M. Wróblewska

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.

Effect of non-digestible oligosaccharides on gut microecosystem in rats

Abstract Effect of commercial or new-developed preparations of non-digestible oligosaccharides: fructo-oligosaccharides, lactulose, corn dextrins and corn resistant starch, on microecology of Wistar rats was investigated. A control group was fed a casein diet with 10% cellulose. The experimental groups were administered diets in which cellulose was replaced by the examined preparations. After 4-week feeding experiments, a high increase in live bifidobacteria number by 1.2 and 1.4 log cfu/g of faeces was found in groups fed resistant starch and lactulose. An increase in coliform number by 0.6–0.8 log cfu/g was found in all the groups. No or only negligible changes in numbers of the total mesophilic aerobic and facultatively anaerobic bacteria count, and the spores of anaerobic and aerobic bacteria, were observed. Fructo-oligosaccharides and lactulose lowered pH and gave the best trophic effect in caecum (significantly increased weights of: caecum with contents, cecal walls and cecal contents as well as dry weight of contents), whereas resistant starch increased markers of unhealthy cecal changes (N-NH3 content and β-glucuronidase activity). The activity of bacterial saccharolytic enzymes changed in a substrate-specific manner in relation to the examined non-digestible oligosaccharide preparations.

The response of rats to feeding with diets containing grapefruit flavonoid extract

In two experiments, the response of rats to feeding with diets containing grapefruit flavonoids was examined. In the first experiment, during 8 weeks, four diets without or with 0.1, 0.2 and 0.4% extract of flavonoid from grapefruit (from 0.05 to 0.2% DM pure flavonoids) were applied. In the second experiment, during 10 days, diets with oxidised fat (100 meq O2/kg) and without or with 0.4% extract of flavonoid were applied. The obtained results showed that the addition of 0.1–0.4% extract of flavonoid from grapefruit did not affect the diet intake and the body weight gain of rats, and slightly increased the antioxidative potential of serum (decreased the MDA content but had no significant effect on the PGx and SOD activities). The addition strongly affected functioning of the blind gut ecosystem causing an increased filling with contents, an increase in the intestinal wall mass and pH, as well as a decrease in the microbiological activity of β-glucuronidase and an increase in the α-galactosidase activity.

Polyphenol-Rich Strawberry Pomace Reduces Serum and Liver Lipids and Alters Gastrointestinal Metabolite Formation in Fructose-Fed Rats

This study compared the effects of supplementation with a polyphenol-rich pomace from strawberry (US) and a strawberry pomace without most of these compounds (PS) on gastrointestinal, blood, and tissue biomarkers in rats fed diets differing in carbohydrate contents for 4 wk. The diets were: corn starch (group CS), high fructose (60% by weight; group F), starch with 7.7% of either US or PS (groups CS+US and CS+PS, respectively), and high fructose with 7.7% of either US or PS (groups F+US and F+PS, respectively). An interaction (P < 0.05) was observed between diet type and strawberry preparation, showing that upon fructose feeding, US had a greater effect than PS on lowering serum insulin, liver total cholesterol, and conjugated dienes. Additionally, the F+US group had lower serum FFA than the F+PS group (P < 0.05). The extraction of polyphenols diminished the physiological effect associated with strawberry intake, suggesting that the fiber component of the pomace was also active in reducing metabolic complications following fructose feeding to rats.

Physiological effects of lactulose and inulin in the caecum of rats

A model experiment was performed on rats to evaluate the effect of partial or total substitution of saccharose (S) and cellulose (C) by preparations of lactulose and inulin on the development and metabolism of the caecum. In the experimental diets given to rats for 4 weeks, the examined preparations were administered either with an equivalent amount of cellulose (each at 4% of the diet) or as sole source of dietary fibre at 8% of the diet. Compared to the saccharose group cellulose had no effect, and low doses of lactulose and inulin in the diet increased to a medium extent the weight of the caecum wall and caecal digesta. The addition of lactulose and inulin at 8% increased significantly the content of caecal digesta (4.62 and 4.11 g/100g BW, respectively) and the weight of the caecal wall (1.10 and 0.86 g/100g BW, respectively), compared to the groups with saccharose and cellulose (0.73, 0.90 and 0.24, 0.28 g/100g BW, respectively). Cellulose and cellulose partially-substituted with lactulose and inulin caused an increase in the dry matter content of caecal digesta (26.5–27.5%), compared to other groups (21.8–22.8%). The administration of lactulose and inulin preparations was accompanied by a significant drop in pH (5.47–5.81), compared to the groups with cellulose or saccharose (6.83–6.91), and a decrease in the ammonia concentration in the caecal digesta, compared to the cellulose control (0.27–0.40 and 0.62 mg/g, respectively). The group with 8% lactulose was characterized by the highest activities of microbiological α- and β-galactosidase and β-glucosidase in the caecal digesta. Cellulose and both preparations significantly decreased the activity of β-glucuronidase, compared to the saccharose group (0.39–0.89 and 1.52 U/g, respectively). The highest concentration of VFA in the caecal digesta was observed in the saccharose group (89.2 μmol/g), and the lowest concentration in the group where cellulose was totally substituted by lactulose and inulin (55.1 and 57.5 μmol/g, respectively). The total production of VFA in the caecum was fourfold higher with 8 % lactulose and inulin (254.7 and 236.4 μmol/100g BW, respectively) than in both controls groups (65.1 and 67.8 μmol/100g BW, respectively). The high dose of inulin and lactulose increased the share of propionic acid in the VFA profile (C2:C3:C4) compared to both control groups. When 4% inulin was added to the diet a significant increase of butyrate concentration in the caecum was observed.

Physiological properties of beetroot crisps applied in standard and dyslipidaemic diets of rats

BackgroundThe objective of the present study was to examine the influence of adding various amounts beetroot (Beta vulgaris) crisps on gastrointestinal function, antioxidant status and blood and liver lipid profiles in a high fat diet-induced dyslipidaemic rat model;ResultsThe intake of a dyslipidaemic diet increased the serum total cholesterol, total cholesterol-to-HDL-cholesterol ratio, atherogenic index, hepatic total cholesterol and triacylglycerols, suppressed production of short-chain fatty acids and decreased total antioxidant status and blood glutathione peroxidase activity. Oral administration of all tested amounts of beetroot crisps prevented the rise in serum total cholesterol and triacylglycerols levels. The treatment with the addition of 3% crisps also decreased hepatic total cholesterol level and activity of AST in serum. The experimental addition of crisps likewise resulted in a tendency towards a higher total SCFA pool and activity of glutathione peroxidase and a lower serum glucose level (p = 0.080, p = 0.061 and p = 0.067, respectively);ConclusionsResults of the presented study suggest that the addition of beetroot crisps could alleviate metabolic changes in dyslipidaemic diet-administered rats.

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.

Metabolic response of the gastrointestinal tract and serum parameters of rabbits to diets containing chicory flour rich in inulin

A 36-day experiment carried out on 54-day-old rabbits addressed the analysis of physiological properties of diets supplemented with chicory roots flour. Twenty-four rabbits were allocated in individual cages to three treatments, in which they were fed each diet with the chicory flour at 0, 25 and 50 g/kg (control, ChF(2.5) and ChF(5) groups respectively). The chicory preparation administered at a higher dose, lowered ileal pH and viscosity, and evoked increased hydration of ileal and caecal digesta, compared to the control treatment (p </= 0.05). The ChF(2.5) group was characterized by the highest increase in the bulk of digesta and concentration of protein in the caecum (p < 0.05 vs. control). The lowest colonic pH was found in the ChF(5) group (p </= 0.05 vs. control). Compared to the control group, both chicory treatments effectively (p </= 0.05) diminished the activity of the potentially harmful bacterial enzymes beta-glucosidase and beta-glucuronidase in the caecal and colonic digesta. The ChF(2.5) group was characterized by a significantly higher volatile fatty acids (VFA) pool size in the caecum, whereas rabbits fed the ChF(5)diet had the highest colonic VFA pool size (p </= 0.05 vs. control). The lowest level of triglycerides and total cholesterol, at concurrently the highest proportion of high-density lipoprotein (HDL) fraction in the HDL/total cholesterol profile, were recorded in the plasma of rabbits fed the ChF(5) diet. In conclusion, the chicory flour rich in inulin, exerted positive effects on the rabbit gastrointestinal tract physiology and would be a potential source of functional feed additives.

Protective effects of polyphenol-rich blackcurrant preparation on biochemical and metabolic biomarkers of rats fed a diet high in fructose

The purpose of the study was to compare in vivo effects of dietary supplementation with blackcurrant pomaces containing variable level of phenolic compounds on blood and internal organ parameters in rats. Forty-eight growing Wistar rats were allocated to six treatment groups in which they were fed ad libitum for 4 weeks the following diets: standard chow (group S), high-fructose diet (group F), standard chow supplemented with 7.7% of either rich in polyphenols unprocessed blackcurrant pomace (UB) or polyphenol-deprived processed pomace (PB) (groups SUB and SPB respectively), and high-fructose diet with 7.7% of either UB or PB (groups FUB and FPB respectively). Blackcurrant pomace, irrespective of its phenolic content, selectively modulated the enzymatic activity of the colon microflora, reducing the activity of enzymes with potentially harmful properties and promoting activities of enzymes that might increase the use of carbohydrates that escaped digestion in the upper gastrointestinal tract. Although both pomaces increased antioxidant status of the liver and blood serum, the unprocessed pomace showed a greater ability to inhibit lipid peroxidation in heart and kidney than the pomace that was less abundant in polyphenols. Both of the examined pomaces had a positive influence on serum lipid profile, but better hypocholesterolemic effect was observed after supplementation of the diet with unprocessed preparation. The biochemical action of unprocessed pomace in the normalization of fructose-induced disturbances was more distinct than those of pomace remaining after extraction.

Effect of buckwheat sprouts and groats on the antioxidant potential of blood and caecal parameters in rats.

The aim of this study was to investigate whether dietary buckwheat sprouts, cultivated without or with light exposure, exerted different effects on the lower gut, antioxidant status, and lipoprotein profile in rats. For 4 weeks, rats were given a diet containing 30 % expanded buckwheat seeds or 5 % buckwheat sprouts, cultivated with or without light exposure. Buckwheat sprouts that were cultivated under light and dark conditions, and expanded seeds, differed in the levels of total phenolic compounds and Trolox Equivalent Antioxidant Capacity values. All buckwheat products added to the diets decreased pH value and dry matter concentration in the caecal digesta compared with the control group. As compared to the control group, the addition of buckwheat products caused a higher glycolytic activity and the production of short-chain fatty acids in the caecum of the rats. There were no significant differences in the plasma concentrations of glucose, total cholesterol, nor triglycerides between the groups. The concentration of high-density lipoprotein (HDL)-cholesterol was significantly higher, and the atherogenic index of plasma was lower in rats administered buckwheat sprouts cultivated in the light, compared to the group fed sprouts cultivated in the dark. Total plasma antioxidant status, activity of glutathione peroxidase, and superoxide dismutase in whole blood were not affected by dietary treatment. Results of the experiment indicated enhanced benefits of dietary supplementation with buckwheat sprouts cultivated under light, especially in relation to the serum lipoprotein profile.