Pectin-interactions and the digestive stability of anthocyanins in thermal and non-thermal processed strawberry pulp

This study investigated the digestive stability of anthocyanins (ACNs) and their interaction with three pectin fractions-water-soluble pectin (WSP), cyclohexanetrans-1,2-diamine tetra-acetic acid-soluble pectin (CSP), and sodium carbonate-soluble pectin (NSP)-in strawberry pulp processed by pasteurization (PS), ultrasound (US), electron beam (EB) irradiation, and high pressure (HP). Compared with the control group, the ACNs content increased to the highest level (312.89 mg/mL), but the retention rate of ACNs in the simulated intestine decreased significantly after US treatment. The monosaccharide compositions indicated that the WSP and CSP possessed more homogalacturonan (HG) domains than the NSP, which contains more rhamngalacturonan-I (RG-I) domains. The microstructure of US-treated pectin was damaged and fragmented. Comprehensive analysis showed that the retention rate of ACNs was closely related to the pectin structure, primarily reflected by the degree of linearity and the integrity of structure. These results revealed the structure-activity relationship between ACNs and pectin during pulp processing.

Improving the digestive stability and prebiotic effect of carboxymethyl chitosan by grafting with gallic acid: In vitro gastrointestinal digestion and colonic fermentation evaluation

Carboxymethyl chitosan (CMCS) is a useful polysaccharide with potential applications in food, cosmetic and biomedical industries. Nonetheless, CMCS is unfavorable for maintaining intestinal flora balance. In this study, gallic acid (GA) was grafted with CMCS through ascorbic acid/hydrogen peroxide initiated graft copolymerization reaction, producing GA grafted CMCS (GA-g-CMCS). The digestive and fermentative behavior of CMCS and GA-g-CMCS were investigated by using in vitro simulated gastrointestinal digestion and colonic fermentation models. Results showed that the average molecular weight (M_w) of CMCS gradually decreased during saliva-gastro-intestinal digestion, changing from original sheet-like morphology to porous and rod-like fragments. However, the M_w and morphology of GA-g-CMCS were almost unchanged under saliva-gastro-intestinal digestion. Meanwhile, the grafted GA moiety was not released from GA-g-CMCS during saliva-gastro-intestinal digestion. As compared with CMCS fermentation, GA-g-CMCS fermentation significantly suppressed the relative abundance of Escherichia-Shigella, Paeniclostridium, Parabacteroides, Lachnoclostridium, Clostridium_sensu_stricto_1, UBA1819 and Butyricimonas, while facilitated the relative abundance of Enterobacter, Enterococcus, Fusobacterium and Lachnospira. In addition, GA-g-CMCS fermentation significantly enhanced the production of short-chain fatty acids. These findings suggested that the digestive stability and prebiotic effect of CMCS were improved by grafting with GA.

Fecal fermentation characteristics of Rheum tanguticum polysaccharide and its effect on the modulation of gut microbial composition

Background

Rheum tanguticum is utilized as one of the well known traditional Chinese medicine for the treatment of gastrointestinal diseases. Recently, R. tanguticum polysaccharides (RP) have received increasing attention due to their diversely pharmacological activities. Usually, the pharmacological activities of polysaccharides are closely correlated to their metabolic properties from the stomach to the intestine. However, the digestive behavior and fecal fermentation characteristics of RP are unknown, which need to be fully investigated.

Methods

In this study, an in vitro simulated gastrointestinal model was carried out for the investigation of the digestive behavior and fecal fermentation characteristics of RP. The possible changes in physicochemical properties of RP, such as molecular weight, monosaccharide composition, reducing sugar released, chemical composition, pH value, and short chain fatty acids, were determined during in vitro simulated digestion and human fecal fermentation, and its effect on the modulation of gut microbial composition was also evaluated.

Results

The results revealed that RP was indigestible under the in vitro simulated digestion conditions according to its stabilities in physicochemical properties. Conversely, the indigestible RP (RPI) could be notably utilized by colonic microbiota in human feces after the in vitro fermentation, especially, at the initial fermentation stage (0–6 h). The fecal fermentation characteristics of RPI were revealed. Results showed that the content of reducing sugars obviously increased from 0.177 to 0.778 mg/mL at the initial stage of fermentation, and its molecular weight notably declined from 2.588 × 10⁵ to 0.828 × 10⁵ Da at the end stage of fermentation. Notably, the utilization of arabinose and galactose in RPI by colonic bacteria was faster than that of galacturonic acid. Besides, RPI could obviously modulate gut microbial composition via promoting the relative abundances of several beneficial bacteria, such as genera Bacteroides, Bifidobacterium, and Megamonas, resulting in the promoted production of several short-chain fatty acids, such as acetic, propionic, and butyric acids.

Conclusions

Results from this study showed that RP was indigestible in the human upper gastrointestinal tract in vitro, but could be easily utilized by colonic microbiota in human feces at the initial stage of fermentation. RP could be used as potential prebiotics for the improvement of intestinal health.

Study on the pharmacokinetics of mulberry fruit polysaccharides through fluorescence labeling

A sensitive and efficient fluorescence labeling method was developed and validated for the microanalysis and detection of polysaccharides. Fluorescein isothiocyanate (FITC) was successfully labeled on mulberry fruit polysaccharides (MFP) through a reductive amination reaction with the assistant of tyramine. The fluorescent labeled polysaccharides (FMFP) was identified by fluorescence, UV-visible, flourier transform infrared (FT-IR) and 1H NMR spectrum. Results demonstrated that the labeling efficiency of FMFP was 0.32%, and the FMFP was stable in simulated digestion fluid without cytotoxicity. The pharmacokinetics and biodistribution after administration were analyzed in rats, which indicated that the FMFP obtained could be absorbed in a short time (tmax 0.50 h) but eliminated slowly (t1/2 8.77 ± 1.38 h). At 24 h after administration, the polysaccharide could be tested mainly in intestine, stomach, liver and kidney. The FITC labeling method lays a foundation for investigating the absorption and metabolism of MFP, and provides references for the microanalysis research of bioactive polysaccharides.

A yellow chlorophyll catabolite in leaves of Urtica dioica L.: An overlooked phytochemical that contributes to health benefits of stinging nettle

Stinging nettle is appreciated for its antioxidant and anti-inflammatory properties, which renders the plant a popular ingredient in a healthy diet in form of salads or smoothies. The most common use, presumably, is of dried leaves as ingredient in tea mixtures. The plant's health benefits are attributed primarily to phenolic phytochemicals. Here we describe the characterization and quantification of a phylloxanthobilin (PxB), a yellow chlorophyll catabolite, in nettle tea. Despite their abundance in the plant kingdom, chlorophyll catabolites have been overlooked as phytochemicals and as part of human nutrition. Our investigations of tea reveal that one cup of nettle tea contains about 50 µg of PxB with large variations depending on the supplier. When investigating the bioactivities of PxB, our observations show that PxB has antioxidative and anti-inflammatory activities comparable to known bioactive small molecules found in nettle, indicating the phylloxanthobilin to be an overlooked ingredient of nettle tea.

Antioxidant activities of chlorogenic acid derivatives with different acyl donor chain lengths and their stabilities during in vitro simulated gastrointestinal digestion

In this study, chlorogenic acid (CA) was acylated with vinyl esters of different carbon chain lengths under the action of the lipase Lipozyme RM. Five CA derivatives (C2-CA, C4-CA, C6-CA, C8-CA, and C12-CA) with different lipophilicities were obtained, and their digestive stabilities and antioxidant activities were evaluated. The lipophilicities were positively correlated with the digestive stabilities of CA derivatives. The antioxidant activities of CA derivatives did not change with the reduction of phenolic hydroxyl groups, and their capacity to scavenge 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS+•) and 1,1-diphenyl-2-picrylhydrazyl (DPPH•) were similar to those of CA. In cellular antioxidant activity (CAA) tests, it was found that the capacity of these derivates to cross cell membranes were enhanced upon enhancing lipophilicity, and their antioxidant activities were improved. C12-CA showed the best antioxidant activity with a median effective dose (EC50) of 9.40 μg/mL, which was significantly lower than that of CA (i.e., 29.08 μg/mL).

Insights on the intestinal absorption of chlorophyll series from microalgae

The bioaccessibility and subsequent uptake by Caco-2 human intestinal cells of chlorophyll pigments from Scenedesmus obliquus were determined for the first time. In order to evaluate the impact of different types of the matrix on bioaccessibility of chlorophyll from microalgae, three different products were evaluated: isolated chlorophyll extract (ICE); wet ultrasonicated biomass (WUB); and whole dried biomass (WDB). The samples were submitted to in vitro digestion model according to the INFOGEST protocol, and Caco-2 cells determined the intestinal uptake. Chlorophyll pigments were determined by HPLC-PDA-MS/MS. A total of ten chlorophyll pigments (8,318.48 µg g^-1) were separated in S. obliquus biomass, with chlorophyll a (3,507.76 µg g^-1) and pheophytin a' (1,598.09 µg g^-1) the major ones. After in vitro digestion, all tested products showed bioaccessible chlorophylls. However, the total bioaccessibility results were as follows: ICE (33.45%), WUB (2.65%), WDB (0.33%). Five compounds were bioaccessible in ICE, three in WUB, and one in WDB. The hydroxypheophytin a showed the highest bioaccessibility (212%) in ICE, while pheophytin a' in WUB (11%) and WDB (2%). As a result, bioavailability estimates of ICE using the Caco-2 cell showed hydroxypheophytin a (102.53%), followed by pheophytin a' (64.69%) as the chlorophyll pigments most abundant in intestinal cells. In summary, from a nutritional perspective, these three types of the matrix (WDB, WUB, and ICE) influence the promotion of chlorophyll bioaccessibility. In this way, the data suggest that chlorophylls bioaccessibility from ICE is greater than that in WDB and WUB. Therefore, ICE should be considered a product that provides bioavailable chlorophyll and could be the best choice, such as ingredients in the development of functional foods chlorophyll-based.

Bioavailability of transgenic microRNAs in genetically modified plants

BACKGROUND

Transgenic expression of small RNAs is a prevalent approach in agrobiotechnology for the global enhancement of plant foods. Meanwhile, emerging studies have, on the one hand, emphasized the potential of transgenic microRNAs (miRNAs) as novel dietary therapeutics and, on the other, suggested potential food safety issues if harmful miRNAs are absorbed and bioactive. For these reasons, it is necessary to evaluate the bioavailability of transgenic miRNAs in genetically modified crops.

RESULTS

As a pilot study, two transgenic Arabidopsis lines ectopically expressing unique miRNAs were compared and contrasted with the plant bioavailable small RNA MIR2911 for digestive stability and serum bioavailability. The expression levels of these transgenic miRNAs in Arabidopsis were found to be comparable to that of MIR2911 in fresh tissues. Assays of digestive stability in vitro and in vivo suggested the transgenic miRNAs and MIR2911 had comparable resistance to degradation. Healthy mice consuming diets rich in Arabidopsis lines expressing these miRNAs displayed MIR2911 in the bloodstream but no detectable levels of the transgenic miRNAs.

CONCLUSIONS

These preliminary results imply digestive stability and high expression levels of miRNAs in plants do not readily equate to bioavailability. This initial work suggests novel engineering strategies be employed to enhance miRNA bioavailability when attempting to use transgenic foods as a delivery platform.