Microbes have made a phenomenal contribution to the health and well-being of people throughout the world. In addition to producing many primary metabolites, such as amino acids, vitamins and nucleotides, they are capable of making secondary metabolites, which constitute half of the pharmaceuticals on the market today and provide agriculture with many essential products. This review centers on these beneficial secondary metabolites, the discovery of which goes back 80 years to the time when penicillin was discovered by Alexander Fleming.

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Microbial drug discovery: 80 years of progress

In this review, recent reports on in vitro starch hydrolysis kinetics are reviewed with regard to the structural characteristics of starches. Factors such as starch granule morphology, amylose to amylopectin ratio, molecular structure, degree of branching in terms of steric hindrance and consequently mass transfer resistance and their effects on the digestibility and absorption of digested carbohydrates have been examined. The physical state of the starch ingested has a major impact on the digestibility therefore effects of processing techniques (thermal processing, extrusion cooking, autoclaving etc.) and starch modification have been discussed. The other constituents of the food matrix, such as proteins, lipids and polysaccharides, play a significant role during processing which affects the physico-chemical characteristics of digesta and the final digestibility of starch. Some molecules naturally occurring in food sources may confer an inhibitory effect during starch hydrolysis.

Starch digestibility in food matrix: a review

Physiology and pathophysiology of intestinal absorption

- Inhibition of α-amylase, enzyme that plays a role in digestion of starch and glycogen, is considered a strategy for the treatment of disorders in carbohydrate uptake, such as diabetes and obesity, as well as, dental caries and periodontal diseases. Plants are an important source of chemical constituents with potential for inhibition of α-amylase and can be used as therapeutic or functional food sources. A review about crude extracts and isolated compounds from plant source that have been tested for α-amylase inhibitory activity has been done. The analysis of the results shows a variety of crude extracts that present α-amylase inhibitory activity and some of them had relevant activity when compared with controls used in the studies. Amongst the phyto-constituents that have been investigated, flavonoids are one of them that demonstrated the highest inhibitory activities with the potential of inhibition related to number of hydroxyl groups in the molecule of the compound. Several phyto-constituents and plant species as α-amylase inhibitors are being reported in this article. Majority of studies have focused on the anti-amylase phenolic compounds.

This article is open to POST-PUBLICATION REVIEW. Registered readers (see “For Readers”) may comment by clicking on on the issue’s contents page.

/pdf/a-amylase-inhibitors-a-review-of-raw-material-and-isolated-4xj6aqk02y.pdf

α-Amylase inhibitors: a review of raw material and isolated compounds from plant source.

In this study we investigated the structural requirements for inhibition of human salivary alpha-amylase by flavonoids. Four flavonols and three flavones, out of the 19 flavonoids tested, exhibited IC50 values less than 100 microM against human salivary alpha-amylase activity. Structure-activity relationships of these inhibitors by computational ligand docking showed that the inhibitory activity of flavonols and flavones depends on (i) hydrogen bonds between the hydroxyl groups of the polyphenol ligands and the catalytic residues of the binding site and (ii) formation of a conjugated pi-system that stabilizes the interaction with the active site. Our findings show that certain naturally occurring flavonoids act as inhibitors of human alpha-amylase, which makes them promising candidates for controlling the digestion of starch and postprandial glycemia.

http://pubs.acs.org/doi/pdf/10.1021/jm800115x

Flavonoids for Controlling Starch Digestion: Structural Requirements for Inhibiting Human α-Amylase

https://www.gastrojournal.org/article/0016-5085(88)90426-X/pdf

Gastrointestinal and metabolic effects of amylase inhibition in diabetics

To further characterize colonic motility in the dog and to examine the effects of intraluminal contents, motor activity in conscious animals was recorded by perfused intraluminal catheters. Animals were studied first with the bowel intact and, later, the colon was fashioned into an isolated loop. In the fasting state, cycles of motility recurred approximately each 30 min. These consisted of sequences of phasic contractions (bursts) that migrated variable distances in either direction; stationary bursts were also recorded. The fasting patterns recorded from intact bowel and isolated loops were not different. Feeding increased colonic motility, and the mean periodicity of cyclic bursts was reduced significantly to approximately 20 min. Moreover, differences were observed between intact bowel and isolated loops in the postprandial period. Diversion of chyme from the colon significantly reduced the motor response to food, but only in the late (2– 4 hr) postprandial period, when the less frequent, fasting cycle returned to the loops. Perfusion of isolated loops with chyme or saline reestablished the postprandial pattern seen in intact bowel. The results suggest that the volume, but not the composition, of luminal contents modify postprandial motility in the canine colon. Additional experiments confirmed that, in particular, volatile fatty acids were probably not important determinants of colonic motility in the dog.

Bernard Flourie

Papers

Gastrointestinal and metabolic effects of amylase inhibition in diabetics

Cyclic motility in canine colon: responses to feeding and perfusion.