A systematic approach for identifying plant components with impact on human health

Brandt, K; Lietz, G; Christensen, LP; Kobaek-Larsen, M

A systematic approach for identifying plant components with impact on human health

Lookup NU author(s): Dr Kirsten Brandt ORCiD, Professor Georg Lietz

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Abstract

Vegetables contain unknown compounds with health promoting effect, since the effects of the known nutrients and other bioactive compounds, such as vitamins, minerals, fatty acids and fibres, cannot explain the benefits of high intake of vegetables. Most biologically active substances have never been investigated for health-promoting properties, often because they have historically been considered health hazards, due to toxicity at high levels of intake. However, to improve the value of vegetables for health, it is necessary to identify which compounds are most important, and find ways to manage "paradoxical" effects where the same compound is good or bad for health depending on dose. However, there are thousands of chemical constituents in plants, and it would be very expensive and time consuming to test each of them thoroughly. The described project defined and tested a two-step screening procedure for identification of compounds with impact on human health, to reduce the number and make this difficult task manageable. Step 1 is initial screening according to three criteria: 1.1, chemically reactive functional groups; 1.2, toxicity at high concentrations or other bioactivity; and 1.3, presence in healthy foods. Step 2 is testing for minimum criteria defining health-promoting compounds: 2.1, positive or biphasic ("hormesis") responses in bioassay; 2.2, human tissue concentrations corresponding to beneficial effects in bioassay; and 2.3, possibility to control content in food. Compounds that pass both screens should be subjected to more extensive (and expensive) investigations in vivo and in vitro (Step 3). The natural pesticide and toxicant falcarinol from carrots fulfilled all 6 criteria and subsequently showed anticancer effect in rats. Several other bioactive compounds in vegetables, mostly classified as toxicants, also have properties that indicate disease-preventing properties, for example glucosinolates in cabbage and its relatives, sesquiterpene lactones in lettuce and glycoalkaloids in potatoes.