The human estrogen receptor (hER) exists as two subtypes, hER a a and hER b b, that differ in the C-terminal ligand-binding domain and in the N-terminal transactivation domain. In this study, we investigated the estrogenic activities of soy isoflavones after digestion with enteric bacteria in competition binding assays with hER a a or hER b b protein, and in a gene expression assay using a yeast system. The estrogenic activities of these isoflavones were also investigated by the growth of MCF-7 breast cancer cells.Isoflavone glycoside binds weakly to both receptors and estrogen receptor-dependent transcriptional expression is poor. The aglycones bind more strongly to hER b b than to hER a a. The binding affinities of genistein, dihydrogenistein and equol are comparable to the binding affinity of 17 b b-estradiol. Equol induces transcription most strongly with hER a a and hER b b. The concentration required for maximal gene expression is much higher than expected from the binding affinities of the compounds, and the maximal activity induced by these compounds is about half the activity of 17 b b-estradiol. Although genistin binds more weakly to the receptors and induces transcription less than does genistein, it stimulates the growth of MCF-7 cells more strongly than does genistein.

Flavonoids are a group of polyphenolic compounds, which have the diphenylpropane (C 6 -C 3 -C 6 ) skeleton, ubiquitously found in fruits and vegetables. The flavonoid family includes flavones, flavonols, flavanones, flavanonols, flavans, flavanols, leucoanthocyanidins, anthocyanidins, aurones, chalcones, and isofavones. The structural difference in each flavonoid family results from the variation in the number and arrangement of the hydroxyl groups and the extent of glycosylation of these groups. 1)Epidemiological studies suggest that the consumption of flavonoids is effective in lowering the risk of coronary heart disease. [2][3][4] In addition, the flavonoids exhibit a wide range of biological activities, including anticarcinogenic, antiinflammatory, antiradical, and antioxidant actions. Especially, they may exert antioxidative effects as free radical scavengers, hydrogen-donating compounds, singlet oxygen quenchers, and metal ion chelators, properties attributed to the phenolic hydroxyl groups attached to the ring structures.Nowadays, it is reported that a reactive oxygen species (ROS) is implicated in a wide range of human diseases such as atherosclerosis and certain cancers. When an imbalance between ROS generation and antioxidants occurs, oxidative damage will spread over all the cell targets (DNA, lipids, proteins). 5) Antioxidants in foods and medicinal plants (or herbs) have attracted interest in recent years. Flavonoids given as biological substances in foodstuffs may contribute to the prevention of diseases, although they do not have strong biological activities. [6][7][8] In the preceding paper, 9) we reported the antioxidative effects of flavon C-glycosides isolated from young green barley (Hordeum vulgare var. nudum) leaves. Herein, we present antioxidative effects of various types of flavonoids obtained from some medicinal plants, using DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity by ESR. MATERIALS AND METHODSFlavonoids Flavone C-glycosides, isovitexin (1), saponarin (2), isovitexin 4Ј,7-diglucoside (3), isovitexin 7-rhamnosylglucoside (4), 6ٞ-sinapoylsaponarin (5), 6ٞ-feruloylsaponarin (6) and 4Ј-glycosyl-6ٞ-sinapoylsaponarin (7) were isolated from young barley leaves.9) A flavone, baicalin 10) (8) was obtained from Scutellariae Radix (Scutellaria baicalensis). Flavonols, quercetin (9), kaempferol (10) and rutin (11) were obtained from Sophorae Flos (Sophora japonica). 11)Flavanols, gallocatechin (12) was obtained from Ephedrae Herba (Ephedra sinica) and epicatechin (13) and their polymers (14-16) were from cinnamon (Cinnamomum cassia).12) Isoflavones, 13) daidzin (17), genistin (18) and glycitin (19), and their metabolites 14) (20-25) were obtained from soybeen (Glycine max). Flavonolignans, silybin (26) and silychristin (27) were isolated from a silymarin group (Silybum marianum).15) (Fig. 1). DPPH Radical Scavenging Activity by ESR The DPPH radical scavenging activity of a test sample was estimated by ESR according to the method of Tateyama et al. 16)Various concentrations ...

Lantana camara L. is indigenous to tropical America, and its leaves have been used in folk medicine for the treatment of bronchitis and stomach disorders and as a sudorific, and are also put into baths to treat rheumatism in South America.2) However, this species has been known to be toxic to livestock, which develop hepatotoxicity and photosensitization on ingestion of the leaves.3) There have been many reports on the biological action of this plant and the toxic constituents. Scores of triterpene derivatives have been isolated, [3][4][5][6] and some of them have been reported to exhibit inhibitory activity against Epstein-Barr virus early antigen activation in Raji cells induced by 12-O-tetradecanoyl-phorbol-13-acetate. 7)L. montevidensis BRIQ. is native to Brazil (Montevideo), and the tea and infusion of the dried leaves have been used in folk medicine for the same purposes as L. camara.2) However, to our knowledge there is only one report on the essential oil from the leaves 2) and there is no report on the other constituents.Among several Verbenaceae plants in which we investigated the antiproliferative activity of the MeOH extracts, L. camara and L. montevidensis exhibited higher activity against tumor cell growth. The MeOH extract of the leaves of L. montevidensis showed 50% growth inhibition (GI 50 ) at the concentrations of 8 mg/ml for human gastric adenocarcinoma (MK-1), 3 mg/ml for human uterus carcinoma (HeLa), and 4 mg/ml for murine melanoma (B16F10), which were more potent than the inhibition by the MeOH extract of the leaves of L. camara (12.5 mg/ml for MK-1 and 25 mg/ml for HeLa and B16F10). The inhibitory activity was found to be localized in the nonglycoside fraction that contains several flavonoids. The nonflavonoid fraction exhibited higher activity, however, the flavonoid fraction also showed significant activity. We therefore first investigated the active constituents in the flavonoid fraction. This paper deals with the isolation and identification of the flavone constituents in the leaves of L. montevidensis and their antiproliferative activity. MATERIALS AND METHODS Materials, Reagents, and InstrumentsThe leaves of L. montevidensis were collected in Munakata City, Fukuoka, Japan, in July 2000 and air-dried. 6-Hydroxyluteolin, desmethoxycentaureidin, and jaceosidin were isolated from the herb of Lippia canescens KUNTH. (Verbenaceae), 1) and eupatilin was isolated from the herb of Artemisia ludoviciana NUTT. subsp. mexicana (WILLD. ex SPRENGEL) (Compositae). 8)Pectolinarigenin was obtained by acid hydrolysis of linariin isolated from the herb of Trifolium dubium SIBTH. (Leguminosae) and identification was performed by comparison of the NMR data with those reported. 9) Chrysin, luteolin, baicalein, and 6-and 7-methoxyflavones were purchased from Aldrich Chemical Company (Milwaukee, WI, U.S.A.). Reagents for culture of the tumor cells and for the bioassay were described in a previous paper.10) The instruments used in this study were a Shimadzu Double Beam Spectrometer UV-200S (UV spectra), JE...

During the course of a study of leguminous plants, cytotoxicity was demonstrated by the crude saponin fraction of Albizia julibrissin. Following chromatographic purification, the structures of three novel saponins, julibrosides I-III (1-3), inclusive of a cytotoxic principle, were elucidated. A comparison of the cytotoxicity of julibrosides (1-3) and their prosapogenins (4-15) prepared by alkaline hydrolysis clearly indicated that both an alpha-L-arabinofuranosyl-(1-->4)-[beta-D-glucopyranosyl-(1-->3)]-alpha- L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranosyl ester unit and a monoterpene-quinovopyranosyl moiety are crucial substituents for cytotoxicity among this class of compounds. The hydroxy group at C-16 of aglycon may play an important role in mediating cytotoxicity, and the N-acetyl-glucosamine moiety at C-3 seems to enhance activity because 3 showed the strongest cytotoxicity.