Abstract
BackgroundThe plant genus Fallopia is well-known in Chinese traditional medicine and includes many species that contain bioactive compounds, namely phytoestrogens. Consumption of phytoestrogens may be linked to decreased incidence of breast and prostate cancers therefore discovery of novel phytoestrogens and novel sources of phytoestrogens is of interest. Although phytoestrogen content has been analyzed in the rhizomes of various Fallopia sp., seeds of a Fallopia sp. have never been examined for phytoestrogen presence.MethodsAnalytical chemistry techniques were used with guidance from an in vitro estrogen receptor bioassay (a stably transfected human ovarian carcinoma cell line) to isolate and identify estrogenic components from seeds of Fallopia convolvulus. A transiently transfected human breast carcinoma cell line was used to characterize the biological activity of the isolated compounds on estrogen receptors (ER) α and β.ResultsTwo compounds, emodin and the novel flavan-3-ol, (−)-epiafzelechin-3-O-p-coumarate (rhodoeosein), were identified to be responsible for estrogenic activity of F. convolvulus seed extract. Absolute stereochemistry of rhodoeosein was determined by 1 and 2D NMR, optical rotation and circular dichroism. Emodin was identified by HPLC/DAD, LC/MS/MS, and FT/ICR-MS. When characterizing the ER specificity in biological activity of rhodoeosein and emodin, rhodoeosein was able to exhibit a four-fold greater relative estrogenic potency (REP) in breast cells transiently-transfected with ERβ as compared to those transfected with ERα, and emodin exhibited a six-fold greater REP in ERβ-transfected breast cells. Cell type-specific differences were observed with rhodoeosein but not emodin; rhodoeosein produced superinduction of reporter gene activity in the human ovarian cell line (> 400% of maximum estradiol [E2] induction) but not in the breast cell line.ConclusionThis study is the first to characterize the novel flavan-3-ol compound, rhodoeosein, and its ability to induce estrogenic activity in human cell lines. Rhodoeosein and emodin may have potential therapeutic applications as natural products activating ERβ, and further characterization of rhodoeosein is necessary to evaluate its selectivity as a cell type-specific ER agonist.
Highlights
The plant genus Fallopia is well-known in Chinese traditional medicine and includes many species that contain bioactive compounds, namely phytoestrogens
Seeds of F. convolvulus were identified as a novel source of phytoestrogens from which we have isolated and chemically characterized a novel phytoestrogen rhodoeosein
Estrogenic activity of rhodoeosein was evaluated in two human cell-lines in which we were able to demonstrate cell-type specific effects of rhodoeosein
Summary
The plant genus Fallopia is well-known in Chinese traditional medicine and includes many species that contain bioactive compounds, namely phytoestrogens. The plant genus Fallopia (Polygonacae) is well known in traditional medicines, and extracts have been used to treat hepatitis, liver damage, inflammation, and postmenopausal diseases [1,2,3,4]. Several polyphenolic compounds exhibiting estrogenic activity (phytoestrogens) have been isolated from the roots and rhizomes of numerous Fallopia (recently Polygonum) species such as F. multiflorum, F. cuspidatum, and F. japonica [8,9,10,11,12]. Many phytoestrogens exhibit preferential activation of estrogen receptor beta (ERβ) over estrogen receptor alpha (ERα) [13], and diets high in phytoestrogen content have been correlated with lower incidence of hormone-related cancers, namely breast and prostate [14]. There is interest in identifying plant sources rich in phytoestrogen content as well as discovering novel ERβ-selective phytoestrogens
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