Promising assets of South Africa? Cyclopia genistoides and Hoodia gordonii

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Previous pharmacological studies have shown that H. gordonii could have different mechanism of action than the already withdrawn sympathomimetic weight-loss medicines, thus a possibly better risk/benefit ratio than the former antiobesity drugs. Yet, sympathomimetic effect with substantial β-receptor-mediated contribution similar to the mechanism of action of several already withdrawn weight loss medications was recorded in our investigation. Hence, the use of Hoodia gordonii as a possible anti-obesity drug is questionable. The phytoestrogenic activity of C. genistoides extracts was linked to compounds, isolated via bioactivity-guided fractionation, using the transgenic plant system pER8:GUS. The extracts of the plant materials were subjected to multiple step chromatographic separation (including CC, VLC, MPLC, HPLC, PLC, RPC) resulting in the isolation of 17 compounds from which 14 were first isolated from this species and 10 from the genus. Antiproliferative MTT assays were also performed on A2780 and T47D human cancer cell lines. The results suggested, that oestrogen induced cell-proliferation or oestrogen independent antiproliferative effect might have played a role. The recorded xanthine oxidase inhibitory activity of two compounds isolated from the dichloromethane layers, added to the long list of bioactivities of Cyclopia species. The effect of fermentation on the phytochemical content was also investigated with the means of HPLC. The results supported the tradition, as the fermented honeybush tea was rich in compounds with stronger phytoestrogenic activity, while the non-fermented tea contained larger amounts from the less active glycoside. However, bacterial fermentation levelled the difference in the concentration of naringenin between the aqueous extracts from fermented and non-fermented plant materials. Although, the quantitative comparison of fermented and non-fermented honeybush implies, that the fermented tea has higher amount of these phytoestrogens except the least active compound, the measured low amounts question the biological activity of the traditionally used infusion. However, it does not exclude the possibility that synergism or antagonism of multiple polyphenols targeting different ER isoforms can result in phytoestrogenic effect of different extracts, even if the individual compounds are small in quantity.

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