Glycyrrhetinic Acids Research Articles

Polymorphism of Butyl Ester of Oleanolic Acid—The Dominance of Dispersive Interactions over Electrostatic

Oleanolic (OA) and glycyrrhetinic acids (GE), as well as their derivatives, show a variety of pharmacological properties. Their crystal structures provide valuable information related to the assembly modes of these biologically active compounds. In the known-to-date crystals of OA esters, their 11-oxo derivatives, and GE ester crystals, triterpenes associate, forming different types of ribbons and layers whose construction is based mainly on van der Waals forces and weak C-H···O interactions. New crystal structures of 11-oxo OA methyl ester and the polymorph of OA butyl ester reveal an alternative aggregation mode. Supramolecular architectures consist of helical chains which are stabilized by hydrogen bonds of O-H···O type. It was found that two polymorphic forms of butyl OA ester (layered and helical) are related monotropically. In a structure of metastable form, O-H···O hydrogen bonds occur, while the thermodynamically preferred phase is governed mainly by van der Waals interactions. The intermolecular interaction energies calculated using CrystalExplorer, PIXEL, and Psi4 programs showed that even in motifs formed through O-H···O hydrogen bonds, the dispersive forces have a significant impact.

Rosmarinic and Glycyrrhetinic Acid-Modified Layered Double Hydroxides as Functional Additives for Poly(Lactic Acid)/Poly(Butylene Succinate) Blends.

Immobilizing natural antioxidant and biologically active molecules in layered double hydroxides (LDHs) is an excellent method to retain and release these substances in a controlled manner, as well as protect them from thermal and photochemical degradation. Herein, we describe the preparation of host-guest systems based on LDHs and rosmarinic and glycyrrhetinic acids, two molecules obtained from the extraction of herbs and licorice root, respectively, with antioxidant, antimicrobial, and anti-inflammatory properties. Intercalation between the lamellae of the mono-deprotonated anions of rosmarinic and glycyrrhetinic acid (RA and GA), alone or in the presence of an alkyl surfactant, allows for readily dispersible systems in biobased polymer matrices such as poly(lactic acid) (PLA), poly(butylene succinate) (PBS), and a 60/40 wt./wt. PLA/PBS blend. The composites based on the PLA/PBS blend showed better interphase compatibility than the neat blend, correlated with increased adhesion at the interface and a decreased dispersed phase size. In addition, we proved that the active species migrate slowly from thin films of the composite materials in a hydroalcoholic solvent, confirming the optimization of the release process. Finally, both host-guest systems and polymeric composites showed antioxidant capacity and, in the case of the PLA composite containing LDH-RA, excellent inhibitory capacity against E. coli and S. aureus.

Licorice (Glycyrrhiza glabra) Extracts-Suitable Pharmacological Interventions for COVID-19? A Review.

Even though vaccination has started against COVID-19, people should continue maintaining personal and social caution as it takes months or years to get everyone vaccinated, and we are not sure how long the vaccine remains efficacious. In order to contribute to the mitigation of COVID-19 symptoms, the pharmaceutical industry aims to develop antiviral drugs to inhibit the SARS-CoV-2 replication and produce anti-inflammatory medications that will inhibit the acute respiratory distress syndrome (ARDS), which is the primary cause of mortality among the COVID-19 patients. In reference to these tasks, this article considers the properties of a medicinal plant named licorice (Glycyrrhiza glabra), whose phytochemicals have shown both antiviral and anti-inflammatory tendencies through previous studies. All the literature was selected through extensive search in various databases such as google scholar, Scopus, the Web of Science, and PubMed. In addition to the antiviral and anti-inflammatory properties, one of the licorice components has an autophagy-enhancing mechanism that studies have suggested to be necessary for COVID-19 treatment. Based on reviewing relevant professional and historical literature regarding the medicinal properties of licorice, it is suggested that it may be worthwhile to conduct in vitro and in vivo studies, including clinical trials with glycyrrhizic and glycyrrhetinic acids together with other flavonoids found in licorice, as there is the potentiality to provide natural interventions against COVID-19 symptoms.

Low molecular weight gelators based on steroid derivatives and pentacyclic triterpenoids

The article is an overview of the latest achievements in the study of low molecular weight gelling agents based on steroids - cholesterol, estradiol, dehydroepi-androsterone and pentacyclic triterpenoids - arjunolic, glycyrrhetinic acids. These compounds are used as components of smart gels and are of interest for supramolecular chemistry. A gelling agent is a substance that is able to bind various solvents at low concentrations, and the resulting gel has a solid structure which rheological properties are similar to those of solids. Non-covalent interactions: dipole-dipole, van der Waals, electrostatic, hydrogen bonds and π-stacking, are considered as the driving forces for the formation a fibrous network by low molecular weight gelator. In contrast to decades of research into the gelation of polymers, proteins and inorganic substances, low molecular weight organic gelling agents have only recently begun to be actively studied. Their chemical structure is derived from urea, amino acids, carbohydrates, cholesterol and bile acids. Unlike steroid-based gels, information on the use of pentacyclic triterpenoids for the development of low molecular weight gelling agents is extremely limited. The interest in such systems is due to the fact that, like steroids, they have a developed, rigidly organized nanosized molecular platform, making them capable of self-association in polar and nonpolar organic solvents. In addition, the presence of molecules of these compounds in several functional groups that are easily chemically modified, low toxicity and biocompatibility allows them to be considered as promising starting materials for the pharmaceutical industry, in particular for the development of mild dosage forms.

Cytotoxic Potential of a-Azepano- and 3-Amino-3,4-SeCo-Triterpenoids.

Semi-synthetic triterpenoids, holding an amino substituted seven-membered A-ring (azepano-ring), which could be synthesized from triterpenic oximes through a Beckmann type rearrangement followed by a reduction of lactame fragment, are considered to be novel promising agents exhibiting anti-microbial, alpha-glucosidase, and butyrylcholinesterase inhibitory activities. In this study, in an attempt to develop new antitumor candidates, a series of A-ring azepano- and 3-amino-3,4-seco-derivatives of betulin, oleanolic, ursolic, and glycyrrhetinic acids were evaluated for their cytotoxic activity against five human cancer cell lines and non-malignant mouse fibroblasts by means of a colorimetric sulforhodamine assay. Azepanoallobetulinic acid amide derivative 11 was the most cytotoxic compound of this series but showed little selectivity between the different human tumor cell lines. Flow cytometry experiments showed compound 11 to act mainly by apoptosis (44.3%) and late apoptosis (21.4%). The compounds were further screened at the National Cancer Institute towards a panel of 60 cancer cell lines. It was found that compounds 3, 4, 7, 8, 9, 11, 15, 16, 19, and 20 showed growth inhibitory (GI50) against the most sensitive cell lines at submicromolar concentrations (0.20–0.94 μM), and their cytotoxic activity (LC50) was also high (1–6 μM). Derivatives 3, 8, 11, 15, and 16 demonstrated a certain selectivity profile at GI50 level from 5.16 to 9.56 towards K-562, CCRF-CEM, HL-60(TB), and RPMI-8226 (Leukemia), HT29 (Colon cancer), and OVCAR-4 (Ovarian cancer) cell lines. Selectivity indexes of azepanoerythrodiol 3 at TGI level ranged from 5.93 (CNS cancer cell lines SF-539, SNB-19 and SNB-75) to 14.89 for HCT-116 (colon cancer) with SI 9.56 at GI50 level for the leukemia cell line K-562. The present study highlighted the importance of A-azepano-ring in the triterpenic core for the development of novel antitumor agents, and a future aim to increase the selectivity profile will thus lie in the area of modifications of azepano-triterpenic acids at their carboxyl group.

Exploring the Pivotal Immunomodulatory and Anti-Inflammatory Potentials of Glycyrrhizic and Glycyrrhetinic Acids.

Licorice extract is a Chinese herbal medication most often used as a demulcent or elixir. The extract usually consists of many components but the key ingredients are glycyrrhizic (GL) and glycyrrhetinic acid (GA). GL and GA function as potent antioxidants, anti-inflammatory, antiviral, antitumor agents, and immuneregulators. GL and GA have potent activities against hepatitis A, B, and C viruses, human immunodeficiency virus type 1, vesicular stomatitis virus, herpes simplex virus, influenza A, severe acute respiratory syndrome-related coronavirus, respiratory syncytial virus, vaccinia virus, and arboviruses. Also, GA was observed to be of therapeutic valve in human enterovirus 71, which was recognized as the utmost regular virus responsible for hand, foot, and mouth disease. The anti-inflammatory mechanism of GL and GA is realized via cytokines like interferon-γ, tumor necrotizing factor-α, interleukin- (IL-) 1β, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12, and IL-17. They also modulate anti-inflammatory mechanisms like intercellular cell adhesion molecule 1 and P-selectin, enzymes like inducible nitric oxide synthase (iNOS), and transcription factors such as nuclear factor-kappa B, signal transducer and activator of transcription- (STAT-) 3, and STAT-6. Furthermore, DCs treated with GL were capable of influencing T-cell differentiation toward Th1 subset. Moreover, GA is capable of blocking prostaglandin-E2 synthesis via blockade of cyclooxygenase- (COX-) 2 resulting in concurrent augmentation nitric oxide production through the enhancement of iNOS2 mRNA secretion in Leishmania-infected macrophages. GA is capable of inhibiting toll-like receptors as well as high-mobility group box 1.

Hijacking SARS-CoV-2/ACE2 Receptor Interaction by Natural and Semi-synthetic Steroidal Agents Acting on Functional Pockets on the Receptor Binding Domain.

The coronavirus disease 2019 (COVID-19) is a respiratory tract infection caused by the severe acute respiratory syndrome coronavirus (SARS)-CoV-2. In light of the urgent need to identify novel approaches to be used in the emergency phase, we have embarked on an exploratory campaign aimed at repurposing natural substances and clinically available drugs as potential anti-SARS-CoV2-2 agents by targeting viral proteins. Here we report on a strategy based on the virtual screening of druggable pockets located in the central β-sheet core of the SARS-CoV-2 Spike's protein receptor binding domain (RBD). By combining an in silico approach and molecular in vitro testing we have been able to identify several triterpenoid/steroidal agents that inhibit interaction of the Spike RBD with the carboxypeptidase domain of the Angiotensin Converting Enzyme (ACE2). In detail, we provide evidence that potential binding sites exist in the RBD of the SARS CoV-2 Spike protein and that occupancy of these pockets reduces the ability of the RBD to bind to the ACE2 consensus in vitro. Naturally occurring and clinically available triterpenoids such as glycyrrhetinic and oleanolic acids, as well as primary and secondary bile acids and their amidated derivatives such as glyco-ursodeoxycholic acid and semi-synthetic derivatives such as obeticholic acid reduces the RBD/ACE2 binding. In aggregate, these results might help to define novel approaches to COVID-19 based on SARS-CoV-2 entry inhibitors.

Synthesis and cholinesterase inhibiting potential of A-ring azepano- and 3-amino-3,4-seco-triterpenoids

In this study, a series of A-ring azepano- and 3-amino-3,4-seco-derivatives were synthesized from betulin, oleanolic, ursolic and glycyrrhetinic acids aiming to develop new cholinesterase inhibitors. Azepanobetulin, azepanoerythrodiol and azepanouvaol were modified to give amide and tosyl derivatives, while azepano-anhydrobetulines and azepano-glycyrrhetols were obtained for the first time. Oleanane and ursane type 3-amino-3,4-seco-4(23)-en triterpenic alcohols were synthesized by reducing the corresponding 2-cyano-derivatives accessible from Beckmann type 2 rearrangements. The compounds were screened in colorimetric Ellman’s assays to determine their ability to act as inhibitors for the enzymes acetylcholinesterase (AChE, from electric eel) and butyrylcholinesterase (BChE, from equine serum). While most of these compounds were only moderate inhibitors for AChE, several of them were shown to be inhibitors for BChE acting as mixed-type inhibitors. Azepanobetulin 1, its C28-amide derivatives 7 and 8, azepano-11-deoxo-glycyrrhetol 12 and azepanouvaol 18 held inhibition constants Ki ranging between 0.21 ± 0.06 to 0.68 ± 0.19 μM. Thus, they were approximately 4 to 10 times more active than standard galantamine hydrobromide. For all of the compounds reasonably high docking scores for BChE were obtained being in good agreement with the experimental results from the enzymatic studies. As a result, A-ring azepano-triterpenoids were found to be new scaffolds for the development of BChE inhibitors.

Design and preparation of derivatives of oleanolic and glycyrrhetinic acids with cytotoxic properties.

BackgroundThe structural modification of natural products with the aim to improve the anticancer activity is a popular current research direction. The pentacyclic triterpenoid compounds oleanolic acid (OA) and glycyrrhetinic acid (GA) are distributed widely in nature.MethodsIn this study, various oleanolic acids and glycyrrhetinic acids were designed and synthesized by using the combination principle. The in vitro anticancer activities of new OA and GA derivatives were tested by the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) method with SGC-7901 (gastric cancer), MCF-7 (breast cancer), Eca-109 (esophageal cancer), HeLa (cervical cancer), Hep-G2 (hepatoma cancer) and HSF (normal human skin fibroblast) cells.Results and conclusionThe screening results showed that the compound 3m presented the highest inhibitory activities against SGC-7901, MCF-7 and Eca-109 cell lines with IC50 values of 7.57±0.64 μM, 5.51±0.41 μM and 5.03±0.56 μM, respectively. In addition, this compound also showed effective inhibition of Hep-G2 cells with an IC50 value of 4.11±0.73 μM. Moreover, compound 5b showed the strongest inhibitory activity against Hep-G2 cells with an IC50 value of 3.74±0.18 μM and compound 3l showed strong selective inhibition of the HeLa cells with the lowest IC50 value of 4.32±0.89 μM. A series of pharmacology experiments indicated that compound 5b could induce Hep-G2 cells autophagy and apoptosis. These compounds will expand the structural diversity of anti-cancer targets and confirm the prospects for further research.

Design and Synthesis of New Anticancer Glycyrrhetinic Acids and Oleanolic Acids.

A series of new glycyrrhetinic acids and oleanolic acids has been designed and synthesized based on the principles of combinatorial chemical synthesis. Their anticancer activities were further studied by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method with hepatocellular carcinoma (Hep-G2), breast cancer (MCF-7) cell lines and a normal hepatic cell (LO2). Cytotoxicity tests (in vitro) indicated that compound 6a showed the highest cytotoxicity with the lowest IC50 values of 23.34 µM on Hep-G2 cells, 12.23 µM on MCF-7 cells, and 44.47 µM on LO2, which would widen the structural diversity of these anticancer targets and confirm the perspectives of further investigations.

An Evaluation the Effect of Glycyrrhetinic and Glycyrrhizic Acids Derived from Licorice Extract on Gastric Cancer Cell Lines

BACKGROUND AND OBJECTIVE: Gastric cancer is the second most prevalent carcinogenic disease and surgery, chemotherapy and radiation are its principal treatment modalities. However, in most cases, poor response to treatment and adverse side effects are observed regarding these modalities. Given the lack of response to treatment and growing rates of gastric cancer, researchers are trying to come up with more efficient treatments with fewer side effects. In the traditional medicine, licorice has been suggested as a cancer treatment considering its high antioxidant properties and few side effects. This study aimed to evaluate the effect of licorice extract on gastric cancer cell lines. METHODS: In this experimental study, adenocarcinoma gastric cell lines were prepared from cell bank and were cultured. After passage, the cells were transferred into a 96-well plate. In each well, approximately 2,000 cells in RPMI-1640 culture medium with FBS (10%) were placed. The cells were repeatedly exposed to different concentrations of Glycyrrhetinic acid (0, 1, 10 and100.1 μM) and Glycyrrhizic acid (10, 1, 100 and 0.1 μM) for 24 and 48 hours. Finally, the obtained results of the experimental and control groups were compared with each other. FINDINGS: According to our results, the toxic effect of Glycyrrhetinic and Glycyrrhizic acids is dose and time dependent. In 24 hours, the mean optical density (MOD) in 100 μM concentration of Glycyrrhetinic acid was 0.41±0.02 and 0.79±0.04 in the experimental and control groups, respectively (p=0.0002). After 48 hours, MOD was 0.16±0.004 and 1.749±0.24 in the experimental and control groups, respectively (p=0.0003). Moreover, the MOD of 100 μM concentration of Glycyrrhizic acid was 0.78±0.53 and 2.09±0.49 in the experimental and control groups in 48 hours. There was a significant difference between the experimental and control groups (p=0.035). CONCLUSION: The results of this study demonstrated that the licorice compounds have a toxic effect on carcinogenic cells. Therefore, it is recommended to perform more study on both Glycyrrhizic and Glycyrrhizic acids as effective compounds on gastric cancer treatment

Synthesis and Pro‐Apoptotic Activity of Novel Glycyrrhetinic Acid Derivatives

Triterpenoids are used for medicinal purposes in many countries. Some, such as oleanolic and glycyrrhetinic acids, are known to be anti-inflammatory and anticarcinogenic. However, the biological activities of these naturally occurring molecules against their particular targets are weak, so the synthesis of new synthetic analogues with enhanced potency is needed. By combining modifications to both the A and C rings of 18βH-glycyrrhetinic acid, the novel synthetic derivative methyl 2-cyano-3,12-dioxo-18βH-olean-9(11),1(2)-dien-30-oate was obtained. This derivative displays high antiproliferative activity in cancer cells, including a cell line with a multidrug-resistance phenotype. It causes cell death by inducing the intrinsic caspase-dependent apoptotic pathway.

Chemical modifications of natural triterpenes—glycyrrhetinic and boswellic acids: evaluation of their biological activity

Synthetic analogues of naturally occurring triterpenoids; glycyrrhetinic acid, arjunolic acid, and boswellic acids, by modification of A-ring with a cyano- and enone-functionality, have been reported. A novel method of synthesis of α-cyanoenones from isoxazoles is reported. Bioassays using primary mouse macrophages and tumor cell lines indicate potent anti-inflammatory and cytotoxic activities associated with cyano-enones of boswellic acid and glycyrrhetinic acid.

Blockade of gap junction coupling by glycyrrhetinic acids in guinea pig cochlear artery: a whole-cell voltage- and current-clamp study.

Glycyrrhetinic acids (GAs) are widely used as gap junction blockers, but their efficacy and side effects have not been well determined. Whole-cell electrical recordings were made from vascular smooth muscle cells (VSMCs) embedded in or dissociated from, guinea pig cochlear artery segments. 18beta- & 18alpha-GA concentration-dependently increased membrane input resistance (R(in)) of in situ VSMCs, with a maximal input conductance (G(in)=1/R(in)) reduction of 92% & 77% and IC(50) of 2.0 & 4.4 microm, respectively. 18betaGA (30 microM) resulted in a R(in) of 2.2 GOmega and C(in) of 12 pF, comparable to those of freshly dissociated VSMCs (3.1 GOmega & 6.1 pF). The GAs (> or =30 microM) caused a depolarization in VSMCs in situ. In dispersed VSMCs, they both inhibited delayed rectifiers; 18betaGA also activated a non-selective cation conductance while 18alphaGA inactivated a voltage-independent K+-conductance. ACh induced an outward current in VSMCs in situ at -40 mV, with a positive slope I/V relation and a reversal potential near E(K). The ACh-induced current was attenuated by 18beta- & 18alphaGA with an IC(50) of 4.3 & 7.8 microM, respectively. 18betaGA blocked the vascular gap junctions, achieving a complete electrical isolation of the recorded VSMC at > or =30 microM while causing a mild depolarization by a complex conductance alteration. 18betaGA suppressed the ACh-induced current in VSMC by blocking the myoendothelial gap junction and by a non-junctional action. 18alphaGA at 30-100 microM failed to fully block the gap junctions while exerting side actions.

Synthesis of Norhydroperoxides from Natural Triterpenic Acids

Treatment of triterpenoids derived from ursolic and glycyrrhetinic acids with the oxidative mixture H2O2-(CF3COO)2Hg-Na2CO3-THF results in oxidative decarboxylation. The reaction of 3O-acetylursolic acid (1) and 3O-acetyl-18β-glycyrrhetinic acid (3) affords stable norhydroperoxides, whereas decarboxylation of 3O-acetyl-11-oxoursolic acid (6) leads to unstable norhydroperoxide. The difference in properties of the norhydroperoxides is explained by the presence of a conjugated ketone, which activates the 12,13-C=C double bond for nucleophilic addition and makes possible intramolecular Michael-type addition of peroxo anion.

Steroid hormones and hypertension: The cortisol-cortisone shuttle

The role of adrenal steroid hormones in hypertension has, until recently, focused on disorders of secretion. We describe a new form of mineralocorticoid hypertension which arises from impaired metabolism of physiological glucocorticoid. 11 β-hydroxysteroid dehydrogenase (11 β-HSD) is responsible for the inactivation of cortisol to cortisone. Congenital absence of this enzyme (the syndrome of apparent mineralocorticoid excess) results in cortisol acting as a potent mineralocorticoid. Furthermore, inhibition of this enzyme by glycyrrhizic and glycyrrhetinic acids also accounts for the mineralocorticoid excess states seen following licorice and carbenoxolone ingestion. Whilst impaired 11 β-HSD activity has been shown in patients with “essential” hypertension, the significance of this finding remains unknown. These clinical studies, however, have uncovered a novel physiological mechanism, whereby the mineralocorticoid receptor (which in vitro has an equal affinity for cortisol and aldosterone) is protected from cortisol excess by the action of 11 β-HSD. Thus 11 β-HSD plays a crucial role in determining the in vivo specificity for this receptor. (Steroids 58:614–620, 1993)

Licorice inhibits 11 beta-hydroxysteroid dehydrogenase messenger ribonucleic acid levels and potentiates glucocorticoid hormone action

11 beta-Hydroxysteroid dehydrogenase (11 beta HSD) is responsible for the interconversion of cortisol to cortisone [corticosterone (B) to 11-dehydrocorticosterone in rodents] and confers ligand specificity to the mineralocorticoid receptor. Inhibition of 11 beta HSD by licorice derivatives [glycyrrhizic and glycyrrhetinic (GE) acids] results in cortisol/B and not aldosterone acting as a potent mineralocorticoid. 11 beta HSD is ubiquitously expressed and, by converting active glucocorticoid to inactive metabolites, may be an important prereceptor regulator of ligand access to the glucocorticoid receptor (GR). To investigate this further, we have studied the effect of 11 beta HSD inhibition by licorice derivatives on PRL gene expression (a known glucocorticoid target gene) in rat pituitary GH3 cells. Glycyrrhizic acid administration to rats in vivo (75 mg/kg.day for 5 days) resulted in inhibition of 11 beta HSD activity, as previously reported, but also a significant reduction in steady state 11 beta HSD mRNA levels in both predominantly mineralocorticoid (kidney and distal colon) and glucocorticoid (liver and pituitary) target tissues. In vitro, 11 beta HSD mRNA and activity were present in rat pituitary GH3 cells (81% conversion of B to 11-dehydrocorticosterone/4 x 10(6) cells after 24-h incubation) and inhibited by GE in a dose-dependent fashion. While B or GE alone (10(-8)-10(-5) M) had little or no effect on PRL mRNA levels or immunoassayable PRL, combinations of GE plus B resulted in marked inhibition of PRL mRNA levels and secretion, to such an extent that a concentration of 10(-6) M B with 10(-6) M GE was more potent than equimolar concentration of the synthetic GR agonist RU 28362. This inhibitory effect on PRL mRNA levels was blocked by a 10-fold excess of the GR antagonist RU 38486, but not by a 10-fold excess of the mineralocorticoid receptor antagonist RU 26752, confirming that this potentiation of glucocorticoid hormone action was operating through the GR and not the mineralocorticoid receptor. In addition to its established role as a competitive inhibitor of 11 beta HSD, licorice results in pretranslational inhibition of 11 beta HSD both in vitro and in vivo. 11 beta HSD is clearly an important mechanism in regulating tissue levels of active glucocorticoid and, hence, ligand supply to the GR.

Licorice inhibits 11 beta-hydroxysteroid dehydrogenase messenger ribonucleic acid levels and potentiates glucocorticoid hormone action.

11 beta-Hydroxysteroid dehydrogenase (11 beta HSD) is responsible for the interconversion of cortisol to cortisone [corticosterone (B) to 11-dehydrocorticosterone in rodents] and confers ligand specificity to the mineralocorticoid receptor. Inhibition of 11 beta HSD by licorice derivatives [glycyrrhizic and glycyrrhetinic (GE) acids] results in cortisol/B and not aldosterone acting as a potent mineralocorticoid. 11 beta HSD is ubiquitously expressed and, by converting active glucocorticoid to inactive metabolites, may be an important prereceptor regulator of ligand access to the glucocorticoid receptor (GR). To investigate this further, we have studied the effect of 11 beta HSD inhibition by licorice derivatives on PRL gene expression (a known glucocorticoid target gene) in rat pituitary GH3 cells. Glycyrrhizic acid administration to rats in vivo (75 mg/kg.day for 5 days) resulted in inhibition of 11 beta HSD activity, as previously reported, but also a significant reduction in steady state 11 beta HSD mRNA levels in both predominantly mineralocorticoid (kidney and distal colon) and glucocorticoid (liver and pituitary) target tissues. In vitro, 11 beta HSD mRNA and activity were present in rat pituitary GH3 cells (81% conversion of B to 11-dehydrocorticosterone/4 x 10(6) cells after 24-h incubation) and inhibited by GE in a dose-dependent fashion. While B or GE alone (10(-8)-10(-5) M) had little or no effect on PRL mRNA levels or immunoassayable PRL, combinations of GE plus B resulted in marked inhibition of PRL mRNA levels and secretion, to such an extent that a concentration of 10(-6) M B with 10(-6) M GE was more potent than equimolar concentration of the synthetic GR agonist RU 28362. This inhibitory effect on PRL mRNA levels was blocked by a 10-fold excess of the GR antagonist RU 38486, but not by a 10-fold excess of the mineralocorticoid receptor antagonist RU 26752, confirming that this potentiation of glucocorticoid hormone action was operating through the GR and not the mineralocorticoid receptor. In addition to its established role as a competitive inhibitor of 11 beta HSD, licorice results in pretranslational inhibition of 11 beta HSD both in vitro and in vivo. 11 beta HSD is clearly an important mechanism in regulating tissue levels of active glucocorticoid and, hence, ligand supply to the GR.

High-performance liquid chromatographic determination of 18 alpha-glycyrrhetinic acid and 18 beta-glycyrrhetinic acid in rat plasma: application to pharmacokinetic study.

A high-performance liquid chromatographic method for the separation and determination of 18 alpha-glycyrrhetinic acid and 18 beta-glycyrrhetinic acid has been developed. Indomethacin was used as an internal standard. The drugs were separated on a reversed-phase column and detected by UV detection at a wavelength of 254 nm. Methanol-water-perchloric acid-ammonia (80:20:0.4:0.4, v/v) was used as the mobile phase at pH of 7.0-7.5. The detection limit of both compounds was 0.1 microgram/ml in rat plasma. The method was applied to pharmacokinetic studies of glycyrrhetinic acids in rats. The results suggest that the pharmacokinetics appeared to be non-linear in nature.

Determination of glycyrrhizinic and glycyrrhetinic acids in pharmaceuticals by high-performance liquid chromatography

Glycyrrhizinic acid (GZ) occurs as its potassium-calcium salt in liquorice root, and is a component of a number of pharmaceutical formulations and food products. During acidic hydrolysis the GZ molecule releases two molecules of glucuronic acid to form the aglycone, 18 @glycyrrhetinic acid (18 P-GT). It has not been established whether this aglycone normally occurs in liquorice root. Many analytical methods have been employed for the determination of GZ. Gravimetric, volumetric and calorimetric methods have lacked sensitivity and accuracy, whilst HPLC methods in general are superior [l-5]. Authors have used both ionexchange columns with gradient [6-81 or isocratic elution [4, 9, lo] and reversed-phase columns with gradient [ 11-131 or isocratic elution [l, 5, 14-261. In one method an ionpairing reagent, tetrabutylammonium hydroxide was used as a component of the mobile phase. Most of the papers cited above, however, do not describe the simultaneous determination of GZ and 18 P-GT, and for the determination of both compounds two different mobile phases [17, 23,251 or even two different columns [19] have been used. In those papers where both compounds were determined in one chromatographic run, gradient elution was employed and retention times of GZ and GT were large, e.g. 44 and 68 min [ll]. Considering it is more difficult to obtain the reproducible results employing gradient elution [27] and that the need for column re-equilibration increases the time required for analysis, this study was undertaken to obtain isocratic conditions suitable for the routine simultaneous analysis of GZ and 18 l3-GT in pharmaceutical preparations, in a reasonable time.