Effect of legume dietary fiber on rat disaccharidase activity in vitro

Abstract

PurposeBrush border intestinal disaccharidases (maltase, sucrase and lactase) play an important role in carbohydrate assimilation. These enzymes are located on the brush border and may interact with legume seed components such as dietary fiber and polyphenols. The purpose of this paper is to assess the effect of legume dietary fiber on rat disaccharidase in vitro.Design/methodology/approachRat intestinal disaccharidases from Sprague‐Dawley rats fed a basal diet for 21 days were partially purified from intestinal scrapings. Enzyme activities were tested in vitro in the absence and presence of total dietary fiber isolated from Phaseolus vulgaris (Varieties Tacarigua and Montalbán) and Vigna unguiculata (Varieties Unare and Tuy) seeds that differ in fiber and polyphenol content. Dietary fiber was purified using the AOAC method.FindingsThe specific activities of the intestinal brush‐border disaccharidases from rats fed the basal diet were 3.29 ± 0.06, 3.13 ± 0.62 and 0.18 ± 0.04 umoles of glucose released/mg of protein/min for maltase, sucrase and lactase, respectively. Total dietary fiber from the legume tested inhibited both sucrase and maltase. Fiber from the four seeds tested affected sucrase similarly (average inhibition 35 per cent) whereas the fiber residue from P. vulgaris Montalbán was more effective on maltase (26.7 per cent) than that from P. vulgaris Tacarigua (12.2 per cent). Effect of V. unguiculata fibers on maltase was similar and somewhat in between those from P. vulgaris.Originality/valueThese results suggest that dietary fiber, as well as other factors from beans with anti‐physiological effect, such as condensed tannins and fitic acid possibly associated with the dietary fiber, may impair carbohydrate availability and may contribute to the low glycemic index proper of these foodstuffs.