High-Resolution 1H and 13C NMR of Glycyrrhizic Acid and Its Esters

In vitro and in silico investigation of glycyrrhizic acid encapsulated zein nanoparticles: A synergistic targeted drug delivery approach for breast cancer

This study presents an innovative approach for targeted drug delivery through the development of Glycyrrhizic acid-loaded zein nanoparticles (GA-LNPs) as a proficient carrier system. The juxtaposition of zein, a hydrophobic biological macromolecule as a protein carrier, and Glycyrrhizic acid (GA), a hydrophilic therapeutic compound, exemplifies the adaptability of hydrocolloids within cutting-edge drug delivery systems. The characterization and functional traits of research encompass multifaceted analyses of natural macromolecules, which elucidate the homogeneous and spherical morphology of GA-LNPs with an average size of 170.49 nm. The controlled drug release profile of GA, orchestrated under simulated gastrointestinal conditions, adheres to diffusion-based Higuchi kinetics, reflecting the controlled release of the natural macromolecules. The intermolecular interactions among Zein, GA, and cross-linker EDC, facilitated through molecular dynamics simulations, fortify the structural integrity of the encapsulation matrix. In Vitro studies revealed enhanced cellular uptake of GA-LNPs in MCF-7 breast cancer cells. This cellular internalization was further confirmed through cytotoxicity assessments using MTT and apoptosis assays (fluorescence microscopy), which demonstrated the prominent anticancer effects of GA-LNPs on MCF-7 in time/dose-dependent manner. The successful formulation of GA-LNPs, coupled with their sustained release and potent anticancer properties, makes them a potential platform for advanced targeted therapeutic strategies in biomedical applications.

Potential of glycyrrhizic and glycyrrhetinic acids against influenza type A and B viruses: A perspective to develop new anti-influenza compounds and drug delivery systems

Despite the recent dynamic development of medicine, influenza is still a significant epidemiological problem for people around the world. The growing resistance of influenza viruses to currently available antiviral drugs makes it necessary to search for new compounds or drug forms with potential high efficacy against human influenza A and B viruses. One of the methods of obtaining new active compounds is to chemically modify privileged structures occurring in the natural environment. The second solution, that is gaining more and more interest, is the use of modern drug carriers, which significantly improve physicochemical and pharmacokinetic parameters of the transported substances. Molecules known from the earliest times for their numerous therapeutic properties are glycyrrhizinic acid (GA) and glycyrrhetinic acid (GE). Both compounds constitute the main active agents of the licorice (Glycyrrhiza glabra, Leguminosae) root and, according to a number of scientific reports, show antiviral properties against both DNA and RNA viruses. The above information prompted many scientific teams around the world to obtain and test in vitro and/or in vivo new synthetic GA and GE derivatives against influenza A and B viruses. Similarly, in recent years, a significant amount of GA and GE-based drug delivery systems (DDS) such as nanoparticles, micelles, liposomes, nanocrystals, and carbon dots has been prepared and tested for antiviral activity, including those against influenza A and B viruses. This work systematizes the attempts undertaken to study the antiviral activity of new GA and GE analogs and modern DDS against clinically significant human influenza viruses, at the same time indicating the directions of their further development.

Is 18α-Glycyrrhizin a real natural product? Improved preparation of 18α-Glycyrrhizin from 18β-Glycyrrhizin as a positive standard for HPLC analysis of licorice extracts

18α-Glycyrrhizin is an epimer of 18β-glycyrrhizin, a major component of licorice (Glycyrrhiza sp.), which is widely used as a traditional medicine. Whether 18α-glycyrrhizin is a real natural product has been debated in the long history of glycyrrhizin chemistry because 18β-glycyrrhizin is epimerizable to a more thermodynamically stable 18α-glycyrrhizin under aqueous alkali conditions. We improved the preparation of 18α-glycyrrhizin from 18β-glycyrrhizin by successive epimerization reactions of 18β-glycyrrhizin, trimethyl esterification of the resulting epimerized mixture, and alkaline hydrolysis of a purified 18α-glycyrrhizin trimethyl ester. Approaches to the possible presence of 18α-glycyrrhizin in licorice extracts by HPLC using synthetic 18α-glycyrrhizin as a positive standard strongly suggested that 18α-glycyrrhizin could naturally exist as a minor congener of glycyrrhizin derivatives in Glycyrrhiza species.

Synthesis of Glycyrrhizic Acid Conjugates with Amino-Acid Methyl Esters and their Ability to Stimulate Antibody Genesis in Mice

Conjugates of glycyrrhizic acid (GA) with methyl esters of L-amino acids (valine, methionine, and glutamic acid) containing the amino-acid residues in the carbohydrate moiety of the glycoside were synthesized using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide. The resulting GA conjugates at a dose of 2 mg/kg stimulated a primary immune response (production of antibody-forming cells, AFCs) in outbred mice by 1.6 - 3 times as compared with the control. The conjugate of GA with Glu(OMe)₂ stimulated antibody genesis in outbred mice 1.7 times more efficiently than N-acetylmuramyl dipeptide and showed a stimulating effect on AFC production in the spleen of CBA mice.

Indole- and Pyrazole-Glycyrrhetinic Acid Derivatives as PTP1B Inhibitors: Synthesis, In Vitro and In Silico Studies

Regulating insulin and leptin levels using a protein tyrosine phosphatase 1B (PTP1B) inhibitor is an attractive strategy to treat diabetes and obesity. Glycyrrhetinic acid (GA), a triterpenoid, may weakly inhibit this enzyme. Nonetheless, semisynthetic derivatives of GA have not been developed as PTP1B inhibitors to date. Herein we describe the synthesis and evaluation of two series of indole- and N-phenylpyrazole-GA derivatives (4a-f and 5a-f). We measured their inhibitory activity and enzyme kinetics against PTP1B using p-nitrophenylphosphate (pNPP) assay. GA derivatives bearing substituted indoles or N-phenylpyrazoles fused to their A-ring showed a 50% inhibitory concentration for PTP1B in a range from 2.5 to 10.1 µM. The trifluoromethyl derivative of indole-GA (4f) exhibited non-competitive inhibition of PTP1B as well as higher potency (IC₅₀ = 2.5 µM) than that of positive controls ursolic acid (IC₅₀ = 5.6 µM), claramine (IC₅₀ = 13.7 µM) and suramin (IC₅₀ = 4.1 µM). Finally, docking and molecular dynamics simulations provided the theoretical basis for the favorable activity of the designed compounds.

Preparative Separation and Purification of Liquiritin and Glycyrrhizic Acid from Glycyrrhiza uralensis Fisch by High-Speed Countercurrent Chromatography

The technique of high-speed countercurrent chromatography (HSCCC) was applied to the preparative isolation and purification of liquiritin and glycyrrhizic acid from a crude extract of Glycyrrhiza uralensis Fisch for the first time. Using single factor and orthogonal design experiments, the best extraction conditions were 70% ethanol, 1:25 ratio of solid-to-liquid (w/v) and extracted 1.5 h at 80°C. The contents of liquiritin and glycyrrhizic acid in the crude extract were 1.3 and 5.3%, respectively. Using the two-phase solvent system of ethyl acetate-methanol-water (5:2:5, v/v), 6.0 mg liquiritin (the purity was 96.7%, and the recovery was 89.3%), and 20.5 mg glycyrrhizic acid (the purity was 98.9%, and the recovery was 77.1%) were obtained from 500 mg crude extraction by HSCCC, respectively. The retention rate of stationary phase was 51.0%. Their structures were identified by high-performance liquid chromatography, melting points, ultraviolet radiation, Fourier transform infrared (FTIR), Electrospray ionization mass spectrometry (ESI-MS), 1H Nuclear Magnetic Resonance (NMR) and 13C NMR spectra. The scavenging abilities of glycyrrhizic acid to 1,1-diphenyl-2-picrylhydrazyl and hydroxyl free radicals were stronger than those of liquiritin.

Review of Constituents and Biological Activities of Triterpene Saponins from Glycyrrhizae Radix et Rhizoma and Its Solubilization Characteristics

Glycyrrhizae Radix et Rhizoma is regarded as one of the most popular and commonly used herbal medicines and has been used in traditional Chinese medicine (TCM) prescriptions for over 2000 years. Pentacyclic triterpene saponins are common secondary metabolites in these plants, which are synthesized via the isoprenoid pathway to produce a hydrophobic triterpenoid aglycone containing a hydrophilic sugar chain. This paper systematically summarizes the chemical structures of triterpene saponins in Glycyrrhizae Radix et Rhizoma and reviews and updates their main biological activities studies. Furthermore, the solubilization characteristics, influences, and mechanisms of Glycyrrhizae Radix et Rhizoma are elaborated. Solubilization of the triterpene saponins from Glycyrrhizae Radix et Rhizoma occurs because they contain the nonpolar sapogenin and water-soluble sidechain. The possible factors affecting the solubilization of Glycyrrhizae Radix et Rhizoma are mainly other crude drugs and the pH of the decoction. Triterpene saponins represented by glycyrrhizin from Glycyrrhizae Radix et Rhizoma characteristically form micelles due to amphiphilicity, which makes solubilization possible. This overview provides guidance regarding a better understanding of GlycyrrhizaeRadix et Rhizoma and its TCM compatibility, alongside a theoretical basis for the further development and utilization of Glycyrrhizae Radix et Rhizoma.

Glycyrrhizic acid derivatives as Dengue virus inhibitors

•

It is the first report to display structure-anti-DENV activity relationships of Glycyrrhizic acid (GL) derivatives.

•

GL conjugates with isoleucine 13 and 11-aminoundecanoic acid 17 have been identified as potent DENV2 inhibitors.

•

GL derivatives 13 and 17 showed lower IC50 values (1.2–1.3 μM) against DENV2 infectivity in Vero E6 cells than GL (IC50 8.1 μM).

Dengue virus (DENV) is one of the most geographically distributed pathogenic flaviviruses transmitted by mosquitoes Aedes sps. In this study, the structure-antiviral activity relationships of Glycyrrhizic acid (GL) derivatives was evaluated by the inhibitory assays on the cytopathic effect (CPE) and viral infectivity of DENV type 2 (DENV2) in Vero E6 cells. GL (96% purity) had a low cytotoxicity to Vero E6 cells, inhibited DENV2-induced CPE, and reduced the DENV-2 infectivity with the IC50 of 8.1 μM. Conjugation of GL with amino acids or their methyl esters and the introduction of aromatic acylhydrazide residues into the carbohydrate part strongly influenced on the antiviral activity. Among compounds tested GL conjugates with isoleucine 13 and 11-aminoundecanoic acid 17 were found as potent anti-DENV2 inhibitors (IC50 1.2–1.3 μM). Therefore, modification of GL is a perspective way in the search of new antivirals against DENV2 infection.

Saponins from European Licorice Roots ( Glycyrrhiza glabra)

European licorice roots ( Glycyrrhiza glabra), used in the food and beverage industry due to their distinctive sweet and typical licorice flavor, were fractionated, with the triterpenoid saponins isolated and their chemical structures determined by means of ESIMS, ESIMS/MS, HRESIMS, and 1D/2D NMR experiments. Next to the quantitatively predominant saponin glycyrrhizin (11) and some previously known saponins, the structures of 10 monodesmosidic saponins were assigned unequivocally for the first time, namely, 30-hydroxyglycyrrhizin (1), glycyrrhizin-20-methanoate (2), 24-hydroxyglucoglycyrrhizin (3), rhaoglycyrrhizin (4), 11-deoxorhaoglycyrrhizin (5), rhaoglucoglycyrrhizin (6), rhaogalactoglycyrrhizin (7), 11-deoxo-20α-glycyrrhizin (8), 20α-galacturonoylglycyrrhizin (9), and 20α-rhaoglycyrrhizin (10).

Synthesis and antiviral activity of novel glycyrrhizic acid conjugates with D-amino acid esters

Glycyrrhizic acid (GA) conjugates with methyl and ethyl esters of D-amino acids (D-Trp, D-Phe, D-Tyr, D-Val, D-Leu) have been synthesized by the activated esters method using mixtures of N-hydroxybenzotriazole or N-hydroxysuccinimide with N,N'-dicyclohexylcarbodiimide. GA conjugate with D-Trp ethyl ester exhibited antiviral activity against influenza viruses A/H3N2, A/H1N1/pdm09, A/H5N1, B (SI > 10-29), and HRSV (SI > 25). GA conjugate with D-Trp methyl ester inhibited influenza virus A/H1N1/pdm09 (SI > 30).

Glycyrrhizic acid derivatives as influenza A/H1N1 virus inhibitors

This Letter describes the synthesis and antiviral activity study of some glycyrrhizic acid (GL) derivatives against influenza A/H1N1/pdm09 virus in MDCK cells. Conjugation of GL with l-amino acids or their methyl esters, and amino sugar (d-galactose amine) dramatically changed its activity. The most active compounds were GL conjugates with aromatic amino acids methyl esters (phenylalanine and tyrosine) (SI=61 and 38), and S-benzyl-cysteine (SI=71). Thus modification of GL is a perspective route in the search of new antivirals, and some of GL derivatives are potent as anti-influenza A/H1N1 agents.

Uralsaponins M-Y, antiviral triterpenoid saponins from the roots of Glycyrrhiza uralensis

Thirteen new oleanane-type triterpenoid saponins, uralsaponins M-Y (1-13), and 15 known analogues (14-28) were isolated from the roots of Glycyrrhiza uralensis Fisch. The structures of 1-13 were identified on the basis of extensive NMR and MS data analyses. The sugar residues were identified by gas chromatography and ion chromatography coupled with pulsed amperometric detection after hydrolysis. Saponins containing a galacturonic acid (1-3) or xylose (5) residue are reported from Glycyrrhiza species for the first time. Compounds 1, 7, 8, and 24 exhibited good inhibitory activities against the influenza virus A/WSN/33 (H1N1) in MDCK cells with IC50 values of 48.0, 42.7, 39.6, and 49.1 μM, respectively, versus 45.6 μM of the positive control oseltamivir phosphate. In addition, compounds 24 and 28 showed anti-HIV activities with IC50 values of 29.5 and 41.7 μM, respectively.

Chemical analysis of the Chinese herbal medicine Gan-Cao (licorice)

Gan-Cao, or licorice, is a popular Chinese herbal medicine derived from the dried roots and rhizomes of Glycyrrhiza uralensis, G. glabra, and G. inflata. The main bioactive constituents of licorice are triterpene saponins and various types of flavonoids. The contents of these compounds may vary in different licorice batches and thus affect the therapeutic effects. In order to ensure its efficacy and safety, sensitive and accurate methods for the qualitative and quantitative analyses of saponins and flavonoids are of significance for the comprehensive quality control of licorice. This review describes the progress in chemical analysis of licorice and its preparations since 2000. Newly established methods are summarized, including spectroscopy, thin-layer chromatography, gas chromatography, high-performance liquid chromatography (HPLC), liquid chromatography/mass spectrometry (LC/MS), capillary electrophoresis, high-speed counter-current chromatography (HSCCC), electrochemistry, and immunoassay. The sensitivity, selectivity and powerful separation capability of HPLC and CE allows the simultaneous detection of multiple compounds in licorice. LC/MS provides characteristic fragmentations for the rapid structural identification of licorice saponins and flavonoids. The combination of HPLC and LC/MS is currently the most powerful technique for the quality control of licorice.

Triterpenoids

This review covers the isolation and structure determination of triterpenoids including squalene derivatives, protostanes, lanostanes, holostanes, cycloartanes, dammaranes, euphanes, tirucallanes, tetranortriterpenoids, quassinoids, lupanes, oleananes, friedelanes, ursanes, hopanes, isomalabaricanes and saponins. The literature from January 2005 to December 2006 is reviewed and 478 references are cited.