Component Of Licorice Research Articles

Pharmacokinetic profiling and network pharmacology of honey-fried Licorice: An Integrative workflow to study traditional Chinese medicines (TCMs)

Licorice, known as the “elder statesman,” is commonly used in traditional Chinese medicine (TCM) formulations. This study aims to establish a workflow combining animal and in silico experiments to elucidate the mechanisms of TCMs at both qualitative and quantitative levels. UPLC-Q-TOF-MS/MS was employed to qualitatively characterize the total components of honey-fried licorice and the plasma components after oral administration in Beagle dogs. A UPLC-Q-Trap-MS/MS method was developed for the pharmacokinetic study of honey-fried licorice components in Beagle dog plasma. Network pharmacology and molecular docking were utilized to explore the primary functional targets and pathways. In total, we identified 68 constituents in honey-fried licorice, with 28 detected in Beagle dog plasma, and 18 of them, mainly belong to flavonoids and terpenoids, showing significant exposure. The plasma pharmacokinetic study of these 18 constituents revealed that compounds like liquiritin, glycyrrhizic acid, licoricesaponin G2, and glycyrrhetic acid-3-o-glucuronide had significant exposure. Network pharmacology and molecular docking analyses identified MAPK3, PIK3CB, PIK3CA, RAF1, and EGFR as the main targets of the active constituents of honey-fried licorice, involved in pathways such as the Ras signaling pathway, human cytomegalovirus infection, and the MAPK signaling pathway. This study provides a comprehensive profile and pharmacokinetic characteristics of honey-fried licorice, offering insights into its pharmacological, toxicological, and clinical aspects. The established workflow can serve as a standard for investigating other TCMs.

Anti-Proliferative and Anti-Migratory Activity of Licorice Extract and Glycyrrhetinic Acid on Papillary Thyroid Cancer Cell Cultures

Papillary thyroid cancer (PTC) is the 8th most common cancer among women overall. Licorice contains over 300 active compounds, many of them with anti-cancer properties. Glycyrrhetinic acid (GA) is a major component of licorice. The aim of this study was to investigate the potential anti-proliferative effects of licorice and GA on PTC cell cultures. Licorice extract (LE) was produced from the root and tested on BCPAP and K1 cell lines, as well as GA and aldosterone. We used the MTT test to investigate the anti-proliferative activity, the wound healing test for the migratory activity, and finally, we analyzed cell cycle distribution, apoptosis, and oxidative stress after LE, GA, or aldosterone incubation. Both LE and GA reduced cell viability at 48 h and cell migration at 24 h in both PTC cultures. Aldosterone reduced cell migration only in K1 cells. LE and GA induced cell cycle arrest in the G0/G1 phase in the BCPAP cell line, while LE and aldosterone induced it in the K1 culture. GA but not LE increased the apoptosis rate in both cell lines, whereas LE but not GA increased oxidative stress in both cultures. This study presents the first evidence of the in vitro anti-proliferative and anti-migratory activity of LE and GA on PTC.

3-epi-18β-Glycyrrhetinic Acid or Its Glucuronide, the Metabolites of Glycyrrhizinic Acid with Individual Differences, Correlated with Diagnostic Marker for Licorice-Induced Pseudoaldosteronism in Humans.

Licorice is a crude drug that is used in traditional Japanese Kampo medicine and is also used as a sweetener. Occasionally, it causes pseudoaldosteronism (PsA) as a side effect. The major symptoms include hypokalemia, hypertension, edema, and low plasma aldosterone levels. PsA might be caused by the metabolites of glycyrrhizinic acid (GL), a component of licorice. The development of PsA markedly varies among individuals; however, the factors that cause these individual differences remain unknown. In this study, 78 patients who consumed Kampo medicines containing licorice were enrolled, and their laboratory data, including serum potassium levels, plasma aldosterone concentrations (PAC), and the concentrations of GL metabolites in the residual blood and/or urine samples were evaluated. Of the 78 participants, 18β-glycyrrhetinic acid (GA), 3-epi-GA, 3-oxo-GA, 18β-glycyrrhetinyl-30-O-glucuronide (GA30G), and 3-epi-GA30G were detected in the serum samples of 65, 47, 63, 62, and three participants, respectively. Of the 29 urine samples collected, GA30G and 3-epi-GA30G were detected in 27 and 19 samples. 3-epi-GA30G is a newly found GL metabolite. Moreover, 3-epi-GA, 3-oxo-GA, and 3-epi-GA30G were identified in human samples for the first time. High individual differences were found in the appearances of 3-epi-GA in serum and 3-epi-GA30G in urine, and the concentrations of these metabolites were correlated with serum PsA markers. The inhibitory titers of 3-epi-GA, 3-oxo-GA, GA30G, and 3-epi-GA30G on human 11β-hydroxysteroid dehydrogenase type 2 were almost similar. These findings suggest that 3-epi-GA and/or 3-epi-GA30G are associated with individual differences in the development of PsA. SIGNIFICANCE STATEMENT: In this study, we detected 3-epi-18β-glycyrrhetinic acid (3-epi-GA) in human serum for the first time. We also identified 3-epi-18β-glycyrrhetinyl-30-O-glucuronide (3-epi-GA30G) as a novel glycyrrhizinic acid (GL) metabolite in human urine. These GL metabolite levels showed correlations with markers of PsA. Additionally, there are individual differences in whether they appear in the serum/urine. In conclusion, 3-epi-GA/3-epi-GA30G correlates with individual differences in the development of PsA.

Licochalcone A: a review of its pharmacology activities and molecular mechanisms.

Licorice, derived from the root of Glycyrrhiza uralensis Fisch, is a key Traditional Chinese Medicine known for its detoxifying, spleen-nourishing, and qi-replenishing properties. Licochalcone A (Lico A), a significant component of licorice, has garnered interest due to its molecular versatility and receptor-binding affinity. This review explores the specific roles of Lico A in various diseases, providing new insights into its characteristics and guiding the rational use of licorice. Comprehensive literature searches using terms such as "licorice application" and "pharmacological activity of Lico A" were conducted across databases including CNKI, PubMed, and Google Scholar to gather relevant studies on Lico A's pharmacological activities and mechanisms. Lico A, a representative chalcone in licorice, targets specific mechanisms in anti-cancer and anti-inflammatory activities. It also plays a role in post-transcriptional regulation. This review delineates the similarities and differences in the anti-cancer and anti-inflammatory mechanisms of Lico A, concluding that its effects on non-coding RNA through post-transcriptional mechanisms deserve further exploration.

18-β-Glycyrrhetinic Acid Promotes Hair Growth by Stimulating the Proliferation of Dermal Papilla Cells and Outer Root Sheath Cells, and Extends the Anagen Phase by Inhibiting 5α-Reductase.

18-β-Glycyrrhetinic acid, a major component of licorice, stimulated the proliferation of both dermal papilla cells and outer root sheath cells isolated from human hair follicles. Thus, suggesting that this compound promotes hair growth. Furthermore, this compound inhibited the activity of testosterone 5α-reductase, an enzyme responsible for converting androgen to dihydroandrogen, with an IC50 of 137.1 µM. 18-β-Glycyrrhetinic acid also suppressed the expression of transforming growth factor-β1 (TGF-β1), which shifts the hair cycle from the anagen phase to the telogen phase. It suggested that this compound may prolong the anagen phase. Based on these findings, this compound could be a potentially effective treatment for androgenetic alopecia.

Exploring the anti-inflammatory and immunomodulatory potential of licochalcone B against psoralidin-induced liver injury

Ethnopharmacological relevanceHerb-induced liver injury (HILI) represents an exacerbated inflammatory response, with Psoraleae fructus (PF) and its preparations recently associated with hepatotoxicity. Licorice, historically recognized as a detoxifying herbal remedy, is considered to possess hepatoprotective properties. Our previous research identified bavachin, bakuchiol, and psoralidin (PSO) as potential toxic constituents in PF, while licochalcone B (LCB) and echinatin were identified as bioactive components in licorice. However, evidence regarding the interactions of active compounds in herbs and their underlying mechanisms remains limited. Aim of the studyThe objective of this study is to assess the potential mechanisms through which LCB modulates immunological and anti-inflammatory responses to treat PSO-induced liver injury by using human hepatocyte cells (L02) and LPS-primed mice. MethodsThe ameliorative effects of LCB and echinatin on bavachin, bakuchiol, and PSO-induced liver injury were demonstrated in L02 cells. Subsequently, the efficacy of LCB on PSO-induced idiosyncratic liver injury was further validated in C57BL/6 mice under moderate inflammatory stress induced by LPS priming. The mechanisms were preliminarily explored with an integrated strategy of molecular docking, RT-PCR verification, and untargeted metabolomics. ResultsThe study shows that LCB significantly reduced cell injury induced by the three chemicals in PF and provided substantial protection against PSO-induced hepatic damage, as indicated by the levels of ALT, AST, and LDH. LCB normalized liver function and remarkedly alleviated hepatic lesions and inflammation caused by PSO in mice under moderate inflammatory stress. The mRNA profiles of both L02 cells and mice liver tissue revealed that LCB mitigated PSO-induced hepatotoxicity by regulating the gene expression of pro-inflammatory cytokines IL1B and TNF, as well as immunoinflammatory genes PIK3CA, AKT1, NFKB1, and NLRP3. Furthermore, untargeted metabolomics of liver tissue indicated that LCB could reverse the abnormal expression of 11 discriminatory metabolites, with the interrelationship between differential metabolites and target genes primarily clustering in glycerophospholipid metabolism, arachidonic acid metabolism, and phosphatidylinositol signaling system. ConclusionLCB demonstrated a superior anti-inflammatory and immunomodulatory effect on PSO-induced hepatotoxicity by modulating the inflammatory response and metabolic signaling system. Key interactive targets included phosphatidylcholine, phosphatidic acid, and subunit isoforms of PI3K.

18β-glycyrrhetinic acid ameliorates bleomycin-induced idiopathic pulmonary fibrosis via inhibiting TGF-β1/JAK2/STAT3 signaling axis

Idiopathic pulmonary fibrosis (IPF) is a debilitating and progressive lung disease with an unknown cause that has few treatment options. 18β-Glycyrrhetinic acid (18β-GA) is the main bioactive component in licorice, exhibiting anti-inflammatory and antioxidant effects, while also holding certain application value in the metabolism and regulation of steroids. In this study, we demonstrated that 18β-GA effectively alleviates bleomycin (BLM)-induced IPF by inhibiting the TGF-β1/JAK2/STAT3 signaling axis. In vivo experiments demonstrate that 18β-GA significantly attenuates pulmonary fibrosis progression by reducing lung inflammation, improving lung function, and decreasing collagen deposition. In vitro experiments reveal that 18β-GA inhibits the activation and migration of TGF-β1-induced fibroblasts. Furthermore, it regulates the expression of vimentin, N-cadherin and E-cadherin proteins, thereby inhibiting TGF-β1-induced epithelial-mesenchymal transition (EMT) in lung alveolar epithelial cells. Mechanistically, 18β-GA ameliorates pulmonary fibrosis by modulating the TGF-β1/JAK2/STAT3 signaling pathway in activated fibroblasts. Taken together, our findings demonstrate the potential and underlying mechanisms of 18β-GA in ameliorating IPF, emphasizing its potential as a novel therapeutic drug for the treatment of this devastating disease.

An efficient method for rapid screening of triterpenoid saponins in three Glycyrrhiza species using rapid resolution liquid chromatography quadrupole time-of-flight mass spectrometry combined with mass defect filtering

Triterpenoid saponins, a major bioactive component of liquorice, possess high hydrophilicity and often co-occur with other impurities of similar polarity. Additionally, subtle structural differences of some triterpenoid saponins bring challenges to comprehensive characterisation. In this study, triterpenoid saponins of three Glycyrrhiza species were systematically analysed using rapid resolution liquid chromatography quadrupole time-of-flight mass spectrometry (RRLC-Q-TOF-MS) coupled with mass defect filtering (MDF). Firstly, comprehensive date acquisition was achieved using RRLC-Q-TOF-MS. Secondly, a polygonal MDF method was established by summarizing known and speculated substituents and modifications based on the core structure to rapidly screen potential triterpenoid saponins. Thirdly, based on the fragmentation patterns of reference compounds, an identification strategy for characterisation of triterpenoid saponins was proposed. The strategy divided triterpenoid saponins into three distinct classes. By this strategy, 98 triterpenoid saponins including 10 potential new ones were tentatively characterised. Finally, triterpenoid saponins of three Glycyrrhiza species were further analysed using principle component analysis (PCA) and orthogonality partial least squares discriminant analysis (OPLS-DA). Among these, 18 compounds with variable importance in projections (VIP) > 1.0 and P values < 0.05 were selected to distinguish three Glycyrrhiza species. Overall, our study provided a reference for quality control and rational use of the three species.

Theoretical Study of Radical Scavenging Antioxidant Activity of Coumarin Derivatives in Licorice Using DFT

Nowdays, much research is focused on exploring antioxidant activity based on natural compounds. Licorice, a traditional natural product rich in antioxidant components, has been widely used in clinical medicine. However, there is a lack of theoretical studies on the active components in licorice. In this context, the antioxidant activity of several common active components of coumarin derivatives in licorice was investigated using a density flooding theory (DFT) approach. The free radical scavenging ability of the compounds was achieved by hydrogen atom transfer (HAT), sequential electron transfer proton transfer (SET-PT) and sequential proton loss electron transfer (SPLET) mechanisms. The effect of solvent on antioxidant activity was also investigated. It was found that in the gas and benzene phases, the compounds studied preferred to undergo the HAT mechanism, while SPLET was favoured in polar solvents. In addition to the above mechanism, the HOMO and LUMO energies of the compounds as well as molecular descriptors and electrostatic potential maps were calculated and applied to predict the antioxidant activity of the compounds. The above studies allow a better understanding of the mechanism of free radical scavenging activity of coumarin derivatives from licorice.

Exploring the molecular mechanism of targeted extraction of novel flavonoid components in licorice using natural deep eutectic solvent

In the previous study of our research group, it was found that choline chloride (ChCl)- glycolic acid (GA) deep eutectic solvent (DES), as a green solvent, has good solubility for licorice flavonoids. However, the molecular mechanism of whether ChCl-GA DES can selectively extract licorice flavonoids is still unclear. Therefore, in this study, ChCl-GA DES was used as the extraction solvent to explore the molecular mechanism of DES-targeted extraction of licorice flavonoids. LC-MS studies have shown that DES exhibits good separation performance for licorice flavonoids and has successfully identified seven novel flavonoid compounds that have not been previously reported in licorice. Molecular dynamics and quantum computational studies have revealed that the favorable molecular interactions between DES and licorice flavonoids are the main reason for their targeted separation. Network pharmacology studies have indicated that licorice flavonoids extracted by DES exhibit significant antioxidant activity, which has been verified through molecular docking and in vitro and in vivo experiments. Based on the findings of this study, it can be concluded that DES holds promise as a new green solvent for the extraction of flavonoid compounds in natural products, suggesting its potential for various applications.

Exploring the Mechanism of Echinatin against Cervical Cancer Based on Network Pharmacology

Cervical cancer significantly impacts women’s health due to its high mortality rate and increasing prevalence among younger individuals, thereby posing a severe threat. Echinatin is the primary active component of licorice in traditional Chinese medicine. However, studies on its use in cervical cancer treatment are limited. In our study, 198 targets of Echinatin were identified by some databases. Among these, 40 core targets related to cervical cancer were selected. Enrichment analyses revealed that Echinatin operated through genes associated with cell cycle, apoptosis, senescence, and various cancer-related signaling pathways. Differential expression of intersecting targets was verified in the GEO database, and molecular docking also indicated a strong binding capacity between active compounds and identified targets. Moreover, the results of western blot provided further evidence at the protein level. Echinatin hindered the proliferation, migration, and invasion of HeLa and SiHa cells while increasing their apoptosis. This study predicted the potential targets and beneficial effects of Echinatin in cervical cancer treatment, which provides a new avenue for further research into the molecular mechanisms underlying the role of Echinatin in cervical cancer treatment.

Quercetin Promotes Apoptosis of Gastric Cancer Cells through the EGFR-ERK Signaling Pathway

Previous studies have shown that various active components of licorice have anticancer effects. However, few studies have investigated the mechanism of action of licorice in gastric cancer. The effect of active compounds in licorice on the biological activity of gastric cancer cells was investigated in vitro (MKN-45 cells). Network pharmacology and molecular docking were used to predict the potential targets of licorice against gastric cancer and verify the binding stability of target proteins to compounds. In addition, the anticancer effect of licorice was assessed using a mouse model of gastric cancer. The licorice-active component (quercetin) effectively inhibited proliferation, caused cell cycle arrest, and promoted apoptosis in MKN-45 cells, accompanied by increased Cyt-C, decreased BCL-2, and decreased mitochondrial membrane potential and mitochondrial damage. Further research showed that quercetin targeted EGFR, blocked the ERK signaling pathway, and downregulated PTGS2. In the in vivo experiment, quercetin treatment resulted in reduced tumor volume, decreased Ki67 and BCL-2 expression in tumor tissue, increased caspase 3 and BAX levels, and induced mitochondrial damage.

A Comprehensive Review of Licorice: The Preparation, Chemical Composition, Bioactivities and Its Applications.

Licorice (Glycyrrhiza) is a medicinal and food homologue of perennial plants derived from the dried roots and rhizomes of the genus Glycyrrhiza in the legume family. In recent years, the comprehensive utilization of licorice resources has attracted people's attention. It is widely utilized to treat diseases, health food products, food production, and other industrial applications. Furthermore, numerous bioactive components of licorice are found using advanced extraction processes, which mainly include polyphenols (flavonoids, dihydrostilbenes, benzofurans, and coumarin), triterpenoids, polysaccharides, alkaloids, and volatile oils, all of which have been reported to possess a variety of pharmacological characteristics, including anti-oxidant, anti-inflammatory, antibacterial, antiviral, anticancer, neuroprotective, antidepressive, antidiabetic, antiparasitic, antisex hormone, skin effects, anticariogenic, antitussive, and expectorant activities. Thereby, all of these compounds promote the development of novel and more effective licorice-derived products. This paper reviews the progress of research on extraction techniques, chemical composition, bioactivities, and applications of licorice to provide a reference for further development and application of licorice in different areas.

A case of chronic licorice intoxication-induced apparent mineralocorticoid excess syndrome

Licorice is a perennial herb belonging to the legume family that mainly grows in northeastern China, Mongolia, Siberia, and other regions. It is used in traditional medicine in the form of dried roots in the East and the West. The main active component of licorice, glycyrrhizin, is known to produce mineralocorticoid effects when consumed chronically, which can lead to apparent mineralocorticoid excess syndrome. Herein, we present the case of a 72-year-old woman who was admitted to the emergency room with severe generalized weakness and difficulty keeping her neck upright, which had developed after daily consumption of licorice-infused water for the past 2 months. Blood tests revealed metabolic alkalosis and severe hypokalemia, and an electrocardiogram showed ventricular bigeminy. The patient was treated with daily potassium and spironolactone supplements, leading to a significant improvement in muscle strength after a week. One week later, the patient was discharged, showing rare ventricular premature contractions on electrocardiography, but with no specific complaints. Chronic licorice ingestion leading to hypokalemia and muscle weakness can be life-threatening, necessitating the discontinuation of the causative agent, close monitoring, and cautious supplementation of potassium and spironolactone as treatment.

Glabridin improves autoimmune disease in Trex1-deficient mice by reducing type I interferon production

BackgroundThe cGAS-STING signaling pathway is an essential section of the natural immune system. In recent years, an increasing number of studies have shown a strong link between abnormal activation of the cGAS-STING signaling pathway, a natural immune pathway mediated by the nucleic acid receptor cGAS, and the development and progression of autoimmune diseases. Therefore, it is important to identify an effective compound to specifically downregulate this pathway for disease.MethodsThe effect of Glabridin (Glab) was investigated in BMDMs and Peripheral blood mononuclear cell (PBMC) by establishing an in vitro model of cGAS-STING signaling pathway activation. An activation model stimulated by DMXAA was also established in mice to study the effect of Glab. On the other hand, we investigated the possible mechanism of action of Glab and the effect of Glab on Trex1-deficient mice.ResultsIn this research, we report that Glab, a major component of licorice, specifically inhibits the cGAS-STING signaling pathway by inhibiting the level of type I interferon and inflammatory cytokines (IL-6 and TNF-α). In addition, Glab has a therapeutic effect on innate immune diseases caused by abnormal cytoplasmic DNA in Trex1-deficient mice. Mechanistically, Glab can specifically inhibit the interaction of STING with IRF3.ConclusionGlab is a specific inhibitor of the cGAS-STING signaling pathway and may be used in the clinical therapy of cGAS-STING pathway-mediated autoimmune diseases.

Identification and quantification of compounds with Angiotensin-converting enzyme inhibitory activity in licorice by UPLC-MS.

Licorice is a famous medicine-food herb for treating cardiovascular diseases in many compound prescriptions. Angiotensin-converting enzyme (ACE) is a key target of cardiovascular diseases. Despite its significance, there is limited scientific investigation regarding the ACE inhibitory effects of licorice. In this study, we used an activity-guided approach with an aggregation-induced emission (AIE) fluorescent probe to identify compounds with ACE-inhibitory activity in licorice. Nine components of licorice were found to have ACE inhibitory activity, in which 46 compounds were identified by using UPLC-QTOF-MS. Seven active compounds were found in this study. Among them, licochalcone B had best ACE inhibitory activity (IC50=0.24μM). Finally, an UPLC-Q-MS method was established to quantify the five major active compounds in three batches of licorice. The findings of this study offer valuable insights into the potential of licorice as a source of ACE inhibitors and its relevance in the development of related products.

Network Pharmacology Combined with Machine Learning to Reveal the Action Mechanism of Licochalcone Intervention in Liver Cancer

There are reports indicating that licochalcones can inhibit the proliferation, migration, and invasion of cancer cells by promoting the expression of autophagy-related proteins, inhibiting the expression of cell cycle proteins and angiogenic factors, and regulating autophagy and apoptosis. This study aims to reveal the potential mechanisms of licochalcone A (LCA), licochalcone B (LCB), licochalcone C (LCC), licochalcone D (LCD), licochalcone E (LCE), licochalcone F (LCF), and licochalcone G (LCG) inhibition in liver cancer through computer-aided screening strategies. By using machine learning clustering analysis to search for other structurally similar components in licorice, quantitative calculations were conducted to collect the structural commonalities of these components related to liver cancer and to identify key residues involved in the interactions between small molecules and key target proteins. Our research results show that the seven licochalcones molecules interfere with the cancer signaling pathway via the NF-κB signaling pathway, PDL1 expression and PD1 checkpoint pathway in cancer, and others. Glypallichalcone, Echinatin, and 3,4,3′,4′-Tetrahydroxy-2-methoxychalcone in licorice also have similar structures to the seven licochalcones, which may indicate their similar effects. We also identified the key residues (including ASN364, GLY365, TRP366, and TYR485) involved in the interactions between ten flavonoids and the key target protein (nitric oxide synthase 2). In summary, we provide valuable insights into the molecular mechanisms of the anticancer effects of licorice flavonoids, providing new ideas for the design of small molecules for liver cancer drugs.

Pharmacological Mechanisms and Adjuvant Properties of Licorice Glycyrrhiza in Treating Gastric Cancer.

Licorice is a remarkable traditional Chinese medicine obtained from the dried root and rhizomes of the Glycyrrhiza genus, and t has been utilized in China for many centuries. It consists of more than 300 compounds that are mainly divided into triterpene saponins, flavonoids, polysaccharides, and phenolic components. The active compounds of licorice have been found to possess multiple biological activities, including antitumor, anti-inflammatory, antiviral, antimicrobial, immunoregulatory, cardioprotective, and neuroprotective functions. In addition to providing a brief overview of licorice's adjuvant properties, this review describes and analyzes the pharmacological mechanisms by which licorice components function to treat gastric cancer. Furthermore, licorice compounds are also found to be potent adjuvant chemotherapy agents, as they can improve the quality of life of cancer patients and alleviate chemotherapy-induced adverse effects.

Licorice metabolite 18β-glycyrrhetinic acid activates G protein-gated inwardly rectifying K+ channels.

Licorice (liquorice) is a common food additive and is used in Chinese medicine. Excess licorice intake can induce atrial fibrillation. Patients with atrial fibrillation possess constitutively activated G protein-gated inwardly rectifying K+ (GIRK) channels. Whether licorice affects GIRK channel activity is unknown. We aimed to clarify the effects of licorice ingredients on GIRK current and the mechanism of action. A major component of licorice, glycyrrhizic acid (GA), and its metabolite, 18β-glycyrrhetinic acid (18β-GA), were tested. We performed electrophysiological recordings in Xenopus oocytes to examine the effects of GA and 18β-GA on various GIRK subunits (Kir 3.1-Kir 3.4), mutagenesis analyses to identify the crucial residues for drug action and motion analysis in cultured rat atrial myocytes to clarify effects of 18β-GA on atrial functions. GA inhibited Kir 3.1-containing channels, while 18β-GA activated all Kir 3.x subunits. A pore helix residue Phe137 in Kir 3.1 was critical for GA-mediated inhibition, and the corresponding Ser148 in Kir 3.2 was critical for 18β-GA-mediated activation. 18β-GA activated GIRK channel in a Gβγ -independent manner, whereas phosphatidylinositol 4,5-bisphosphate (PIP2 ) was essential for activation. Glu236 located at the cytoplasmic pore of Kir 3.2 appeared to be important to interactions with 18β-GA. In rat atrial myocytes, 18β-GA suppressed spontaneous beating via activation of GIRK channels. GA acts as a novel GIRK inhibitor, and 18β-GA acts as a novel GIRK activator. 18β-GA alters atrial function via activation of GIRK channels. This study elucidates the pharmacological activity of licorice ingredients and provides information for drug design.

Inhibition of AKR1Cs by liquiritigenin and the structural basis

In vivo and in vitro studies have confirmed that liquiritigenin (LQ), the primary active component of licorice, acts as an antitumor agent. However, how LQ diminishes or inhibits tumor growth is not fully understood. Here, we report the enzymatic inhibition of LQ and six other flavanone analogues towards AKR1Cs (AKR1C1, AKR1C2 and AKR1C3), which are involved in prostate cancer, breast cancer, and resistance of anticancer drugs. Crystallographic studies revealed AKR1C3 inhibition of LQ is related to its complementarity with the active site and the hydrogen bonds net in the catalytic site formed through C7–OH, aided by its nonplanar and compact structure due to the saturation of the C2C3 double bond. Comparison of the LQ conformations in the structures of AKR1C1 and AKR1C3 revealed the induced-fit conformation changes, which explains the lack of isoform selectivity of LQ. Our findings will be helpful for better understanding the antitumor effects of LQ on hormonally dependent cancers and the rational design of selective AKR1Cs inhibitors.