S. Frejnagel

Biological activity of polyphenol extracts from different plant sources

Abstract In experiments on rats, five diets without or supplemented with polyphenol extracts from different sources (flavons from skullcap, catechins from green tea, anthocyanins from chokeberry and condensed tannins from faba bean) were applied. Obtained results suggested that when catechin extracts were added to the diets in large amounts (0.8%), beneficial effects (reduction of total cholesterol and LDL fraction in serum) were observed, but also reduction in protein digestibility and protein efficiency ratio (from 94.6 to 93.1% and from 2.57 to 2.40, respectively), compared to the control group. All extracts decreased the activity of erythrocyte superoxide dismutase and increased the activity of alanine aminotransferase in the serum. Only the tannin extract decreased the content of calcium in femur. More profitable biological properties were found for catechin extract from green tea and flavons extract from skullcap, compared to anthocyanins from chokeberry and condensed tannins from faba bean.

Influence of alkaloids and oligosaccharides from white lupin seeds on utilization of diets by rats and absorption of nutrients in the small intestine

Abstract The influence of quinolizidine alkaloids and oligosaccharides from white lupin seeds was studied on the absorption of nutrients in the small intestine and utilization of diets by rats. The source of oligosaccharides and alkaloids was the ethanol extract from high- and low-alkaloid seeds. The respective content of alkaloids in the extracts was 118.7 and 7.9 g kg −1 d.m., and of oligosaccharides 546.5 and 867.9 g kg −1 d.m. The alkaloid fraction obtained from the ethanol extract of high-alkaloid seeds by fractionation with organic solvents and ion exchange chromatography was also used. A distinct reduction of true protein digestibility (from 95.7% to 90.5%) was found in the experiment in which oligosaccharides were added to the casein diet in the amount of 17.09 g kg −1 (the amount contained in the diets with 150 g kg −1 low-alkaloid white lupin seeds). An adverse influence of alkaloids on casein digestibility was found only for the highest addition of alkaloids (0.32 g kg −1 ), corresponding to their level in the diet with 500 g kg −1 low-alkaloid lupin seeds. Using the perfusion technique, it was found that oligosaccharides decreased the absorption rates of glucose and methionine in the rat small intestine. Application of 203.53 mg of oligosaccharides during 1-h perfusion, i.e., the amount present in the 24-h diet with 100 g kg −1 lupin seeds decreased the absorption of glucose (from 88.42 to 66.21 mg h −1 ) and methionine (from 0.332 to 0.116 mg h −1 ) from the perfusion fluid compared to the control fluid. Glucose and methionine absorption did not correlate with alkaloid content in the perfusion fluid, whereas it correlated with oligosaccharide content in this fluid: r =−0.561 ** and r =−0.645 ** , respectively. Extraction of alkaloids and oligosaccharides resulted in an increase of the utilization of protein from lupin seeds. The highest PER (2.40) was noted for the diet with extracted low-alkaloid seeds, which contained low levels of alkaloids and oligosaccharides: 0.09 and 1.13 g kg −1 , respectively. Significantly lower PER was noted for the diet containing crude seeds of low-alkaloid lupin variety (alkaloid level 0.16 g kg −1 ) and the highest amount of oligosaccharides (29.2 g kg −1 ).

Comparative Effect of Green Tea, Chokeberry and Honeysuckle Polyphenols on Nutrients and Mineral Absorption and Digestibility in Rats

Background/Aims: Natural polyphenols are chemically and biologically active. This study aimed at examining the physiological effects of high doses of polyphenol extracts from green tea and new polyphenol-rich sources (chokeberry and honeysuckle fruits) on nutrient absorption. Methods: 32 male Wistar rats were divided into four groups and fed a diet supplemented with one of the three polyphenolic extracts (at 0.4%) or a control diet for 4 weeks. A perfusion technique was used to study the effects at intestinal level. Pure polyphenols from the three sources were introduced into perfusion fluid at a concentration of 0.4% and allowed to cross the intestinal tract in 1.5 h. Results: In the perfusion experiment, addition of the extracts caused a strong and statistically significant reduction in absorption of the selected nutrients (water, glucose, cholesterol, amino acids and minerals) compared to control animals. In the nutritional experiment, we recorded a slight decrease in diet utilization and growth in rats on polyphenolic diets relative to control group. In the same experiment, we observed a reduction of Zn and Cu absorption, but this was not accompanied by diminished concentrations in the bone femur. Conclusions: The presence of the polyphenolic extracts in the perfusion liquids significantly reduced absorption from the small intestine, but the nutritional experiment did not confirm deleterious consequences of the consumption of high extract doses.

Caecal parameters of rats fed diets supplemented with inulin in exchange for sucrose

Abstract The effects of different modes of inulin supplementation on caecal fermentation were evaluated in rats. Groups S and IN were fed diets containing 5% of sucrose or inulin, respectively, for the whole experimental period of 40 days. Group IN/S was fed IN and S diets, whereas group S/IN was fed S and IN diets, in the first and the second 20-day period, respectively. Groups INup and INdown were fed diets in which the content of inulin increased from 1 – 5% and decreased from 5 – 1%, every 8 days, respectively. The common effects of inulin on caecal fermentation, i.e. enlargement of tissue, acidification of digesta, a decrease in activities of potentially harmful bacterial enzymes (β-glucuronidase and β-glucosidase), and an increase in the total volatile fatty acids concentration and pool, were especially observed in the IN, S/IN and INup groups. The results suggested that the intensity of caecal fermentation is increased when inulin is present at a relatively high dietary level and that these changes are easily reversible after inulin withdrawal from feed.