Chemistry of phenolic compounds of licorice (Glycyrrhiza species) and their estrogenic and cytotoxic activities

<jats:title>Abstract</jats:title> <jats:p> The genus <jats:italic>Glycyrrhiza</jats:italic> consists of about 30 species in which <jats:italic>G. glabra</jats:italic> , <jats:italic>G. uralensis</jats:italic> , <jats:italic>G. inflata</jats:italic> , <jats:italic>G. aspera</jats:italic> , <jats:italic>G. korshinskyi</jats:italic> , and <jats:italic>G. eurycarpa</jats:italic> are generally recognized as licorice because of their sweet taste. Except <jats:italic>G. korshinskyi</jats:italic> , we examined isoprenoid-substituted phenols of these licorices. Each plant could be characterized by some isoprenoid phenols. We also investigated the biological activities of the <jats:italic>Glycyrrhiza</jats:italic> phenols. In the course of screening phytoestrogen in medicinal plants, six Glycyrrhiza phenols exhibited the binding affinities for the bovine uterine estrogen receptor. The affinity of a dihydrostilbene with two 3-methyl-2-butenyl (prenyl) groups, gancaonin R, was higher than those of isoflavone phytoestrogens (genistein and daidzein) in dietary foods. The affinities of the other five phenols, a flavanone (liquiritigenin), two prenylflavanones (isobavachin and sigmoidin B), a prenylated coumestan (glycyrol), and a pyranoisoflav-3-ene (glabrene), were similar to that of the dietary isoflavone, genistein or daidzein. Cytotoxic activities of the <jats:italic>Glycyrrhiza</jats:italic> phenols against human oral tumor cell lines and HIV-infected MT-4 cells were also reviewed. </jats:p>