Starch digestion in the upper gastrointestinal tract of humans

Abstract

Starch provides a large proportion of the dietary energy consumed worldwide. The breakdown of dietary starch is driven by α-amylase produced by the salivary glands and pancreatic acini and is completed by a range of brushborder bound enzymes. This enzymatic digestion is aided by mechanical and secretory actions of the gastrointestinal tract. The absorption of the resultant glucose in the small intestine is primarily driven by two separate transport proteins À SGLT1 and GLUT2. The control of processes that govern starch digestion is complex and still not fully understood, although it appears that the human gut has the ability to sense both glucose and non-sweet glucose oligomers. Recent work has also suggested that variations in the genes encoding for α-amylase also appear to be associated with health outcomes. The authors consider the physiological factors that govern starch digestion and absorption, consider other dietary factors that may impact on this process and attempt to highlight the limitations in current knowledge to help focus future research needs in relation to starch digestion the upper gastrointestinal tract.

A study towards drug discovery for the management of type 2 diabetes mellitus through inhibition of the carbohydrate-hydrolyzing enzymes α-amylase and α-glucosidase by chalcone derivatives

“…The compounds were divided as chalcones 1-28, with the 1,3-diarylprop-2-en-1-one framework, and chalcone analogues 29-41, known as cinnamylideneacetophenones, which hold two double bonds linking the A and B rings. In the first set of compounds (1-28), one is unsubstituted (1), four are hydroxylated (2-5), ten are hydroxylated and methoxylated (6)(7)(8)(9)(10)(11)(12)(13)(14)(15), two are only methoxylated (16,17), two display methyl substituents (18,19), two display nitro groups (20,21) and seven possess chloro substituents (22)(23)(24)(25)(26)(27)(28). Among the chalcone analogues (29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41), one is unsubstituted (29), eleven present a single substitution, including methyl (30,36), methoxy (31,37), chloro (32), fluoro (33), bromo (34), nitro (35,38,39) and hydroxy…”

“…Chalcone 2, with a 2′-hydroxy group at the A ring, and chalcone 3 with hydroxy groups at C-2′ and C-4′ of the A ring, both without substituents at the B ring, showed no inhibitory activity. Considering the hydroxylated and methoxylated chalcones (6)(7)(8)(9)(10)(11)(12)(13)(14)(15) and the methoxylated chalcones (16 and 17), only chalcone 9 bearing a 2′-hydroxy group at the A ring, a 3-methoxy substituent, and a 4-hydroxy group at the B ring showed slight inhibitory activity of 34 ± 4%, at 150 μM.…”

“…Concerning α-glucosidase, the studies with compounds holding hydroxy groups (2)(3)(4)(5) and the hydroxylated and/or methoxylated compounds (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17), chalcone 4 (butein) was the only chalcone that showed potent inhibitory activity. Negligible activities were found for the remaining hydroxylated and/or methoxylated chalcones (2,3,(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17), except chalcone 9 which has a 2′-hydroxy group at the A ring, 3-methoxy and 4-hydroxy substituents at the B ring, which showed a slight inhibitory activity. These results suggest that the presence of the hydroxy groups is crucial for the inhibition of α-glucosidase activity.…”

“…This slow process continues in the stomach, but mainly in the upper part of the small bowel where the pH allows optimal activity of additional pancreatic α-amylase secreted into the intestinal lumen and α-glucosidase. 7 As a result, pancreatic α-amylase catalyses a more extensive hydrolysis of α-(1,4)-glycosidic bonds into maltose, maltotriose, trisaccharides, and other larger oligosaccharides. 8 Final absorbable monosaccharides, namely glucose, are produced through the activity of the enzyme α-glucosidase located in the brush borders of the enterocytes of the jejunum.…”

Cinnamon Shows Antidiabetic Properties that Are Species-Specific: Effects on Enzyme Activity Inhibition and Starch Digestion

“…4). Although enzyme activity should be reduced by the low pH, the buffering effects of foods can retain activity in gastric conditions for up to 30 min [31] and may explain the sustained effects of cinnamon on starch digestion. No studies have assessed the effects of gastric pH on cinnamon constituent functionality and this is an important area worthy of study.…”