This study examined trans‐dehydrocrotonin (t‐DCTN), a nor‐clerodane diterpene isolated from the Brazilian medicinal plant Croton cajucara Benth., for a possible antioestrogenic activity using immature rats as a model system for bioassay of oestrogen, and for an antiimplantation effect in regularly cycling rats of proven fertility. In the antioestrogen test, t‐DCTN (25 and 50 mg/kg) effectively prevented oestrogen‐induced increases of uterine wet weights. In addition, the vaginal openings provoked by oestrogen were completely prevented by t‐DCTN. However, blastocyst‐implantation was only insignificantly affected in t‐DCTN pretreated animals. These results suggest that t‐DCTN may be an antioestrogen and warrants further studies with regard to its mechanism of action. Copyright © 1999 John Wiley & Sons, Ltd.

The effects of five antiinflammatory plant extracts on ovoimplantation was investigated in albino rats. Rats treated with plant extracts from days 4 to 6 (periimplantation) of pregnancy showed either a total absence (20%-40%) or a considerably reduced number of implantations in utero. The observation suggests that the use of antiinflammatory plant extracts during the periimplantation period impairs fertility probably by reducing the vascular permeability which is an obligate accompaniment of normal implantation.