Herbal teas: their potential as health promoting beverages and bioactive functional foods

In recent times, there is a growing interest in nutrition and preventive health care in the development and evaluation of natural bioactive and antioxidant active products from plant materials. It is well known that polyphenol compounds are responsible for the potential antioxidant activity and radical scavenging capacity of plant foods. Consumption of a diet rich in polyphenol substances has been linked with a reduced risk for cardiovascular diseases and certain types of cancer. Dietary natural antioxidants strengthen the endogenous antioxidant system by reducing oxidative stress and the risk of toxic diseases. Radical scavenging antioxidants are particularly important in antioxidant defense to protect cells from the injurious effects of free radicals. Free radicals are very reactive chemical species, eventually evoking uncontrolled reactions, resulting in oxidative damage of important biological macromolecules. Polyunsaturated fatty acids which are major constituents of cell membranes are particularly susceptible to free-radical-mediated oxidation because of their conjugated bond structure. Consequently, the process of lipid peroxidation can lead to disturbances in membrane structure and function. Furthermore, and viewed in a global sense, polyphenol compounds as free radical scavengers can act as anti-inflammatory, antibacterial, anti-carcinogenic, anti-allergic and immune-stimulating agents.