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In vitro antimycobacterial and antilegionella activity of licochalcone A from Chinese licorice roots.

Licochalcone A, extracted and purified from Chinese licorice roots, showed in vitro inhibitory effect on human pathogenic Mycobacteria species and Legionella species. M. tuberculosis, M. bovis and BCG were inhibited by < 20 mg/l licochalcone A, whereas all non- M. tuberculosis complex species were resistant to > 20 mg/l Legionella pneumophila (serogroups 1 - 7) and L. bozemanii, L. dumoffii, L. feelei, L. longbeacheae and L. wadsworthii were inhibited by licochalcone A 1 - 4 mg/l, whereas L. gormanii and L. micdadei were inhibited by licochalcone A 500 - 1000 mg/l. These data indicate that licochalcone A might be of interest as a new class of antibacterial drug in the treatment of severe lung-infections.

Anti-Bacterial Agents↗

An antileishmanial chalcone from Chinese licorice roots.

A bioassay guided fractionation of an extract of Chinese licorice roots led to the isolation of (E)-1-[2,4-dihydroxy-3-(3-methyl-2-butenyl)phenyl]-3-[4- hydroxy-3-(3-methyl-2-butenyl]phenyl-2-propen-1-one, which in vitro showed potent antileishmanial activity. In addition, the novel chalcone (E)-1-[2,4-dihydroxy-3-(3-methyl-2- butenyl)phenyl]-3-(2,2-dimethyl-8-hydroxy-2H-benzopyran-6-yl)-2-prope n-1-one was isolated from the roots. The latter compound only showed antileishmanial activity at high concentrations.

Animals↗

Effect of licorice extract (Fm100) on release of secretin and exocrine pancreatic secretion in humans.

We investigated the effect of a fraction of licorice extract (Fm100) on release of endogenous secretin in seven human volunteers using radioimmunoassay and exocrine pancreatic secretion using a dye dilution technique with polyethylene glycol 4000 as a non-absorbable marker. Intrajejunal administration of Fm100 (pH 6.5) in three different doses (200, 400, and 800 mg/30 min) resulted in significant increases in both plasma secretin concentration and pancreatic bicarbonate output in a dose-dependent manner (r = 0.737, p less than 0.001, and r = 0.483, p less than 0.01, respectively). However, it did not influence pancreatic secretion of protein or amylase. The correlation between plasma secretin concentrations and bicarbonate outputs was also significant (r = 0.483; p less than 0.01). These results indicate that endogenous secretin is released by Fm100 in humans and suggest strongly that the increased pancreatic bicarbonate secretion is attributable to the increased plasma concentration of secretin.

Adult↗

Cloning and functional expression of a cytochrome P450 cDNA encoding 2-hydroxyisoflavanone synthase involved in biosynthesis of the isoflavonoid skeleton in licorice.

Isoflavonoids are distributed predominantly in leguminous plants and play critical roles in plant physiology. A cytochrome P450 (P450), 2-hydroxyisoflavanone synthase, is the key enzyme in their biosynthesis. In cultured licorice (Glycyrrhiza echinata L., Fabaceae) cells, the production of both an isoflavonoid-derived phytoalexin (medicarpin) and a retrochalcone (echinatin) is rapidly induced upon elicitation. In this study, we obtained a full-length P450 cDNA, CYP Ge-8 (CYP93C2), from the cDNA library of elicited G. echinata cells. When the flavanones liquiritigenin and naringenin were incubated with the recombinant yeast microsome expressing CYP93C2, major products emerged and were readily converted to the isoflavones daidzein and genistein by acid treatment. The chemical structures of the products from liquiritigenin (2-hydroxyisoflavanone and isoflavone) were confirmed by mass spectrometry. CYP93C2 was thus shown to encode 2-hydroxyisoflavanone synthase, which catalyzes the hydroxylation associated with 1,2-aryl migration of flavanones. Northern-blot analysis revealed that transcripts of CYP93C2, in addition to those of other P450s involved in phenylpropanoid/flavonoid pathways, transiently accumulate upon elicitation.

Amino Acid Sequence↗

Isoliquiritigenin, a flavonoid from licorice, reduces prostaglandin E2 and nitric oxide, causes apoptosis, and suppresses aberrant crypt foci development.

Isoliquiritigenin (ILTG), a flavonoid group compound, exists in some foodstuffs and herbal medicines such as licorice (Glycyrrhiza uralensis Fisher). Previously, we showed that ILTG can suppress azoxymethane (AOM)-induced colon carcinogenesis in ddY mice. In the present report, we present evidence that ILTG markedly decreases both prostaglandin E2 (PGE2) and nitric oxide (NO) production in RAW264.7 mouse macrophage cells. The decrease of PGE2 was dependent on cyclooxygenase-2 (COX-2) expression and the decrease of NO appeared due to a decrease in inducible nitric oxide synthase (iNOS) protein expression. In mouse and human colon carcinoma cells, ILTG treatment suppressed cell growth and caused apoptosis. Furthermore, in vivo administration of ILTG inhibited the induction of preneoplastic aberrant crypt foci (ACF) in the male F344 rat colon. Our results suggest that ILTG is a promising chemopreventive agent against colon carcinogenesis.

Aldehyde Reductase↗

The inhibitory effect of glabridin from licorice extracts on melanogenesis and inflammation.

Glabridin is the main ingredient in hydrophobic fraction of licorice extract affecting on skins. In this study, we investigated inhibitory effects of glabridin on melanogenesis and inflammation using cultured B16 murine melanoma cells and guinea pig skins. The results indicated that glabridin inhibits tyrosinase activity of these cells at concentrations of 0.1 to 1.0 microg/ml and had no detectable effect on their DNA synthesis. Combined analysis of SDS-polyacrylamide gel electrophoresis and DOPA staining on the large granule fraction of these cells disclosed that glabridin decreased specifically the activities of T1 and T3 tyrosinase isozymes. It was also shown that UVB-induced pigmentation and erythema in the skins of guinea pigs were inhibited by topical applications of 0.5% glabridin. Anti-inflammatory effects of glabridin in vitro were also shown by its inhibition of superoxide anion productions and cyclooxygenase activities. These data indicated that glabridin is a unique compound possessing more than one function; not only the inhibition of melanogenesis but also the inhibition of inflammation in the skins. By replacing each of hydroxyl groups of glabridin with others, it was revealed that the inhibitory effect of 2'-O-ethyl glabridin was significantly stronger than that of 4'-O-ethyl-glabridin on melanin synthesis in cultured B16 cells at the concentration of 1.0 mg/ml. With replacement of both of two hydroxyl groups, the inhibitory effect was totally lost. Based on these data, we concluded that two hydroxyl groups of glabridin are important for the inhibition of melanin synthesis and that the hydroxyl group at the 4' position of this compound is more closely related to melanin synthesis.

Administration, Topical↗

Glabridin, an isoflavan from licorice root, inhibits inducible nitric-oxide synthase expression and improves survival of mice in experimental model of septic shock.

(R)-4-(3,4-Dihydro-8,8-dimethyl)-2H,8H-benzo[1,2-b:3,4-b']dipyran-3yl)-1,3-benzenediol (glabridin), a flavonoid present in licorice extract, is known to have antimicrobial, anti-inflammatory, and cardiovascular protective activities. In the present study, we report the inhibitory effect of glabridin on nitric oxide (NO) production and inducible nitric oxide (iNOS) gene expression in murine macrophages. Glabridin attenuated lipopolysaccharide (LPS)-induced NO production in isolated mouse peritoneal macrophages and RAW 264.7 cells, a mouse macrophage-like cell line. Moreover, iNOS mRNA expression was also blocked by glabridin treatment in LPS-stimulated RAW 264.7 cells. Further study demonstrated that the LPS-induced nuclear factor (NF)-kappaB/Rel DNA binding activity and NF-kappaB/Rel-dependent reporter gene activity were significantly inhibited by glabridin in RAW 264.7 cells and that this effect was mediated through the inhibition of inhibitory factor-kappaB degradation and p65 nuclear translocation. Moreover, reactive oxygen species generation was also suppressed by glabridin treatment in RAW 264.7 cells. In contrast, the activity of mitogen-activated protein kinases was unaffected by glabridin treatment. In animal model, in vivo administration of glabridin increased the rate of survival of LPS-treated mice and inhibited LPS-induced increase in plasma concentrations of nitrite/nitrate and tumor necrosis factor-alpha. Collectively, these data suggest that glabridin inhibits NO production and iNOS gene expression by blocking NF-kappaB/Rel activation and that this effect was mediated, at least in part, by inhibiting reactive oxygen species generation. Furthermore, in vivo anti-inflammatory effect of glabridin suggests a possible therapeutic application of this agent in inflammatory diseases.

Active Transport, Cell Nucleus↗

Glycyrrhizin, an active component of licorice roots, reduces morbidity and mortality of mice infected with lethal doses of influenza virus.

The antiviral effect of glycyrrhizin (GR), an active component of licorice roots, was investigated in mice infected with influenza virus A2 (H2N2). When mice that had been exposed to 10 50% lethal doses of the virus were treated intraperitoneally with 10 mg of GR per kg of body weight 1 day before infection and 1 and 4 days postinfection, all of the mice survived over the 21-day experimental period. At the end of this period, the mean survival time (in days) for control mice treated with saline was 10.5 days, and there were no survivors. The grade of pulmonary consolidations and the virus titers in the lung tissues of infected mice treated with GR were significantly lower than those in the lung tissues of infected mice treated with saline. GR did not show any effects on the viability or replication of influenza virus A2 in vitro. When splenic T cells from GR-treated mice were adoptively transferred to mice exposed to influenza virus, 100% of the recipients survived, compared to 0% survival for recipient mice inoculated with naive T cells or splenic B cells and macrophages from GR-treated mice. In addition, the antiviral activities of GR on influenza virus infection in mice were not demonstrated when it was administered to infected mice in combination with anti-gamma interferon (anti-IFN-gamma) monoclonal antibody. These results suggest that GR may protect mice exposed to a lethal amount of influenza virus through the stimulation of IFN-gamma production by T cells, because T cells have been shown to be producer cells of IFN-gamma stimulated with the compound.

Adoptive Transfer↗

Licking latency with licorice.

Numerous viruses cause latent infections in humans, and reactivation often results in pain and suffering. While vaccines for several of these viruses are available or currently being studied in clinical trials, and antiviral therapies have been successful in preventing or treating active infection, therapy to eradicate latent infection has lagged behind. A new study reported in this issue of the JCI shows that treatment of cells latently infected with Kaposi sarcoma-associated herpesvirus (KSHV) with glycyrrhizic acid, a component of licorice, reduces synthesis of a viral latency protein and induces apoptosis of infected cells. This finding suggests a novel way to interrupt latency.

Animals↗

Inhibition of lysoPAF acetyltransferase activity by components of licorice root.

Licorice root traditionally used as an anti-inflammatory drug exhibited an inhibitory effect on lysoPAF (platelet-activating factor) acetyltransferase in vitro: the ether soluble fraction of the crude drug produced a 27.3% inhibition at a concentration 10 microg/ml. From this fraction, licoricidin (1), 1-methoxyphaseollin (2), 6,8-diprenylgenistein (3) and 1-methoxyphaseollidin (4) were isolated as active components, whose IC50 values were 7.7, 57, 19 and 48 microM, respectively. Licoricidin (1) seems to be one of the most potent compounds of plant origin isolated so far.

Acetyltransferases↗

Identification of licocoumarone as an apoptosis-inducing component in licorice.

The 70% methanol soluble fraction from a licorice acetone extract was found to inhibit cell proliferation in human monoblastic leukemia U937 cells by inducing apoptosis. Separation by the methods including preparative HPLC provided us with an active compound, which was identified as licocoumarone. Several lines of evidence indicated that licocoumarone induced apoptosis in U937 cells. Thus, licocoumarone is suggested to be potentially useful as a natural anti-cancer agent.

Apoptosis↗

Effects of FM100, a fraction of licorice root, on serum gastrin concentration in rats and dogs.

The effects of FM100, a fraction of licorice root with antiulcer activity, on serum gastrin concentration were investigated in rats and dogs. The basal serum gastrin concentration in conscious rats was not affected by 400 mg/kg. p.o. of FM100, but was increased by 800 mg/kg, p.o. of FM100. The serum gastrin concentration of rats in which the antrum had been separated from the fundus was decreased by intraduodenal administration of FM100 in a dose-dependent manner. In conscious beagles, the increase in serum gastrin concentration induced by feeding was not affected by pretreatment with 400 mg/kg p.o. of FM100. However, in anesthetized dogs in which the antrum had been separated from the fundus, the increase in acid output and serum gastrin concentration after administration of peptone solution was prevented by the intraduodenal administration of 200 mg/kg of FM100. These results suggest that the gastric anti-secretory action of FM100 may be due to the inhibition of endogenous gastrin release.

Animals↗

Interaction of licorice on glycyrrhizin pharmacokinetics.

The effects of components of aqueous licorice root extract (LE) on the pharmacokinetics of glycyrrhizin (G) and glycyrrhetic acid (GA) were investigated in rats and humans. The aim of this work was to define the role of pharmacokinetics in G toxicity. In the procedure, G and GA were detected in biological fluids by means of recently improved HPLC methods. Significantly lower G and GA plasma levels were found in rats and humans treated with LE compared to the levels obtained with those in which G alone was administered. The pharmacokinetic curves showed significant differences in the areas under the plasma-time curve (AUC), Cmax, and Tmax parameters. The data obtained from urine samples are in agreement with the above results and confirm a reduced bioavailability of G present in LE compared to pure G. This should be attributed to the interaction during intestinal absorption between the G constituent and the several components in LE. The modified bioavailability could explain the various clinical adverse effects resulting from the chronic oral administration of G alone as opposed to LE.

Administration, Oral↗

Antibacterial compounds of licorice against upper airway respiratory tract pathogens.

The antibacterial activity of compounds obtained from licorice was measured against upper airway respiratory tract bacteria such as Streptococcus pyogenes, Haemophilus influenzae and Moraxella catarrhalis. Among the tested compounds, licoricidin exhibited the highest activity against all tested microorganisms with an MIC of 12.5 microg/mL. Three coumarin derivatives, glycyrol, glycyrin and glycycoumarin also showed antibacterial activity.

Anti-Bacterial Agents↗

Upper limb ischemia induced by chronic licorice ingestion.

A young woman had an acute embolic episode that affected her right upper limb. An axillo-brachial thromboembolectomy was performed after which distal pulses were recovered. The patient had a long lasting history, longer than ten years, of continuous licorice ingestion. Blood samples showed severe hypokalemia that caused EKG changes. Transesophageal echocardiogram discovered mild mitral valve prolapse. The combination of surgery and potassium supplements was successful in treating this rare and potentially life-threatening disease.

Adult↗

Estrogenic and antiproliferative properties of glabridin from licorice in human breast cancer cells.

There is an increasing demand for natural compounds that improve women's health by mimicking the critical benefits of estrogen to the bones and the cardiovascular system but avoiding its deleterious effects on the breast and uterus. The estrogenic properties of glabridin, the major isoflavan in licorice root, were tested in view of the resemblance of its structure and lipophilicity to those of estradiol. The results indicate that glabridin is a phytoestrogen, binding to the human estrogen receptor and stimulating creatine kinase activity in rat uterus, epiphyseal cartilage, diaphyseal bone, aorta, and left ventricle of the heart. The stimulatory effects of 2.5-25 microg/animal glabridin were similar to those of 5 microg/animal estradiol. Chemical modification of glabridin showed that the position of the hydroxyl groups has a significant role in binding to the human estrogen receptor and in proliferation-inducing activity. Glabridin was found to be three to four times more active than 2'-O-methylglabridin and 4'-O-methylglabridin, and both derivatives were more active than 2',4'-O-methylglabridin. The effect of increasing concentrations of glabridin on the growth of breast tumor cells was biphasic. Glabridin showed an estrogen receptor-dependent, growth-promoting effect at low concentrations (10 nM-10 microM) and estrogen receptor-independent antiproliferative activity at concentrations of > 15 microM. This is the first study to indicate that isoflavans have estrogen-like activities. Glabridin and its derivatives exhibited varying degrees of estrogen receptor agonism in different tests and demonstrated growth-inhibitory actions on breast cancer cells.

Animals↗