Toxicological assessment of liquorice: biliary excretion in rats

Herbal Medicine of the 21st Century: A Focus on the Chemistry, Pharmacokinetics and Toxicity of Five Widely Advocated Phytotherapies

Widely advocated for their health benefits worldwide, herbal medicines (HMs) have evolved into a billion dollar generating industry. Much is known regarding their wellness inducing properties, prophylactic and therapeutic benefits for the relief of both minor to chronic ailment conditions given their long-standing use among various cultures worldwide. On the other hand, their equally meaningful chemistry, pharmacokinetic profile in humans, interaction and toxicity profile have been poorly researched and documented. Consequently, this review is an attempt to highlight the health benefits, pharmacokinetics, interaction, and toxicity profile of five globally famous HMs. A systematic literature search was conducted by browsing major scientific databases such as Bentham Science, SciFinder, ScienceDirect, PubMed, Google Scholar and EBSCO to include 196 articles. In general, ginsenosides, glycyrrhizin and curcumin demonstrate low bioavailability when orally administered. Ginkgo biloba L. induces both CYP3A4 and CYP2C9 and alters the AUC and Cmax of conventional medications including midazolam, tolbutamide, lopinavir and nifedipine. Ginsenosides Re stimulates CYP2C9, decreasing the anticoagulant activity of warfarin. Camellia sinensis (L.) Kuntze increases the bioavailability of buspirone and is rich in vitamin K thereby inhibiting the activity of anticoagulant agents. Glycyrrhiza glabra L. displaces serum bound cardiovascular drugs such as diltiazem, nifedipine and verapamil. Herbal medicine can directly affect hepatocytes leading to hepatoxicity based on both intrinsic and extrinsic factors. The potentiation of the activity of concurrently administered conventional agents is potentially lethal especially if the drugs bear dangerous side effects and have a low therapeutic window.

Glycyrrhiza glabra

Liquorice foliage

A simple semi-preparative reversed-phase HPLC/PDA method for separation and quantification of glycyrrhizin in nine samples of Glycyrrhiza glabra root collected from different geographical origins

INTRODUCTION

Glycyrrhiza glabra L. (Fabaceae), commonly known as 'liquorice', is one of the most popular ingredients in several traditional herbal medicinal preparations, and glycyrrhizin is the major glycoside present in this plant. The content of glycyrrhizin may vary among G. glabra samples collected from various geographical origins, which may affect the therapeutic efficacy. Thus, quantification of glycyrrhizin in G. glabra samples is important.

OBJECTIVE

To develop and validate a simple semi-preparative reversed-phase HPLC with photodiode array (PDA) method for separation and quantification of glycyrrhizin in nine samples of G. glabra root collected from various geographical origins.

METHODS

Dried and ground root of G. glabra was Soxhlet-extracted sequentially with n-hexane and methanol (MeOH). The separation and quantification of glycyrrhizin was achieved on a C18 reversed-phase semi-preparative column using a gradient mobile phase, 30-100% solvent B in solvent A in 30 min (solvent A: 0.1% v/v trifluoroacetic acid (TFA) in water and solvent B: 0.1% v/v of TFA in MeOH), at a flow rate of 3.00 mL/min and UV detection at 254 nm.

RESULTS

A simple semi-preparative reversed-phase HPLC/PDA method allowing clear separation and quantification of glycyrrhizin content in nine samples has been validated in terms of linearity, selectivity, limits of detection, precision, accuracy and detection. Concentration levels of glycyrrhizin were between 0.177 and 0.688% w/w of dry materials.

CONCLUSION

This method is precise, less time consuming and more cost effective, and can be used for the quality control of any G. glabra sample with regard to its glycyrrhizin contents.

Liquorice, a unique "guide drug" of traditional Chinese medicine: a review of its role in drug interactions

ETHNOPHARMACOLOGICAL RELEVANCE

Liquorice is the root of Glycyrrhiza uralensis Fisch. or Glycyrrhiza glabra L., Leguminosae. It is a widely used herbal medicine native to southern Europe and parts of Asia and has beneficial applications in both the medicinal and the confectionery sectors. Unlike its usage in Europe, liquorice in traditional Chinese medicine is commonly combined with other herbs in a single prescription, as a unique "guide drug" to enhance the effectiveness of other ingredients, to reduce toxicity, and to improve flavor in almost half of Chinese herbal formulas. A review on phytochemical and pharmacological research to explain this unique "guide" effect is suggested for future investigations.

MATERIALS AND METHODS

The information was collected from scientific journals, books, and pharmacopeia. The studies about the traditional uses, randomized controlled trials, chemical, pharmacological and pharmacokinetic data related to liquorice-herb/drug interaction or combination were included in the review.

RESULTS

According to recent reports, the "guide" effect of liquorice is partially through components transformed in liquorice-drug interaction; altering enzyme activity of P450 isoforms, as evidenced by induction of model probe substrates; and modulation of drug transporter proteins such as intestinal P-glycoprotein.

CONCLUSION

The overview and comparison of traditional uses of liquorice with recent pharmacological studies and randomized controlled trials provide new insights into this ancient drug for future investigations and clinical use, especially in drug combination.

Alleviation of lung injury by glycyrrhizic acid in benzo(a)pyrene exposed rats: Probable role of soluble epoxide hydrolase and thioredoxin reductase

Benzo(a)pyrene [B(a)P] is known to alter lung physiology by interfering in various intracellular pathways including alterations in NF-κB activities, cytokine release and cell survival. NF-κB suppression/activation plays a major role in cell survival status. Present investigation deals with such kind of effects of B(a)P on lungs in relation with soluble epoxide hydrolase (sEH) and thioredoxin reductase (TrxR) activities. Glycyrrhizic acid (GA), an active principle of Glycyrrhiza glabra (Licorice), is known to modulate various molecular processes. In the present study, we investigated the protective effects of GA against B(a)P induced debilities in lungs of Wistar rats. Intratracheal instillation of B(a)P significantly suppressed NF-κB translocation, sEH, TrxR and catalase activities in lung tissue. A marked induction of H(2)O(2) levels along with caspases activation (caspases-2, -3, -6, -8, and -9) in lung tissue after B(a)P exposure was observed. Lung injury was assessed by measuring lactate dehydrogenase (LDH), alkaline phosphatase (ALP), total cell count, total protein, neutrophil elastase activity in bronchoalveolar lavage fluid (BALF). Reduction in phospholipid content further potentiated these parameters. GA oral administration (50 and 100mg/kg b.wt.) significantly showed protection of lung epithelium by suppression of caspases activities in lung tissue and reduction of total protein, total cells, elastase activity, LDH and ALP activities along with fortification of phospholipids in BALF. Histological observations also confirm the findings in above mentioned parameters. Results indicate a strong correlation between amelioration of sEH and TrxR activities, and NF-κB activation. The present investigation gives an insight into probable mechanisms of lung injuries induced by short term exposures of B(a)P and prevention by glycyrrhizic acid.

Final report on the safety assessment of Glycyrrhetinic Acid, Potassium Glycyrrhetinate, Disodium Succinoyl Glycyrrhetinate, Glyceryl Glycyrrhetinate, Glycyrrhetinyl Stearate, Stearyl Glycyrrhetinate, Glycyrrhizic Acid, Ammonium Glycyrrhizate, Dipotassium Glycyrrhizate, Disodium Glycyrrhizate, Trisodium Glycyrrhizate, Methyl Glycyrrhizate, and Potassium Glycyrrhizinate

Glycyrrhetinic Acid and its salts and esters and Glycyrrhizic Acid and its salts and esters are cosmetic ingredients that function as flavoring agents or skin-conditioning agents - miscellaneous or both. These chemicals may be isolated from licorice plants. Glycyrrhetinc Acid is described as at least 98% pure, with 0.6% 24-OH-Glycyrrhetinic Acid, not more than 20 mu g/g of heavy metals and not more than 2 mu g/g of arsenic. Ammonium Glycyrrhizate has been found to be at least 98% pure and Dipotassium Glycyrrhizate has been found to be at least 95% pure. Glycyrrhetinic Acid is used in cosmetics at concentrations of up to 2%; Stearyl Glycyrrhetinate, up to 1%; Glycyrrhizic Acid, up to 0.1%; Ammonium Glycyrrhizate, up to 5%; Dipotassium Glycyrrhizate, up to 1%; and Potassium Glycyrretinate, up to 1%. Although Glycyrrhizic Acid is poorly absorbed by the intestinal tract, it may be hydrolyzed to Glycyrrhetinic Acid by a beta -glucuronidase produced by intestinal bacteria. Glycyrrhetinic Acid and Glycyrrhizic Acid bind to rat and human albumin, but do not absorb well into tissues. Glycyrrhetinic Acid and Glycyrrhizic Acid and metabolites are mostly excreted in the bile, with very little excreted in urine. Dipotassium Glycyrrhizate was undetectable in the receptor chamber when tested for transepidermal permeation through pig skin. Glycyrrhizic Acid increased the dermal penetration of diclofenac sodium in rat skin. Dipotassium Glycyrrhizate increased the intestinal absorption of calcitonin in rats. In humans, Glycyrrhetinic Acid potentiated the effects of hydrocortisone in the skin. Moderate chronic or high acute exposure to Glycyrrhizic Acid, Ammonium Glycyrrhizate, and their metabolites have been demonstrated to cause transient systemic alterations, including increased potassium excretion, sodium and water retention, body weight gain, alkalosis, suppression of the renin-angiotensis-aldosterone system, hypertension, and muscular paralysis; possibly through inhibition of 11beta -hydroxysteroid dehydrogenase-2 (11beta -OHSD2) in the kidney. Glycyrrhetinic Acid and its derivatives block gap junction intracellular communication in a dose-dependent manner in animal and human cells, including epithelial cells, fibroblasts, osteoblasts, hepatocytes, and astrocytes; at high concentrations, it is cytotoxic. Glycyrrhetinic Acid and Glycyrrhizic Acid protect liver tissue from carbon tetrachloride. Glycyrrhizic Acid has been used to treat chronic hepatitis, inhibiting the penetration of the hepatitis A virus into hepatocytes. Glycyrrhetinic Acid and Glycyrrhizic Acid have anti-inflammatory effects in rats and mice. The acute intraperitoneal LD(50) for Glycyrrhetinic Acid in mice was 308 mg/kg and the oral LD(50) was > 610 mg/kg. The oral LD(50) in rats was reported to be 610 mg/kg. Higher LD(50) values were generally reported for salts. Little short-term, subchronic, or chronic toxicity was seen in rats given ammonium, dipotassium, or disodium salts of Glycyrrhizic Acid. Glycyrrhetinic Acid was not irritating to shaved rabbit skin, but was considered slightly irritating in an in vitro test. Glycyrrhetinic Acid inhibited the mutagenic activity of benzo[a]pyrene and inhibited tumor initiation and promotion by other agents in mice. Glycyrrhizic Acid inhibited tumor initiation by another agent, but did not prevent tumor promotion in mice. Glycyrrhizic Acid delayed mortality in mice injected with Erlich ascites tumor cells, but did not reduce the mortality rate. Ammonium Glycyrrhizate was not genotoxic in in vivo and in vitro cytogenetics assays, the dominant lethal assay, an Ames assay, and heritable translocation tests, except for possible increase in dominant lethal mutations in rats given 2000 mg/kg day(-1) in their diet. Disodium Glycyrrhizate was not carcinogenic in mice in a drinking water study at exposure levels up to 12.2 mg/kg day(-1) for 96 weeks. Glycyrrhizate salts produced no reproductive or developmental toxicity in rats, mice, golden hamsters, or Dutch-belted rabbits, except for a dose-dependent increase (at 238.8 and 679.9 mg/kg day(-1)) in sternebral variants in a study using rats. Sedation, hypnosis, hypothermia, and respiratory depression were seen in mice given 1250 mg/kg Glycyrrhetinic Acid intraperitoneally. Rats fed a powdered diet containing up to 4% Ammonium Glycyrrhizate had no treatment related effects in motor function tests, but active avoidance was facilitated at 4%, unaffected at 3%, and depressed at 2%. In a study of 39 healthy volunteers, a no effect level of 2 mg/kg/day was determined for Glycyrrhizic Acid given orally for 8 weeks. Clinical tests in seven normal individuals given oral Ammonium Glycyrrhizate at 6 g/day for 3 days revealed reduced renal and thermal sweat excretion of Na+ and K+, but carbohydrate and protein metabolism were not affected. Glycyrrhetinic Acid at concentrations up to 6% was not a skin irritant or a sensitizer in clinical tests. Neither Glycyrrhizic Acid, Ammonium Glycyrrhizate, nor Dipotassium Glycyrrhizate at 5% were phototoxic agents or photosensitizers. Birth weight and maternal blood pressure were unrelated to the level of consumption of Glycyrrhizic Acid in 1049 Finnish women with infants, but babies whose mother consumed > 500 mg/wk were more likely to be born before 38 weeks. The Cosmetic Ingredient Review (CIR) Expert Panel noted that the ingredients in this safety assessment are not plant extracts, powders, or juices, but rather are specific chemical species that may be isolated from the licorice plant. Because these chemicals may be isolated from plant sources, however, steps should be taken to assure that pesticide and toxic metal residues are below acceptable levels. The Panel advised the industry that total polychlorobiphenyl (PCB)/pesticide contamination should be limited to not more than 40 ppm, with not more than 10 ppm for any specific residue, and that toxic metal levels must not contain more than 3 mg/kg of arsenic (as As), not more than 0.002% heavy metals, and not more than 1 mg/kg of lead (as Pb). Although the Panel noted that Glycyrrhizic Acid is cytotoxic at high doses and ingestion can have physiological effects, there is little acute, short-term, subchronic, or chronic toxicity and it is expected that these ingredients would be poorly absorbed through the skin. These ingredients are not considered to be irritants, sensitizers, phototoxic agents, or photosensitizers at the current maximum concentration of use. Accordingly, the CIR Expert Panel concluded that these ingredients are safe in the current practices of use and concentration. The Panel recognizes that certain ingredients in this group are reportedly used in a given product category, but the concentration of use is not available. For other ingredients in this group, information regarding use concentration for specific product categories is provided, but the number of such products is not known. In still other cases, an ingredient is not in current use, but may be used in the future. Although there are gaps in knowledge about product use, the overall information available on the types of products in which these ingredients are used and at what concentration indicate a pattern of use. Within this overall pattern of use, the Expert Panel considers all ingredients in this group to be safe.

Determination of glycyrrhizin in liqueurs by on-line coupled capillary isotachophoresis with capillary zone electrophoresis

An on-line coupled capillary isotachophoresis-capillary zone electrophoresis method for the determination of glycyrrhizin in liqueurs is described. The optimised electrolyte system was 5 mM HCl+11 mM epsilon-aminocaproic acid+0.05% hydroxyethylcellulose+30% methanol (leading electrolyte), 5 mM caproic acid+30% methanol (terminating electrolyte) and 20 mM caproic acid+10 mM histidine+0.1% hydroxyethylcellulose+30% methanol (background electrolyte). Method characteristics, i.e., linearity (20-500 ng/ml), accuracy (recovery 99+/-4%), intra-assay repeatability (2%), intermediate repeatability (3.8%) and detection limit (8 ng/ml) were determined. Speed of analysis, low laboriousness, high sensitivity and low-running cost are the typical attributes of the capillary isotachophoresis-capillary zone electrophoresis method. Developed method was successfully applied to analysis of liqueurs with liquorice extract and some foods (sweets and food supplements) containing liquorice. Found levels of glycyrrhizin in liqueurs, sweets and food supplements varied between 1-16 mg/l, 850-1050 mg/kg and 1.6-1.8 g/kg, respectively.

Risk and safety assessment on the consumption of Licorice root (Glycyrrhiza sp.), its extract and powder as a food ingredient, with emphasis on the pharmacology and toxicology of glycyrrhizin

Licorice (or 'liquorice') is a plant of ancient origin and steeped in history. Licorice extracts and its principle component, glycyrrhizin, have extensive use in foods, tobacco and in both traditional and herbal medicine. As a result, there is a high level of use of licorice and glycyrrhizin in the US with an estimated consumption of 0.027-3.6 mg glycyrrhizin/kg/day. Both products have been approved for use in foods by most national and supranational regulatory agencies. Biochemical studies indicate that glycyrrhizinates inhibit 11beta-hydroxysteroid dehydrogenase, the enzyme responsible for inactivating cortisol. As a result, the continuous, high level exposure to glycyrrhizin compounds can produce hypermineralocorticoid-like effects in both animals and humans. These effects are reversible upon withdrawal of licorice or glycyrrhizin. Other in vivo and clinical studies have reported beneficial effects of both licorice and glycyrrhizin consumption including anti-ulcer, anti-viral, and hepatoprotective responses. Various genotoxic studies have indicated that glycyrrhizin is neither teratogenic nor mutagenic, and may possess anti-genotoxic properties under certain conditions. The pharmacokinetics of glycyrrhizin have been described and show that its bioavailability is reduced when consumed as licorice; this has hampered attempts to establish clear dose-effect levels in animals and humans. Based on the in vivo and clinical evidence, we propose an acceptable daily intake of 0.015-0.229 mg glycyrrhizin/kg body weight/day.

Effect of the co-occurring components from green tea on the intestinal absorption and disposition of green tea polyphenols in Caco-2 monolayer model

This study aimed to investigate the effect of co-occurring components from green tea on the intestinal absorption and disposition of green tea polyphenols (GTPs) using the Caco-2 cell monolayer model. The absorption and secretion transport of the four GTPs, in the form of individual pure compounds, pure compound mixtures and green tea extract, were studied in the Caco-2 cell model. Four GTPs and their metabolites were analysed by HPLC/MS and HPLC coupled with electrochemical detector. The apparent permeability coefficients (P(app)) of each compound, as well as the metabolites (mainly sulfation and methylation conjugates) generated, were compared for the different dosing formulations utilized. The results showed that the absorption transport of the four GTPs in different dosing formulations was similar. However, the secretion transport profiles of (-)-epicatechin (EC), (-)-epigallocatechin (EGC) and (-)-epigallocatechin gallate (EGCG) were altered when the GTP mixture was administered. It was suggested that transporter competition resulting in reduced efflux of EC, as well as metabolic competition resulting in reduced formation of EGC sulfate and methylated EGC sulfate, might be involved during the secretion transport of GTP mixture.

Ex vivo/in vitro absorption of STW 5 (Iberogast) and its extract components

To correlate the pharmacological effects of the fixed herbal combination STW 5 (Iberogast) containing nine extract components with its confirmed clinical efficacy, ex vivo/in vitro absorption tests were performed. For the investigation, the everted gut sac technique and, in a pilot study, the Caco-2-cell model were used. The absorption rate of the extracts was determined by measuring characteristic marker substances of each of the individual extracts using HPLC or GC techniques. The results allow us to conclude that the investigated substances from STW 5 possess a good bioavailability, which is in accordance with the rapid onset of the therapeutic efficacy and explains its known pharmacological effects and clinical efficacy in terms of multiple drug action and multi-target therapy, respectively.

Comparative pharmacokinetic behavior of glycyrrhetic acid after oral administration of glycyrrhizic acid and Gancao-Fuzi-Tang

Comparative pharmacokinetic profiles of glycyrrhetic acid (GA), glycyrrhizic acid (GL) and Gancao-Fuzi-Tang (KF) after oral administration of GL and KF were studied. Plasma samples taken from rats were acidified with acetic acid and GA was extracted with isopropanol-ethyl ether (1 : 1). Separation of GA was performed on a C(18) column with the detection wavelength set at 254 nm. The mobile phase was methanol-acetonitrile-water-acetic acid (58 : 18 : 24 : 1 v/v). The results showed that the mean residence time and area under the curve of GA in KF-administered rats were 27.6+/-1.5 h and 122.8+/-46.7 microg.h/ml respectively, which were significantly different from those in GL-administered rats (15.0+/-2.0 h and 40.9+/-9.6 microg.h/ml, respectively). The results suggest the increased effect of GA after oral administration of KF in comparison with GL.

Sensitive Detection of Glycyrrhizin and Evaluation of the Affinity Constants by a Surface Plasmon Resonance-based Immunosensor

A sensitive and selective determination of glycyrrhizin (GC) based on surface plasmon resonance (SPR) was performed by using an anti-GC monoclonal antibody (GC-MAb) and GC-bovine serum albumin (GC-BSA) conjugate (antigen). GC-BSA was immobilized on an Au thin film of the SPR sensor chip by physical adsorption, and GC determinations were performed by an indirect competitive method. The addition of GC into the GC-MAb solution (5 microg/ml) was found to decrease the incident-angle shift sharply because of an inhibition effect of GC. The RSDs (n = 3) of each point were less than 4%. The lowest detection limit for GC by SPR was almost the same as that by ELISA, 60-75 ng/ml. An evaluation of the affinity constant between GC-MAb and GC using the data from ELISA and those from SPR measurements was performed. The values of the association constant (KA) from three different analyses of ELISA data and from SPR measurements are discussed in detail. As a whole, the affinity constant (KA) between GC-MAb and GC was on the order of 10(7) M(-1).

Liquorice (Glycyrrhiza glabra) and the adrenal-kidney-pituitary axis in rats

The effect of oral administration of a water freeze-dried extract of Glycyrrhiza glabra (liquorice) has been studied at doses of 100, 250 and 500 mg/kg in rats on the plasma concentration of cortisol, adrenocorticotrophic hormone (ACTH), aldosterone, renin, sodium (Na) and potassium (K). The results indicated that treatment induced dose-dependent and mostly significant decreases in the concentration of cortisol, ACTH, aldosterone and K. There were concomitant dose-dependent increases in the concentrations of renin and Na. The results suggest a strong and dose-dependent suppression of the adrenal-pituitary axis, accompanied by stimulation of renin production from the kidney.

Licorice and cancer

Licorice root is one of the oldest and most frequently employed botanicals in Chinese medicine. In the United States, licorice products are most often used as flavoring and sweetening agents in food products. Constituents of licorice include triterpenoids, such as glycyrrhizin and its aglycone glycyrrhizic acid, various polyphenols, and polysaccharides. A number of pharmaceutical effects of licorice are known or suspected (anti-inflammatory, antivirus, antiulcer, anticarcinogenesis, and others). Licorice and its derivatives may protect against carcinogen-induced DNA damage and may be suppressive agents as well. Glycyrrhizic acid is an inhibitor of lipoxygenase and cyclooxygenase, inhibits protein kinase C, and downregulates the epidermal growth factor receptor. Licorice polyphenols induce apoptosis in cancer cells. These and other activities of licorice are reviewed, and a rationale is suggested for combinations of agents in preventive clinical trials.