Cecal parameters of rats fed diets containing grapefruit polyphenols and inulin as single supplements or in a combination

Abstract

Objective We compared the effects of grapefruit flavonoids and inulin, as single dietary components or in a combination, on cecal fermentation in rats adapted to a semipurified diet. Methods The experimental diets contained 0.3% flavonoid extract and 5% or 10% inulin and a combination of both supplements. The large bowel metabolism assessment was based on cecal parameters: bulk effect, pH, microbial enzymes activity, and short-chain fatty acid production. Results Both supplements induced significant enlargement of the cecal digesta weight. Acidification of cecal digesta was more pronounced, with a higher inulin addition to the diet. Cecal pH was the highest with the flavonoid-rich diets and lowest in the case of a simultaneous addition of flavonoids and a high content of inulin. The flavonoid extract applied as a single dietary supplement was observed to decrease the activity of bacterial β-glucosidase and β- and α-galactosidases in the cecal digesta. In contrast, addition of the grapefruit extract to inulin-containing diets increased the activity of α-glucosidase, α-galactosidase, and β-galactosidase. Great accumulation of cecal digesta in rats consuming the flavonoid-diet caused a considerable increase in the short-chain fatty acid pool, mainly acetic acid. Inulin added to the diet decreased the excessive enlargement of digesta caused by dietary flavonoids. Dietary addition of inulin to the flavonoid-diet also normalized hydration of cecal digesta and significantly decreased the pH of digesta. The presence of polyphenols in the inulin-containing diets did not change total short-chain fatty acid production in the cecum of rats. Conclusion Our results suggested that simultaneous intake of inulin and polyphenols can decrease the detrimental effects of the latter on cecal fermentation.