A systematic review of in vitro studies evaluating the inhibitory effects of polyphenol-rich fruit extracts on carbohydrate digestive enzymes activity: a focus on culinary fruits consumed in Europe.

Evidence shows that polyphenols can attenuate postprandial blood glucose responses to meals containing digestible carbohydrate. Polyphenol-rich plant extracts are emerging as potential ingredients in functional foods and/or beverages despite limited understanding of their physiological effects. Many studies have investigated the mechanisms of polyphenol-rich fruit extracts on inhibition of digestive enzymes. However, the evidence available has yet to be critically evaluated systematically. This report reviews the in vitro literature to quantify the effect of fruit polyphenol extracts on the activities of digestive carbohydrases. A systematic literature search was conducted using six science databases. Included studies, totaling 34 in number, were in vitro digestion models which quantified gut digestive enzyme(s) activity on starch digestion in the presence of fruit polyphenol extracts. Most studies assessed the effects of fruit extracts on either α-amylase (n = 30) or α-glucosidase (n = 30) activity. Studies were consistent overall in showing stronger inhibition of α-amylase compared to α-glucosidase by proanthocyanidin- and/or ellagitannin-rich fruit extracts. Recommendations are proposed for future reporting of this type of research to enable meaningful synthesis of the literature as a whole. Such knowledge could allow effective choices to be made for development of novel functional foods and beverages.

Applicability of the Ussing chamber technique to permeability determinations in functionally distinct regions of the gastrointestinal tract in the rat.

BACKGROUND: Ussing chambers are commonly utilized for in vitro investigations into gastrointestinal permeability. However, their sensitivity and applicability to the small intestine have not been well characterized. METHODS: In order to investigate the effects of experimentally induced damage and the relative contribution of the mucosa and muscularis externa layers to transmural permeability in the small intestine, stomach and colon, normal rat intestinal tissues were mounted in Ussing chambers with or without removal of the muscularis externa or mucosal layers. Gastric tissues were damaged in vivo by exposure to indomethacin (100 mg kg(-1)), while ileal tissues were damaged in vitro by 0.4 M NaCl. Tissue damage was assessed histologically, while permeability parameters included conductance (G), potential difference (PD) and mucosal to serosal flux of horseradish peroxidase (HRP). RESULTS: Damage localized to the tissue edges (edge damage) accounted for 25%-50% of the exposed epithelial length in the ileum, while less than 20% of stomach and colon epithelium was affected by edge damage. In the damaged stomach, a 20% reduction in epithelialization was accompanied by increases in G (P < 0.001) and HRP (P < 0.01) flux. Removal of the muscularis externa did not affect mucosal viability in the undamaged ileum or colon although HRP flux in the colon, but not ileum, was increased (P < 0.01). Removal of the ileal mucosa produced increases in G and HRP flux, while PD was maintained. CONCLUSION: We conclude that the Ussing chamber technique is suitable for application to studies of gastric and colonic permeability in rats. However, owing to the prevalence and extent of edge damage in the small intestine, we would caution against the use of this technique for permeability studies in this region of the gastrointestinal tract in the rat.