Identification and Biological Characterization of Progestins from Botanicals In Vitro and In Vivo

Extensive studies have been conducted on botanicals for the presence of estrogenic molecules, unfortunately, very little has ever been done to identify plant-based progestins. This underexplored area is troubling especially since there is a body of scientific evidence supporting the presence of progesterone receptor (PR) modulators in plant material that may affect endocrine function. The goal of this dissertation was to identify and characterize natural progesterone (P4)-like compounds from botanical extracts for the improvement of women’s health. Red clover, hops, angelica, black cohosh, kudzu, dogwood, and chaste-tree berry were investigated for their ability to interact with purified PR, to activate PRE-luciferase transcription in human breast cancer cells, and for tissue specific regulation of P4 inducible genes. Kaempferol was identified as having P4-like activity and may function in a cell-specific manner. In vivo studies revealed that kaempferol exhibited P4-like effects in ovariectomized Sprague-Dawley rat model. Since genistein is a phytoestrogen that previously demonstrated to increase uterine weight and proliferation, the ability of kaempferol to block genistein action in the uterus was investigated. Analyses of proliferation, steroid receptor expression, and induction of well-established PR-regulated targets Areg and Hand2 were completed. In addition, kaempferol in silico binding analysis was completed for PR, as was the activation of ER and AR signaling in vitro in order to determine receptor specificity. The data from this dissertation suggest that kaempferol interacts with PR, activates the receptor without stimulating its degradation, induces known PR target genes in vitro and in vivo and blocked genistein-induced proliferation in the luminal epithelial cells in Sprague-Dawley rat uteri. The toxicity of hops extracts in cell-based assays precluded further investigation in vitro, but an initial bioassay screen suggested that natural progestins can be identified from hops extracts. Further chemical and biological analyses are warranted to identify and characterize progestins from hops. The comprehensive framework outlined in this thesis will provide a promising avenue for the identification of potentially better and safer compounds capable of activating PR signaling from botanical extracts used for women's health.