Chemical composition of polyphenols extracted from strawberry pomace and their effect on physiological properties of diets supplemented with different types of dietary fibre in rats

The objective of this study was to establish the composition of polyphenolic preparations obtained from industrial strawberry pomace with two methods of extraction: the water and the water-alcoholic one and then to analyse their effects in the gastrointestinal tract depending on the composition of dietary fibre-cellulose or fructooligosaccharides (FOS). Freeze-dried water extract (PTW), containing 5.1 % of ellagic acid, 0.2 % of proanthocyanidins, and soluble carbohydrates as a major part, and water-alcohol extract (PTE), containing 17.1 % of ellagic acid and 10.9 % of proanthocyanidins, were administered, in the equivalent quantity of 0.06 % of ellagic acid, to 4- to 8-week-old rats (8 animals per group), as a component of modified AIN-93 diets containing 5 % of cellulose or FOS. The addition of strawberry pomace extracts had no effect on either the diet intake or the body weight of experimental rats. Both extracts, similarly to FOS, beneficially reduced the activity of beta-glucuronidase in caecal digesta, with the PTW effect being significantly higher than that of PTE (7.59 vs. 9.20 mu mol/h/g, P = 0.001). In comparison with PTE, the PTW extract significantly increased the caecal digesta mass (1.45 vs. 1.27 k/kg BW) and the total production of SCFA (86.1 vs. 71.4 mu mol/100 g BW). The extract enhanced the physiological effect of FOS by inhibiting the activity of beta-glucuronidase, increasing the caecal digesta mass and SCFA production. Such an effect was not recorded in the case of the PTE preparation. The addition of strawberry pomace extracts affected the activity of certain enzymes of intestinal microflora and its most important products.