Estrogenic And Chemopreventive Properties of Licorice Species Used For Menopausal Symptoms

Hormone therapy (HT) has been the most efficacious treatment for relieving menopausal symptoms. However, Women’s Health Initiative showed an increased breast cancer risk associated with HT. Therefore, menopausal women have turned to alternative options such as licorice. Glycyrrhiza glabra (GG), Glycyrrhiza uralensis (GU), and Glycyrrhiza inflata (GI) have been considered medicinal licorice; however, their estrogenic efficacy and their role in chemoprevention have not been well documented. In this study GG, GU, and GI induced estrogen responsive alkaline phosphatase activity in Ishikawa cells, estrogen responsive element (ERE)-luciferase in MCF-7 cells, and Tff1 mRNA in T47D cells. The estrogenic activity decreased as GU > GI > GG. Liquiritigenin (LigF) the principle phytoestrogen of licorice showed better binding affinity for estrogen receptor (ER) β. Isoliquiritigenin (LigC) the precursor chalcone of LigF demonstrated estrogenic activity which could be the result of its cyclization to LigF under physiological conditions. GG, GU, and LigF did not exhibit uterine proliferation in immature rats; however, LigF suppressed E2-induced uterine growth which could be associated with its ERβ as well as partial agonist effects. Licorice species were studied for activating a chemoprevention marker, NAD(P)H:quinone oxidoreductase 1 (NQO1) as they contain Michael acceptors such as LigC and also licochalcone A (LicA) from GI. Extracts activated NQO1 in hepa1c1c7 cells with the rank order GI > GG ≅ GU. The rank order for the compounds was LigC > LicA ≫ LigF. GG, GU, and LigC enhanced NQO1 levels in MCF-10A cells. Activation of antioxidant response element in HepG2-ARE-C8 cells suggested the involvement of Keap1-Nrf2 pathway. When GG and GU were orally administered to mature female rats LigC and LigF were detected in liver, serum, and mammary tissues with a significant increase in NQO1 activity in mammary glands. LigC did not enhance NQO1 activity in vivo likely due to rapid metabolism. This study showed the impact of chemical profile on the biological activities of licorice species and further supported the importance of simultaneous chemical and biological evaluation as well as standardization of botanicals

Evaluation of estrogenic activity of licorice species in comparison with hops used in botanicals for menopausal symptoms.

The increased cancer risk associated with hormone therapies has encouraged many women to seek non-hormonal alternatives including botanical supplements such as hops (Humulus lupulus) and licorice (Glycyrrhiza spec.) to manage menopausal symptoms. Previous studies have shown estrogenic properties for hops, likely due to the presence of 8-prenylnarigenin, and chemopreventive effects mainly attributed to xanthohumol. Similarly, a combination of estrogenic and chemopreventive properties has been reported for various Glycyrrhiza species. The major goal of the current study was to evaluate the potential estrogenic effects of three licorice species (Glycyrrhiza glabra, G. uralensis, and G. inflata) in comparison with hops. Extracts of Glycyrrhiza species and spent hops induced estrogen responsive alkaline phosphatase activity in endometrial cancer cells, estrogen responsive element (ERE)-luciferase in MCF-7 cells, and Tff1 mRNA in T47D cells. The estrogenic activity decreased in the order H. lupulus > G. uralensis > G. inflata > G. glabra. Liquiritigenin was found to be the principle phytoestrogen of the licorice extracts; however, it exhibited lower estrogenic effects compared to 8-prenylnaringenin in functional assays. Isoliquiritigenin, the precursor chalcone of liquiritigenin, demonstrated significant estrogenic activities while xanthohumol, a metabolic precursor of 8-prenylnaringenin, was not estrogenic. Liquiritigenin showed ERβ selectivity in competitive binding assay and isoliquiritigenin was equipotent for ER subtypes. The estrogenic activity of isoliquiritigenin could be the result of its cyclization to liquiritigenin under physiological conditions. 8-Prenylnaringenin had nanomolar estrogenic potency without ER selectivity while xanthohumol did not bind ERs. These data demonstrated that Glycyrrhiza species with different contents of liquiritigenin have various levels of estrogenic activities, suggesting the importance of precise labeling of botanical supplements. Although hops shows strong estrogenic properties via ERα, licorice might have different estrogenic activities due to its ERβ selectivity, partial estrogen agonist activity, and non-enzymatic conversion of isoliquiritigenin to liquiritigenin

Breast cancer prevention with liquiritigenin from licorice through the inhibition of aromatase and protein biosynthesis in high-risk women’s breast tissue

Abstract Breast cancer risk continues to increase post menopause. Anti-estrogen therapies are available to prevent postmenopausal breast cancer in high-risk women. However, their adverse effects have reduced acceptability and overall success in cancer prevention. Natural products such as hops (Humulus lupulus) and three pharmacopeial licorice (Glycyrrhiza) species have demonstrated estrogenic and chemopreventive properties, but little is known regarding their effects on aromatase expression and activity as well as pro-proliferation pathways in human breast tissue. We show that Gycyrrhiza inflata (GI) has the highest aromatase inhibition potency among these plant extracts. Moreover, phytoestrogens such as liquiritigenin which is common in all licorice species have potent aromatase inhibitory activity, which is further supported by computational docking of their structures in the binding pocket of aromatase. In addition, GI extract and liquiritigenin suppress aromatase expression in the breast tissue of high-risk postmenopausal women. Although liquiritigenin has estrogenic effects in vitro, with preferential activity through estrogen receptor (ER)-β, it reduces estradiol-induced uterine growth in vivo. It downregulates RNA translation, protein biosynthesis, and metabolism in high-risk women’s breast tissue. Finally, it reduces the rate of MCF-7 cell proliferation, with repeated dosing. Collectively, these data suggest that liquiritigenin has breast cancer prevention potential for high-risk postmenopausal women

Dynamic Residual Complexity of the Isoliquiritigenin–Liquiritigenin Interconversion During Bioassay

Bioactive components in food plants can undergo dynamic processes that involve multiple chemical species. For example, 2′-hydroxychalcones can readily isomerize into flavanones. Although chemically well documented, this reaction has barely been explored in the context of cell-based assays. The present time-resolved study fills this gap by investigating the isomerization of isoliquiritigenin (a 2′-hydroxychalcone) and liquiritigenin (a flavanone) in two culture media (Dulbecco’s modified eagle medium and Roswell Park Memorial Institute medium) with and without MCF-7 cells, using high-performance liquid chromatography–diode array detector–electrospray ionization/atmospheric pressure chemical ionization–mass spectrometry for analysis. Both compounds were isomerized and epimerized under all investigated biological conditions, leading to mixtures of isoliquiritigenin and <i>R</i>/<i>S</i>-liquiritigenin, with 19.6% <i>R</i> enantiomeric excess. Consequently, all three species can potentially modulate the biological responses. This exemplifies dynamic residual complexity and demonstrates how both nonchiral reactions and enantiomeric discrimination can occur in bioassay media, with or without cells. The findings highlight the importance of controlling in situ chemical reactivity, influenced by biological systems when evaluating the mode of action of bioactives

Different <i>Glycyrrhiza</i> species and their bioactive compounds induce ER dependent estrogenic response in MCF-7 cells.

<p>ERE-luciferase induction in ERα (+) MCF-7 cells by A) licorice and hops extracts and B) their respective compounds. Cells were cotransfected with pERE and pRL-TK 24 h before being treated with either extracts (2 µg/mL, open bars and 10 µg/mL, closed bars) or pure compounds (0.1 µM, open bars and 1 µM, closed bars). 17β-Estradiol (1 nM) was used as positive control. Since hops extract showed a considerable estrogenic activity at 2 μg/mL, higher concentrations were not tested. Chemiluminescence analysis was performed after 24 h. Results were normalized for transfection efficiency, and they are shown as a fold induction relative to the level observed in cells treated with vehicle only. Results are the means of three independent determinations in duplicates ± SD.</p

Estrogenic compounds in licorice and hops are formed from chalcones.

<p>Metabolism of bioactive compounds from <b>A</b>) hops and <b>B</b>) licorice.</p

Different <i>Glycyrrhiza</i> species and their bioactive compounds are partial ER agonists with varied estrogenic potency and efficacy in Ishikawa cells.

<p>Induction of alkaline phosphatase in Ishikawa cells by A) crude extracts of <i>Glycyrrhiza glabra</i>; <i>GG</i>, <i>Glycyrrhiza uralensis</i>; <i>GU</i>, <i>Glycyrrhiza Inflata</i>; <i>GI</i> in comparison to hops and estradiol and B) isolated compounds liquiritigenin and isoliquiritigenin in comparison to 8-PN and estradiol. Results were normalized to DMSO and are shown as fold induction. Results are the means of three independent determinations. Dose-response curves were generated by non-linear regression analysis.</p