Flavonoids and human health: evidences and mechanisms

C. G. FRAGA

Vancouver

Congreso; 2012 Canadian Nutrition Society Annual Meeting; 2012

Canadian Nutrition Society

A high consumption of fruits and vegetables seems to be associated to lower incidence and prevalence of disease. Flavonoids and several related phenolic compounds are among the most abundant secondary metabolites present in plants that are part of human diets. The consumption of flavonoid-rich plants is receiving growing attention, given certain relationships that have been observed and that could be of clinical significance, e.g. green tea, soybean in cancer, cocoa in vascular and inflammatory disease. However, the underlying mechanisms are poorly understood. The chemical structure of flavonoids support a potential prevention of free radical-related diseases based on their capacity of trapping radicals and chelating redox-active metals. These antioxidant actions can be extended to the capacity of flavonoids to regulate cell oxidant production and antioxidant defenses, and hence cell redox state. In addition, specific flavonoid interactions can modulate the activity and biological reactions of cell signaling proteins, and the regulation of membrane-associated cell signaling, independently of any redox-related activity. Finally, it is important to note, that all these actions are dependent on flavonoid bioavailability at the target tissue. For example, high micromolar concentrations in the digestive tract, allow a kinetically favorable free radical scavenging action as well as the regulation of intestine epithelium permeability/inflammation. The low micromolar?high nanomolar concentrations in blood, could allow a flavonoid action on the vascular endothelium and the smooth muscle layer covering blood vessels. Lower concentrations in other tissues and cells would need more specific molecular interactions to justify a physiological relevance. In this direction, studies focused on identifying the effectors and molecular targets of the biological action are of critical relevance. Considering present evidence on flavonoid positive effects on human health, it can be concluded that: 1) flavonoids are molecules with several reaction centers, and consequently can exert different molecular actions; 2) flavonoid intake seems to affect vascular function and certain oncogenic processes; and 3) flavonoid?s health protective mechanisms could be in part explained by the capacity of flavonoids and related polyphenols to modulate redox, inflammatory and oncogenic signals.