The in vitro effects of glycyrrhizin and the derivatives of glycyrrhetinic acid on the activity of cAMP-dependent protein kinase and phosphorylation of cellular polypeptide by the kinase from Ehrlich ascites tumor cells

Network Pharmacology-Based Strategy for Elucidating the Molecular Basis Forthe Pharmacologic Effects of Licorice (Glycyrrhiza spp.)

Licorice (Glycyrrhiza spp.) is used widely in traditional Chinese medicine (TCM) due to its numerous pharmacologic effects. However, the mechanisms of action of the chemical constituents of licorice and their structure–function relationships are not fully understood. To address these points, we analyzed the chemical compounds in licorice listed in the TCM Systems Pharmacology database and TCM Integrated database. Target proteins of the compounds were predicted using Integrative Pharmacology-based Research Platform of TCM v2.0. Information on the pharmacologic effects of licorice was obtained from the 2020 Chinese Pharmacopoeia, and disease-related genes that have been linked to these effects were identified from the Encyclopedia of TCM database. Pathway analyses using the Kyoto Encyclopedia of Genes and Genomes database were carried out for target proteins, and pharmacologic networks were constructed based on drug target–disease-related gene and protein–protein interactions. A total of 451 compounds were analyzed, of which 211 were from the medicinal parts of the licorice plant. The 241 putative targets of 106 bioactive compounds in licorice comprised 52 flavonoids, 47 triterpenoids, and seven coumarins. Four distinct pharmacologic effects of licorice were defined: 61 major hubs were the putative targets of 23 compounds in heat-clearing and detoxifying effects; 68 were targets of six compounds in spleen-invigorating and qi-replenishing effects; 28 were targets of six compounds in phlegm-expulsion and cough-suppressant effects; 25 compounds were targets of six compounds in spasm-relieving and analgesic effects. The major bioactive compounds of licorice were identified by ultra-high-performance liquid chromatography–quadrupole time-of-flight–tandem mass spectrometry. The anti-inflammatory properties of liquiritin apioside, liquiritigenin, glycyrrhizic acid and isoliquiritin apioside were demonstrated by enzyme-linked immunosorbent assay (ELISA) and Western blot analysis. Liquiritin apioside, liquiritigenin, isoliquiritin, isoliquiritin apioside, kaempferol, and kumatakenin were the main active flavonoids, and 18α- and 18β-glycyrrhetinic acid were the main active triterpenoids of licorice. The former were associated with heat-clearing and detoxifying effects, whereas the latter were implicated in the other three pharmacologic effects. Thus, the compounds in licorice have distinct pharmacologic effects according to their chemical structure. These results provide a reference for investigating the potential of licorice in treatment of various diseases.

Monoclonal antibody-based enzyme-linked immunosorbent assay for glycyrrhizin and its aglycon, glycyrrhetic acid

Monoclonal antibodies (MoAbs) specific for glycyrrhetic acid (GA) were prepared and characterized. Obtained MoAbs (AGA-1, AGA-3, and AGA-6) reacted with GA dose-dependently, but not with glycyrrhizin (GL), carbenoxolone, and steroids. Next, an enzyme-linked immunosorbent assay (ELISA) system using AGA-1 was established. The standard curve showed good linearity between 0.01 and 1000 ng/ml of GA, and the detection limit was 5 pg/ml. Recovery, and intra- and interassay variations of this assay system was satisfactory. GL was also measurable quantitatively after acid-hydrolysis of the samples. The developed ELISA system would be useful to determine GL and GA in biological samples or drugs as an alternative method to high performance liquid chromatography (HPLC).

Inhibition of rat acute inflammatory paw oedema by dihemiphthalate of glycyrrhetinic acid derivatives: comparison with glycyrrhetinic acid

The anti-inflammatory profile of dihemiphthalate compounds of glycyrrhetinic acid derivatives in acute rat paw oedema induced by various vasoactive agents was compared with the parent compound. Three dihemiphthalate compounds (the di-sodium salt of 18 beta-olean-12-ene- 3 beta,30-diol di-O-hemiphthalate, 18 beta-olean-9(11),12-dione-3 beta,30-diol di-O-hemiphthalate and olean-11,13(18)-diene-3 beta,30-diol di-O-hemiphthalate), significantly inhibited development of carrageenan-induced rat paw oedema during the first 3 h (ED50 70, 90, and 108 mg kg-1 respectively, p.o.), while glycyrrhetinic acid (ED50, 200 mg kg-1) showed a significant inhibition of paw oedema 3 h after carrageenan treatment. The dihemiphthalate compounds also suppressed mouse paw oedema induced by histamine, bradykinin, and PAF acether at doses of less than 100 mg kg-1. However, these compounds failed to inhibit 5-HT-induced mouse paw oedema. Glycyrrhetinic acid had little effect on mouse paw inflammation induced by the above irritants. The three compounds at 10(-7)-10(-4) M, inhibited histamine-induced contraction of guinea-pig isolated ileum. However, concentration-response curves to 5-HT and bradykinin were not affected by the same compounds. These results suggest that the dihemiphthalate compounds modulate vascular permeability caused by endogenous vasoactive agents as one of the anti-inflammatory mechanisms. This action is quite different from that of glycyrrhetinic acid.