Protective effect of glycyrrhetinic acid against cantharidin-induced hepatotoxicity through reducing oxidative stress in mice

Background:Cantharidin(CTD)is a commonly used natural product with anticancer properties;however,it has significant adverse effects,particularly hepatotoxicity.Glycyrrhetinic acid(GA),the active component of licorice,shows potential hepatoprotective effects.The protective effects and mechanism of GA against CTD-induced hepatotoxicity are still unclear.Objective:This study aims to elucidate the effect and mechanism of GA on CTD-induced hepatotoxicity in mice experiments.Methods:Construction of CTD-induced hepatotoxicity models and oral gavage GA intervention for 14 d.The liver index,ALT,AST and LDH levels in the serum of the mice were examined;HE staining was performed to observe pathological changes in the liver.The MDA level and SOD activities in liver tissue were tested.Western blot was conducted to determine Keap1/Nrf2 signaling pathway-related protein expression.Results:The results showed that GA significantly reduced the levels of ALT,AST,and LDH in the serum,which were increased by CTD.Additionally,it also exerted a substantial inhibitory effect on the reduction of SOD activity and the elevation of malondialdehyde content in liver tissue.Notably,the phenomena of nuclear swelling,necrosis,and inflammatory infiltration of liver tissue were significantly attenuated following oral administration of GA in mice.Subsequent research has demonstrated that GA effectively suppressed the CTD-triggered upregulation of Keap1 while increasing the CTD-induced downregulation of Nrf2,HO-1,and NQO1.Conclusion:These findings suggested that GA may protect against CTD-induced hepatotoxicity in mice by exerting antioxidative stress through the Keap1/Nrf2 signaling pathway.

Regulating effect of glycyrrhetinic acid on bronchial asthma smooth muscle proliferation and apoptosis as well as inflammatory factor expression through ERK1/2 signaling pathway

Objective: To study the influence of glycyrrhetinic acid(GA) on bronchial asthma(BA)smooth muscle proliferation and apoptosis as well as inflammatory factor expression and its molecular mechanism.Methods: Male SD guinea pigs were selected and made into asthma models, bronchial asthma smooth muscle cells were cultured and divided into BA group, GA group and GA + LM group that were treated with serum-free RPMI1640 culture medium, serumfree RPMI1640 culture medium containing 50 ng/mL glycyrrhetinic acid, serum-free RPMI1640 culture medium containing 50 ng/mL glycyrrhetinic acid and 100 ng/mL LM22B-10 respectively; normal guinea pigs were collected and bronchial smooth muscle cells were cultured as control group. The cell proliferation activity as well as the expression of proliferation and apoptosis genes, inflammatory factors and p-ERK1/2 was determined.Results: Proliferation activity value and m RNA expression of Bcl-2, TNF-α, IL-4, IL-6,YKL-40, protein expression of p-ERK1/2 of airway smooth muscle cell in BA group were significantly higher than those of control group while m RNA expression levels of Bax,caspase-9 as well as caspase-3 were significantly lower than that of control group(P < 0.05); proliferation activity value and m RNA expression of Bcl-2, TNF-α, IL-4, IL-6, YKL-40, protein expression of p-ERK1/2 of airway smooth muscle cell in GA group were significantly lower than those of BA group(P < 0.05) while the m RNA expression levels of Bax, caspase-9 as well as caspase-3 were significantly higher than those of BA group(P < 0.05); proliferation activity value and m RNA expression of Bcl-2, TNF-α, IL-4, IL-6, YKL-40 of airway smooth muscle cell in GA + LM group were significantly higher than those of GA group(P < 0.05) while m RNA expression levels of Bax, caspase-9 as well as caspase-3 were significantly lower that of GA group(P < 0.05).Conclusion: GA can inhibit the proliferation of bronchial smooth muscle cells and reduce the expression of inflammatory factors by inhibiting the phosphorylation of ERK1/2.

Effects of glycyrrhetinic acid on collagen metabolism of hepatic stellate cells at different stages of liver fibrosis in rats

INTRODUCTIONLiver fibrosis is a dynamic course leading tocirrhosis from a various chronic liver diseases. Thepathological basis of fibrosis is the disturbance ofproduction and degradation of the extracellularmatrix (ECM), which causes accumulation of ECMin the liver[1,2].

Glycyrrhetinic acid-triggered cytoprotective autophagy via inositolrequiring enzyme 1α-c-Jun N-terminal kinase cascade in non-small cell lung cancer cells

OBJECTIVE Glycyrrhetinic acid(GA),one of the main bioactive constituents of the famous Chinese medicinal herb Glycyrrhizauralensis Fisch,presents potent cytotoxicity to various cancer cells both in vitro and in vivo.Herein,we′d like to determine whether GA triggers autophagy in non-small cell lung cancer cells and the mechanisms involved.METHODS Cell proliferation was determined by MTT assay and colony formation.AnnexinⅤ/PI staining,Hoechst33342 staining,and Western blotting were used to detect GA-induced apoptosis.GA-induced autophagy was measured by expression of the lipid modification of light chain-3(LC3)and transfected with GFP-LC3 or GFP-RFP-LC3 plasmid.Pharmacological regulators,siRNA,and plasmid transfection were used to study the mechanisms of GA-triggered autophagy.RESULTS GA inhibited cell proliferation and induced apoptosis in a concentrationdependent manner in non-small cell lung cancer A549 cells.GA induced autophagyas evidenced by up-regulation of LC3-Ⅱexpression when combined treatment with chloroquine and induction of the red punta after GFP-RFP-LC3 plasmid transfection.Knockdown of autophagy related proteins(ATG)7,ATG 5,or beclin 1by siRNA,the expression of LC3-Ⅱand GFP-LC3 punt atriggered by GA were decreased.Furthermore,the c-Jun N-terminal kinase(JNK)pathways were activated after treatment with GA,and pretreatment with JNK inhibitor SP600125 or silence of JNK pathway by siRNA of JNK or c-jun obviously reduced GA-induced LC3-Ⅱexpression and GFP-LC3 punta formation.GA also stimulate dendoplasmic reticulum stress response by triggering inositol-requiring enzyme 1α(IRE1α)pathway,and knockdown of IRE1αinhibited the activation of JNK pathway and autophagy induced by GA.In addition,GA-induced cell proliferative inhibition and apoptosis were both enhanced when silence of autophagy as well as JNK pathway.CONCLUSION Our study demonstrated,for the first time,that GA induced a cytoprotective autophagy in non-small cell lung cancer cells by activating the IRE1α-JNK pathway,which might decreased the anti-cancer effects of GA.

18beta-glycyrrhetinic acid induces ROS-mediated apoptosis to ameliorate hepatic fibrosis by targeting PRDX1/2 in activated HSCs

Hepatic stellate cells(HSCs)are essential drivers of fibrogenesis.Inducing activated-HSC apoptosis is a promising strategy for treating hepatic fibrosis.18beta-glycyrrhetinic acid(18b-GA)is a natural compound that exists widely in herbal medicines,such as Glycyrrhiza uralensis Fisch,which is used for treating multiple liver diseases,especially in Asia.In the present study,we demonstrated that 18b-GA decreased hepatic fibrosis by inducing the apoptosis in activated HSCs.18b-GA inhibited the expression of a-smooth muscle actin and collagen type Ⅰ alpha-1.Using a chemoproteomic approach derived from activity-based protein profiling,together with cellular thermal shift assay and surface plasmon resonance,we found that 18b-GA covalently targeted peroxiredoxin 1(PRDX1)and peroxiredoxin 2(PRDX2)proteins via binding to active cysteine residues and thereby inhibited their enzymatic activities.18b-GA induced the elevation of reactive oxygen species(ROS),resulting in the apoptosis of activated HSCs.PRDX1 knockdown also led to ROS-mediated apoptosis in activated HSCs.Collectively,our findings revealed the target proteins and molecular mechanisms of 18b-GA in ameliorating hepatic fibrosis,highlighting the future development of 18b-GA as a novel therapeutic drug for hepatic fibrosis.

18β-Glycyrrhetinic Acid Improves Cardiac Diastolic Function by Attenuating Intracellular Calcium Overload

Summary:Ranolazine,a late sodium current inhibitor,has been demonstrated to be effective on heart failure.18B-glycyrrhetinic acid(18β-GA)has the similar inhibitory effect on late sodium currents.However,its effect on diastolic function is still unknown.This study aimed to determine whether 18β-GA can improve the diastolic function and to explore the underlying mechanisms.Eighty male Sprague Dawley(SD)rats of Langendorff model were randomly divided into the following groups:group A,normal cardiac perfusion group;group B,ischemia-reperfusion group;group C,ischemia-reperfusion with anemoniasulcata toxinⅡ(ATX-Ⅱ);group D,ranolazine group;and group E,18β-GA group with four different concentrations.Furthermore,a pressure-overloaded rat model induced by trans-aortic constriction(TAC)was established.Echocardiography and hemodynamics were used to evaluate diastolic function at 14th day after TAC.Changes of free intracellular calcium(Ca27)concentration was indirectly detected by laser scanning confocal microscope to confirm the inhibition of late sodium currents.With the intervention of ATX-Ⅱon ischemia reperfusion injury group,5 umol/L ranolazine,and 5,10,20,40μmol/L 18β-GA could improve ATX-I-induced cardiac diastolic dysfunction.630 mg/kg glycyrrhizin tablets could improve cardiac diastolic function in the pressure-overloaded rats.18B-GA and ranolazine had similar effects on reducing the free calcium in cardiomyocytes.The study demonstrates that 18B-GA and glycyrrhizin could improve diastolic dysfunction induced by ischemia-reperfusion injury in Langendorff-perfused rat hearts and pressure-overloaded rats.The mechanism may be attributed to the inhibition of enhanced late sodium currents.

Exploring the targets and molecular mechanism of glycyrrhetinic acid against diabetic nephropathy based on network pharmacology and molecular docking

BACKGROUND Diabetic nephropathy(DN)stands as the most prevalent chronic microvascular complication of diabetes mellitus.Approximately 50%of DN patients progress to end-stage renal disease,posing a substantial health burden.AIM To employ network pharmacology and molecular docking methods to predict the mechanism by which glycyrrhetinic acid(GA)treats DN,subsequently validating these predictions through experimental means.METHODS The study initially identified GA targets using Pharm Mapper and the TCMSP database.Targets relevant to DN were obtained from the Genecards,OMIM,and TTD databases.The Venny database facilitated the acquisition of intersecting targets between GA and DN.The String database was used to construct a protein interaction network,while DAVID database was used to conducted Kyoto Encyclopedia of Genes and Genomes(KEGG)pathway analysis and Gene Ontology(GO)analysis.Molecular docking experiments were performed using Autodock software with selected proteins.Experimental validation was conducted using renal proximal tubular cells(HK-2)as the study subjects.A hyperglycemic environment was simulated using glucose solution,and the effect of GA on cell viability was assessed through the cell counting kit-8 method.Flow cytometry was employed to detect cell cycle and apoptosis,and protein immunoblot(western blot)was used to measure the expression of proteins of the phosphatidylinositol 3-kinase(PI3K)/protein kinase B(AKT)signaling pathway and insulin resistance pathway,including insulin receptor(INSR),PI3K,p-PI3K,AKT,p-AKT,and glycogen synthase kinase-3(GSK3).RESULTS A total of 186 intersecting targets between GA and DN were identified,which were associated with 144 KEGGrelated enrichment pathways,375 GO biological process entries,45 GO cellular component entries,and 112 GO cellular function entries.Molecular docking demonstrated strong binding of GA to mitogen-activated protein kinase(MAPK)-1,SRC,PIK3R1,HSP90AA1,CASPASE9,HARS,KRAS,and MAPK14.In vitro experiments revealed that GA inhibited HK-2 cell viability,induced cell cycle arrest at the G2/M phase,and reduced apoptosis with increasing drug concentration.Western blot analysis showed that GA differentially up-regulated GSK3 protein expression,up-regulated AKT/p-AKT expression,down-regulated INSR,AKT,p-AKT,PI3K,and p-PI3K protein expression,and reduced p-PI3K/PI3K levels under high glucose conditions.CONCLUSION GA may protect renal intrinsic cells by modulating the PI3K/AKT signaling pathway,thereby inhibiting HK-2 cell viability,reducing HK-2 cell apoptosis,and inducing cell cycle arrest at the G0/G1 phase.

EFFECT OF GLYCYRRHETINIC ACID ON DNA DAMAGE AND UNSCHEDULED DNA SYNTHESIS INDUCED BY BENZO（α）PYRENE

Glyeyrrhetinic acid (GA) is an active component of Glycyrrhiza uraleusis fisch,In this study,GA was found to inhibit ear edema and ornithine decarboxylase (ODC)activity induced by croton oil in mice. GA could also protect rapid DNA damage and decrease the unscheduled DNA synthesis induced by benzo(α)pyrene. The results demonstrate that GA has a potential cancer chemopreventive activity.

Advances in Research on Anti-cancer Mechanism of 18β Glycyrrhetinic Acid

Glycyrrhiza uralensis Fisch has been used to treat the symptoms of organ fever, food poisoning, typhoid fever, sore throat, cough due to lung heat, children's diseases and so on since the ancient times. It is a solid Chinese herbal medicine which is good for the health. In recent years, it has been found that licorice extract also has excellent anti-cancer effect. The 18β glycyrrhetinic acid, obtained by hydrolysis of precursor glycyrrhizic acid, is a relatively efficient anti-cancer ingredient. 18β glycyrrhetinic acid can exert anti-cancer effects by inhibiting cancer cell proliferation, inducing apoptosis of cancer cells, inhibiting invasion and metastasis of cancer cells, preventing oxidation, inhibiting neovascularization, inhibiting lymphangiogenesis, and regulating hormone secretion. This paper reviewed the advances in research of the anticancer mechanism of 18β glycyrrhetinic acid, to provide a theoretical basis for future research.

Pressured Microwave-assisted Hydrolysis of Crude Glycyrrhizic Acid for Preparation of Glycyrrhetinic Acid

A pressured microwave-assisted hydrolysis （PMAH） technique has been developed for hydrolyzing the crude glycyrrhizic acid （GA） extracted from licorice root to prepare glycyrrhetinic acid （GRA）. In order to optimize the efficiency of PMAH, several experimental parameters were investigated, including liquid-solid ratio, hydrolysis time, sulfuric acid concentration and hydrolysis temperature. The optimized hydrolysis conditions were as follows：pressured microwave-assisted hydrolysis of crude GA for 21 min （taking 15 min to reach 150 ℃, and holding it for 6 rain） at 150 ℃ （at a radiation power of 450 W） in 3%-5% sulfuric acid solution with the liquid-solid （ml.g-1 crude GA） ratio of 25 ： 1. As a result of the considerable saving in time and higher product yields （up to 90%）, PMAH was proved more effective than conventional methods.

Synthesis and Anti-tumor Activity of Novel Glycyrrhetinic Acid Derivatives

Twenty-five derivatives of glycyrrhetinic acid（GA） modified on the A-ring,at C30 and C11 positions were synthesized.Their in vitro cytotoxicity against various cancer cell lines[henrietta lacks strain of cancer cells（HeLa）,human hepatocellular liver carcinoma cells（HepG2） and human gastric carcinoma cells（BGC-823）] was evaluated by standard MTT[3-（4,5-dimethyl-2-thiazol-yl）-2,5-diphenyl-2H-tetrazolium bromide] assay.All the tested derivatives were found to have stronger cell growth inhibitory than their parent compound GA.Among them,compounds 3a,5a,and 8d have similar activity on HeLa cell line,and compound 8a has similar activity on HeLa,HepG2 and BGC-823 cell lines as Gefitinib.

Potential therapeutic targets for the prevention of diabetic nephropathy:Glycyrrhetinic acid

Uncontrolled hyperglycemia or poorly managed disease increases the propensityfor a number of diabetes-related complications targeting major organs includingthe heart, eyes, and kidney. Although the mechanisms by which diabetes inducescardiovascular diseases include oxidative stress and inflammation, when insulinresistance remains the key to the pathogenesis, as implicated in the two reviews inthis issue. This editorial mainly comments on the potential preventive applicationof glycyrrhetinic acid (or 18β-GA) in relation to diabetic nephropathy. The therapeuticor preventive effects of 18β-GA, as a hydrolytic product of glycy-rrhizicacid that is a component of licorice, have been appreciated in other disorders, buthave received much less attention in relation to diabetic complications. A study inthis issue has identified 18β-GA as a therapeutic for preventing diabeticnephropathy and provides evidence to support efficacy in cultured human renaltubule cells in vitro. Although it represents a pilot study, the observations supporta new therapeutic approach that warrants further ex-ploration.

Effect of glycyrrhetinic acid on Th1/Th2 balance in cough variant asthma mice

Objective:To evaluate the therapeutic effect of Glycyrrhetinic Acid on cough variant asthma(CVA)mice and to investigate the possible mechanism in reducing lung inflammation.Methods:48 young female Balb/c mice were divided into Control,CVA,Prednisone Acetate,Glycyrrhetinic Acid high-dose,Glycyrrhetinic Acid middle-dose and Glycyrrhetinic Acid lowdose groups randomly,with 8 mice in each group.The CVA mice model was established by ovalbumin(OVA)sensitization and OVA challenge,the animal asthma behavior was observed after drug administration,and the index of the lung of mice were recorded.The level of OVAsIgE in the bronchoalveolar lavage fluid(BALF)was tested by ELISA.The pathological changes of the lung tissue were observed by Hematoxylin and Eosin(H&E)staining.The protein expressions of T-bet,IFN-γ,Gata3,IL-4 and IL-13 in the lung tissue were determined by Western blot.Results:Compared with the CVA group,the index of lung of mice,the OVA-sIgE level in BALF and expression levels of Th2-related factor in the lung tissue of mice in Prednisone Acetate and Glycyrrhetinic Acid groups were significantly decreased(P<0.05 or P<0.01),the infiltration of inflammatory cells in the lung tissue was reduced,while expressions of Th1-related factor in the lung tissue was significantly increased(P<0.05 or P<0.01).Conclusion:Glycyrrhetinic acid has therapeutic effect on CVA mice,the underlying mechanism of Glycyrrhetinic acid alleviating lung impairment and airway inflammation may be associated with mediating the Th1/Th2 imbalance in the lung tissue.

Glycyrrhetinic acid binds to the conserved P-loop region and interferes with the interaction of RAS-effector proteins

Members of the RAS proto-oncogene superfamily are indispensable molecular switches that play critical roles in cell proliferation, differentiation, and cell survival. Recent studies have attempted to prevent the interaction of RAS/GTP with RAS guanine nucleotide exchange factors(GEFs), impair RASeffector interactions, and suppress RAS localization to prevent oncogenic signalling. The present study aimed to investigate the effect of the natural triterpenoic acid inhibitor glycyrrhetinic acid, which is isolated from the roots of Glycyrrhiza plant species, on RAS stability. We found that glycyrrhetinic acid may bind to the P-loop of RAS and alter its stability. Based on our biochemical tests and structural analysis results, glycyrrhetinic acid induced a conformational change in RAS. Meanwhile, glycyrrhetinic acid abolishes the function of RAS by interfering with the effector protein RAF kinase activation and RAS/MAPK signalling.

Protective mechanisms of hypaconitine and glycyrrhetinic acid compatibility in oxygen and glucose deprivation injury

This study investigated the protective effect of the compatibility of hypaconitine （HA） and glycyrrhetinic acid （GA） on H9c2 cells under oxygen and glucose deprivation （OGD）-induced injury, and the possible mechanisms. We found that HA＋GA significantly improved pathology and morphology of the nucleus and ultrastructure of H9c2 cells under OGD as determined by Hoechst 33342 staining and transmission electron microscopy （TEM） tests. It also reduced the releases of lactate dehydrogenase （LDH）, creatine kinase-myocardial band isoenzyme （CK-MB）, and aspartate transaminase （AST） from the cultured supernatant of H9c2 cells, which were tested by enzyme-linked immune sorbent assay （ELISA） kits. In addition, it lessened the apoptotic rate as determined by a fluorescein isothiocyanate-annexin V/propidium iodide （FITC-AV/PI） double staining assay. It was also found that HA＋GA might regulate the protein expression associated with the phosphatidylinositol 3-kinase （PI3K）/Akt signaling pathway. Overall, the study demonstrated that HA＋GA protected H9c2 cells against OGD-induced injury, and the signaling mechanism might be related to the PI3K/Akt signaling pathway.

Liver metabonomics study on the protective effect of glycyrrhetinic acid against realgar-induced liver injury

Glycyrrhetinic acid(GA)is the bioactive ingredient in Glycyrrhizae Radix et Rhizoma.Our previous study has reported that GA has protective effect on realgar-induced hepatotoxicity.However,the details of the hepatoprotective mechanisms of GA on realgar-induced liver injury remain to be elucidated.In the study,mice were divided into control,GA-control,realgar,and co-treated groups.Their liver tissues were used for metabonomics study by ultra-performance liquid chromatography-mass spectrometry(UPLCMS)method.The results illustrate that GA significantly ameliorate the liver injury and metabolic perturbations caused by realgar.Some metabolites,such as phenylalanine,pyroglutamic acid(PGA),proline,carnitine,nicotinamide,choline,lysophosphatidylcholine(LPC)16:0 and LPC 18:2 were found responsible for the hepatoprotective effect of GA.These metabolites are associated with the methylation metabolism of arsenic,cell membrane structure,energy metabolism and oxidative stress.From the results of this study,we infer that the potential hepatoprotective mechanism of GA on realgar-induced liver injury may be associated with reducing arsenic accumulation and its methylation metabolism in the liver,promoting the conjugation of arsenic and GSH to play detoxification effect,and ameliorating the liver metabolic perturbations caused by realgar.

Laminaria japonica increases plasma exposure of glycyrrhetinic acid following oral administration of Liquorice extract in rats

The present study was designed to investigate the effects of Laminaria japonica(Laminaria) on pharmacokinetics of glycyrrhetinic acid(GA) following oral administration of Liquorice extract in rats.Following oral administrations of single-dose and multi-dose Liquorice extract and Liquorice-Laminaria extract,respectively,plasma samples were obtained at various times and the concentrations of GA,liquiritigenin,and isoliquiritigenin were measured by LC-MS.The effects of Laminaria extract on pharmacokinetics of GA were also investigated,following single-dose and multidose of glycyrrhizic acid(GL).The effects of Laminaria extract on intestinal absorption of GA and GL were studied using the in situ single-pass intestinal perfusion model.The metabolism of GL to GA in the contents of small and large intestines was also studied.The results showed Liquorice-Laminaria extract markedly increased the plasma concentration of GA,accompanied by a shorter Tmax.Similar alteration was observed following multidose administration.However,pharmacokinetics of neither liquiritigenin nor isoliquiritigenin was affected by Laminaria.Similarly,Laminaria markedly increased concentration and decreased Tmax of GA following oral GL were observed.The data from the intestinal perfusion model showed that Laminaria markedly increased GL absorption in duodenum and jejunum,but did not affect the intestinal absorption of GA.It was found that Laminaria enhanced the metabolism of GL to GA in large intestine.In conclusion,Laminaria increased plasma exposures of GA following oral administration of liquorice or GL,which partly resulted from increased intestinal absorption of GL and metabolism of GL to GA in large intestine.

Improved anti-tumor activity and safety profile of a paclitaxel-loaded glycyrrhetinic acid-graft-hyaluronic acid conjugate as a synergistically targeted drug delivery system

The present study was designed to develop and evaluate glycyrrhetinic acid-graft-hyaluronic acid(HGA) conjugate for intravenous paclitaxel(PTX) delivery. Lyophilized PTX-loaded self-assembled HGA nanoparticles(PTX/HGAs) were prepared and characterized by dynamic light scattering measurements. Hemolysis test, intravenous irritation assessment, and in vitro and in vivo pharmacodynamic studies were carried out. B16F10 and HepG2 cells were used in the cell apoptosis analysis. The mouse MDA-MB-231 xenograft model was used for the evaluation of in vivo anticancer activity of the drugs, by the analysis of tumor growth and side effects on other tissues. PTX/HGAs showed high stability and good biocompability. Compared with PTX plus GA plus HA solution, PTX/HGAs displayed obvious superiority in inducing the apoptosis of the cancer cells. Following systemic administration, PTX/HGAs efficiently suppressed tumor growth, with mean tumor inhibition ratio(TIR) being 65.08%, which was significantly higher than that of PTX plus GA plus HA treatment. In conclusion, PTX/HGAs demonstrated inhibitory effects tumor growth without unwanted side effects, suggesting that HGA conjugates hold a great potential as a delivery carrier for cancer chemotherapeutics to improve therapeutic efficacy and minimize adverse effects.

Microbial transformation of glycyrrhetinic acid and potent neural anti-inflammatory activity of the metabolites

The microbial transformation of glycyrrhetinic acid（1） by Cunninghamella blakesleana CGMCC 3.970 led to the production of five new metabolites（2-6）.The structures of the metabolites were determined by extensive spectroscopic（HR-ESIMS,1D and 2D NMR） data analyses.The involved reactions exhibited specific hydroxylations at C-24,C-7,and C-15,and oxidation at C-3.Moreover,compounds 2,5,and 6showed significant neural anti-inflammatory activity by inhibiting lipopolysaccharide-induced NO production in mouse microglia BV2 cells with IC（50） values of 0.76,0.94,and 0.16μmol/L,respectively.

Tunable UCST thermoresponsive copolymers based on natural glycyrrhetinic acid

Water-soluble thermoresponsive polymers present either upper critical solution temperature(UCST) or lower critical solution tempe rature(LCST) depending on the location of their miscibility range with water at high temperatures or at low temperatures.Compared with LCST polymers,the water-soluble UCST polymers are still less explored until now.In this work three copolymers of P(AAm-co-GAA) were synthesized by copolymerizing two acrylamide monomers,acrylamide(AAm) and acrylamide functionalized with natural glycyrrhetinic acid(GAA),using reversible addition-fragmentation chain transfer(RAFT) polymerization.These copolymers exhibited the typical UCST thermoresponsive behavior,and their phase transition temperatures could be easily tuned to around 37℃ for potential biological applications.Moreover,the UCST of P(AAm-co-GAA) can be adjusted not only by the content of glycyrrhetinic acid(GA) and polymer concentrations,but also by the host-guest interactions between GA and cyclodextrins(β-and γ-CD).The suitable value of UCST and the biocompatible nature of GA and CDs may endow these copolymers with practical applications in biomedical chemistry.