Many of the traditional herbal formulations contain extracts of Piper longum and Glycyrrhiza glabra, piperine and glycyrrhetinic acid respectively, being active constituents of these two herbs. An attempt has been made to develop a simple, precise, rapid, and cost-effective high-performance thin-layer chromatographic (HPTLC) method for simultaneous estimation of these in a herbomineral formulation (Efiplus® Capsules). Precoated silica gel 60 F254 plates with toluene-ethyl acetate-glacial acetic acid 12.5:7.5:0.5, as mobile phase were used in chromatographic determinations. The plates were scanned and the compounds were quantified at their wavelengths of maximum absorption of 260 and 331 nm for glycyrrhetinic acid and piperine respectively. The respective RF, values of glycyrrhetinic acid and piperine were 0.51 and 0.55. Under these experimental conditions linearity was observed between 0.8-2.6 μg/ spot for glycyrrhetinic acid and between 10-50 ng/ spot for piperine and average recovery was 96.25% for glycyrrhetinic acid and 98.55% for piperine.
HPTLC; glycyrrhetinic acid; piperine; herbomineral formulation
Active components of complementary/alternative medicines and natural supplements are often anionic compounds and flavonoids. As such, organic anion transporters (OATs) may play a key role in their pharmacokinetic and pharmacological profiles, and represent sites for adverse drug-drug interactions. Therefore, we assessed the inhibitory effects of nine natural products, including flavonoids (catechin and epicatechin), chlorogenic acids (1,3- and 1,5-dicaffeoylquinic acid), phenolic acids (ginkgolic acids (13 : 0), (15 : 1), and (17 : 1)), and the organic acids ursolic acid and 18β-glycyrrhetinic acid, on the transport activity of the human OATs, hOAT1 (SLC22A6), hOAT3 (SLC22A8), and hOAT4 (SLC22A11). Four compounds, 1,3- and 1,5-dicaffeoylquinic acid, ginkgolic acid (17 : 1), and 18β-glycyrrhetinic acid, significantly inhibited hOAT1-mediated transport (50 μM inhibitor versus 1 μM substrate). Five compounds, 1,3- and 1,5-dicaffeoylquinic acid, ginkgolic acids (15 : 1) and (17 : 1), and epicatechin, significantly inhibited hOAT3 transport under similar conditions. Only catechin inhibited hOAT4. Dose-dependency studies were conducted for 1,3-dicaffeoylquinic acid and 18β-glycyrrhetinic acid on hOAT1, and IC50 values were estimated as 1.2 ± 0.4 μM and 2.7 ± 0.2 μM, respectively. These data suggest that 1,3-dicaffeoylquinic acid and 18β-glycyrrhetinic acid may cause significant hOAT1-mediated DDIs in vivo; potential should be considered for safety issues during use and in future drug development.
This study discovered that glycyrrhetinic acid inhibited the human 20S proteasome at 22.3 µM. Esterification of the C-3 hydroxyl group on glycyrrhetinic acid with various carboxylic acid reagents yielded a series of analogs with marked improved potency. Among the derivatives, glycyrrhetinic acid 3-O-isophthalate (17) was the most potent compound with IC50 of 0.22 µM, which was approximately 100-fold more potent than glycyrrhetinic acid.
Glycyrrhetinic acid; proteasome inhibitor; triterpene
The present study examined the inhibitory effect of licorice compounds glycyrrhizin and a metabolite 18β-glycyrrhetinic acid on the neurotoxicity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in the mouse and on the 1-methyl-4-phenylpyridinium (MPP+)-induced cell death in differentiated PC12 cells. MPTP treatment increased the activities of total superoxide dismutase, catalase and glutathione peroxidase and the levels of malondialdehyde and carbonyls in the brain compared to control mouse brain. Co-administration of glycyrrhizin (16.8 mg/kg) attenuated the MPTP effect on the enzyme activities and formation of tissue peroxidation products. In vitro assay, licorice compounds attenuated the MPP+-induced cell death and caspase-3 activation in PC12 cells. Glycyrrhizin up to 100µM significantly attenuated the toxicity of MPP+. Meanwhile, 18β-glycyrrhetinic acid showed a maximum inhibitory effect at 10µM; beyond this concentration the inhibitory effect declined. Glycyrrhizin and 18β-glycyrrhetinic acid attenuated the hydrogen peroxide- or nitrogen species-induced cell death. Results from this study indicate that glycyrrhizin may attenuate brain tissue damage in mice treated with MPTP through inhibitory effect on oxidative tissue damage. Glycyrrhizin and 18β-glycyrrhetinic acid may reduce the MPP+ toxicity in PC12 cells by suppressing caspase-3 activation. The effect seems to be ascribed to the antioxidant effect.
Glycyrrhizin; MPTP; MPP+; Brain tissue damage; Cell death; Inhibitory effect
The purpose of this study was to compare the efficacy of alginic acid alone versus alginic acid combined with low doses of pure glycyrrhetinic acid and bilberry anthocyanosides as an addon to conventional proton pump inhibitor therapy in relieving symptoms associated with nonerosive reflux disease.
This prospective, randomized, 8-week, open-label trial was conducted at two centers. Sixty-three patients with persistent symptoms of gastroesophageal reflux disease and normal upper gastrointestinal endoscopy were eligible for the study. Patients in group A (n = 31) were treated with pantoprazole and a formula (Mirgeal®) containing alginic acid and low doses of pure glycyrrhetinic acid + standardized Vaccinium myrtillus extract for 4 weeks, then crossed over to the multi-ingredient formula for a further 4 weeks. Patients in group B (n = 32) were treated pantoprazole and alginic acid alone twice daily, then crossed over to alginic acid twice daily for a further 4 weeks. Efficacy was assessed by medical evaluation of a symptom relief score, estimated using a visual analog scale (0–10). Side effects, tolerability, and compliance were also assessed.
Of the 63 patients enrolled in the study, 58 (29 in group A and 29 in group B) completed the 8-week trial. The baseline characteristics were comparable between the two groups. During the study, significant differences were recorded in symptom scores for both groups. In group A, symptoms of chest pain, heartburn, and abdominal swelling were less serious than in group B. Treatment A was better tolerated, did not induce hypertension, and had fewer side effects than treatment B. No significant differences in compliance were found between the two groups.
Use of low doses of pure glycyrrhetinic acid + bilberry anthocyanosides, together with alginic acid as addon therapy, substantially improves symptoms in patients with nonerosive reflux disease without increasing side effects or worsening tolerability or compliance.
proton pump inhibitors; alginic acid; glycyrrhetinic acid; anthocyanosides; nonerosive reflux disease; gastroesophageal reflux disease
Derivatives of oleanolic acid, ursolic acid and glycyrrhetinic acid substituted with electron withdrawing groups at the 2-position in the A-ring which also contains a 1-en-3-one structure are potent inhibitors of cancer cell growth. In this study, we have compared the effects of several 2-substituted analogs of triterpenoid acid methyl esters derived from ursolic and glycyrrhetinic acid on proliferation of KU7 and 253JB-V bladder and Panc-1 and Panc-28 pancreatic cancer cells. The results show that the 2-cyano and 2-trifluoromethyl derivatives were the most active compounds. The glycyrrhetinic acid derivatives with the rearranged C-ring containing the 9(11)-en-12-one structure were generally more active than the corresponding 12-en-11-one isomers. However, differences in growth inhibitory IC50 values were highly variable and dependent on the 2- substitutent (CN vs. CF3) and cancer cell context.
glycyrrhetinate analogs; growth inhibition; bladder cancer; pancreatic cancer
The triblock 18β-glycyrrhetinic acid-poly(ethylene glycol)-18β-glycyrrhetinic acid conjugates (GA-PEG-GA) based self-assembled micelles were synthesized and characterized by FTIR, NMR, transmission electron microscopy, and particle size analysis. The GA-PEG-GA conjugates having the critical micelle concentration of 6 × 10−5 M were used to form nanosized micelles, with mean diameters of 159.21 ± 2.2 nm, and then paclitaxel (PTX) was incorporated into GA-PEG-GA micelles by self-assembly method. The physicochemical properties of the PTX loaded GA-PEG-GA micelles were evaluated including in vitro cellular uptake, cytotoxicity, drug release profile, and in vivo tissue distribution. The results demonstrate that the GA-PEG-GA micelles had low cytotoxicity and good ability of selectively delivering drug to hepatic cells in vitro and in vivo by the targeting moiety glycyrrhetinic acid. In conclusion, the GA-PEG-GA conjugates have potential medical applications for targeted delivery of poor soluble drug delivery.
Eosinophils circulate in the blood and are recruited in tissues during allergic inflammation. Gap junctions mediate direct communication between adjacent cells and may represent a new way of communication between immune cells distinct from communication through cytokines and chemokines. We characterized the expression of connexin (Cx)43 by eosinophils isolated from atopic individuals using RT-PCR, Western blotting, and confocal microscopy and studied the biological functions of gap junctions on eosinophils. The formation of functional gap junctions was evaluated measuring dye transfer using flow cytometry. The role of gap junctions on eosinophil transendothelial migration was studied using the inhibitor 18-a-glycyrrhetinic acid. Peripheral blood eosinophils express Cx43 mRNA and protein. Cx43 is localized not only in the cytoplasm but also on the plasma membrane. The membrane impermeable dye BCECF transferred from eosinophils to epithelial or endothelial cells following coculture in a dose and time dependent fashion. The gap junction inhibitors 18-a-glycyrrhetinic acid and octanol did not have a significant effect on dye transfer but reduced dye exit from eosinophils. The gap junction inhibitor 18-a-glycyrrhetinic acid inhibited eosinophil transendothelial migration in a dose dependent manner. Thus, eosinophils from atopic individuals express Cx43 constitutively and Cx43 may play an important role in eosinophil transendothelial migration and function in sites of inflammation.
To compare the effects of two stereoisomeric forms of glycyrrhetinic acid on different components of Na+ current, HERG and Kv1.5 channel currents.
Wild-type (WT) and long QT syndrome type 3 (LQT-3) mutant ΔKPQ Nav1.5 channels, as well as HERG and Kv1.5 channels were expressed in Xenopus oocytes. In addition, isolated human atrial myocytes were used. Two-microelectrode voltage-clamp technique was used to record the voltage-activated currents.
Superfusion of 18β-glycyrrhetinic acid (18β-GA, 1–100 μmol/L) blocked both the peak current (INa,P) and late current (INa,L) generated by WT and ΔKPQ Nav1.5 channels in a concentration-dependent manner, while 18α-glycyrrhetinic acid (18α-GA) at the same concentrations had no effects. 18β-GA preferentially blocked INa,L (IC50=37.2±14.4 μmol/L) to INa,P (IC50=100.4±11.2 μmol/L) generated by ΔKPQ Nav1.5 channels. In human atrial myocytes, 18β-GA (30 μmol/L) inhibited 47% of INa,P and 87% of INa,L induced by Anemonia sulcata toxin (ATX-II, 30 nmol/L). Superfusion of 18β-GA (100 μmol/L) had no effects on HERG and Kv1.5 channel currents.
18β-GA preferentially blocked the late Na current without affecting HERG and Kv1.5 channels.
anti-arrhythmia agent; 18β-glycyrrhetinic acid; Nav1.5 channel; HERG channel; Kv1.5 channel; human atrial myocyte; Anemonia sulcata toxin; long QT syndrome
Many cell types in the retina are coupled via gap junctions and so there is a pressing need for a potent and reversible gap junction antagonist. We screened a series of potential gap junction antagonists by evaluating their effects on dye coupling in the network of A-type horizontal cells. We evaluated the following compounds: meclofenamic acid (MFA), mefloquine, 2-aminoethyldiphenyl borate (2-APB), 18-α-glycyrrhetinic acid, 18-β-glycyrrhetinic acid (18-β-GA), retinoic acid, flufenamic acid, niflumic acid, and carbenoxolone. The efficacy of each drug was determined by measuring the diffusion coefficient for Neurobiotin (Mills & Massey, 1998). MFA, 18-β-GA, 2-APB and mefloquine were the most effective antagonists, completely eliminating A-type horizontal cell coupling at a concentration of 200 μM. Niflumic acid, flufenamic acid, and carbenoxolone were less potent. Additionally, carbenoxolone was difficult to wash out and also may be harmful, as the retina became opaque and swollen. MFA, 18-β-GA, 2-APB and mefloquine also blocked coupling in B-type horizontal cells and AII amacrine cells. Because these cell types express different connexins, this suggests that the antagonists were relatively non-selective across several different types of gap junction. It should be emphasized that MFA was water-soluble and its effects on dye coupling were easily reversible. In contrast, the other gap junction antagonists, except carbenoxolone, required DMSO to make stock solutions and were difficult to wash out of the preparation at the doses required to block coupling in A-type HCs. The combination of potency, water solubility and reversibility suggest that MFA may be a useful compound to manipulate gap junction coupling.
Horizontal cells; Retina; Gap junction antagonist
Synthetic analogues of naturally occurring triterpenoids; glycyrrhetinic acid, arjunolic acid and boswellic acids, by modification of A-ring with a cyano- and enone- functionalities, have been reported. A novel method of synthesis of α-cyanoenones from isoxazoles is reported. Bio-assays using primary mouse macrophages and tumor cell lines indicate potent anti-inflammatory and cytotoxic activities associated with cyanoenones of boswellic acid and glycyrrhetinic acid.
We cloned the β-glucuronidase gene (AtGUS) from Aspergillus terreus Li-20 encoding 657 amino acids (aa), which can transform glycyrrhizin into glycyrrhetinic acid monoglucuronide (GAMG) and glycyrrhetinic acid (GA). Based on sequence alignment, the C-terminal non-conservative sequence showed low identity with those of other species; thus, the partial sequence AtGUS(-3t) (1–592 aa) was amplified to determine the effects of the non-conservative sequence on the enzymatic properties. AtGUS and AtGUS(-3t) were expressed in E. coli BL21, producing AtGUS-E and AtGUS(-3t)-E, respectively. At the similar optimum temperature (55°C) and pH (AtGUS-E, 6.6; AtGUS(-3t)-E, 7.0) conditions, the thermal stability of AtGUS(-3t)-E was enhanced at 65°C, and the metal ions Co2+, Ca2+ and Ni2+ showed opposite effects on AtGUS-E and AtGUS(-3t)-E, respectively. Furthermore, Km of AtGUS(-3t)-E (1.95 mM) was just nearly one-seventh that of AtGUS-E (12.9 mM), whereas the catalytic efficiency of AtGUS(-3t)-E was 3.2 fold higher than that of AtGUS-E (7.16 vs. 2.24 mM s−1), revealing that the truncation of non-conservative sequence can significantly improve the catalytic efficiency of AtGUS. Conformational analysis illustrated significant difference in the secondary structure between AtGUS-E and AtGUS(-3t)-E by circular dichroism (CD). The results showed that the truncation of the non-conservative sequence could preferably alter and influence the stability and catalytic efficiency of enzyme.
The title compound, C34H52N2O7·CH4O, is the methanol solvate of a difunctionalized derivative of the therapeutic agent 18β-glycyrrhetinic acid, a pentacyclic triterpene. The five six-membered rings of the glycyrrhetinic acid moiety show normal geometries, with four rings in chair conformations and the unsaturated ring in a half-chair conformation. This moiety is substituted by a nitrate ester group and an O-ethylglycine group. In the crystal, the nonsolvent molecules are packed parallel to (010) in a herringbone fashion with the nitrato, ethylglycine and methanol-O atom being proximate. The methanol solvent molecule is anchored via a donated O—H⋯Oacyl and an accepted N—H⋯O hydrogen bond, giving rise to infinite zigzag chains of hydrogen bonds parallel to . Two weak intermolecular C—H⋯O interactions to the methanol and to an acyl oxygen establish links along  and , respectively.
Structural analysis of the high-mobility group protein B1 (HMGB1)-DNA complex and a docking simulation between
glycyrrhetinic acid (GA) and the HMGB1-DNA complex were performed with a software package the Molecular Operating
Environment (MOE). An HMGB1-DNA (PDB code: 2GZK) was selected for the 3D structure modeling of the HMGB1-DNA
complex. The Site Finder module of the MOE identified 16 possible ligand-binding sites in the modeled HMGB1-DNA complex.
The docking simulation revealed that GA possibly inhibits functions of HMGB1 interfering with Lys90, Arg91, Ser101, Tyr149, C230 and
C231 in the HMGB1-DNA complex. To the best of our knowledge, this is the first report of an HMGB1-DNA complex with GA, and
our data verify that the GA-HMGB1-DNA model can be utilized for application to target HMGB1 for the development of antitumor
ASE-Dock - alpha sphere and excluded volume-based ligand-protein docking,
CNS - central nervous system,
GA - glycyrrhetinic acid,
GL - glycyrrhizin,
HMGB1 - high-mobility group protein B1,
LBS - ligand-biding site,
MOE - Molecular Operating Environment,
SRY - sex-determining region on the Y chromosome.
Antitumor drug; MOE; HMGB1; GA
Nanoparticle drug delivery (NDDS) is a novel system in which the drugs are delivered to the site of action by small particles in the nanometer range. Natural or synthetic polymers are used as vectors in NDDS, as they provide targeted, sustained release and biodegradability. Here, we used the chitosan and hepatoma cell-specific binding molecule, glycyrrhetinic acid (GA), to synthesize glycyrrhetinic acid-modified chitosan (GA-CTS). The synthetic product was confirmed by Fourier transformed infrared spectroscopy (FT-IR) and 1H-nuclear magnetic resonance (1H-NMR). By combining GA-CTS and 5-FU (5-fluorouracil), we obtained a GA-CTS/5-FU nanoparticle, with a particle size of 217.2 nm, a drug loading of 1.56% and a polydispersity index of 0.003. The GA-CTS/5-FU nanoparticle provided a sustained release system comprising three distinct phases of quick, steady and slow release. We demonstrated that the nanoparticle accumulated in the liver. In vitro data indicated that it had a dose- and time-dependent anti-cancer effect. The effective drug exposure time against hepatic cancer cells was increased in comparison with that observed with 5-FU. Additionally, GA-CTS/5-FU significantly inhibited the growth of drug-resistant hepatoma, which may compensate for the drug-resistance of 5-FU. In vivo studies on an orthotropic liver cancer mouse model demonstrated that GA-CTS/5-FU significantly inhibited tumor growth, resulting in increased survival time.
hepatic carcinoma; regulatory T-cells; glycyrrhetinic acid; targeted therapy; 5-fluorouracil
Modified chitosan nanoparticles are a promising platform for drug, such as 5-fluorouracil (5-FU), gene, and vaccine delivery. Here, we used chitosan and hepatoma cell-specific binding molecule glycyrrhetinic acid (GA) to synthesize glycyrrhetinic acid-modified chitosan (GA-CTS). The synthetic product was confirmed by infrared spectroscopy and hydrogen nuclear magnetic resonance. By combining GA-CTS and 5-FU, we obtained a GA-CTS/5-FU nanoparticle, with a particle size of 193.7 nm, drug loading of 1.56%, and a polydispersity index of 0.003. The GA-CTS/5-FU nanoparticle provided a sustained-release system comprising three distinct phases of quick, steady, and slow release. In vitro data indicated that it had a dose- and time-dependent anticancer effect. The effective drug exposure time against hepatic cancer cells was increased in comparison with that observed with 5-FU. In vivo studies on an orthotropic liver cancer mouse model demonstrated that GA-CTS/5-FU significantly inhibited cancer cell proliferation, resulting in increased survival time. The antitumor mechanisms for GA-CTS/5-FU nanoparticle were possibly associated with an increased expression of regulatory T-cells, decreased expression of cytotoxic T-cell and natural killer cells, and reduced levels of interleukin-2 and interferon gamma.
hepatic carcinoma; regulatory T cells; glycyrrhetinic acid; targeted therapy; 5-fluorouracil
The nanoparticle drug delivery system, which uses natural or synthetic polymeric material as a carrier to deliver drugs to targeted tissues, has a broad prospect for clinical application for its targeting, slow-release, and biodegradable properties. Here, we used chitosan (CTS) and hepatoma cell-specific binding molecule glycyrrhetinic acid to synthesize glycyrrhetinic acid-modified chitosan (GA-CTS). The synthetic product was confirmed by infrared (IR) spectra and hydrogen-1 nuclear magnetic resonance. The GA-CTS/5-fluorouracil (5-FU) nanoparticles were synthesized by combining GA-CTS and 5-FU and conjugating 5-FU onto the GA-CTS nanomaterial. The central composite design was performed to optimize the preparation process as CTS:tripolyphosphate sodium (TPP) weight ratio =5:1, 5-FU:CTS weight ratio =1:1, TPP concentration =0.05% (w/v), and cross-link time =50 minutes. GA-CTS/5-FU nanoparticles had a mean particle size of 193.7 nm, a polydispersity index of 0.003, a zeta potential of +27.4 mV, and a drug loading of 1.56%. The GA-CTS/5-FU nanoparticle had a protective effect on the drug against plasma degrading enzyme, and provided a sustained release system comprising three distinct phases of quick, steady, and slow release. Our study showed that the peak time, half-life time, mean residence time and area under the curve of GA-CTS/5-FU were longer or more than those of the 5-FU group, but the maximum concentration (Cmax) was lower. We demonstrated that the nanoparticles accumulated in the liver and have significantly inhibited tumor growth in an orthotropic liver cancer mouse model.
liver cancer; targeted therapy; chemotherapy; pharmacokinetics efficacy
The physicochemical properties (pH and osmolarity), ingredients, and impurities containing in compound glycyrrhizin injections (eight items) marketed in China were compared with those in bland-name drug (Stronger Neo-Minophagen C injection). Glycyrrhizin (GZ), glycine (Gly), and l-cysteine (CysH) as the ingredients, moreover, glycyrrhetinic acid (GA), 3-monoglucuronyl-glycyrrhetinic acid (MGGA), and l-cystine (CysS) as the impurity were determined by HPLC. The pH and osmolarity were different every each pharmaceutical product, but the variation between batch was very small. On the other hand, although the contents of GZ, Gly, and CysH in bland-name drug were approximately 100% of the label claim, the contents of GZ in generic drugs were the range of 91.8-100.9%, indicating the GZ contents in four products were clearly less than value indicated in label (<97%). The remarkable difference was not accepted by impurities content such as GA and MGGA. The contents of CysH in generic drugs were the range of 79.9-100.4%, and CysS was determined in all generic drugs, suggesting that CysH may decompose to be CysS depending on the pH of injections in generic drug only. Because the variation of the ingredient content was big and products with a little quantity for the ingredients were recognized, establishment of the preparation that can maintain the prescribed ingredient content and the severity of the assay will be required.
Generic drug; glycyrrhetinic acid; glycyrrhizae radix; glycyrrhizin; quality evaluation
Glycyrrhiza glabra, commonly known as licorice, is a popular herbal supplement used for the treatment of chronic inflammatory conditions and as sweetener in the food industry. This species contains a myriad of phytochemicals including the major saponin glycoside glycyrrhizin (G) of Glycyrrhetinic acid (GA) aglycone. In this study, 2D-ROESY NMR technique was successfully applied for distinguishing 18α and 18β glycyrrhetinic acid (GA). ROESY spectra acquired from G. glabra, Glycyrrhiza uralensis and Glycyrrhiza inflata crude extracts revealed the presence of G in its β-form. Anti-inflammatory activity of four Glycyrrhiza species, G, glabra, G. uralensis, G. inflata, and G. echinata roots was assessed against COX-1 inhibition revealing that phenolics rather than glycyrrhizin are biologically active in this assay. G. inflata exhibits a strong cytotoxic effect against PC3 and HT29 cells lines, whereas other species are inactive. This study presents an effective NMR method for G isomer assignment in licorice extracts that does not require any preliminary chromatography or any other purification step.
G. glabra; G. inflata; G. uralensis; Glycyrrhizin; Licorice; ROESY
ATP is rapidly released from osteoblasts in response to mechanical load. We examined the mechanisms involved in this release and established that shear-induced ATP release was mediated through vesicular fusion and was dependent on Ca2+ entry into the cell via L-type voltage-sensitive Ca2+ channels. Degradation of secreted ATP by apyrase prevented shear-induced PGE2 release.
Fluid shear induces a rapid rise in intracellular calcium ([Ca2+]i) in osteoblasts that mediates many of the cellular responses associated with mechanotransduction in bone. A potential mechanism for this increase in [Ca2+]i is the activation of purinergic (P2) receptors resulting from shear-induced extracellular release of ATP. This study was designed to determine the effects of fluid shear on ATP release and the possible mechanisms associated with this release.
MC3T3-E1 preosteoblasts were plated on type I collagen, allowed to proliferate to 90% confluency, then subjected to 12 dynes/cm2 laminar fluid flow using a parallel plate flow chamber. ATP release into the flow media was measured using a luciferin/luciferase assay. Inhibitors of channels, gap junctional intercellular communication (GJIC) and vesicular formation were added prior to shear and maintained in the flow medium for the duration of the experiment.
Results and Conclusions
Fluid shear produced a transient increase in ATP release compared to static MC3T3-E1 cells (59.8±15.7nM vs. 6.2±1.8nM, respectively), peaking within 1 min of onset. Inhibition of calcium entry through the L-type voltage-sensitive Ca2+ channel (L-VSCC) with nifedipine or verapamil significantly attenuated shear-induced ATP release. Channel inhibition had no effect on basal ATP release in static cells. Ca2+ -dependent ATP release in response to shear appeared to result from vesicular release, and not through gap hemichannels, since vesicle disruption with N-ethylmaleimide, brefeldin A, or monensin prevented increases in flow-induced ATP release, whereas inhibition of gap hemichannels with either 18α-glycyrrhetinic acid or 18β-glycyrrhetinic acid did not. Degradation of extracellular ATP with apyrase prevented shear-induced increases in PGE2 release. These data suggest a time line of mechanotransduction wherein fluid shear activates L-VSCC's to promote Ca2+ entry that, in turn, stimulates vesicular ATP release. Further, these data suggest that P2 receptor activation by secreted ATP mediates flow-induced prostaglandin release.
ATP release; mechanotransduction; Ca2+ signaling; osteoblasts; fluid shear
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.
antitumor agents; apoptosis; biological activity; glycyrrhetinic acid derivatives; medicinal chemistry
The title compound, C33H49NO3, is the propargylamide of 18β-glycyrrhetinic acid, a pentacyclic triterpenoid of interest as a therapeutic agent. The five six-membered rings of the glycyrrhetinic acid moiety show normal geometries, with four rings in chair conformations and the unsaturated ring C in a half-chair conformation. In the crystal, the terminal N-propargylcarboxamide group has remarkable structural effects on weak hydrogen-bond-like interactions. Particularly noteworthy are an intermolecular O—H⋯π interaction accepted side-on by the terminal alkyne group [O⋯C = 3.097 (2) and 3.356 (2) Å] and a short intermolecular C—H⋯O interaction [C⋯O = 3.115 (2) Å] donated by the alkyne C—H group. An N—H⋯O [N⋯O = 3.251 (2) Å] and a Calkyl—H⋯O [C⋯O = 3.254 (2) Å] interaction complement the crystal structure.
Triterpenoids such as betulinic acid (BA) and synthetic analogs of oleanolic acid [2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO)] and glycyrrhetinic acid [2-cyano-3,11-dioxo-18β-oleana-1,12-dien-30-oc acid (CDODA)] are potent anticancer agents that exhibit antiproliferative, antiangiogenic, anti-inflammatory and pro-apoptotic activities. Although their effects on multiple pathways have been reported, unifying mechanisms of action have not been reported. Studies in this laboratory have now demonstrated that several triterpenoids including BA and some derivatives, celastrol, methyl ursolatee, β-boswellic acid derivatives, and the synthetic analogs CDDO, CDODA and their esters decreased expression of specificity protein (Sp) transcription factors and several pro-oncogenic Sp-regulated genes in multiple cancer cell lines. The mechanisms of this response are both compound- and cell context-dependent and include activation of both proteasome-dependent and -independent pathways. Triterpenoid-mediated induction of reactive oxygen species (ROS) has now been characterized as an important proteasome-independent pathway for downregulation of Sp transcription factors. ROS decreases expression of microRNA-27a (miR-27a) and miR-20a/miR-17-5p and this results in the induction of the transcriptional “Sp-repressors” ZBTB10 and ZBTB4, respectively, which in turn downregulate Sp and Sp-regulated genes. Triterpenoids also activate or deactive nuclear receptors and G-protein coupled receptors, and these pathways contribute to their antitumorigenic activity and may also play a role in targeting Sp1, Sp3 and Sp4 which are highly overexpressed in multiple cancers and appear to be important for maintaining the cancer phenotype.
Sp transcription factors; downregulation; reactive oxygen species
Glycyrrhizic acid (GA) is a triterpene glycoside found in the roots of licorice plants (Glycyrrhiza glabra). GA is the most important active ingredient in the licorice root, and possesses a wide range of pharmacological and biological activities. GA coupled with glycyrrhetinic acid and 18-beta-glycyrrhetic acid was developed in China or Japan as an anti-inflammatory, antiviral, and antiallergic drug for liver disease. This review summarizes the current biological activities of GA and its medical applications in liver diseases. The pharmacological actions of GA include inhibition of hepatic apoptosis and necrosis; anti-inflammatory and immune regulatory actions; antiviral effects; and antitumor effects. This paper will be a useful reference for physicians and biologists researching GA and will open the door to novel agents in drug discovery and development from Chinese herbs. With additional research, GA may be more widely used in the treatment of liver diseases or other conditions.
Carbenoxolone (Biogastrone, Berk) has been shown to reduce the peptic activity and total acidity of gastric juice obtained from anaesthetized pylorus-ligated rats without affecting significantly the volume of gastric juice secreted or the K+ concentration. Glycyrrhetinic acid was less potent in reducing peptic activity and caused no reduction in total acidity.
Antipeptic activity of carbenoxolone has also been demonstrated in vitro using the pepsin plate technique and the haemoglobin pepsin assay.
It is suggested that these actions of carbenoxolone may contribute to the increased rate of healing of peptic ulcer in patients treated with the drug.