Bioactive substances of plant origin in food--impact on genomics

In the past decade, substantial progress has been made concerning our knowledge of bioactive components in plant foods and their links to health. Human diets of plant origin contain many hundreds of compounds which cannot be considered as nutrients, but appear to play a role in the maintenance of health. These substances are called nutraceuticals. In some cases where the disease process is at least partially understood, elements of protection can be related to a single compound or structurally related group of compounds in the diet. Bioactive components of food which are of special interest include the following groups: polyphenols, phytoestrogens, phytosterols, phytates and polyunsaturated fatty acids. Most of them are featured by antioxidant properties. In the first part of this review, we indicate the main groups of bioactive compounds giving a description of their localisation, chemical properties and biological actions. Recently, it was shown, however, that the bioavailability of potential antioxidants from plant foods is generally too low to have any substantial direct effect on reactive oxygen species. As a result of that it is postulated that dietary compounds, even in very low concentrations, may have a far greater impact than previously appreciated on the regulation of gene expression. The second part of this paper concerns the action of the literally most important bioactive substances on the molecular mechanisms of the control of genes which in turn affect cellular metabolism. A few current studies on the action of selected nutraceuticals on the activity of transcription factors such as AP-1, NF-kappaB, SREBPs, PPARs as final targets in the signal transduction cascade and gene regulation are included. A detailed analysis of numerous factors of dietary origin with their targets is far beyond the scope of this paper. However, continuing research on the effects of nutraceuticals on gene expression should provide insight into the mechanisms of prevention of diseases such as obesity, diabetes, atherosclerosis, hypertension and cancer by dietary manipulations.