Blood Glucose Lowering Efficacy of Strawberry Extracts rich in Ellagitannins with Different Degree of Polymerization in Rats

Abstract

In two experiments on rats it was analyzed whether the lowering rate of postprandial glycaemia depends on the degree of polymerization of strawberry ellagitannins (ET). Two types of highly-concentrated polyphenolic extracts were used, one rich in monomeric ET (ETM; 94.9% polyphenols and 67% ETM in it), the second in dimeric ET (ETD; 95.9% polyphenols, and 78.0% ETD in it). The experiment 1 comprised three oral sugar tolerance tests, GTT (with glucose; to examine monosaccharide transport across epithelium), SuTT (with sucrose; to examine the activity of mucosal disaccharidase) and StTT (with starch; to examine the action of salivary alpha-amylase, and then of pancreatic amylase in the small intestine as well as all the aforementioned mechanisms), while in the experiment 2 the healthy and pre-diabetic rats were subjected to 1-h small intestine perfusion with fl uids containing glucose or sucrose. Considering the shape of blood glucose concentration curve following GTT and SuTT, as well as changes in glycaemia and mucosal disaccharidases activity observed within and after small intestine perfusion, the ETM (vs. ETD) extract more positively mitigated sugar-induced postprandial glycaemic load. Contrary to expectations, the effect of extracts on pre-diabetic rats was negligible. The extract ETD, in turn, potently mitigated starch-induced postprandial glycaemic load during test StTT. The results clearly showed that the separate mechanisms (glucose transport across the intestine, intestinal mucosal disaccharidases inhibition activity, pancreatic α-amylase inhibitory activity) leading to decreased postprandial glycaemia upon dietary administration of strawberry ellagitannins largely depended on their chemical structure, i.e. degree of polymerization.Unauthenticated Download Date | 5/8/18 6:07 AM

Agrimoniin, an Active Ellagitannin from Comarum palustre Herb with Anti-α-Glucosidase and Antidiabetic Potential in Streptozotocin-Induced Diabetic Rats

“…There is increasing evidence that polyphenolic compounds, especially ellagitannins, from plants can cause insulin-like effects on glucose utilization [ 39 , 40 , 41 ]. Earlier, the ability of dimeric ellagitannins from strawberry extract to reduce elevated blood glucose was shown [ 42 ]. In this connection, we decided to estimate the hypoglycaemic activity of C. palustre extracts (A and B) and evaluate the same activity for the predominant dimeric ellagitannin agrimoniin.…”

Protective Effects of Ellagitannin-Rich Strawberry Extracts on Biochemical and Metabolic Disturbances in Rats Fed a Diet High in Fructose

“…It is well known that even a small change in the chemical structure of a molecule is of paramount importance to its biological activity in the host’s body [ 10 , 11 , 12 ]. Our recent study showed that the separate mechanisms leading to decreased postprandial glycaemia upon dietary administration of strawberry ETs largely depends on their chemical structure, i.e., degree of polymerization [ 13 ]. In the study on rats it was presented that extract with monomeric ETs was mitigated the glucose- or sucrose-induced postprandial glycemic load more beneficially than extract with dimeric ETs [ 13 ].…”

“…Our recent study showed that the separate mechanisms leading to decreased postprandial glycaemia upon dietary administration of strawberry ETs largely depends on their chemical structure, i.e., degree of polymerization [ 13 ]. In the study on rats it was presented that extract with monomeric ETs was mitigated the glucose- or sucrose-induced postprandial glycemic load more beneficially than extract with dimeric ETs [ 13 ]. Another study by Jurgoński et al [ 14 ] showed strong antibacterial activity of a dietary combination of monomeric strawberry ETs with fructooligosaccharides (FOSs) in the rat cecum, and this effect was not observed with dimeric ETs or in treatments without FOSs.…”

Nutritional and Pharmacological Properties of Agro-Industrial by-Products From Commonly Consumed Fruits

“…Ellagitanins from strawberry pomace decreased postprandial glycaemia in rats by mitigated glucose-, starch-or sucrose-induced postprandial glycemic load. It also decreased the activities of mucosal sucrose and maltase in the jejunum [105].…”