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

Abstract

PurposeThe 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).MethodsFreeze-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.ResultsThe 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 β-glucuronidase in caecal digesta, with the PTW effect being significantly higher than that of PTE (7.59 vs. 9.20 μmol/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 μmol/100 g BW). The extract enhanced the physiological effect of FOS by inhibiting the activity of β-glucuronidase, increasing the caecal digesta mass and SCFA production. Such an effect was not recorded in the case of the PTE preparation.ConclusionsThe addition of strawberry pomace extracts affected the activity of certain enzymes of intestinal microflora and its most important products.

Physiological Properties of Dietary Ellagitannin-Rich Preparations Obtained from Strawberry Pomace Using Different Extraction Methods

“…In terms of the composition of the polyphenolic fraction, the EF preparation was similar to the water extract obtained in an earlier study by Kosmala et al [2014]. In the presented experiment, the addition of enzymes in the process of water extraction increased the content of soluble dietary fibre to 33%, compared to its 22% content noted in the preparation produced through three-stage water extraction at 65-70°C [Kosmala et al, 2014].…”

“…In many earlier experiments with the use of similar or even higher concentrations of fruit polyphenols in diets, no negative effects of these compounds were demonstrated on feed intake and growth of experimental animals [Zduńczyk et al, 2006;Frejnagel & Juśkiewicz, 2011;Jurgoński et al, 2011;Kosmala et al, 2011Kosmala et al, , 2014. In the presented study, doses of ellagitannins applied in a daily diet (0.015 and 0.016 g/kg BW 0.75 ) did not affect feed intake and body weight gains of rats.…”

“…In terms of the composition of the polyphenolic fraction, the EF preparation was similar to the water extract obtained in an earlier study by Kosmala et al [2014]. In the presented experiment, the addition of enzymes in the process of water extraction increased the content of soluble dietary fibre to 33%, compared to its 22% content noted in the preparation produced through three-stage water extraction at 65-70°C [Kosmala et al, 2014]. This result indicates that the additional application of glycolytic enzymes in water extraction of ellagitannins, aimed at reducing energy consumption of this process, does not change the composition of the polyphenolic fraction, but only increases the content of soluble dietary fibre in the resultant product.…”

“…Only trace amounts of ellagitannin metabolites are absorbed in the stomach and small intestine [Espin et al, 2007], however, the majority of these substances are metabolised by the large intestinal microbiota [Mertens-Talcott et al, 2006;Tomas-Barberan et al, 2008]. The presence of polyphenols in digesta may affect the basic functions of intestine, including hydration and pH value of digesta [Zdunczyk et al, 2006], caecal digesta mass [Kosmala et al, 2014;Jurgoński et al, 2011] and ammonia concentration . In the reported experiment, both preparations were observed to similarly lower ammonia concentration in digesta and to differently affect the mass and pH value of caecal digesta, namely the ET preparation with dietary fibre had no effect on these parameters whereas the ET preparation with proanthocyanidins (with ratio of both groups of polyphenols at ca.…”

“…More effective extraction is that with the use of organic solvents which enables minimising the content of carbohydrates in the resultant extract. Due to differences in the chemical composition of fruit pomace and diverse efficiency of various solvents, the extracts may differ in composition and physiological properties [Kosmala et al, 2014]. Results of earlier studies by Aprikian et al.…”