Abstract
Raspberry pomace is a source of polyphenols, which nutritional and health promoting properties are not sufficiently known. The aim of this 8-weeks study was to scrutinize if raspberry extracts (REs) with different ellagitannins to flavan-3-ols ratios might favorably affect the caecal fermentation processes and blood lipid profile in rats. Forty male Wistar rats were fed with a standard diet or its modification with two types of REs (E1 and E2) characterized by different ratios of ellagitannins to flavan-3-ols (7.7 and 3.1 for E1 and E2, respectively) and added to a diet at two dosages of polyphenolic compounds (0.15 and 0.30% of a diet; L and H treatments, respectively). Irrespective of polyphenols dietary level, both REs reduced the activity of bacterial β-glucuronidase, increased production of butyric acid in the caecum and reduced triacylglycerols in blood plasma. The E1 treatment at both dosages caused more effective reduction in the concentration of ammonia and elevated acetate level in the caecal digesta than E2. On the other hand, only the E2 treatment lowered value of the atherogenic index when compared with control group. When comparing dosages of REs, a higher one was more potent to reduce the activity of bacterial β-glucosidase, β-, α-galactosidase and lowered value of the HDL profile in plasma. To conclude, REs may favorably modulate the activity of the caecal microbiota and blood lipid profile in rats; however, the intensity of these effects may be related to the dosages of dietary polyphenols and to their profile, e.g., ellagitannins to flavan-3-ols ratio.
Highlights
Raspberries are one of the most widely consumed fruit in various forms, both fresh and processed
The polyphenols dietary treatment was determined to correlate to a daily consumption of fresh raspberry by an adult weighing 70 kg in amount of 0.095 ́0.291 kg and 0.19 ́0.582 kg when compared with diet supplemented with Extract 1 (E1) and extract 2 (E2) raspberry extract, respectively
Irrespective of polyphenol dietary levels, both examined raspberry extracts obtained from pomace exerted an additional favorable effect on microbial functioning by reducing activity of the β-glucuronidase and elevating production of the butyric acid in the caecum as well as on lipid metabolism by reducing TG in rat’s plasma
Summary
Raspberries are one of the most widely consumed fruit in various forms, both fresh and processed These fruits are known as a rich source of dietary antioxidants largely due to their high level of phenolic compounds, which are primarily comprised of cyanidins, anthocyanins, ellagitannins, conjugates of ellagic acid and quercetin [1,2]. In addition to their strong antioxidant properties, raspberries have shown other beneficial bioactivities including anti-inflammation and anti-microbial activity against pathogenic intestinal bacteria [3]. The need to study the exploitation, e.g., of phenolic by-products from raspberry processing, for the manufacture of functional additives to food is substantiated [6]
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