Phenolic compounds, health effects and antioxidant properties of berries

The biological value of berries relies on their nutritive and non-nutritive constituents. They are good sources of vitamins (vitamin A, C, E, folic acid), pro-vitamins and related compounds (carotene and lutein), minerals (calcium and selenium) and phytosterols, but the proposed health benefit is usually connected with phenolics as the main biologically active compound of berries. Berry phenolics include anthocyanins, flavonols, flavanols, condensed tannins (proanthocyanidins), hidrolyzable tannins (ellagitannins and gallotannins) and phenolic acids. Berries are recognized as the best dietary sources of anthocyanins. Different berries are distinguished by the presence of different classes of phenolics or compounds within the same class, their content and chemical structure (substituents, glycosylation, conjugation), potentially influencing their physiological properties and health effects. Analytical assessment of the phytochemical content of berries, the effects of storage and processing and putative interaction with other dietary compounds is essential for evaluation of their health benefit. It is of great importance to emphasize the biodiversity in the context of different phytochemical content in wild versus cultivated species, different varieties of the same species, or influenced by different cultivating conditions. Beneficial effects of berries consumption in health promotion and prevention of chronic diseases, such as cancer or cardiovascular diseases are shown in numerous epidemiological studies. In in vitro and animals studies berry fruits, their extracts and isolated compounds showed antioxidant, anticancer, antidiabetic, hypoholesterolemic, anti-inflammatory, vasoprotective, cardioprotecive, antiplatelet, antitrombotic or antimicrobial effects. Some of these effects are also shown in clinical trials in humans. Phenolic compounds of berries and their extracts have strong antioxidant potential that is often used to explain their health-promoting properties. Recent studies postulated that their antioxidant potential, as a basic mechanism of biological activity, is compromised by their low bioavailability. Consequently further research in this area is targeted towards other mechanisms of action, the evaluation of main sites of action and further elucidation of potential of berry phenolic compounds as antioxidants, based on their structure or metabolism, both in vitro and within the human body