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Metabolic and microbial modulation of phenolic compounds from raspberry leaf extract under in vitro digestion and fermentation

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International Journal of Food Science & Technology
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Jing Yang
Jing Yang
Jing Yang
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Yuxin Hao
Yuxin Hao
Yuxin Hao
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Nana Li
Nana Li
Nana Li
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Chunyu Wang
Chunyu Wang
Chunyu Wang
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Abstract and Figures

Raspberry leaves, by‐products in raspberry production, are also a rich source of bioactive phytochemicals. In this study, the changes of phenolic compounds in raspberries leaf extract (RLE) under in vitro digestion and colonic fermentation were further studied by HPLC‐MS analysis and 16S rRNA. The results showed that the phenolic compounds in RLE were relatively stable during in vitro gastric digestion; however, in the subsequent intestinal digestion and colonic fermentation, their content decreased sharply. A large amount of hydroxyphenylpropionic acid, hydroxyphenylacetic acid and urolithins were produced under the action of gut microbiota. Moreover, compared with corresponding control, RLE significantly reduced the ratio of Firmicutes/Bacteroidetes in all volunteers, increased the relative abundances of some beneficial bacteria, Enterococcus, Prevotella, and decreased the relative abundances of potential pathogens, Clostridium and Faecalibacterium. These findings suggest that RLE during in vitro digestion and fermentation has positive effects on gut microbiota and potential value of maintaining intestinal health.
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Original article
Metabolic and microbial modulation of phenolic compounds from
raspberry leaf extract under in vitro digestion and fermentation
Jing Yang,
1,2
*
†
Yuxin Hao,
1†
Nana Li,
1
Chunyu Wang
1
& Yongping Liu
1
1 School of Chemical Engineering and Technology, North University of China, Taiyuan Shanxi, 030051, China
2 Dezhou Graduate School, North University of China, Dezhou Shandong, 253034, China
(Received 4 January 2021; Accepted in revised form 27 April 2021)
Summary Raspberry leaves, by-products in raspberry production, are also a rich source of bioactive phytochemicals.
In this study, the changes of phenolic compounds in raspberries leaf extract (RLE) under in vitro diges-
tion and colonic fermentation were further studied by HPLC-MS analysis and 16S rRNA. The results
showed that the phenolic compounds in RLE were relatively stable during in vitro gastric digestion; how-
ever, in the subsequent intestinal digestion and colonic fermentation, their content decreased sharply. A
large amount of hydroxyphenylpropionic acid, hydroxyphenylacetic acid and urolithins were produced
under the action of gut microbiota. Moreover, compared with corresponding control, RLE significantly
reduced the ratio of Firmicutes/Bacteroidetes in all volunteers, increased the relative abundances of some
beneficial bacteria, Enterococcus,Prevotella, and decreased the relative abundances of potential pathogens,
Clostridium and Faecalibacterium. These findings suggest that RLE during in vitro digestion and fermenta-
tion has positive effects on gut microbiota and potential value of maintaining intestinal health.
Keywords Colonic fermentation, gut microbiota, Rubus idaeus, urolithins.
Introduction
Raspberry is a Rubus plant in Rosaceae, also known
as Fu Pen Zi in China. Compared with raspberry fruit
with high nutritional value, raspberry leaf is also a rich
source of bioactive phenolic compounds which have
multi-functions, including inhibition of oxidation,
inflammation and cancer (Anastasia-Varvara & Fotini,
2016; Yu et al., 2019). A large number of raspberry
leaves are by-products of raspberry production. In our
previous study, the total phenolic contents (TPCs) by
colorimetry in raspberry leave extract (RLE) was 50%,
and the main polyphenols of RLE are free ellagic acid,
ellagitannin and quercetin-3-glucuronide (Q3G) (Yang
et al., 2019). Moreover, the TPCs of raspberry leaves
and fruits ranked 9
th
and 26
th
, respectively, in 54 plant
materials (Chen et al., 2020). Furthermore, another
study on mice fed RLE (100 mg day
1
kg
1
) for two
weeks suggested that RLE not only inhibited the
weight gain of mice, but also prolonged swimming
exhaustion time (Yang et al., 2020b). In Australia,
leaves are used to treat diarrhoea, while fruits are used
for prevention of constipation. However, despite the
long-term and in-depth research of pharmacologists in
the world, the efficacy of raspberry fruits, leaves and
roots is always between medicinal and/or edible. It
may be used as a ‘prodrug’ for target tissues or to pro-
mote health by improving intestinal flora, indicating
long-term and low toxicity (Yu et al., 2019; Sheng
et al., 2020).
It has been estimated that the whole colonising micro-
biota is made up of approximately 10
14
cells, and the
collective bacterial genome is 100 times larger than the
entire human genome (Sender et al., 2016). The gut
microbiota, a complex microbial community, changes
the physiological function of the host through the pro-
duction of signal molecules and neurotransmitters,
which helps to regulate the host energy metabolism, sys-
tematic immune response and maintain the stability of
the homeostasis (Nicholson et al., 2012). Part of the
dietary polyphenols (e.g. ellagitannin) that are not
digested and absorbed in small intestine will be metabo-
lised by gut microbiota in colon into a series of bioavail-
able metabolites, such as urolithins (Kang et al., 2016).
Urolithin A has reduced fat synthesis and triglyceride
accumulation in adipocytes and hepatocytes and
increased fat oxidation dependent on AMPK metabolic
pathway; however, iso-urolithin A and urolithin B have
no such activities (Kang et al., 2016a; Kang et al.,
*Correspondent: E-mail: yangjing5152@163.com
†
These authors are co-first authors.
International Journal of Food Science and Technology 2021, 56, 5168–5177
doi:10.1111/ijfs.15083
©2021 Institute of Food Science and Technology
5168
... α-amylase and α-glucosidase [10]. Raspberry leaves are rich in polyphenols, ellagictannins, quercetin, and kaempferol derivatives, and have good antioxidant, anti-inflammatory, and anti-diabetic properties, as well as the ability to improve obesity and intestinal flora balance, thus being of high healthcare value and industrial value [6,[10][11][12][13]. ...
... Our previous results showed that raspberry leaf extract with 50% total phenolic content (TPC) had positive effects on gut microbiota during in vitro digestion and fermentation, and reduced the ratio of Firmicutes/Bacteroidetes and the relative abundance of potential pathogens in the feces of all volunteers. The extract also increased the relative abundance of some bacteria, e.g., Enterococcus and Prevotella, that have been shown to have beneficial value in maintaining intestinal health [6]. Moreover, it was shown to have a potential role in HFD-induced body weight control in mice [7]. ...
... Their adsorption kinetic properties were analyzed using pseudo-first-order (Equation (6)) and pseudo-second-order (Equation (7)) models. ln q t − q e = −k 1 t + lnq e (6) t q t = 1 k 2 q 2 e + t q e (7) q e is the adsorption equilibrium capacity (mg). q t is the adsorption capacity (mg) at interval time t. ...
An Integrated Extraction–Purification Process for Raspberry Leaf Polyphenols and Their In Vitro Activities
Article
Full-text available
To improve the utilization value of raspberry leaves, the extraction and purification conditions of phenolic compounds from raspberry leaves were optimized, and the contents of phenolic compounds and the biological activities of extracts were studied. After steam explosion pretreatment at 115 °C for 15 min, raspberry leaf extract with a total phenolic content (TPC) of 136.30~140.51 mg GAE/g was obtained via homogenization and ultrasound-assisted extraction. In addition, the adsorption relationship between raspberry leaf polyphenols and middle polar XDA-6 macroporous resin was best described by the Langmuir model, and tended to be monolayer adsorption. Its adsorption kinetics best resembled the pseudo second-order kinetic model, and it was speculated that this was influenced by multiple factors. According to the optimal integrated extraction–purification process, the TPC of the extracts increased to 738.98 mg GAE/g after one application of purification and 905.27 mg GAE/g after two applications of purification. Moreover, the latter case showed the highest antioxidant activity and α-glucosidase inhibition activity, and the content of the most typical compound, quercetin-3-glucuronide, reached 199.69 mg/g. SE has a double-edged effect, and is more conducive to the release of active substances as a pre-treatment method. This study provides a theoretical basis for the efficient use of raspberry leaves, further improving their medicinal and economic value.
View
... A review of current research on RL suggests that it may exhibit comparable effects in managing chronic diseases [54]. For example, RL extract has been shown to positively influence the gut microbiota during in vitro digestion and fermentation, suggesting a role in intestinal health [42]. These effects indicate that RL extract may support gut microbiome balance and contribute to obesity management [38][39][40][41][42][43]. ...
... For example, RL extract has been shown to positively influence the gut microbiota during in vitro digestion and fermentation, suggesting a role in intestinal health [42]. These effects indicate that RL extract may support gut microbiome balance and contribute to obesity management [38][39][40][41][42][43]. Additionally, RL extract has demonstrated significant inhibitory effects on α-glucosidase and α-amylase enzymes in in vitro studies, thereby enhancing glucose metabolism and promoting glucose consumption in cells [98]. ...
Determination of the Polyphenol Composition of Raspberry Leaf Using LC-MS/MS
Article
Full-text available
Background: Raspberry leaf (RL; Rubus idaeus) is a by-product of raspberry cultivation and has been proposed to be a rich source of micronutrients and potential bioactive components, including polyphenols. However, the precise chemical composition of the non-nutrient (poly)phenols in RL has not been as extensively studied. Objective: To evaluate the (poly)phenolic content of six RL samples from different geographical locations and to explore the impact of brewing duration on the levels of phenolic compounds available for absorption following consumption. Methods: A total of 52 polyphenolic constituents were investigated in the RL samples using Liquid Chromatography–Mass Spectrometry (LC-MS), and RL tea samples were analysed for ellagitannins, flavonoids, and phenolic acids. Tea samples were extracted using 80:20 (v/v) methanol/acidified water (0.1% formic acid) to maximise polyphenol recovery, with two sonication steps (30 and 25 min), followed by centrifugation, filtration, and storage at −18 °C. Extractions were performed in triplicate for comprehensive profiling. Additionally, raspberry leaf tea (2 g) was brewed in 200 mL of boiling water at various times (0.5–20 min) to simulate standard consumption practices; this was also performed in triplicate. This approach aimed to quantify polyphenols in the brew and identify optimal steeping times for maximum polyphenol release. Results: Raspberry leaf (RL) samples from six geographical sources were analysed, with 37 compounds identified in methanol and 37 in water out of the 52 targeted compounds, with only 7 compounds not detected in either methanol or water extracts. The analysis indicated that the total measured polyphenol content across the six samples from various sources ranged between 358.66 and 601.65 mg/100 g (p < 0.001). Ellagitannins were identified as the predominant polyphenolic compound in all RL samples, ranging from 155.27 to 394.22 mg/100 g. The phenolic acid and flavonoid concentrations in these samples exhibited a relatively narrow range, with the phenolic acids spanning from 38.87 to 119.03 mg/100 g and the flavonoids ranging from 125.03 to 156.73 mg/100 g. When brewing the tea, the 5 min extraction time was observed to yield the highest level of polyphenols (505.65 mg/100 g) (p< 0.001), which was significantly higher than that with shorter (409.84 mg/100g) and longer extraction times (429.28 mg/100 g). Notably, ellagic acid levels were highest at 5 min (380.29 mg/100 g), while phenolic acid peaked at 15 min (50.96 mg/100 g). The flavonoid content was shown to be highest at 4 min (82.58 mg/100 g). Conclusions: RL contains a relatively high level of polyphenols, particularly ellagic acid; thus, its consumption may contribute to the daily intake of these health-beneficial non-nutrient components.
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... Therefore, gut microbiota plays a very important role in the decomposition and metabolism of phenolic compounds (Ozdal, Sela, Xiao, Boyacioglu, Chen, & Capanoglu, 2016). The gut microbiota helps to regulate the host energy metabolism and systematic immune response, while a decrease in gut microbial diversity and temporal instability may underlie some systemic metabolic diseases and related chronic diseases (Yang, Hao, Li, Wang, & Liu, 2021). In recent years, many in vitro and in vivo studies have shown the prebiotic effect of dietary phenolic compounds on gut microbiota (Dong, Qin, Li, Wu, & Liu, 2022;Moorthy, Chaiyakunapruk, Jacob, & Palanisamy, 2020). ...
... The fecal samples were mixed with sterile phosphatebuffered saline (PBS, pH 7.4) at a ratio of 1:10 under stirring (200 rpm) for 2 min (de Medeiros et al., 2021). The anaerobic medium (pH 7.0) contained peptone (2 g/L), yeast extract (2 g/L), NaCl (0.1 g/L), K 2 HPO 4 (0.04 g/L), KH 2 PO 4 (0.04 g/L), MgSO 4 ⋅7H 2 O (0.01 g/L), CaCl 2 ⋅6H 2 O (0.01 g/L), NaHCO 3 (2 g/L), Tween 80 (2 mL/L), bile salts (0.5 g/L) and Vitamin K1 (10 μL/L) (Yang et al., 2021). Each batch was composed of 40 % of the fermentation medium (v/v), 40 % of pooled human fecal inoculum (v/v), and 20 % of the oat phenolic samples (w/ v). ...
The positive correlation of antioxidant activity and prebiotic effect about naked oat phenolic compounds
Article
  • Feb 2023
  • FOOD CHEM
The correlation of antioxidant activity and prebiotic effect about naked oat phenolic compounds was invested, while there exists limited studies. Free and bound phenolic compounds were separated from ethyl acetate, n-butanol and aqueous fractions. Fluorescence in situ hybridization was used to investigate gut microbiota of in vitro fermentation samples. The results showed that ethyl acetate fraction possesses higher total phenolics contents than that of aqueous fraction (p < 0.01). The bound-n-butanol and free-ethyl acetate fraction exhibited the higher antioxidant capacity (p < 0.01). The phenolic compounds with more powerful antioxidant capacity could promote the proliferation of gut microbiota (Lactobacillus/Enterococcus spp. and Bifidobacterium spp.) (p < 0.05) and inhibit the growth of gut microbiota (Bacteroides spp. and Clostridium/histolyticum group). There is a positive correlation of antioxidant activity and prebiotic effect about oat phenolic compounds. This study provides a basis for the correlation between antioxidant stress and gut microbiota regulation in vivo.
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... In our previous studies, it was shown that the total phenolic content (TPC) of raspberry leaf extract (RLE) reached 540.32 ± 8.96 mg g −1 , and RLE supplementation reduced body weight and adipose percentage in mice after ingestion (19). In addition, the 16 s RNA sequencing results of co-cultivation of RLE with volunteer feces showed that RLE has potential value in maintaining intestinal health (20). ...
Integrated 16s RNA sequencing and network pharmacology to explore the effects of polyphenol-rich raspberry leaf extract on weight control
Article
Full-text available
  • Jan 2024
Introduction Obesity is recognized as a chronic low-grade inflammation associated with intestinal flora imbalance, leading to dyslipidemia and inflammation. Modern research has found that polyphenols have anti-obesity effects. However, the mechanism of action of raspberry leaf extract (RLE) with high polyphenols in regulating obesity is still unknown. This study investigated the improvement effect of supplementing RLE on high-fat diet (HFD) induced obesity in mice. Methods RLE was used to intervene in HFD induced C57BL/6J male mice during prevention stage (1-16 weeks) and treatment stage (17-20 weeks). Their weight changes and obesity-related biochemical indicators were measured. The changes in intestinal flora were analyzed using 16S rRNA sequencing, and finally the targets and pathways of the 7 typical polyphenols (quercetin-3-O-glucuronide, ellagic acid, kaempferol-3-O-rutinoside, chlorogenic acid, brevifolin carboxylic acid, quercetin-3-O-rutinoside, and quercetin) of RLE in the regulation of obesity were predicted by network pharmacology approach. Results and discussion The results showed that RLE effectively prevented and treated weight gain in obese mice induced by HFD, alleviated adipocyte hypertrophy, reduced Interleukin-6 and Tumor Necrosis Factor Alpha levels, and improved intestinal flora, especially Muriaculaceae, Alistipes and Alloprevotella, and decreased the Firmicutes/Bacteroidota ratio. Network pharmacology analysis selected 60 common targets for 7 RLE polyphenols and obesity. Combined with protein-protein interaction network, enrichment analysis and experimental results, TNF, IL-6, AKT1, and PPAR were predicted as potential key targets for RLE polyphenols. Conclusion The potential mechanism by which polyphenol-rich RLE regulates obesity may be attributed to the specific polyphenols of RLE and their synergistic effects, therefore RLE has a great anti-obesity potential and may be used as a means to alleviate obesity and related diseases.
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... In turn, phenolic compounds are extremely unstable in neutral or alkaline environments and are prone to break glycosidic bonds and/or ring fission of the parent molecule (J. Yang et al. 2021). However, as phenolic compounds are frequently linked to difficult-to-digest fibrous components, they can escape intestinal digestion and enter the colon. ...
Coffee by-products: An underexplored source of prebiotic ingredients
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Consumers' demand for foods with high nutritional value and health benefits has fueled the development of prebiotic foods. In coffee industry, cherries transformation into roasted beans generates a large amount of waste/by-products (pulp/husks, mucilage, parchment, defective beans, silverskin and spent coffee grounds) that usually end up in landfills. The possibility to use coffee by-products as relevant sources of prebiotic ingredients is herein ascertained. As a prelude to this discussion, an overview of pertinent literature on prebiotic action was conducted, including on biotransformation of prebiotics, gut microbiota, and metabolites. Existing research indicates that coffee by-products contain significant levels of dietary fiber and other components that can improve gut health by stimulating beneficial bacteria in the colon, making them excellent candidates for prebiotic ingredients. Oligosaccharides from coffee by-products have lower digestibility than inulin and can be fermented by gut microbiota into functional metabolites, such as short-chain fatty acids. Depending on the concentration, melanoidins and chlorogenic acids may also have prebiotic action. Nevertheless, there is still a lack of in vivo studies to validate such findings in vitro. This review shows how coffee by-products can be interesting for the development of functional foods, contributing to sustainability, circular economy, food security, and health.
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Rubus chingii Hu: an overview of botany, traditional uses, phytochemistry, and pharmacology
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  • Jun 2020
Rubus chingii Hu, a member of the rosaceae family, is extensively distributed in China and Japan. Its unripe fruits (Fupenzi in Chinese) have a long history of use as an herbal tonic in traditional Chinese medicine for treating various diseases commonly associated with kidney deficiency, and they are still in use today. Phytochemical investigations on the fruits and leaves of R. chingii indicate the presence of terpenoids, flavonoids, steroids, alkaloids, phenylpropanoids, phenolics, and organic acids. Extracts or active substances from this plant are reported to have various pharmacological properties, including antioxidant, anti-inflammatory, antitumor, antifungal, antithrombotic, antiosteoporotic, hypoglycemic, and central nervous system-regulating effects. This review provides up-to-date information on the botanical characterizations, traditional usages, chemical constituents, pharmacological activities, toxicity, and quality control of R. chingii. Possible directions for future research are also briefly proposed. This review aims to supply fundamental data for the further study of R. chingii and contribute to the development of its clinical use.
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Determination of active compounds in raspberry leaf extracts and the effects of extract intake on mice
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Full-text available
  • Nov 2019
Twelve typical polyphenols in raspberry leaf powder (RLP), raspberry leaf extract 1 (RLE) and raspberry leaf extract 2 (RLE-H) were analyzed by HPLC-MS. The sum of their contents in three samples were in the following order: RLP (8.6 mg g-1) < RLE (35.0 mg g-1) < RLE-H (44.1 mg g-1). Ellagic acid and quercetin-3-O-glucuronide were the principal compounds in the samples and accounted for more than 75% of the sum content. A gelled mixture of RLE, pectin, and sodium alginate administrated to mice via gavage resulted in reduced weight gain and adiposity percentage, increased teste percentage, prolonged exhaustion time, furthermore alleviated intestinal flatulence possibly induced by RLE or RLE-H alone. These results could help in making rational use of this high polyphenol extract from raspberry leaves.
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Nanoencapsulation of synergistic antioxidant fruit and vegetable concentrates and their stability during in vitro digestion
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Dried unripe raspberry of Rubus chingii, were prepared as the following four extracts: unpurified raspberry extract (URE), purified raspberry extract (PRE), URE after high temperature-high pressure (UPE-H, HTHP), and PRE after HTHP (PRE-H). The total polyphenolic contents (TPCs) and total flavonoid contents (TFCs) of the four extracts, as assessed by colorimetry, significantly increased in the following order: URE < URE-H < PRE < PRE-H. The antioxidant capacity and antibacterial activity were as follows: PRE-H > PRE ≈ URE-H > URE. Moreover, 11 typical polyphenols were quantified using a HPLC-MS analysis showed that HTHP treatments were conducive to releasing more (+)-catechin, (−)-epicatechin, proanthocyanidin B1 and ellagic acid, reaching ~70% ‒1,100%, but decreased the rutin, quercetin-3-O-glucuronide, kaempferol-3-O-rutinoside and kaempferol-3-O-glucoside levels by ~10% –20%. The purification of macroporous resin was beneficial to the enrichment of all polyphenols, by ~30%–300%. Ellagic acid was the main polyphenol found in the extracts, accounting for ~67%-74%. The study indicated that changes in the polyphenols of raspberry extracts after resin purification and/or HTHP treatment were correlated with the extract’s antioxidant capacity and antibacterial activity. Further evaluations of the correlation between bioactive ingredients and treatments should reveal that HTHP and resin purification methods are effective means of preparing extracts.
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Rubus chingii Hu (R. chingii), referred to as “Fu-Pen-Zi” in Chinese, has great medicinal and dietary values since ancient times. The dried fruits of R. chingii have been widely used in traditional Chinese medicine (TCM) for the treatment of kidney enuresis and urinary frequency for centuries. According to current findings, R. chingii has been reported to contain a variety of chemical constituents, mostly triterpenoids, diterpenoids, flavonoids, and organic acids. These compounds have been demonstrated to be the major bioactive components responsible for pharmacological effects such as anticomplementary, anticancer, antioxidant, antimicrobial, and anti-inflammatory functions. Therefore, this review focused on the up-to-date published data of the literature about R. chingii and comprehensively summarized its phytochemistry, pharmacology, quality control, and toxicity to provide a beneficial support to its further investigations and applications in medicines and foods.
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Raspberry extract (RE) is a raspberry product with high anthocyanins and low sugar. In the present study, to evaluate the metabolic behavior of phenolic compounds of RE under in vitro digestion (gastric (GF), gastric to intestinal (G-IF), and colonic fermentation (CF)), the changes of 30 phenolic compounds were investigated by High Performance Liquid Chromatography-Mass Spectrometry. The results showed that phenolic compounds were relatively stable in GF, but rapidly decreased in G-IF and CF. Five anthocyanins accounted for 61.1% of total polyphenol contents (TPCs). Among them, anthocyanins bound to glucose or with two hydroxyl groups on B-ring were metabolized more quickly. The catabolic activity of the human microbiota resulted in the production of a series of low molecular weight phenolics, such as hydroxybenzoic acids. Ellagic acid, accounting for 17.7% of TPCs, was rapidly metabolized to urolithin B and urolithin C in CF. Moreover, urolithin C showed the highest antioxidant activity in all ellagic acid metabolites by DPPH assay. Consequently, the metabolic behavior of phenolic compounds was mainly influenced by pH and intestinal microbiota, which provided the basis for further in vivo and in vitro study and efficient utilization of the extract.
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Evaluation of physicochemical properties in three raspberries (Rubus idaeus) at five ripening stages in northern China
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To evaluate the physicochemical properties of raspberries (Rubus idaeus L.) at five ripening stages in Shanxi, northern China (non-traditional area of cultivation), 25 physicochemical indexes including 5 anthocyanins and 10 phenolic compounds by HPLC-MS, fruit weight, moisture content, soluble solids content, sugar-acid ratio (SAR), of three commercial cultivars, cv. Reveille, Tulameen and Heritage, were investigated. The fruit qualities of the three cultivars were close to those of fruit produced in the traditional cultivation areas, especially cv. Tulameen at the overripe stage (Stage 5), which had the largest fruit weight of 4.20 g, and the highest SAR of 4.01 and total anthocyanin content of 103 mg 100 g⁻¹ fresh weight. By intercropping the annual-fruiting ‘Heritage’ and the biennial-fruiting ‘Reveille’ and ‘Tulameen’, the raspberry season in Shanxi, China was extended without a break from mid-June to early October. The unripen raspberries (Stages 1 and 2) with high levels of non-anthoycanin phenols, especially ellagictannin were suitable as a plant-derived polyphenol materials. The ripe raspberries (Stages 3 and 4) with a high anthocyanin level and SAR, were suitable for fresh use and processing. The overripe raspberries (Stage 5) which quickly rotted, with the highest anthocyanin level, moisture content and SAR, were suitable as raw materials for anthocyanin extraction. Cyanidin-3-sophoroside, cyanidin-3-glucoside, and cyanidin-3-rutinoside were the main anthocyanins in cv. Heritage, Tulameen, and Reveille, respectively. Thus, commercial raspberries can be utilized on the basis of their properties and active compounds at different ripening stages, and we provide basic data for their production in Shanxi, northern China.
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The effects of carbohydrate structure on the composition and functionality of the human gut microbiota
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  • Mar 2020
  • TRENDS FOOD SCI TECH
Background Human health depends on a population of microorganisms that inhabit the gut and contribute to homeostasis of the host, including nutrition, immunity and metabolism. Many of the organisms are interactive and mutually dependent, where the end-products for one organism become the fuel for another through substrate and metabolic cross-feeding. To optimise the gut microbiota using diet, the composition and functionality of the gut microbiota, including these interacting networks, must be understood. Microbial composition and functionality is affected by the structure of the energy input, which is primarily dietary fibre for the gut microbiota. The structure of dietary fibre has been reviewed by carbohydrate chemists, but knowledge of how dietary fibre structure affects the gut microbiota is limited. Scope and approach The hierarchical structures of dietary fibre are reviewed, encompassing macrostructure, mesostructure and molecular structure, and how they are affected by food processing and digestion. These factors are considered in relation to their affects on microbial composition and functionality, to provide insight on the interactions between diet, the microbiota, and human health. Key findings and conclusions Food processing and digestion affect food structure, primarily through the removal of some soluble fractions and increased solubilisation of insoluble fractions. The provision of insoluble carbohydrates to the colon appears important for the sustenance of ‘keystone’ species that play a crucial role in stabilising the gut community. Further work is needed at the microbial strain level to understand the impact of increasing fibre solubility. This should be done in studies using well-characterised carbohydrates that consider the impact of food processing and digestion.
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Metabolism of ellagitannins from jabuticaba (Myrciaria jaboticaba) in normoweight, overweight and obese Brazilians: Unexpected laxative effects influence urolithins urinary excretion and metabotype distribution
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  • Jun 2019
This is the first study on ellagitannin metabolism in a non-European population, through consumption of jabuticaba, a Brazilian berry. From 35 volunteers (19 normoweight and 16 overweight or obese), 63% reported the occurrence of diarrhea, probably caused by the high amount of ellagitannins consumed. Urolithin excretion showed high interindividual variability (1.77–522 μmol) and was reduced by diarrhea, but not affected by gender or nutritional status. As reported for Europeans, three urolithin metabotypes (A, B and 0) were observed in Brazilians, with a higher prevalence of metabotype B in overweight and obese individuals (37.5%) than normoweight (21.1%). However, metabotype 0 prevalence (17.1%) was higher than that previously described (∼10%), probably due to diarrhea. This unexpected side effect reinforces the essential role of gut microbiota in ellagitannin metabolism. Besides, despite cultural and ethnical differences between Europeans and Brazilians, their gut microbiota composition may be similar in terms of ellagitannin metabolism.
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Dietary Black Raspberries Impact the Colonic Microbiome and Phytochemical Metabolites in Mice
Article
  • Feb 2019
Scope Black raspberries (BRB) are a rich source of bioactive phytochemicals, including anthocyanins and ellagitannins. These phytochemicals are poorly absorbed and we hypothesize that upon reaching the colon they may be transformed by gut microbiota into various metabolites that may impact the colonic mucosa or upon absorption have systemic bioactivity. The objective of this study was to define the impact of a BRB‐containing diet on the colon microbiome in mice and quantify the phytochemical metabolites in the colon contents and the circulation. Methods and results Male mice were fed 10% (w/w) freeze‐dried BRB powder for 6 weeks. The colonic microbiota was evaluated by 16S rRNA gene sequencing. Anthocyanin and ellagitannin metabolites, protocatechuic acid and urolithins, were analyzed by HPLC‐MS/MS. The BRB diet impacted colon mucosal microbial composition with a more robust effect observed on the luminal microflora. BRB derived protocatechuic acid and urolithins were quantified in the colon, luminal contents, plasma, liver and prostate with protocatechuic acid present in higher concentrations compared to urolithins. Conclusion This study highlights the complex interactions between dietary phytochemicals, the host microbiome, and metabolism. We demonstrate that microbially‐produced phytochemical metabolites are present in the colon and systemic circulation where they may exert biological activity. This article is protected by copyright. All rights reserved
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