Determination of in vitro biological effects of extracts from fruits and berries related to polyphenol composition

Epidemiological studies have shown that consumption of fruits and vegetables is associated with a lower risk of chronic diseases such as cancer, cardiovascular disease and diabetes. Polyphenols are present in especially high concentrations in peels and se eds of fruits and berries. During production of fruit juices a substantially part of the fruit material, mainly peels and seeds, remains in the presscake, leading to a considerable loss of polyphenols during processing.Many of the positive effects of the polyphenols have been attributed to their antioxidant activities. However, it has gradually become clear that the mechanisms of action go beyond their activity as antioxidants. There is increasing focus on effects of polyphenols in the gastrointestinal tr act where they are present in high concentrations. Among the suggested mode of action of polyphenols is as modulators of activity of enzymes in the human digestive tract. Polyphenol extracts have been found to inhibit alfa-glucosidase and alfa-amylase act ivity. Inhibition of intestinal alfa-glucosidase and alfa-amylase activity may influence the digestion of carbohydrates and thereby prevent hyperglycemia and diabetes mellitus in the long term. Berry polyphenols have also been shown to inhibit pancreatic lipase activity in vitro and can thus contribute to suppression of fat intake and thereby influence obesity. The aims of the present project are 1) to establish methods for measuring effects of polyphenols on digestive enzymes, e.g. inhibition of intest inal alfa-glucosidase, alfa-amylase and pancreatic lipase activities. 2) To characterize extracts from press-residues after production of fruit juices by measuring phenolic contents and antioxidant capacities, in addition to the established methods for me asuring inhibition of digestive enzymes. 3) To classify the samples and find correlations between the results obtained by different methods.