to estrogen-based hormone therapy in reducing the risk of neurodegenerative diseases such as Alzheimer's disease.

Protection afforded by a herbal medicine, Sho-seiryu-to (TJ-19), against oleic acid-induced acute lung injury in guinea-pigs

Objectives

The effect of a herbal medicine, Sho-seiryu-to (TJ-19), on oleic acid-induced lung injury, an animal model of acute respiratory distress syndrome or acute lung injury (ARDS/ALI), was examined.

Methods

Acute lung injury was induced by an intravenous injection of 15 μl/kg oleic acid to guinea-pigs. TJ-19 was administered by a single oral dose (3 g/kg) or by multiple oral doses (0.75 g/kg).

Key findings

The decrease in partial oxygen pressure of arterial blood (Pao2) and the increase in airway vascular permeability induced by the oleic acid injection were attenuated by a single dose of TJ-19. When TJ-19 was administered orally twice a day for two weeks and then oleic acid was injected, a potent prophylactic effect of the drug was observed. TJ-19 also prevented airway vascular hyperpermeability, lung cell injury, oxidative stress and thromboxane A2 generation, associated with the oleic acid injection.

Conclusions

TJ-19 significantly attenuated the oleic acid-induced lung injury probably through the antioxidative effect and inhibitory effect of thromboxane A2 generation, although the precise inhibitory mechanisms were not fully elucidated due to the diversity in constituents of the herbal medicine. We suggest that TJ-19 is a promising drug candidate and a medicinal resource for preventing ARDS/ALI.

Knockdown of superoxide dismutase 2 enhances acetaminophen-induced hepatotoxicity in rat

Drug-induced hepatotoxicity is a major problem in drug development, and oxidative stress is known as one of the causes. Superoxide dismutases (SODs) are important antioxidant enzymes against reactive oxygen species (ROS). Mitochondria are the major source of superoxide production, and SOD2 is mainly localized in mitochondria and, with other SODs, plays an important role in scavenging superoxide. Previously, we reported the establishment of an adenovirus vector with short hairpin RNA against rat SOD2 (AdSOD2-shRNA), and applied this to evaluate drug-induced cytotoxicity. In this study, infection of AdSOD2-shRNA to Fisher 344 rats resulted in a significant decrease of SOD2 mRNA, protein expression, and SOD2 enzyme activity to 28%, 35%, and 39%, respectively, 7 days after infection. Serum AST and ALT were significantly increased by single oral administration of acetaminophen (1000 mg/kg) to these SOD2-knockdown rats without fasting compared with the control adenovirus infected groups. Heme oxygenase-1 protein, known to be induced by oxidative stress, was detected in SOD2-knockdown rats administered acetaminophen. In addition, protein carbonyl and lipid peroxidation, also known to be induced by oxidative stress, were significantly increased in SOD2 knockdown rats. This is the first report of a SOD2-knockdown rat model that could be useful to evaluate the drug-induced hepatotoxicity with high sensitivity.

Liquiritigenin inhibits Abeta(25-35)-induced neurotoxicity and secretion of Abeta(1-40) in rat hippocampal neurons

AIM

To examine whether liquiritigenin, a newly found agonist of selective estrogen receptor-beta, has neuroprotective activity against beta-amyloid peptide (Abeta) in rat hippocampal neurons.

METHODS

Primary cultures of rat hippocampal neurons were pretreated with liquiritigenin (0.02, 0.2, and 2 micromol/L) prior to Abeta(25-35) exposure. Following treatment, viability of the cells was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide analysis and by a lactate dehydrogenase activity-based cytotoxicity assay. Intracellular Ca(2+) concentration ([Ca(2+)](i)) and levels of reactive oxygen species (ROS), as well as apoptotic rates, were determined. Our studies were extended in tests of whether liquiritigenin treatment could inhibit the secretion of Abeta(1-40) as measured using an ELISA method. In order to analyze which genes may be involved, we used a microarray assay to compare gene expression patterns. Finally, the levels of specific proteins related to neurotrophy and neurodenegeration were detected by Western blotting.

RESULTS

Pretreated neurons with liquiritigenin in the presence of Abeta(25-35) increased cell viability in a concentration-dependent manner. Liquiritigenin treatment also attenuated Abeta(25-35)-induced increases in [Ca(2+)](i) and ROS level and decreased the apoptotic rate of neurons. Some genes, including B-cell lymphoma/leukemia-2 (Bcl-2), neurotrophin 3 (Ntf-3) and amyloid beta (A4) precursor protein-binding, family B, member 1 (Apbb-1) were regulated by liquiritigenin; similar results were shown at the protein level by Western blotting.

CONCLUSION

Our results demonstrate that liquiritigenin exhibits neuroprotective effects against Abeta(25-35)-induced neurotoxicity and that it can decrease the secretion of Abeta(1-40). Therefore, liquiritigenin may be useful for further study as a prodrug for treatment of Alzheimer's disease.Acta Pharmacologica Sinica (2009) 30: 899-906; doi: 10.1038/aps.2009.74.

Oxidized metabolites of oltipraz exert cytoprotective effects against arachidonic acid through AMP-activated protein kinase-dependent cellular antioxidant effect and mitochondrial protection

Oltipraz protects cells from chemical-induced carcinogenesis partly because of phase 2 enzyme induction. Certain oltipraz metabolites also induce phase 2 enzymes. This study investigated the cytoprotective effects of the oxidized metabolites of oltipraz against arachidonic acid (AA), a proinflammatory fatty acid that causes cellular reactive oxygen species (ROS) production and mitochondrial impairment, and the mechanistic basis of their action in HepG2 cells. Treatment with 4-methyl-5-(pyrazin-2-yl)-3H-1,2-dithiol-3-one (M1) or 7-methyl-6,8-bis(methylthio)H-pyrrolo[1,2-a]-pyrazine (M2), but not 7-methyl-8-(methylsulfinyl)-6-(methylthio)H-pyrrolo[1,2-a]pyrazine (M3) or 7-methyl-6,8-bis(methylsulfinyl)H-pyrrolo[1,2-a]pyrazine (M4), enabled cells to protect against AA-induced apoptosis. M1 and M2 treatment protected cells from ROS produced by AA and inhibited AA-induced glutathione depletion. Moreover, both M1 and M2 effectively inhibited mitochondrial dysfunction induced by AA, although M2 alone slightly elicited it at a relatively high concentration. M1 and M2 activated AMP-activated protein kinase (AMPK), but M3 and M4 failed to do so. AMPK activation by M1 and M2 contributed to cell survival against AA through a decrease in cellular ROS production and prevention of mitochondrial dysfunction, as shown by the reversal of the metabolites' restoration of mitochondrial membrane potential by compound C treatment or overexpression of a dominant-negative mutant AMPK. Consistently, 5-aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside, an AMPK activator, also had a cytoprotective and antioxidant effect against AA. Our results demonstrate that, of the major metabolites of oltipraz, M1 and M2 are capable of protecting cells from AA-induced ROS production and mitochondrial dysfunction, which may be associated with AMPK activation.

Licorice flavonoids inhibit eotaxin-1 secretion by human fetal lung fibroblasts in vitro

Glycyrrhiza uralensis (Gan-Cao), commonly called "licorice", is one of the most commonly used herbs in traditional Chinese medicine (TCM). In the United States, licorice products are most often consumed as flavoring and sweetening agents in food products. The licorice triterpenoid glycyrrhizin has several biological activities, including anti-inflammatory activity. Other potential anti-inflammatory constituents in G. uralensis have not been fully investigated. Airway eosinophilic inflammation is a major feature of allergic asthma. Eotaxin-1 (eotaxin) is involved in the recruitment of eosinophils to sites of antigen-induced inflammation in asthmatic airways. Because human lung fibroblasts are the major source of eotaxin, inhibition of eosinophil recruitment by suppression of fibroblast eotaxin production is a potentially valuable approach for the pharmacological intervention in asthma. A systematic bioassay-guided purification of G. uralensis yielded five flavonoids: liquiritin, liquiritigenin, isoliquiritigenin, 7,4'-dihydroxyflavone, and isoononin. The structures of the compounds were established by (1)H and (13)C nuclear magnetic resonance (NMR) and liquid chromatography-mass spectrometry (LC-MS) studies. The potential ability of these isolated pure compounds and glycyrrhizin to inhibit secretion of eotaxin-1 by human fetal lung fibroblasts (HFL-1) was tested. Liquiritigenin, isoliquiritigenin, and 7,4'-dihydroxyflavone were more effective than liquiritin, isoononin, and glycyrrhizin in suppressing eotaxin secretion. A concentration-response study showed the IC(50) concentrations of liquiritigenin, isoliquiritigenin, and 7,4'-dihydroxyflavone were 4.2, 0.92, and 0.21 microg/mL, respectively, demonstrating that Glycyrrhiza flavonoids inhibit eotaxin-1 secretion in vitro.

Simultaneous extraction and separation of liquiritin, glycyrrhizic acid, and glabridin from licorice root with analytical and preparative chromatography

Simultaneous extraction and separation of liquiritin, glycyrrhizic acid, and glabridin from licorice were developed by liquidliquid extraction with liquid chromatography separation. By utilizing different extraction solvents, procedures, and times, the optimum extraction conditions were established. The extracts of licorice were separated and determined using a C₁₈ column with a mobile phase consisting of acetonitrile-water (containing 1.0% acetic acid) with a gradient elution of 0∼10 min from 20:80 to 60:40 (v/v). Preparative columns with different packing sizes were investigated to isolate the three compounds from the extracts of licorice. The 12 μm chromatographic column showed better separation for the three compounds from licorice. 0.29 mg/g for liquiritin, 1.43 mg/g for glycyrrhizic acid, and 0.07 mg/g for glabridin were obtained and the recoveries were 80.8, 89.7, and 72.5%, respectively.

Liquiritigenin, a flavonoid aglycone from licorice, has a choleretic effect and the ability to induce hepatic transporters and phase-II enzymes

Liquiritigenin (LQ), an active component of licorice, has an inhibitory effect on LPS-induced inhibitory nitric oxide synthase expression. This study investigated the effects of LQ on choleresis, the expression of hepatic transporters and phase-II enzymes, and fulminant hepatitis. The choleretic effect and the pharmacokinetics of LQ and its glucuronides were monitored in rats. After intravenous administration of LQ, the total area under the plasma concentration-time curve of glucuronyl metabolites was greater than that of LQ in plasma, which accompanied elevations in bile flow rate and biliary excretion of bile acid, glutathione, and bilirubin. The expressions of hepatocellular transporters and phase-II enzymes were assessed by immunoblots, real-time PCR, and immunohistochemistry. In the livers of rats treated with LQ, the protein and mRNA levels of multidrug resistance protein 2 and bile salt export pump were increased in the liver, which was verified by their increased localizations in canalicular membrane. In addition, LQ treatment enhanced the expression levels of major hepatic phase-II enzymes. Consistent with these results, LQ treatments attenuated galactosamine/LPS-induced hepatitis in rats, as supported by decreases in the plasma alanine aminotransferase, liver necrosis, and plasma TNF-alpha. These results demonstrate that LQ has a choleretic effect and the ability to induce transporters and phase-II enzymes in the liver, which may be associated with a hepatoprotective effect against galactosamine/LPS. Our findings may provide insight into understanding the action of LQ and its therapeutic use for liver disease.

Anti-inflammatory effects of liquiritigenin as a consequence of the inhibition of NF-kappaB-dependent iNOS and proinflammatory cytokines production

BACKGROUND AND PURPOSE

Glycyrrhizae radix has been widely used as a cytoprotective, plant-derived medicine. We have identified a flavanoid, liquiritigenin, as an active component in extracts of Glycyrrhizae radix. This research investigated the effects of liquiritigenin on the induction of inducible NOS (iNOS) and proinflammatory cytokines by lipopolysaccharide (LPS) in Raw264.7 cells, and on paw oedema in rats.

EXPERIMENTAL APPROACH

iNOS expression was determined by western blotting, real-time reverse transcription-PCR and reporter gene analyses. Tumour necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta and IL-6 were assayed by ELISA. Gel shift assay and immunoblotting were used to assess NF-kappaB activation. The effect of liquiritigenin on acute inflammation in vivo was evaluated using carrageenan-induced paw oedema.

KEY RESULTS

Treatment of Raw264.7 cells with liquiritigenin caused inhibition of LPS-induced NF-kappaB DNA binding activity, due to repression of I-kappaBalpha phosphorylation and degradation. Liquiritigenin treatment prevented LPS from increasing the levels of iNOS protein and mRNA in a concentration-dependent manner. Liquiritigenin also suppressed the production of TNF-alpha, IL-1beta and IL-6 from Raw264.7 cells after LPS. In rats, liquiritigenin treatment inhibited formation of paw oedema induced by carrageenan.

CONCLUSION AND IMPLICATIONS

These results demonstrate that liquiritigenin exerts anti-inflammatory effects, which results from the inhibition of NF-kappaB activation in macrophages, thereby decreasing production of iNOS and proinflammatory cytokines. Our findings showing inhibition by liquiritigenin of paw oedema as well as inflammatory gene induction will help to understand the pharmacology and mode of action of liquiritigenin, and of the anti-inflammatory use of Glycyrrhizae radix.

Hepatoprotective Activity of Licorice Water Extract against Cadmium-induced Toxicity in Rats

Licorice is commonly used as a cure for digestive disorders and as a detoxification agent in East Asia. This study investigated the protective effect of licorice water extract against cadmium (CdCl₂, Cd)-induced liver toxicity in rats. To induce acute toxicity, Cd (4 mg/kg body weight) was dissolved in normal saline and intravenously (i.v.) injected into rats. The rats then received either a vehicle or licorice water extract (50, 100 mg/kg/day) for 3 days, and were subsequently exposed to a single injection of Cd 24 h after the last licorice/vehicle treatment. Alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) were significantly increased by Cd treatment. In contrast, pretreatment with licorice reduced ALT, AST and LDH. In histopathological analysis, licorice decreased the central necrosis around central veins, the peripheral hemorrhage around portal triads, the percentage of degenerative hepatic regions (%/mm² hepatic parenchyma) and the number of degenerative hepatic cells (N/100 hepatic cells). Licorice also inhibited the increment of Bad (a BH3 domain-containing protein) translocation by Cd in liver cells. These results demonstrate that licorice could have a hepatoprotective effect by inhibiting the translocation of Bad to the mitochondria in Cd-intoxificated rats.

Knock Down of γ-Glutamylcysteine Synthetase in Rat Causes Acetaminophen-induced Hepatotoxicity

Drug-induced hepatotoxicity is mainly caused by hepatic glutathione (GSH) depletion. In general, the activity of rodent glutathione S-transferase is 10 to 20 times higher than that of humans, which could make the prediction of drug-induced hepatotoxicity in human more difficult. Gamma-glutamylcysteine synthetase (gamma-GCS) mainly regulates de novo synthesis of GSH in mammalian cells and plays a central role in the antioxidant capacity of cells. In this study, we constructed a GSH-depletion experimental rat model for the prediction of human hepatotoxicity. An adenovirus vector with short hairpin RNA against rat gamma-GCS heavy chain subunit (GCSh) (AdGCSh-shRNA) was constructed and used to knock down the GCSh. In in vitro study in H4IIE cells, a rat hepatoma cell line, GCSh mRNA and protein were significantly decreased by 80% and GSH was significantly decreased by 50% 3 days after AdGCSh-shRNA infection. In the in vivo study in rat, the hepatic GSH level was decreased by 80% 14 days after a single dose of AdGCSh-shRNA (2 x 10(11) pfu/ml/body), and this depletion continued for at least 2 weeks. Using this GSH knockdown rat model, acetaminophen-induced hepatotoxicity was shown to be significantly potentiated compared with normal rats. This is the first report of a GSH knockdown rat model, which could be useful for highly sensitive tests of acute and subacute toxicity for drug candidates in preclinical drug development.