Health Effects Of Polyphenols Research Articles

Absorption and metabolism of polyphenols in the gut and impact on health.

Polyphenols are the most abundant antioxidants in the human diet. They show a considerable structural diversity, which largely influences their bioavailability. Phenolic acids like caffeic acid are easily absorbed through the gut barrier, whereas large molecular weight polyphenols such as proanthocyanidins are very poorly absorbed. Once absorbed, polyphenols are conjugated to glucuronide, sulphate and methyl groups in the gut mucosa and inner tissues. Non-conjugated polyphenols are virtually absent in plasma. Such reactions facilitate their excretion and limit their potential toxicity. The polyphenols reaching the colon are extensively metabolised by the microflora into a wide array of low molecular weight phenolic acids. The biological properties of both conjugated derivatives and microbial metabolites have rarely been examined. Their study will be essential to better assess the health effects of dietary polyphenols. Alternatively, some health effects of polyphenols may not require their absorption through the gut barrier. Their role as iron chelators in the gut lumen is briefly discussed.

Chemistry, Biochemistry, and Dietary Role of Potato Polyphenols. A Review

Potatoes and other plant foods accumulate a variety of secondary metabolites, including phenolic compounds, phytoalexins, protease inhibitors, and glycoalkaloids, as a protection against adverse effects of mechanical bruising, light, and injury by predators including beetles, fungi, and insects. Since these phytochemicals are consumed by insects, animals, and humans as part of their normal diet, a need exists to develop a better understanding of the role of these compounds in both the plant and the diet. To contribute to this effort, this multidisciplinary overview describes analytical and compositional aspects of phenolic compounds in potatoes; their biosynthesis, molecular genetics, and role in host-plant resistance relationships; bruising-, ferrous ion-, and heat-induced discolorations such as after-cooking blackening and blackspot formation, which affect appearance and sensory properties of potatoes; polyphenol-oxidase-catalyzed enzymatic browning reactions and their prevention by chemical and plant molecular biology techniques; and effects of baking, cooking, microwaving, light, and γ-radiation on the stability of the major potato polyphenol, chlorogenic acid. Also covered are beneficial effects of phenolic compounds in the diet as antioxidants, antimutagens, anticarcinogens, antiglycemic, and hypocholesterolemic agents; adverse effects on protein nutritional quality; and recommendations for future research. Understanding the biochemical basis of stress-induced formation of polyphenols in plants, the chemistry of their transformations in the plant and in foods, and their functions in plant physiology, food science, nutrition, and health should stimulate interest in maximizing beneficial sensory, nutritional, and health effects of polyphenols in the diet. Such efforts should lead to better foods and improved human health. Keywords: Antioxidant; blackspot; browning; browning prevention; chlorogenic acid; food quality; food safety; glycoalkaloids; health; host-plant resistance; nutrition; plant genetics; plant physiology; polyphenol oxidase; polyphenols; potatoes; γ-radiation; Solanum tuberosum; storage