Bioactivity guided isolation of phytoestrogenic compounds from Cyclopia genistoides by the pER8:GUS reporter system

Abstract

The popular South African herbal tea, honeybush, is made from several . Cyclopia species (family: . Fabaceae), amongst them . Cyclopia genistoides. Phytoestrogenic potential of . C. genistoides. has been recently reported, however bioactivity-guided isolation of compounds with estrogenic activity has not yet been performed.A transgenic plant system, . Arabidopsis thaliana pER8:GUS, was used to assay the estrogen-like activity of . C. genistoides. The quantitative determination of the active compounds in the fermented and non-fermented plant material was performed by HPLC. Subsequent bioactivity-guided fractionation led to the isolation of genistein, naringenin, isoliquiritigenin, luteolin, helichrysin B and 5,7,3',5'-tetrahydroxyflavanone, four of them first reported in the genus.Helichrysin B, naringenin and 5,7,3',5'-tetrahydroxyflavanone differed in quantity in the fermented and unfermented herbs, the fermented plant material contained two compounds with substantial estrogenic-like activity in higher concentration (naringenin and 5,7,3',5'-tetrahydroxyflavanone), whereas the less active helichrysin B was more abundant in the unfermented herb. The fractions as well as compounds inhibited the growth of human cancer cell lines A2780 and T47D.These results underline the phytoestrogenic activity of . C. genistoides and support the rationale to the fermentation process. © 2016 South African Association of Botanists.