Detection of Estrogenic and Anti‐estrogenic Activities of Dietary Plant Extracts by In Vitro Reporter Assays

Phytoestrogens are plant polyphenolic compounds which structurally and functionally mimic the mammalian estrogen hormone. This study aimed to establish the estrogenic agonism and antagonism of some dietary plants in Ericaceae , Moraceae , Rosaceae , and Vitaceae families. A steroid‐regulated transcription system in Saccharomyces cerevisiae containing a human estrogen receptor alpha expression plasmid and a β‐galactosidase gene reporter plasmid was employed in this study. Estrogenic activities of plant extracts were detected by assessing their effects on estrogen receptor mediated transactivation of the reporter gene as compared to estradiol. The degree of the weak estrogenic activities of ethanolic fruit extracts ranked as follows: California grape ( Vitis californica) > red raspberry ( Rubus ideaus) > strawberry ( Fragaria ananassa) > Blackberry ( R. fruticosus) . Fruit extracts of blueberry ( Vaccinium corymbosum ), jackfruit ( Artocarpus heterophyllus ) and black raspberry ( R. occidentalis ) exhibited no estrogenic activities. Some extracts showed anti‐estrogenic properties by lowering the transcriptional activity induced by estradiol in transgenic yeast. Black and red raspberry extracts showed anti‐estrogenic activities in dose‐dependent manner. Blackberry, blueberry, and jackfruit extracts lowered estradiol activity by 25‐35% at all concentrations used. Strawberry extract exhibited partial antagonism of estradiol at low concentrations and partial agonism at high concentrations. This study reports for the first time anti‐estrogenic activities of the above plant extracts and it may lead to detection of new more potent phytoestrogens for possible chemopreventive effects and cancer treatments.