Phenolic constituents of licorice. II. Structures of licopyranocoumarin, licoarylcoumarin and glisoflavone, and inhibitory effects of licorice phenolics on xanthine oxidase

Desmoarylcoumarin and episoyasapogenol B: two new compounds from Desmodium salicifolium (Poir.) DC (Fabaceae)

A new 3-arylcoumarin, 7-hydroxy-6-(1,1-dimethylallyl)-2',5'-dihydroxy-4'-(3,3dimethylprenyl)-3-arylcoumarin (desmoarylcoumarin) 1, a previously unreported oleanane-type triterpenoid, 3β,22β,23-trihydroxyolean-12-en (episoyasapogenol B) 2, together with five known flavonoids including darbergioidin (3), isoferreirin (4), quercetin (5), vitexin (6), swertizin (7), and one carbohydrate, sucrose (8) were isolated from the methanolic extract of the roots of Desmodium salicifolium. Their structures were elucidated mainly by extensive spectroscopic analysis (1D and 2D) and mass spectrometric (HRFAB-MS) data. The methanolic extract, EtOAc and n-BuOH fractions as well as some isolated compounds were assessed for their antibacterial and antioxidant activities. The EtOAc fraction exhibited moderate activity against Enterococcus faecalis with MIC value of 128 µg/mL. The methanolic extract and the EtOAc fraction displayed DPPH scavenging activity with EC50 values of 5.99 and 2.06 μg/mL, respectively. Compound 1 showed a moderate antibacterial activity against Enterococcus faecalis with a MIC of 16 µg/mL. It also showed moderate DPPH scavenging activity.

Developments in the stereoselective synthesis of benzopyran, benzopyrone and flavonoid based natural product analogues using C-glycosides as an intrinsic chiral synthon

Stereoselective synthesis is essential for propelling mainstream academia toward a relentless pursuit of novel and cutting-edge strategies for constructing molecules with unparalleled precision. Naturally derived benzopyrans, benzopyrones, and flavonoids are an essentially prominent group of oxa-heterocycles, highly significant targets in medicinal chemistry owing to their extensive abundance in biologically active natural products and pharmaceuticals. The molecular complexity and stereoselectivity induced by heterocycles embedded with C-glycosides have attracted considerable interest and emerged as a fascinating area of research for synthetic organic chemists. This present article emphasizes the existing growths in the strategies involving the diastereoselective synthesis of C-glycosylated benzopyrans, benzopyrones, and flavonoids using naturally acquired glycones as chiral synthons.

Pharmacological effects and mechanism of Maxing Shigan decoction in the treatment of Pseudomonas aeruginosa pneumonia

ETHNOPHARMACOLOGICAL RELEVANCE

Maxing Shigan Decoction (MXSG) is a traditional Chinese Medicine effectively used in respiratory infections and bacterial pneumonia. However, the mechanism of MXSG treating acute Pseudomonas aeruginosa (P. aeruginosa) pneumonia is still unclear.

AIM OF THE STUDY

This study aimed to investigate the therapeutic effects of MXSG on acute P. aeruginosa pneumonia and explore its potential mechanisms.

MATERIALS AND METHODS

HPLC-MS analysis was performed to analyze the chemical composition. Antibacterial effects in vitro were evaluated by minimum inhibitory concentration (MIC). Forty-five male BALB/c mice were divided into control group, model group, levofloxacin group, MXSG-L (7.7 g/kg/d), and MXSG-H group (15.4 g/kg/d). Mice were intranasal instillation with P. aeruginosa to induce acute P. aeruginosa pneumonia model. Levofloxacin and MXSG were administered by oral gavage once a day. After 3 days of treatment, the lung index measurement, micro-CT, arterial blood gas analysis, bacteria load determination, and HE staining were performed. Network pharmacological analysis and transcriptome sequencing were employed to predict the potential mechanisms of MXSG on bacterial pneumonia. The expressions of relating genes were detected by immunofluorescence, Western blot, and RT-PCR.

RESULTS

In vitro, MIC of P. aeruginosa is greater than 500 mg/mL. In the treatment of acute P. aeruginosa pneumonia model, MXSG significantly improved body weight loss, lung index, and pulmonary lesions. MXSG treatment also reduced the bacterial load and ameliorated oxygen saturation significantly. Transcriptomes, immunofluorescence, Western blot, and RT-PCR analysis showed MXSG treating acute P. aeruginosa pneumonia through the IL-17 signaling pathway and HIF-1α/IL-6/STAT3 signaling pathway.

CONCLUSIONS

We demonstrated the efficacy and mechanism of MXSG in the treatment of acute P. aeruginosa pneumonia, which provides a scientific basis for its clinical application.

Identification of natural xanthine oxidase inhibitors: Virtual screening, anti-xanthine oxidase activity, and interaction mechanism

Xanthine oxidase (XO) is a crucial target for hyperuricemia treatment(s). Naturally occurred XO inhibitors with minimal toxicity and high efficacy have attracted researchers' attention. With the goal of quickly identifying natural XO inhibitors, an integrated computational screening strategy was constructed by molecular docking and calculating the free energy of binding. Twenty-seven hits were achieved from a database containing 19,377 natural molecules. This includes fourteen known XO inhibitors and four firstly-reported inhibitors (isolicoflavonol, 5,7-dihydroxycoumarin, parvifolol D and clauszoline M, IC50 < 40 μM). Iolicoflavonol (hit 8, IC50 = 8.45 ± 0.68 μM) and 5,7-dihydroxycoumarin (hit 25, IC50 = 10.91 ± 0.71 μM) displayed the great potency as mixed-type inhibitors. Docking study and molecular dynamics simulation revealed that both hits could interact with XO's primarily active site residues ARG880, MOS1328, and ASN768 of XO. Fluorescence spectroscopy studies showed that hit 8 bound to the active cavity region of XO, causing changes in XO's conformation and hydrophobicity. Hits 8 and 25 exhibit favorable Absorption, Distribution, Metabolism, and Excretion (ADME) properties. Additionally, no cytotoxicity against human liver cells was observed at their median inhibition concentrations against XO. Therefore, the present study offers isolicoflavonol and 5,7-dihydroxycoumarin with the potential to be disease-modifying agents for hyperuricemia.

The Electronic Effects of 3-Methoxycarbonylcoumarin Substituents on Spectral, Antioxidant, and Protein Binding Properties

Coumarin derivatives are a class of compounds with pronounced biological activities that depend primarily on the present substituents. Four 3-methoxycarbonylcoumarin derivatives with substituents of different electron-donating/electron-withdrawing abilities (Br, NO₂, OH, and OMe) were investigated structurally by NMR, IR, and UV-VIS spectroscopies and density functional theory methods. The appropriate level of theory (B3LYP-D3BJ/6-311++G(d,p) was selected after comparing similar compounds' experimental and theoretical structural parameters. The natural bond orbital and quantum theory of atoms in molecules were employed to investigate the intramolecular interactions governing stability. The electronic effects of substituents mostly affected the aromatic ring that the substituents are directly attached to. The antioxidant properties were investigated by electron paramagnetic resonance spectroscopy towards HO^•, and the percentages of reduction were between 13% (6-Br) and 23% (6-OMe). The protein binding properties towards transport proteins were assessed by spectrofluorimetry, molecular docking, and molecular dynamics (MD). The experimentally determined binding energies were well reproduced by molecular docking, showing that the spontaneity of ibuprofen binding was comparable to the investigated compounds. The flexibility of HSA in MD simulations depended on the substituents. These results proved the importance of electronic effects for the protein binding affinities and antioxidant properties of coumarin derivatives.

Transcriptome and metabolome analyses of Shatian pomelo (Citrus grandis var. Shatinyu Hort) leaves provide insights into the overexpression of the gibberellin-induced gene CcGASA4

The gibberellic acid (GA)-stimulated Arabidopsis (GASA) gene family is highly specific to plants and plays crucial roles in plant growth and development. CcGASA4 is a member of the GASA gene family in citrus plants; however, the current understanding of its function in citrus is limited. We used CcGASA4-overexpression transgenic citrus (OEGA) and control (CON) plants to study the role of CcGASA4 in Shatian pomelo. The RNA sequencing (RNA-seq) analysis showed that 3,522 genes, including 1,578 upregulated and 1,944 downregulated genes, were significantly differentially expressed in the CON versus OEGA groups. The Gene Ontology enrichment analysis showed that 178 of the differentially-expressed genes (DEGs) were associated with flowers. A Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that the DEGs were enriched in 134 pathways, including "plant-pathogen interaction", "MAPK signaling pathway-plant", "phenylpropane biosynthesis", "plant hormone signal transduction", "phenylalanine, tyrosine and tryptophan biosynthesis", and "flavonoid and flavonol biosynthesis". The most significantly-enriched pathway was "plant-pathogen interaction", in which 203 DEGs were enriched (126 DEGs were upregulated and 78 were downregulated). The metabolome analysis showed that 644 metabolites were detected in the OEGA and CON samples, including 294 differentially-accumulated metabolites (DAMs; 83 upregulated versus 211 downregulated in OEGA compared to CON). The metabolic pathway analysis showed that these DAMs were mainly involved in the metabolic pathways of secondary metabolites, such as phenylpropanoids, phenylalanine, flavone, and flavonol biosynthesis. Thirteen flavonoids and isoflavones were identified as DAMs in OEGA and CON. We also discovered 25 OEGA-specific accumulated metabolites and found 10 that were associated with disease resistance. CcGASA4 may therefore play a functional role in activating the expression of MAPK signaling transduction pathway and disease resistance genes, inhibiting the expression of auxin- and ethylene-related genes, and activating or inhibiting the expression of brassinosteroid biosynthesis- and abscisic acid-related genes. CcGASA4 may also play a role in regulating the composition and abundance of flavonoids, isoflavones, amino acids, purines, and phenolic compounds. This study provides new insights into the molecular mechanisms of action of CcGASA4 in citrus plants.

Investigating the effects and mechanisms of Erchen Decoction in the treatment of colorectal cancer by network pharmacology and experimental validation

Objective: Erchen Decoction (ECD), a well-known traditional Chinese medicine, exerts metabolism-regulatory, immunoregulation, and anti-tumor effects. However, the action and pharmacological mechanism of ECD remain largely unclear. In the present study, we explored the effects and mechanisms of ECD in the treatment of CRC using network pharmacology, molecular docking, and systematic experimental validation.

Methods: The active components of ECD were obtained from the TCMSP database and the potential targets of them were annotated by the STRING database. The CRC-related targets were identified from different databases (OMIM, DisGeNet, GeneCards, and DrugBank). The interactive targets of ECD and CRC were screened and the protein-protein interaction (PPI) networks were constructed. Then, the hub interactive targets were calculated and visualized from the PPI network using the Cytoscape software. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed. In addition, the molecular docking was performed. Finally, systematic in vitro, in vivo and molecular biology experiments were performed to further explore the anti-tumor effects and underlying mechanisms of ECD in CRC.

Results: A total of 116 active components and 246 targets of ECD were predicted based on the component-target network analysis. 2406 CRC-related targets were obtained from different databases and 140 intersective targets were identified between ECD and CRC. 12 hub molecules (STAT3, JUN, MAPK3, TP53, MAPK1, RELA, FOS, ESR1, IL6, MAPK14, MYC, and CDKN1A) were finally screened from PPI network. GO and KEGG pathway enrichment analyses demonstrated that the biological discrepancy was mainly focused on the tumorigenesis-, immune-, and mechanism-related pathways. Based on the experimental validation, ECD could suppress the proliferation of CRC cells by inhibiting cell cycle and promoting cell apoptosis. In addition, ECD could inhibit tumor growth in mice. Finally, the results of molecular biology experiments suggested ECD could regulate the transcriptional levels of several hub molecules during the development of CRC, including MAPKs, PPARs, TP53, and STATs.

Conclusion: This study revealed the potential pharmacodynamic material basis and underlying molecular mechanisms of ECD in the treatment of CRC, providing a novel insight for us to find more effective anti-CRC drugs.

Synthesis and anticancer evaluation of some coumarin and azacoumarin derivatives

Coumarin and its nitrogen analogue 1-aza coumarin are a class of lactones and lactams, respectively, which are indispensable heterocyclic units to both chemists and biochemists. 1-Aza coumarin derivatives, which ultimately metabolize as the corresponding 8-hydroxy coumarins in the biological system are therefore found to be very good anti-inflammatory, anti-cancer, and analgesic agents. A series of hybrid substituted coumarin and azacoumarin-3-carboxylic acid derivatives (8-methoxycoumarin-3-carboxylic acid (4a), 8-methoxyazacoumarin-3-carboxylic acid (4b), 5-bromo-8-methoxycoumarin-3-carboxylic acid (5a), 5-bromo-8-methoxyazacoumarin-3-carboxylic acid (5b), 2-acetoxy-5-bromo-8-methoxyquinoline-3-carboxylic acid (6), and 5,7-di(phenylazo)-8-methoxycoumarin-3-carboxylic acid (7) were synthesized and structurally proved using spectral and elemental analysis data. Substituted coumarin-3-carboxylic acid (4a and 5a) and Substituted azacoumarin-3-carboxylic acid (4b, 5b and 6) were tested for their in vitro cytotoxic activity against MCF-7 and HepG-2 cell lines.

Naturally occurring prenylated chalcones from plants: structural diversity, distribution, activities and biosynthesis

Covering: up to July 2020Naturally occurring chalcones carrying up to three modified or unmodified C5-, C10-, and C15-prenyl moieties on both rings A and B as well as at the α- and β-carbons are widely distributed in plants of the families of Fabaceae, Moraceae, Zingiberaceae and Cannabaceae. Xanthohumol and isobavachalcone being the most investigated representatives, exhibit diverse and remarkable biological and pharmacological activities. The present review deals with their structural characters, biological activities and occurrence in the plant kingdom. Biosynthesis of prenylated chalcones and metabolism of xanthohumol are also discussed.

Natural Products and Extracts as Xantine Oxidase Inhibitors - A Hope for Gout Disease?

Xanthine oxidase (EC 1.17.3.2) (XO) is one of the main enzymatic sources that create reactive oxygen species (ROS) in the living system. It is a dehydrogenase enzyme that performs electron transfer to nicotinamide adenine dinucleotide (NAD+), while oxidizing hypoxanthin, which is an intermediate compound in purine catabolism, first to xanthine and then to uric acid. XO turns into an oxidant enzyme that oxidizes thiol groups under certain stress conditions in the tissue. The last metabolic step, in which hypoxanthin turns into uric acid, is catalyzed by XO. Uric acid, considered a waste product, can cause kidney stones and gouty-type arthritis as it is crystallized, when present in high concentrations. Thus, XO inhibitors are one of the drug classes used against gout, a purine metabolism disease that causes urate crystal storage in the joint and its surroundings caused by hyperuricemia. Urate-lowering therapy includes XO inhibitors that reduce uric acid production as well as uricosuric drugs that increase urea excretion. Current drugs that obstruct uric acid synthesis through XO inhibition are allopurinol, febuxostat, and uricase. However, since the side effects, safety and tolerability problems of some current gout medications still exist, intensive research is ongoing to look for new, effective, and safer XO inhibitors of natural or synthetic origins for the treatment of the disease. In the present review, we aimed to assess in detail XO inhibitory capacities of pure natural compounds along with the extracts from plants and other natural sources via screening Pubmed, Web of Science (WoS), Scopus, and Google Academic. The data pointed out to the fact that natural products, particularly phenolics such as flavonoids (quercetin, apigenin, and scutellarein), tannins (agrimoniin and ellagitannin), chalcones (melanoxethin), triterpenes (ginsenoside Rd and ursolic acid), stilbenes (resveratrol and piceatannol), alkaloids (berberin and palmatin) have a great potential for new XO inhibitors capable of use against gout disease. In addition, not only plants but other biological sources such as microfungi, macrofungi, lichens, insects (silk worms, ants, etc) seem to be the promising sources of novel XO inhibitors.

Pharmacological Activities of Coumarin Compounds in Licorice: A Review

Licorice is a traditional medicine commonly used in China and many other countries. Over the last 50 years, the structure and pharmacological effects of coumarin compounds in licorice have been investigated. However, a comprehensive review of the literature summarizing current trends is currently lacking. Thus, the aim of the present review is to provide an up-to-date summary of the scientific literature regarding the pharmacological effects of coumarin compounds in licorice, thereby laying the foundation for further research and optimal utilization of licorice. We retrieved 111 articles on the coumarin components of licorice and their potential pharmacological effects, based on titles, keywords, and abstracts from databases (including PubMed and Web of Science). Glycycoumarin, isoglycycoumarin, licoarylcoumarin, licopyranocoumarin, glycyrin, isotrifoliol, glycyrol, and glycyrurol have been investigated for their anticancer, hepatoprotective, antispasmodic, immunosuppressive, anti-inflammatory, and antibacterial properties, and use as therapeutic agents in metabolic syndrome, thereby demonstrating their potential for clinical applications. Future research should further explore the pharmacological mechanisms of action of coumarin compounds, including their antibacterial activities. Investigations into the pharmacological activities of different glycycoumarin isomers might open new research frontiers.

Licochalcone A Selectively Resensitizes ABCG2-Overexpressing Multidrug-Resistant Cancer Cells to Chemotherapeutic Drugs

The overexpression of the ATP-binding cassette (ABC) transporter ABCG2 has been linked to clinical multidrug resistance in solid tumors and blood cancers, which remains a significant obstacle to successful cancer chemotherapy. For years, the potential modulatory effect of bioactive compounds derived from natural sources on ABCG2-mediated multidrug resistance has been investigated, as they are inherently well tolerated and offer a broad range of chemical scaffolds. Licochalcone A (LCA), a natural chalcone isolated from the root of Glycyrrhiza inflata, is known to possess a broad spectrum of biological and pharmacological activities, including pro-apoptotic and antiproliferative effects in various cancer cell lines. In this study, the chemosensitization effect of LCA was examined in ABCG2-overexpressing multidrug-resistant cancer cells. Experimental data demonstrated that LCA inhibits the drug transport function of ABCG2 and reverses ABCG2-mediated multidrug resistance in human multidrug-resistant cancer cell lines in a concentration-dependent manner. Results of LCA-stimulated ABCG2 ATPase activity and the in silico docking analysis of LCA to the inward-open conformation of human ABCG2 suggest that LCA binds ABCG2 in the transmembrane substrate-binding pocket. This study provides evidence that LCA should be further evaluated as a modulator of ABCG2 in drug combination therapy trials against ABCG2-expressing drug-resistant tumors.

Anti-acne vulgaris effect including skin barrier improvement and 5α-reductase inhibition by tellimagrandin I from Carpinus tschonoskii

BACKGROUND

Carpinus tschonoskii (CT) has been previously studied for various activities in the improvement of skin diseases. In the present study, we examined the in vitro anti-acne vulgaris (AV) effect of CT leaves (CTL) and tellimagrandin I (TI), one of the main ellagitannins from CT, including skin barrier improvement and 5α-reductase inhibitory activity.

METHODS

To test the anti-AV activities of CTL and TI, firstly, anti-oxidative and anti-inflammatory activities including DPPH radical scavenging activity, nitric oxide (NO) inhibitory activity, and cytokines [interleukin (IL)-6 and IL-8] were tested. Skin barrier improvement experiments were tested using developing cornified envelope (CE) formation, and filaggrin mRNA expression level was determined by RT-PCR. The 5α-reductase inhibitory activity was determined by measuring the testosterone levels in rat liver microsomes.

RESULTS

CTL and TI showed potent anti-oxidative activity and anti-inflammatory activities. Especially, the cytokine production inhibitory activities of TI were found to be similar to the positive control, epigallocatechin gallate (EGCG). CTL and TI enhanced the CE formation and filaggrin mRNA expression levels and showed potent activities compared to that in the positive control, 1.5 mM Ca²⁺. In additionally, CTL and TI showed 5α-reductase inhibitory activities in a dose-dependent manner.

CONCLUSION

The results showed that CTL and TI inhibit AV endogenous factors such as 5α-reductase and inflammatory cytokines and affect exogenous factors such as developing skin barrier function (CE and filaggrin levels). Therefore, CTL and TI may be plant-derived agent, promising in the treatment of acne vulgaris.

Isolation, structural elucidation and in vitro hepatoprotective activity of flavonoids from Glycyrrhiza uralensis

Two new flavonoid glycosides, 2',4'-dihydroxydihydrochalcone-4-O-β-D-glucopyranoside (1) and medicarpin-3-O-β-D-apiofuranosyl (1 → 2)-β-D-glucopyranoside (2), together with 34 known flavonoids were isolated from the 75% EtOH extract of the dried roots of Glycyrrhiza uralensis Fisch. Their structures were elucidated on the basis of spectroscopic analyses. The flavonoids were classified into ten sub-types, namely, dihydrochalcone (1), pterocarpans (2-4), flavones (5-6), flavanones (7-11), chalcones (12-15), retro-chalcones (16-18), isoflavans (19-21), isoflavones (22-28), 3-arylcoumarins (29-30), and coumestans (31-36). The isolated flavonoids were evaluated for in vitro hepatoprotective activity against D-galactosamine-induced toxicity in human hepatoma HepG2 cells.

Mechanisms of action of cytotoxic phenolic compounds from Glycyrrhiza iconica roots

BACKGROUND

Glycyrrhiza (licorice) species are rich in bioactive secondary metabolites and their roots are used traditionally for the treatment of several diseases. In recent years, secondary metabolites of licorice are gaining popularity, especially due to their significant cytotoxic and antitumor effects. However, Glycyrrhiza iconica, an endemic species to Turkey, was not investigated in terms of its anticancer secondary metabolites previously.

PURPOSE

This study aimed to isolate the cytotoxic compounds from G. iconica through bioactivity-guided fractionation and to elucidate mechanisms of action of the most potent compounds.

METHODS

Total MeOH extract and CHCl₃, EtOAc, n-buOH and rH₂O subextracts were prepared from G. iconica roots. Sequential chromatographic techniques were conducted for the isolation studies. The chemical structures of the isolates were established based on NMR and HR-MS analysis. Sulforhodamine B assay was used to evaluate the cytotoxic activity of extracts, main fractions as well as isolates against hepatocellular (Huh7), breast (MCF7) and colorectal (HCT116) cancer cell lines. The mechanisms underlying the cytotoxicity of the most active compounds in Huh7 cells were elucidated by using Hoechst staining, Fluorescence-activated cell sorting and Western blot assays.

RESULTS

A new dihydrochalcone, iconichalcone (1) along with 15 known phenolic compounds were isolated from the active CHCl₃, EtOAc and n-buOH subextracts. Compounds 2-5, 7-16 were found to be responsible for the in vitro cytotoxic activity of G. iconica against all tested cancer cell lines with IC₅₀ values ranging from 2.4 to 33 µM. Amongst these compounds, licoricidin (10), dehydroglyasperin C (12), iconisoflaven (13) and 1-methoxyficifolinol (15) were found to be the most active compounds according to SRB and real time bioactivity assays and submitted to further mechanistic investigations in Huh7 cells. Compounds 10, 12, 13 and 15 caused accumulation of cells in different phases of cell cycle. Moreover, 10, 12, 13 and 15 induced apoptosis through caspase activation. Besides, 12 showed activation of p53 expression and thus G₂/M arrest as well as a condensed nuclei, established very promising results.

CONCLUSION

The results demonstrated that the aforementioned compounds, particularly 12 could be potential lead molecules for anticancer drug development that deserve further in vivo and clinical investigations.

Phenolic compounds from cultivated Glycyrrhiza uralensis and their PD-1/PD-L1 inhibitory activities

One new compound (1) and fifteen known phenolic compounds (2-16) were isolated and identified from the roots and rhizomes of Glycyrrhiza uralensis, including ten flavonoids, four coumarins, and two benzofurans compounds. Their structures were identified by NMR and MS analysis. Most of these compounds showed weak PD-1/PD-L1 inhibitory activities with the inhibition ratios from 30 to 65% at 100 uM. To our knowledge, it is the first time that their PD-1/PD-L1 inhibition activities were reported.

Synthesis and Characterization of 3-(1-((3,4-Dihydroxyphenethyl)amino)ethylidene)-chroman-2,4-dione as a Potential Antitumor Agent

The newly synthesized coumarin derivative with dopamine, 3-(1-((3,4-dihydroxyphenethyl)amino)ethylidene)-chroman-2,4-dione, was completely structurally characterized by X-ray crystallography. It was shown that several types of hydrogen bonds are present, which additionally stabilize the structure. The compound was tested in vitro against different cell lines, healthy human keratinocyte HaCaT, cervical squamous cell carcinoma SiHa, breast carcinoma MCF7, and hepatocellular carcinoma HepG2. Compared to control, the new derivate showed a stronger effect on both healthy and carcinoma cell lines, with the most prominent effect on the breast carcinoma MCF7 cell line. The molecular docking study, obtained for ten different conformations of the new compound, showed its inhibitory nature against CDK_S protein. Lower inhibition constant, relative to one of 4-OH-coumarine, proved stronger and more numerous interactions with CDK_S protein. These interactions were carefully examined for both parent molecule and derivative and explained from a structural point of view.

Direct detection of surface localized specialized metabolites from Glycyrrhiza lepidota (American licorice) by leaf spray mass spectrometry

Leaf spray-MS minimizes tissue manipulation by effectively and quickly assessing in vivo specialized metabolites from intact plant tissue surfaces, including trichome metabolites. Intact leaves of Glycyrrhiza lepidota Pursh. (American licorice) were analyzed by direct electrospray leaf spray-MS, an ambient ionization technique. Comparison of metabolites detected by leaf spray-MS to those from LC-MS of bulk tissue and trichome enriched extracts showed dramatic differences. Leaf spray-MS results suggest that in specific situations this approach could complement traditional LC-MS analysis of bulk extracts. Leaf spray-MS as a metabolomics technique eliminates sample pretreatment and preparation allowing for rapid sampling in real time of living intact tissues. Specialized metabolites on the surface of tissues such as glandular trichomes metabolites are detected by leaf spray-MS.

The prenylated phenolic natural product isoglycycoumarin is a highly selective probe for human cytochrome P450 2A6

Prenylated phenolic compounds are an important class of bioactive natural products. One major in vivo metabolic pathway of these compounds is hydroxylation at terminal methyl of the isoprenyl group. This study aims to identify the P450 isozyme catalyzing this metabolic reaction. In human liver microsomes, 16 out of 24 screened compounds could be metabolized into their hydroxylated derivatives. Chemical inhibition assays using 11 isozyme specific inhibitors indicated the hydroxylation reactions of 12 compounds were primarily catalyzed by cytochrome P450 2A6 (CYP2A6). In particular, CYP2A6 was the major enzyme participating in the metabolism of isoglycycoumarin (IGCM). The product of IGCM was obtained and identified as licopyranocoumarin (4″-hydroxyl isoglycycoumarin) using NMR spectroscopic analysis. The K_m values for human liver microsomes and recombinant human CYP2A6 were 7.98 and 10.14μM, respectively. According to molecular docking analysis, the catalytic mechanism may involve cyclized isoprenyl group of IGCM entering the active cavity of CYP2A6. These results demonstrate that IGCM could serve as an ideal isozyme selective probe to evaluate CYP2A6 activities.

Licocoumarone isolated from Glycyrrhiza uralensis selectively alters LPS-induced inflammatory responses in RAW 264.7 macrophages

The effects of licocoumarone (LC) isolated from Glycyrrhiza uralensis were studied in LPS-stimulated RAW 264.7 macrophages. Our study demonstrated that LC dose-dependently attenuated LPS-induced NO production by down-regulating iNOS expression. Additionally, the treatment with LC inhibited LPS-induced expression of cytokines including IL-1β, IL-6 and IL-10, but not TNF-α, at both mRNA and protein levels. Similar suppressive effects of LC were observed on LPS-stimulated murine peritoneal macrophages as well. Furthermore, LC significantly reduced LPS-stimulated NF-κB activation by inhibition of IκBα degradation and p65 phosphorylation. The results from NF-κB-luc reporter gene assay further support the inhibitory effect of LC on NF-κB activation. Further studies showed that LC also interfered with the MAPKs and STAT3 signaling pathways, which are typical inflammatory signaling pathways triggered by LPS. Taken together, these results show that LC attenuates LPS-induced cytokine gene expression in RAW 264.7 macrophages through mechanisms that involve NF-κB, MAPKs and STAT3 signaling pathways, but the pattern of inhibition differs from that of a global immunosuppresant. Our study indicates that LC is a functional constituent of Glycyrrhiza uralensis with potential implications in infectious and immune-related diseases.

Anti-Melanogenic Effect of Oenothera laciniata Methanol Extract in Melan-a Cells

We evaluated the antioxidant activity and anti-melanogenic effects of Oenothera laciniata methanol extract (OLME) in vitro by using melan-a cells. The total polyphenol and flavonoid content of OLME was 66.3 and 19.0 mg/g, respectively. The electron-donating ability, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical-scavenging activity, and superoxide dismutase (SOD)-like activity of OLME (500 μg/mL) were 94.5%, 95.6%, and 63.6%, respectively. OLME and arbutin treatment at 50 μg/mL significantly decreased melanin content by 35.5% and 14.2%, respectively, compared to control (p < 0.05). OLME and arbutin treatment at 50 μg/mL significantly inhibited intra-cellular tyrosinase activity by 22.6% and 12.6%, respectively, compared to control (p < 0.05). OLME (50 μg/mL) significantly decreased tyrosinase, tyrosinase-related protein-1 (TRP-1), TRP-2, and microphthalmia-associated transcription factor-M (MITF-M) mRNA expression by 57.1%, 67.3%, 99.0%, and 77.0%, respectively, compared to control (p < 0.05). Arbutin (50 μg/mL) significantly decreased tyrosinase, TRP-1, and TRP-2 mRNA expression by 24.2%, 42.9%, and 48.5%, respectively, compared to control (p < 0.05). However, arbutin (50 μg/mL) did not affect MITF-M mRNA expression. Taken together, OLME showed a good antioxidant activity and anti-melanogenic effect in melan-a cells that was superior to that of arbutin, a well-known skin-whitening agent. The potential mechanism underlying the anti-melanogenic effect of OLME was inhibition of tyrosinase activity and down-regulation of tyrosinase, TRP-1, TRP-2, and MITF-M mRNA expression.

Synergic effect of combination of glycyrol and fluconazole against experimental cutaneous candidiasis due to Candida albicans

In this study, we investigated the anti-fungal activity of glycyrol, a coumarine isolated from licorice (Glycyrrhizae Radix), in a murine model of cutaneous candidiasis caused by Candida albicans. Compared to the infected sites, located on the mice's back, of the untreated control mice, the infected sites treated with glycyrol had reduced CFU (colony forming unit) values up to 60 and 85.5 % at 20 and 40 μg/mouse of glycyrol, respectively (P < 0.01). The antifungal activity of glycyrol was synergistically increased when glycyrol (10 μg/mouse) was combined with fluconazole (10 μg/mouse), demonstrating that the combination therapy is approximately 4 times more effective than fluconazole alone at 20 μg/mouse (P < 0.01). Additionally, the combination activity was 1.65 times greater than the antifungal activity of fluconazole alone at 40 μg/mouse (P < 0.05). In seeking glycyrol's antifungal mechanism, we determined that glycyrol inhibited hyphal induction and cell wall adherence of C. albicans. Thus, it is very likely that, by damaging the cell wall, glycyrol helps fluconazole invade C. albicans more readily and attack fluconazole's target in the fungus membrane. In summary, our data indicate that glycyrol may contribute to the development of a novel agent that possesses antifungal activity against cutaneous candidiasis.

Glycyrrhiza glabra

Liquorice foliage

Chemical biology of compounds obtained from screening using disease models

Bioactive compounds are extremely powerful tools for studying biological systems because they can rapidly, conditionally, often reversibly, and dose-dependently modulate the biological function of living cells. Moreover, they are expected to be drug seeds for chemotherapy of several diseases. Two approaches are used to find and obtain bioactive compounds, namely, molecular-target-based screening and phenotypic screening. Through phenotypic screening that mimics tumor metastasis, multi-drug resistance, and Parkinson's disease, we identified several compounds that inhibit cancer cell migration, anti-apoptotic function of Bcl-2/Bcl-xL, and neuronal cell death. By using MEK inhibitor that was developed by target-based screening, we discovered that MEK inhibitor selectively induces apoptosis in tumor cells with β-catenin mutation. Using target-based screening, we identified arabilin, a novel androgen antagonist. In this review, we introduce our recent studies on the identification of bioactive compounds by phenotypic screening and by target-based screening for drug-seed discovery.

Structures of new phenolics isolated from licorice, and the effectiveness of licorice phenolics on vancomycin-resistant Enterococci

Licorice, which is the underground part of Glycyrrhiza species, has been used widely in Asian and Western countries as a traditional medicine and as a food additive. Our continuous investigation on the constituents of roots and stolons of Glycyrrhiza uralensis led to the isolation of two new phenolics, in addition to 14 known compounds. Structural studies including spectroscopic and simple chemical derivatizations revealed that both of the new compounds had 2-aryl-3-methylbenzofuran structures. An examination of the effectiveness of licorice phenolics obtained in this study on vancomycin-resistant strains Enterococcus faecium FN-1 and Enterococcus faecalis NCTC12201 revealed that licoricidin showed the most potent antibacterial effects against both of E. faecalis and E. faecium with a minimum inhibitory concentration (MIC) of 1.9 × 10-5 M. 8-(γ,γ-Dimethylallyl)-wighteone, isoangustone A, 3'-(γ,γ-dimethylallyl)-kievitone, glyasperin C, and one of the new 3-methyl-2-phenylbenzofuran named neoglycybenzofuran also showed potent anti-vancomycin-resistant Enterococci effects (MIC 1.9 × 10-5-4.5 × 10-5 M for E. faecium and E. faecalis). The HPLC condition for simultaneous detection of the phenolics in the extract was investigated to assess the quality control of the natural antibacterial resource, and quantitative estimation of several major phenolics in the extract with the established HPLC condition was also performed. The results showed individual contents of 0.08%-0.57% w/w of EtOAc extract for the major phenolics in the materials examined.

Identification of licopyranocoumarin and glycyrurol from herbal medicines as neuroprotective compounds for Parkinson's disease

In the course of screening for the anti-Parkinsonian drugs from a library of traditional herbal medicines, we found that the extracts of choi-joki-to and daio-kanzo-to protected cells from MPP⁺-induced cell death. Because choi-joki-to and daio-kanzo-to commonly contain the genus Glycyrrhiza, we isolated licopyranocoumarin (LPC) and glycyrurol (GCR) as potent neuroprotective principals from Glycyrrhiza. LPC and GCR markedly blocked MPP⁺-induced neuronal PC12D cell death and disappearance of mitochondrial membrane potential, which were mediated by JNK. LPC and GCR inhibited MPP⁺-induced JNK activation through the suppression of reactive oxygen species (ROS) generation, thereby inhibiting MPP⁺-induced neuronal PC12D cell death. These results indicated that LPC and GCR derived from choi-joki-to and daio-kanzo-to would be promising drug leads for PD treatment in the future.

Structures of two new flavonoids and effects of licorice phenolics on vancomycin-resistant Enterococcus species

Since our previous study revealed that several licorice phenolics have antibacterial effects on methicillin-resistant Staphylococcus aureus (MRSA), and suppressive effects on the oxacillin resistance of MRSA, we further investigated effectiveness of licorice constituents on vancomycin-resistant Enterococcus (VRE) bacteria, and purified 32 phenolic compounds. Two flavonoids among them were characterized structurally, and identified their structures as demethylglycyrol (31) and 5,7-di-O-methylluteone (32), respectively. Examination of antibacterial effects of licorice phenolics showed that 3-arylcoumarins such as licoarylcoumarin (9) and glycycoumarin (26), and 2-arylcoumarones such as gancaonin I (17), have moderate to potent antibacterial effects on the VRE strains used in this study.

Isoflavonoids and coumarins from Glycyrrhiza uralensis: antibacterial activity against oral pathogens and conversion of isoflavans into isoflavan-quinones during purification

Phytochemical investigation of a supercritical fluid extract of Glycyrrhiza uralensis has led to the isolation of 20 known isoflavonoids and coumarins, and glycycarpan (7), a new pterocarpan. The presence of two isoflavan-quinones, licoriquinone A (8) and licoriquinone B (9), in a fraction subjected to gel filtration on Sephadex LH-20 is due to suspected metal-catalyzed oxidative degradation of licoricidin (1) and licorisoflavan A (2). The major compounds in the extract, as well as 8, were evaluated for their ability to inhibit the growth of several major oral pathogens. Compounds 1 and 2 showed the most potent antibacterial activities, causing a marked growth inhibition of the cariogenic species Streptococcus mutans and Streptococcus sobrinus at 10 μg/mL and the periodontopathogenic species Porphyromonas gingivalis (at 5 μg/mL) and Prevotella intermedia (at 5 μg/mL for 1 and 2.5 μg/mL for 2). Only 1 moderately inhibited growth of Fusobacterium nucleatum at the highest concentration tested (10 μg/mL).

Bioassay-guided Isolation and Quantification of the α-Glucosidase Inhibitory Compound, Glycyrrhisoflavone, from Glycyrrhiza uralensis

The EtOAc extract of the roots of Glycyrrhiza uralensis exhibited α-glucosidase inhibitory activity. Bioassay-guided fractionation resulted in the isolation of an active prenylflavonoid, glycyrrhisoflavone. Its structure was elucidated by NMR and MS analyses. A simple method to prepare glycyrrhisoflavone from the 95% EtOH extract of the roots of G. uralensis was developed by combination of Diaion HP-20 column chromatography (CC), silica gel CC, and preparative HPLC. An HPLC-PDA method was developed for quantitative determination of glycyrrhisoflavone in the roots of G. uralensis. The sample was extracted with MeOH and analyzed using a reversed-phase column with isocratic elution with CH3CN-H2O (0.06% trifluoroacetic acid) (42:58) at a flow rate of 1.2 mL/min, a column temperature of 40°C, and a detection wavelength of 260 nm. The method allowed the determination of glycyrrhisoflavone in the concentration range of 5-500 μg/mL. The relative standard deviation values of the precision and repeatability were 0.3% and 2.0%, respectively. The limits of detection and quantification were 0.5 μg/mL and 5 μg/mL, respectively. The relative recovery rate was 100.2 ± 1.8%. Based on the validation results, the HPLC determination method was found to be precise, accurate, and time conservative. This method was applied successfully to nine different root samples of G. uralensis. The amounts of glycyrrhisoflavone in these samples were 15-93 mg/100 g of dried powdered plant material.

Ebenfurans IV-VIII from Onobrychis ebenoides: evidence that C-prenylation is the key determinant of the cytotoxicity of 3-formyl-2-arylbenzofurans

Phytochemical investigation of a methanol extract of Onobrychis ebenoides yielded five new 3-formyl-2-arylbenzofurans, namely, ebenfurans IV-VIII (1-5), together with the known compounds ebenfurans I, II (6), and III (7). Only 1 and 7 exhibited growth inhibitory activity against MCF-7 and Ishikawa cells, suggesting that the prenyl moiety at position C-5 is the key determinant of the cytotoxic activity of this group of compounds.