ASSESSING BIOAVAILABILITY OF SOFT FRUIT POLYPHENOLS IN VITRO

Effect of Spray Drying Encapsulation on Nettle Leaf Extract Powder Properties, Polyphenols and Their Bioavailability

Nettle (Urtica dioica L.) is a plant rich in a health-promoting compounds such as polyphenols, which are sensitive and unstable compounds with low bioavailability, that need to be stabilized and protected from external influences. Therefore, the aim of this study was to examine how the temperature, type of carrier and sample to carrier ratio influence the physicochemical properties and encapsulation and loading capacity of the nettle leaf extract powder and examine the effect of encapsulation on the antioxidant capacity and bioavailability of polyphenols. The process yield ranged from 64.63–87.23%, moisture content from 1.4–7.29%, solubility from 94.76–98.53% and hygroscopicity from 13.35–32.92 g 100 g⁻¹. The highest encapsulation (98.67%) and loading (20.28%) capacities were achieved at 160 °C, β-CD:GA (3:1) and sample:carrier ratio of 1:3. Extracts encapsulated at selected conditions showed high antioxidant capacity and distinct polyphenolic profile comprised of 40 different compounds among which cinnamic acids were the most abundant. Moreover, the encapsulation increased the bioavailability of nettle leaf polyphenols, with the highest amount released in the intestinal phase. Thus, the obtained encapsulated extract represents a valuable source of polyphenols and may therefore be an excellent material for application in value-added and health-promoting products.

Effect of Fortification with Raspberry Juice on the Antioxidant and Potentially Anti-Inflammatory Activity of Wafers Subjected to In Vitro Digestion

The aim of this study was to investigate the effect of raspberry juice addition on the content of phenolic compounds and the antioxidant activity of wafers. The research was carried out on non-supplemented wafers (control) and wafers in which water was replaced with raspberry juice in the amount of 10%, 20%, 50%, 75% and 100%. The potential bioavailability of the phenolic compounds after in vitro digestion was also determined. As shown by the consumer assessment, wafers in which the water was replaced with 100% raspberry juice turned out to be the best variant of the enriched wafers. The content of total phenolic compounds, flavonoids, phenolic acids, and anthocyanins in the tested products increased with the increasing amount of raspberry juice added to the wafers. The fortification of the wafers with raspberry juice had a positive effect on the antioxidant activity, expressed as the ability to neutralize free radicals ABTS (2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)) and DPPH (di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium), the ability to chelate iron ions, and as the reduction power. The simulated digestion increased the content of phenolic compounds and increased the antioxidant activity of the wafers. The ability to inhibit lipoxygenase and cyclooxygenase 1 and 2 (i.e., enzymes involved in the induction of inflammation), varied and depended on both the amount of raspberry juice added and the type of extract.

Nontargeted LC-MSn Profiling of Compounds in Ileal Fluids That Decrease after Raspberry Intake Identifies Consistent Alterations in Bile Acid Composition

Ileostomy studies provide a unique insight into the digestion of foods, allowing identification of physiologically relevant dietary phytochemicals and their metabolites that are important to gut health. We previously reported an increase of components, including novel triterpenoids, in ileal fluids of 11 ileostomates following consumption of raspberries using nontargeted LC-MSⁿ techniques in combination with data deconvolution software. The current study focused on components that consistently decreased postsupplementation. After data deconvolution, 32 components were identified that met exclusion parameters of m/z signals and which decreased significantly in ileal fluids from eight of 11 participants post-raspberry supplementation. Two-thirds of these components were identified putatively from their MS properties. Consistent decreases were observed in components that possibly reflected "washing out" of presupplementation intake of common foods/drinks including (poly)phenol metabolites. Metabolites associated with fat metabolism such as hydroxylated fatty acids and cholate-type bile acids were specifically reduced. However, more directed re-examination of the data revealed that although some cholates were consistently reduced, the more polar glyco- and tauro-linked bile acid derivatives increased consistently, by as much as 100-fold over presupplementation levels. The possible reasons for these substantial alterations in bile acid composition in ileal fluids in response to raspberry intake are discussed.

Mind the gap-deficits in our knowledge of aspects impacting the bioavailability of phytochemicals and their metabolites--a position paper focusing on carotenoids and polyphenols

Various secondary plant metabolites or phytochemicals, including polyphenols and carotenoids, have been associated with a variety of health benefits, such as reduced incidence of type 2 diabetes, cardiovascular diseases, and several types of cancer, most likely due to their involvement in ameliorating inflammation and oxidative stress. However, discrepancies exist between their putative effects when comparing observational and intervention studies, especially when using pure compounds. These discrepancies may in part be explained by differences in intake levels and their bioavailability. Prior to exerting their bioactivity, these compounds must be made bioavailable, and considerable differences may arise due to their matrix release, changes during digestion, uptake, metabolism, and biodistribution, even before considering dose- and host-related factors. Though many insights have been gained on factors affecting secondary plant metabolite bioavailability, many gaps still exist in our knowledge. In this position paper, we highlight several major gaps in our understanding of phytochemical bioavailability, including effects of food processing, changes during digestion, involvement of cellular transporters in influx/efflux through the gastrointestinal epithelium, changes during colonic fermentation, and their phase I and phase II metabolism following absorption.

Tracking (Poly)phenol components from raspberries in ileal fluid

The (poly)phenols in ileal fluid after ingestion of raspberries were analyzed by targeted and nontargeted LC-MS(n) approaches. Targeted approaches identified major anthocyanin and ellagitannin components at varying recoveries and with considerable interindividual variation. Nontargeted LC-MS(n) analysis using an orbitrap mass spectrometer gave exact mass MS data which were sifted using a software program to select peaks that changed significantly after supplementation. This method confirmed the recovery of the targeted components but also identified novel raspberry-specific metabolites. Some components (including ellagitannin and previously unidentified proanthocyanidin derivatives) may have arisen from raspberry seeds that survived intact in ileal samples. Other components include potential breakdown products of anthocyanins, unidentified components, and phenolic metabolites formed either in the gut epithelia or after absorption into the circulatory system and efflux back into the gut lumen. The possible physiological roles of the ileal metabolites in the large bowel are discussed.

Persistence of anticancer activity in berry extracts after simulated gastrointestinal digestion and colonic fermentation

Fruit and vegetable consumption is associated at the population level with a protective effect against colorectal cancer. Phenolic compounds, especially abundant in berries, are of interest due to their putative anticancer activity. After consumption, however, phenolic compounds are subject to digestive conditions within the gastrointestinal tract that alter their structures and potentially their function. However, the majority of phenolic compounds are not efficiently absorbed in the small intestine and a substantial portion pass into the colon. We characterized berry extracts (raspberries, strawberries, blackcurrants) produced by in vitro-simulated upper intestinal tract digestion and subsequent fecal fermentation. These extracts and selected individual colonic metabolites were then evaluated for their putative anticancer activities using in vitro models of colorectal cancer, representing the key stages of initiation, promotion and invasion. Over a physiologically-relevant dose range (0–50 µg/ml gallic acid equivalents), the digested and fermented extracts demonstrated significant anti-genotoxic, anti-mutagenic and anti-invasive activity on colonocytes. This work indicates that phenolic compounds from berries undergo considerable structural modifications during their passage through the gastrointestinal tract but their breakdown products and metabolites retain biological activity and can modulate cellular processes associated with colon cancer.

Berry polyphenols inhibit α-amylase in vitro: identifying active components in rowanberry and raspberry

Polyphenol-rich extracts from a range of berries inhibited α-amylase in vitro, but the most effective were from raspberry and rowanberry (IC50 values of 21.0 and 4.5 μg/mL, respectively). The inhibitory components were examined by different approaches. Extracts from yellow and red raspberries were equally able to inhibit α-amylase. Because the yellow raspberry extracts effectively lacked anthocyanins, this suggested that they were not crucial for amylase inhibition. Notably, however, higher levels of other phenolic components in yellow raspberries (particularly, ellagitannins) did not increase amylase inhibition. Amylase inhibition in rowanberry was recovered in a fraction enriched in proanthocyanidins (PACs). Inhibition was ameliorated by bovine serum albumin, suggesting that PACs acted by binding to amylase. Co-incubation of rowanberry PACs with acarbose reduced the concentration of acarbose required for effective amylase inhibition. Such synergistic interactions could have implications for the current clinical use of acarbose for postprandial glycaemic control in type-2 diabetics.

Current developments on the inhibitory effects of berry polyphenols on digestive enzymes

The recent developments and evidence for the effect of polyphenol components of berries on digestive enzymes has been reviewed. Certain plant polyphenols can inhibit starch digestive enzymes in the gastrointestinal tract and modulate blood glucose control in vivo. Certain berry polyphenol components can inhibit protease activities at levels which could affect protein digestion in the gastrointestinal tract. In addition, other polyphenol components show potential for the inhibition of gastrointestinal lipase activity, which is a proven therapeutic target for the control of obesity through reduced fat digestion. Taking into account the potential synergies for inhibition of starch and lipid digestion by the spectrum of polyphenol components present within berry species, the inhibition of digestive enzymes by dietary polyphenols may be another important mechanism for the health benefits attributed to a diet rich in fruit and vegetables.