Risk benefit analysis of botanical varieties growing in the Mediterranean region

Despite the long history of use of medicinal plants for the treatment and prevention of diseases, the safety of botanicals and botanical preparations is not certain, since some of the contained bioactive phytochemicals can induce undesired effects. Thus, there is need to assure that the risks of the use of botanicals and botanical preparations do not outweigh the benefits. The aim of the present thesis was to reveal potential health benefits and hazards of 18 botanical varieties grown in the Mediterranean region, that are used traditionally for the treatment and prevention of several health conditions, using a series of in vitro bioassays.

Chapter 1 provides background information about the use of botanicals for medicinal purposes, the traditional use and pharmacological properties of the 18 selected botanical varieties, as well as the beneficial and toxicological endpoints selected for a qualitative risk-benefit evaluation. In Chapter 2, an overview of the available in vitro bioassays, suitable for the detection of beneficial and adverse effects of botanicals, botanical preparations and their active constituents and the characteristics that make these assays valuable tools for a qualitative risk-benefit assessment, is presented. The pitfalls of bioassay use are also highlighted, discussing among others the factors that may generate false-positive or false-negative results and the limitations in the extrapolation of in vitro data to the in vivo situation.

Several in vitro bioassays were applied to reveal the potential benefits and hazards of the 18 selected botanical varieties. Methanol extracts compatible with in vitro bioassays were prepared and tested in the EpRE-LUX (Chapter 3) and the PPARγ CALUX® (Chapter 4) reporter gene assays. Results obtained revealed that half of the tested extracts, are able to exert a potential chemopreventive action via activation of EpRE mediated gene expression,  while most of the tested extracts (16 out of 18) may contribute to potential health benefits via the activation of PPARγ mediated gene expression. LC-MS analysis combined with MAGMa (MS Annotation based on in silico Generated Metabolites) software was applied in order to facilitate tentative identification of the active constituents within selected active extracts. Many active ingredients of the methanol extracts from Juglans regia, Rhamnus frangula and Urtica dioica were revealed, albeit in low concentrations, in the respective extracts. The presence of many compounds exerting the same activity and/or synergistic effects between the different constituents, could explain the full potential detected for the extract as a whole.

The possibility that the benefits of these botanical preparations would be contraindicated by potential hazards, was also investigated. In Chapter 5, the potential estrogenic activity of the extracts was assessed in the ERα CALUX® assay resulting 13 extracts that tested positive. The zebrafish embryotoxicity test (ZET), used to reveal potential developmental toxicity, resulted in a concentration dependent drop in the GMS (general morphology score) when zebrafish embryos were exposed to Rhamnus frangula, Ruta graveolens and Achillea millefolium extracts. For the extracts from Rhamnus frangula and Achillea millefilium this drop in the GMS might be ascribed to toxicity, in contrast to the extract from Ruta graveolents that shows specific in vitro developmental toxicity.

In Chapter 6, the potential genotoxicity of the extracts was tested using the AMES test. The extracts from Ruta graveolens, Fumaria officinalis and Juglans regia tested positive for mutagenicity. These results were combined with the all data obtained in Chapters 3, 4 and 5, and with information derived from the EFSA compendium of botanicals containing substances that may raise a concern, enabling an initial qualitative risk-benefit assessment for the 18 Mediterranean botanicals. For some of the botanicals, the risks clearly outweigh the potential benefits, as in the case of the extracts that tested positive for developmental toxicity and mutagenicity, for others it is not possible to come to a conclusion based on the obtained data and for others, especially for Urtica dioica L. and potentially also Equisetum arvense L., Taraxacum officinale and Veronica officinalis L., further development into functional food ingredients would be indicated, focussing in future studies on their further safety assessment and their potential to activate PPARy which could be of interest for therapeutic effects in type II diabetes mellitus.

Chapter 7 summarizes the results obtained in the present thesis and provides the overall discussion and future perspectives, concluding on the value of the results obtained from in vitro bioassays in potential (pre)clinical testing strategies to support the selection of promising candidate botanicals and/or their extracts for the development of functional food ingredients.