Role of dietary polyphenols on gut microbiota, their metabolites and health benefits

Dietary Flavonoids and Human Cognition: A Meta-Analysis

Improving cognition is important in all age groups, from performance in school examinations to prevention of cognitive decline in later life. Dietary polyphenols, in particular flavonoids, have been examined for their benefits to cognitive outcomes. This meta-analysis evaluates the effects of dietary flavonoids on cognition across the lifespan. In January 2020 databases were searched for randomized controlled trials investigating flavonoid effects on human cognition. Eighty studies, comprising 5519 participants, were included in the final meta-analysis. The global analysis indicates dietary flavonoids induced significant benefit to cognitive performance (g = 0.148, p < 0.001), with subgroup analyses revealing that cocoa (g = 0.224, p = 0.036), ginkgo (g = 0.187, p ≤ 0.001), and berries (g = 0.149, p = 0.009) yielded the most notable improvements. Significant benefits were observed from chronic studies, in middle-aged and older adults, and with low and medium doses. The domains of long-term memory, processing speed, and mood showed sensitivity to flavonoid intervention. This meta-analysis provides evidence for the positive effects of flavonoids on cognition and highlights several moderating factors. Flavonoid-based dietary interventions therefore potentially offer a highly accessible, safe, and cost-effective treatment to help tackle the burden of cognitive decline.

Combining Feature-Based Molecular Networking and Contextual Mass Spectral Libraries to Decipher Nutrimetabolomics Profiles

Untargeted metabolomics approaches deal with complex data hindering structural information for the comprehensive analysis of unknown metabolite features. We investigated the metabolite discovery capacity and the possible extension of the annotation coverage of the Feature-Based Molecular Networking (FBMN) approach by adding two novel nutritionally-relevant (contextual) mass spectral libraries to the existing public ones, as compared to widely-used open-source annotation protocols. Two contextual mass spectral libraries in positive and negative ionization mode of ~300 reference molecules relevant for plant-based nutrikinetic studies were created and made publicly available through the GNPS platform. The postprandial urinary metabolome analysis within the intervention of Vaccinium supplements was selected as a case study. Following the FBMN approach in combination with the added contextual mass spectral libraries, 67 berry-related and human endogenous metabolites were annotated, achieving a structural annotation coverage comparable to or higher than existing non-commercial annotation workflows. To further exploit the quantitative data obtained within the FBMN environment, the postprandial behavior of the annotated metabolites was analyzed with Pearson product-moment correlation. This simple chemometric tool linked several molecular families with phase II and phase I metabolism. The proposed approach is a powerful strategy to employ in longitudinal studies since it reduces the unknown chemical space by boosting the annotation power to characterize biochemically relevant metabolites in human biofluids.

A Novel Streptococcus thermophilus FUA329 Isolated from Human Breast Milk Capable of Producing Urolithin A from Ellagic Acid

Urolithin A, a metabolite of ellagic acid, has many beneficial biological activities for people. Strains capable of producing urolithin A from ellagic acid have the hope of becoming the next-generation probiotics. However, only a few species of these strains have been reported. In this study, FUA329, a strain capable of converting ellagic acid to urolithin A in vitro, was isolated from the breast milk of healthy Chinese women. The results of morphological observation, physiological and biochemical tests, and 16S rRNA gene sequence analysis confirmed that the strain FUA329 was Streptococcus thermophilus. In addition, the S. thermophilus FUA329 growth phase is consistent with the degradation of ellagic acid, and urolithin A was produced in the stationary phase, with a maximum concentration of 7.38 μM at 50 h. The corresponding conversion efficiency of urolithin A from ellagic acid was 82%. In summary, S. thermophilus FUA329, a novel urolithin A-producing bacterium, would be useful for the industrial production of urolithin A and may be developed as a next-generation probiotic.

Fatty acids and nutritional components of the seed oil from Wangmo red ball Camellia oleifera grown in the low-heat valley of Guizhou, China

Wangmo red ball Camellia oleifera is the main Camellia species cultivated for oil in the low-heat valley of Guizhou, China. In this study, we evaluated the comprehensive nutritional value of Wangmo C. oleifera seed oil through fatty acid and nutritional component analyses. Twenty excellent Wangmo C. oleifera plants with stable yield and disease resistance were selected from the Camellia oleifera germplasm resource garden in the low-heat valley site of Guizhou University. The unit crown yield, fatty acid content of the seed oil, fatty acid composition and functional nutrients were determined, and the oil quality was comprehensively evaluated using principal component analysis. The fatty acid content of C. oleifera seed oil was 35.03–53.47%, suggesting likely popularization and wide application prospects. The fatty acids included SFAs, MUFAs and PUFAs, and the oleic acid content was 80%, indicating a highly stable and nutritious oil. The oil was also rich in carotenoids, polyphenols, flavonoids, β-sitosterol, squalene and α-Ve, with average content of 7.404 mg/kg, 16.062 mg/kg, 0.401 g/100 g, 265.087 mg/kg, 129.315 mg/kg and 21.505 mg/100 g, respectively. However, the correlations among the nutritional indices were weak. PCA showed that germplasms GH7, GH43, GH28, GH8 and GH31 exhibited the top five nutritional qualities. The rankings in this study provide data for identifying excellent Wangmo C. oleifera plants with high nutritional quality. Additionally, this study provides a valuable reference for the research and development of high-end edible oil and a theoretical basis for the development of economic forest species in low-heat valley areas across the world.

Polyphenols, Saponins and Phytosterols in Lentils and Their Health Benefits: An Overview

The lentil (Lens culinaris L.) is one of the most important legumes (family, Fabaceae). It is a natural functional food rich in many bioactive compounds, such as polyphenols, saponins and phytosterols. Several studies have demonstrated that the consumption of lentils is potentially important in reducing the incidence of a number of chronic diseases, due to their bioactive compounds. The most common polyphenols in lentils include phenolic acids, flavan-3-ol, flavonols, anthocyanidins, proanthocyanidins or condensed tannins, and anthocyanins, which play an important role in the prevention of several degenerative diseases in humans, due to their antioxidant activity. Furthermore, lentil polyphenols are reported to have antidiabetic, cardioprotective and anticancer activities. Lentil saponins are triterpene glycosides, mainly soyasaponins I and βg. These saponins have a plasma cholesterol-lowering effect in humans and are important in reducing the risk of many chronic diseases. Moreover, high levels of phytosterols have been reported in lentils, especially in the seed coat, and β-sitosterol, campesterol, and stigmasterol are the most abundant. Beyond their hypocholesterolemic effect, phytosterols in lentils are known for their anti-inflammatory activity. In this review, the current information on the nutritional composition, bioactive compounds including polyphenols, saponins and phytosterols, and their associated health-promoting effects are discussed.

Fecal microbiota and metabolomics revealed the effect of long-term consumption of gallic acid on canine lipid metabolism and gut health

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Long-term consumption of 0.02%∼0.08% GA had no negative effect on canine body condition.

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GA intervention improved anti-oxidative and anti-inflammatory capacities.

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0.08% GA regulated lipid metabolism in serum.

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0.08% GA increased the relative abundance of SCFAs-producing bacteria.

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0.08% GA regulated carbohydrate metabolism in fece.

Gallic acid (GA) is a natural polyphenolic compound with many health benefits. To assess the potential risk of long-term consumption of GA to gut health, healthy dogs were fed a basal diet supplemented with GA (0%, 0.02%, 0.04%, and 0.08%) for 45 d, and fecal microbiota and metabolomics were evaluated. This study demonstrated that GA supplementation regulated serum lipid metabolism by reducing serum triglyceride, fat digestibility, and Bacteroidetes/Firmicutes ratio. In addition, the relative abundance of Parasutterella was significantly lower, and the SCFAs-producing bacteria were increased along with fecal acetate and total SCFAs contents accumulation in the 0.08% GA group. Metabolomics data further elucidated that 0.08% GA significantly affected carbohydrate metabolism by downregulating succinic acid in fece, thereby alleviating inflammation and oxidative stress. Overall, this study confirmed the beneficial effects of long-term consumption of GA on lipid metabolism and gut health, and the optimal level of GA supplementation was 0.08%.

Anti-aging effects and mechanisms of anthocyanins and their intestinal microflora metabolites

Aging, a natural and inevitable physiological process, is the primary risk factor for all age-related diseases; it severely threatens the health of individuals and places a heavy burden on the public health-care system. Thus, strategies to extend the lifespan and prevent and treat age-related diseases have been gaining increasing scientific interest. Anthocyanins (ACNs) are a subclass of flavonoids widely distributed in fruits and vegetables. Growing evidence suggests that ACNs delay aging and relieve age-related diseases. However, owing to the low bioavailability of ACNs, their gut metabolites have been proposed to play a critical role in mediating health benefits. In this review, we introduce the biological fate of ACNs after consumption and highlight ACNs metabolites (phenolic acids) from intestinal microorganisms. Additionally, ACNs and gut metabolites exhibit outstanding anti-aging ability in Caenorhabditis elegans, Drosophila melanogaster, and mouse models, probably associated with increasing antioxidation, anti-inflammation, protein homeostasis, antiglycation, mitochondrial function, and inhibition of insulin/IGF-1 signaling (IIS). ACNs and gut metabolites have great application prospects as functional foods and drugs to delay aging and manage age-related diseases. Further investigation should focus on the interaction between ACNs and gut microbiota, including clarifying the complex metabolic pathway and maximizing the health effects of ACNs.

Molecular and Cellular Mechanisms of Propolis and Its Polyphenolic Compounds against Cancer

In recent years, interest in natural products such as alternative sources of pharmaceuticals for numerous chronic diseases, including tumors, has been renewed. Propolis, a natural product collected by honeybees, and polyphenolic/flavonoid propolis-related components modulate all steps of the cancer progression process. Anticancer activity of propolis and its compounds relies on various mechanisms: cell-cycle arrest and attenuation of cancer cells proliferation, reduction in the number of cancer stem cells, induction of apoptosis, modulation of oncogene signaling pathways, inhibition of matrix metalloproteinases, prevention of metastasis, anti-angiogenesis, anti-inflammatory effects accompanied by the modulation of the tumor microenvironment (by modifying macrophage activation and polarization), epigenetic regulation, antiviral and bactericidal activities, modulation of gut microbiota, and attenuation of chemotherapy-induced deleterious side effects. Ingredients from propolis also "sensitize" cancer cells to chemotherapeutic agents, likely by blocking the activation of the transcription factor nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). In this review, we summarize the current knowledge related to the the effects of flavonoids and other polyphenolic compounds from propolis on tumor growth and metastasizing ability, and discuss possible molecular and cellular mechanisms involved in the modulation of inflammatory pathways and cellular processes that affect survival, proliferation, invasion, angiogenesis, and metastasis of the tumor.

Interactions between dietary flavonoids and the gut microbiome: a comprehensive review

Flavonoids are natural polyphenol secondary metabolites that are widely produced in planta. Flavonoids are ubiquities in human dietary intake and exhibit a myriad of health benefits. Flavonoids-induced biological activities are strongly influenced by their in situ availability in the human GI tract, as well as the levels of which are modulated by interaction with the gut bacteria. As such, assessing flavonoids–microbiome interactions is considered a key to understand their physiological activities. Here, we review the interaction between the various classes of dietary flavonoids (flavonols, flavones, flavanones, isoflavones, flavan-3-ols and anthocyanins) and gut microbiota. We aim to provide a holistic overview of the nature and identity of flavonoids on diet and highlight how flavonoids chemical structure, metabolism and impact on humans and their microbiomes are interconnected. Emphasis is placed on how flavonoids and their biotransformation products affect gut microbiota population, influence gut homoeostasis and induce measurable physiological changes and biological benefits.

New Insights into Boron Essentiality in Humans and Animals

Boron (B) is considered a prebiotic chemical element with a role in both the origin and evolution of life, as well as an essential micronutrient for some bacteria, plants, fungi, and algae. B has beneficial effects on the biological functions of humans and animals, such as reproduction, growth, calcium metabolism, bone formation, energy metabolism, immunity, and brain function. Naturally organic B (NOB) species may become promising novel prebiotic candidates. NOB-containing compounds have been shown to be essential for the symbiosis between organisms from different kingdoms. New insights into the key role of NOB species in the symbiosis between human/animal hosts and their microbiota will influence the use of natural B-based colon-targeting nutraceuticals. The mechanism of action (MoA) of NOB species is related to the B signaling molecule (autoinducer-2-borate (AI-2B)) as well as the fortification of the colonic mucus gel layer with NOB species from B-rich prebiotic diets. Both the microbiota and the colonic mucus gel layer can become NOB targets. This paper reviews the evidence supporting the essentiality of the NOB species in the symbiosis between the microbiota and the human/animal hosts, with the stated aim of highlighting the MoA and targets of these species.

Effects of Marine Bioactive Compounds on Gut Ecology Based on In Vitro Digestion and Colonic Fermentation Models

Digestion and the absorption of food compounds are necessary steps before nutrients can exert a role in human health. The absorption and utilization of nutrients in the diet is an extremely complex dynamic process. Accurately grasping the digestion and absorption mechanisms of different nutrients or bioactive compounds can provide a better understanding regarding the relationship between health and nutrition. Several in vitro models for simulating human gastrointestinal digestion and colonic fermentation have been established to obtain more accurate data for further understanding of the metabolism of dietary components. Marine media is rich in a wide variety of nutrients that are essential for humans and is gaining increased attention as a research topic. This review summarizes some of the most explored in vitro digestion and colonic fermentation models. It also summarizes the research progress on the digestion and absorption of nutrients and bioactive compounds from marine substrates when subjected to these in vitro models. Additionally, an overview of the changes imparted by the digestion process on these bioactive compounds is provided, in order to support those marine resources that can be utilized for developing new healthy foods.

Egg white protein-based delivery system for bioactive substances: a review

Some bioactive substances in food have problems such as poor solubility, unstable chemical properties and low bioavailability, which limits their application in functional food. Recently, many egg white protein-based delivery carriers have been developed to improve the chemical stability, biological activity and bioavailability of bioactive substances. This article reviewed the structure and properties of several major egg white proteins commonly used to construct bioactive substance delivery systems. Several common carrier types based on egg white proteins, including hydrogels, emulsions, micro/nanoparticles, aerogels and electrospinning were then introduced. The biological functions of common bioactive substances, the limitations, and the role of egg white protein-based delivery systems were also discussed. At present, whole egg white protein, ovalbumin and lysozyme are most widely used in delivery systems, while ovotransferrin, ovomucoid and ovomucin are less developed and applied. Egg white protein-based nanoparticles are currently the most commonly used delivery carriers. Egg white protein-based hydrogels, emulsions, and microparticles are also widely used. Future research on the application of various egg white proteins in developed new delivery systems will provide more choices for the delivery of various bioactive substances.

Microbiota-derived metabolites as drivers of gut-brain communication

Alterations in the gut microbiota composition have been associated with a range of neurodevelopmental, neurodegenerative, and neuropsychiatric disorders. The gut microbes transform and metabolize dietary- and host-derived molecules generating a diverse group of metabolites with local and systemic effects. The bi-directional communication between brain and the microbes residing in the gut, the so-called gut-brain axis, consists of a network of immunological, neuronal, and endocrine signaling pathways. Although the full variety of mechanisms of the gut-brain crosstalk is yet to be established, the existing data demonstrates that a single metabolite or its derivatives are likely among the key inductors within the gut-brain axis communication. However, more research is needed to understand the molecular mechanisms underlying how gut microbiota associated metabolites alter brain functions, and to examine if different interventional approaches targeting the gut microbiota could be used in prevention and treatment of neurological disorders, as reviewed herein.Abbreviations:4-EPS 4-ethylphenylsulfate; 5-AVA(B) 5-aminovaleric acid (betaine); Aβ Amyloid beta protein; AhR Aryl hydrocarbon receptor; ASD Autism spectrum disorder; BBB Blood-brain barrier; BDNF Brain-derived neurotrophic factor; CNS Central nervous system; GABA ɣ-aminobutyric acid; GF Germ-free; MIA Maternal immune activation; SCFA Short-chain fatty acid; 3M-4-TMAB 3-methyl-4-(trimethylammonio)butanoate; 4-TMAP 4-(trimethylammonio)pentanoate; TMA(O) Trimethylamine(-N-oxide); TUDCA Tauroursodeoxycholic acid; ZO Zonula occludens proteins.

The Impact of Plant Phytochemicals on the Gut Microbiota of Humans for a Balanced Life

The gastrointestinal tract of humans is a complex microbial ecosystem known as gut microbiota. The microbiota is involved in several critical physiological processes such as digestion, absorption, and related physiological functions and plays a crucial role in determining the host’s health. The habitual consumption of specific dietary components can impact beyond their nutritional benefits, altering gut microbiota diversity and function and could manipulate health. Phytochemicals are non-nutrient biologically active plant components that can modify the composition of gut microflora through selective stimulation of proliferation or inhibition of certain microbial communities in the intestine. Plants secrete these components, and they accumulate in the cell wall and cell sap compartments (body) for their development and survival. These compounds have low bioavailability and long time-retention in the intestine due to their poor absorption, resulting in beneficial impacts on gut microbiota population. Feeding diets containing phytochemicals to humans and animals may offer a path to improve the gut microbiome resulting in improved performance and/or health and wellbeing. This review discusses the effects of phytochemicals on the modulation of the gut microbiota environment and the resultant benefits to humans; however, the effect of phytochemicals on the gut microbiota of animals is also covered, in brief.

Tea Polyphenols as Prospective Natural Attenuators of Brain Aging

No organism can avoid the process of aging, which is often accompanied by chronic disease. The process of biological aging is driven by a series of interrelated mechanisms through different signal pathways, including oxidative stress, inflammatory states, autophagy and others. In addition, the intestinal microbiota play a key role in regulating oxidative stress of microglia, maintaining homeostasis of microglia and alleviating age-related diseases. Tea polyphenols can effectively regulate the composition of the intestinal microbiota. In recent years, the potential anti-aging benefits of tea polyphenols have attracted increasing attention because they can inhibit neuroinflammation and prevent degenerative effects in the brain. The interaction between human neurological function and the gut microbiota suggests that intervention with tea polyphenols is a possible way to alleviate brain-aging. Studies have been undertaken into the possible mechanisms underpinning the preventative effect of tea polyphenols on brain-aging mediated by the intestinal microbiota. Tea polyphenols may be regarded as potential neuroprotective substances which can act with high efficiency and low toxicity.

Paradigm Shift in Phytochemicals Research: Evolution from Antioxidant Capacity to Anti-Inflammatory Effect and to Roles in Gut Health and Metabolic Syndrome

Food bioactive components, particularly phytochemicals with antioxidant capacity, have been extensively studied over the past two decades. However, as new analytical and molecular biological tools advance, antioxidants related research has undergone significant paradigm shifts. This review is a high-level overview of the evolution of phytochemical antioxidants research. Early research used chemical models to assess the antioxidant capacity of different phytochemicals, which provided important information about the health potential, but the results were overused and misinterpreted despite the lack of biological relevance (Antioxidants v1.0). This led to findings in the anti-inflammatory properties and modulatory effects of cell signaling of phytochemicals (Antioxidants v2.0). Recent advances in the role of diet in modulating gut microbiota have suggested a new phase of food bioactives research along the phytochemicals-gut microbiota-intestinal metabolites-low-grade inflammation-metabolic syndrome axis (Antioxidants v3.0). Polyphenols and carotenoids were discussed in-depth, and future research directions were also provided.

Identification of Gut Microbiome Metabolites via Network Pharmacology Analysis in Treating Alcoholic Liver Disease

Alcoholic liver disease (ALD) is linked to a broad spectrum of diseases, including diabetes, hypertension, atherosclerosis, and even liver carcinoma. The ALD spectrum includes alcoholic fatty liver disease (AFLD), alcoholic hepatitis, and cirrhosis. Most recently, some reports demonstrated that the pathogenesis of ALD is strongly associated with metabolites of human microbiota. AFLD was the onset of disease among ALDs, the initial cause of which is alcohol consumption. Thus, we analyzed the significant metabolites of microbiota against AFLD via the network pharmacology concept. The metabolites from microbiota were retrieved by the gutMGene database; sequentially, AFLD targets were identified by public databases (DisGeNET, OMIM). The final targets were utilized for protein–protein interaction (PPI) networks and signaling pathway analyses. Then, we performed a molecular docking test (MDT) to verify the affinity between metabolite(s) and target(s) utilizing the Autodock 1.5.6 tool. From a holistic viewpoint, we integrated the relationships of microbiota-signaling pathways-targets-metabolites (MSTM) using the R Package. We identified the uppermost six key targets (TLR4, RELA, IL6, PPARG, COX-2, and CYP1A2) against AFLD. The PPI network analysis revealed that TLR4, RELA, IL6, PPARG, and COX-2 had equivalent degrees of value (4); however, CYP1A2 had no associations with the other targets. The bubble chart showed that the PI3K-Akt signaling pathway in nine signaling pathways might be the most significant mechanism with antagonistic functions in the treatment of AFLD. The MDT confirmed that Icaritin is a promising agent to bind stably to RELA (known as NF-Κb). In parallel, Bacterium MRG-PMF-1, the PI3K-Akt signaling pathway, RELA, and Icaritin were the most significant components against AFLD in MSTM networks. In conclusion, we showed that the Icaritin–RELA complex on the PI3K-Akt signaling pathway by bacterial MRG-PMF-1 might have promising therapeutic effects against AFLD, providing crucial evidence for further research.

Beneficial Effects of Theaflavins on Metabolic Syndrome: From Molecular Evidence to Gut Microbiome

In recent years, many natural foods and herbs rich in phytochemicals have been proposed as health supplements for patients with metabolic syndrome (MetS). Theaflavins (TFs) are a polyphenol hydroxyl substance with the structure of diphenol ketone, and they have the potential to prevent and treat a wide range of MetS. However, the stability and bioavailability of TFs are poor. TFs have the marvelous ability to alleviate MetS through antiobesity and lipid-lowering (AMPK-FoxO3A-MnSOD, PPAR, AMPK, PI3K/Akt), hypoglycemic (IRS-1/Akt/GLUT4, Ca2+/CaMKK2-AMPK, SGLT1), and uric-acid-lowering (XO, GLUT9, OAT) effects, and the modulation of the gut microbiota (increasing beneficial gut microbiota such as Akkermansia and Prevotella). This paper summarizes and updates the bioavailability of TFs, and the available signaling pathways and molecular evidence on the functionalities of TFs against metabolic abnormalities in vitro and in vivo, representing a promising opportunity to prevent MetS in the future with the utilization of TFs.

Antibacterial activities of polyphenols against foodborne pathogens and their application as antibacterial agents

Polyphenols are secondary metabolites produced in higher plants. They are known to possess various functional properties in the human body. Polyphenols also exhibit antibacterial activities against foodborne pathogens. Their antibacterial mechanism is based on inhibiting bacterial biofilm formation or inactivating enzymes. Food-derived polyphenols with such antibacterial activity are natural preservatives and can be used as an alternative to synthetic preservatives that can cause side effects, such as allergies, asthma, skin irritation, and cancer. Studies have reported that polyphenols have positive effects, such as decreasing harmful bacteria and increasing beneficial bacteria in the human gut microbiota. Polyphenols can also be used as natural antibacterial agents in food packaging system in the form of emitting sachets, absorbent pads, and edible coatings. We summarized the antibacterial activities, mechanisms and applications of polyphenols as antibacterial agents against foodborne bacteria.

An Infancy-Onset 20-Year Dietary Counselling Intervention and Gut Microbiota Composition in Adulthood

The randomized controlled Special Turku Coronary Risk Factor Intervention Project (STRIP) has completed a 20-year infancy-onset dietary counselling intervention to reduce exposure to atherosclerotic cardiovascular disease risk factors via promotion of a heart-healthy diet. The counselling on, e.g., low intake of saturated fat and cholesterol and promotion of fruit, vegetable, and whole-grain consumption has affected the dietary characteristics of the intervention participants. By leveraging this unique cohort, we further investigated whether this long-term dietary intervention affected the gut microbiota bacterial profile six years after the intervention ceased. Our sub-study comprised 357 individuals aged 26 years (intervention n = 174, control n = 183), whose gut microbiota were profiled using 16S rRNA amplicon sequencing. We observed no differences in microbiota profiles between the intervention and control groups. However, out of the 77 detected microbial genera, the Veillonella genus was more abundant in the intervention group compared to the controls (log2 fold-change 1.58, p < 0.001) after adjusting for multiple comparison. In addition, an association between the study group and overall gut microbiota profile was found only in males. The subtle differences in gut microbiota abundances observed in this unique intervention setting suggest that long-term dietary counselling reflecting dietary guidelines may be associated with alterations in gut microbiota.

Targeting the gut to prevent and counteract metabolic disorders and pathologies during aging

Impairment of gut function is one of the explanatory mechanisms of health status decline in elderly population. These impairments involve a decline in gut digestive physiology, metabolism and immune status, and associated to that, changes in composition and function of the microbiota it harbors. Continuous deteriorations are generally associated with the development of systemic dysregulations and ultimately pathologies that can worsen the initial health status of individuals. All these alterations observed at the gut level can then constitute a wide range of potential targets for development of nutritional strategies that can impact gut tissue or associated microbiota pattern. This can be key, in a preventive manner, to limit gut functionality decline, or in a curative way to help maintaining optimum nutrients bioavailability in a context on increased requirements, as frequently observed in pathological situations. The aim of this review is to give an overview on the alterations that can occur in the gut during aging and lead to the development of altered function in other tissues and organs, ultimately leading to the development of pathologies. Subsequently is discussed how nutritional strategies that target gut tissue and gut microbiota can help to avoid or delay the occurrence of aging-related pathologies.

Dietary Polyphenol, Gut Microbiota, and Health Benefits

Polyphenols, which are probably the most important secondary metabolites produced by plants, have attracted tremendous attention due to their health-promoting effects, including their antioxidant, anti-inflammatory, antibacterial, anti-adipogenic, and neuro-protective activities, as well as health properties. However, due to their complicated structures and high molecular weights, a large proportion of dietary polyphenols remain unabsorbed along the gastrointestinal tract, while in the large intestine they are biotransformed into bioactive, low-molecular-weight phenolic metabolites through the residing gut microbiota. Dietary polyphenols can modulate the composition of intestinal microbes, and in turn, gut microbes catabolize polyphenols to release bioactive metabolites. To better investigate the health benefits of dietary polyphenols, this review provides a summary of their modulation through in vitro and in vivo evidence (animal models and humans), as well as their possible actions through intestinal barrier function and gut microbes. This review aims to provide a basis for better understanding the relationship between dietary polyphenols, gut microbiota, and host health.

Edible plant by-products as source of polyphenols: prebiotic effect and analytical methods

Polyphenols with high chemical diversity are present in vegetables both in the edible parts and by-products. A large proportion of them remains unabsorbed along the gastrointestinal tract, being accumulated in the colon, where they are metabolized by the intestinal microbiota. These polyphenols have been found to have "prebiotic-like" effects. The edible plant industry generates tons of residues called by-products, which consist of unutilized plant tissues (peels, husks, calyxes and seeds). Their disposal requires special and costly treatments to avoid environmental complications. Reintroducing these by-products into the value chain using technological and biotechnological practices is highly appealing since many of them contain nutrients and bioactive compounds, such as polyphenols, with many health-promoting properties. Edible plant by-products as a source of polyphenols highlights the need for analytical methods. Analytical methods are becoming increasingly selective, sensitive and precise, but the great breakthrough lies in the pretreatment of the sample and in particular in the extraction methods. This review shows the importance of edible plant by-products as a source of polyphenols, due to their prebiotic effect, and to compile the most appropriate analytical methods for the determination of the total content of phenolic compounds as well as the detection and quantification of individual polyphenols.

Advances in Protein-Based Nanocarriers of Bioactive Compounds: From Microscopic Molecular Principles to Macroscopical Structural and Functional Attributes

Many proteins can be used to fabricate nanocarriers for encapsulation, protection, and controlled release of nutraceuticals. This review examined the protein-based nanocarriers from microscopic molecular characteristics to the macroscopical structural and functional attributes. Structural, physical, and chemical properties of protein-based nanocarriers were introduced in detail. The spatial size, shape, water dispersibility, colloidal stability, etc. of protein-based nanocarriers were largely determined by the molecular physicochemical principles of protein. Different preparative techniques, including antisolvent precipitation, pH-driven, electrospray, and gelation methods, among others, can be used to fabricate different protein-based nanocarriers. Various modifications based on physical, chemical, and enzymatic approaches can be used to improve the functional performance of these nanocarriers. Protein is a natural resource with a wide range of sources, including plant, animal, and microbial, which are usually used to fabricate the nanocarriers. Protein-based nanocarriers have many advantages in aid of the application of bioactive ingredients to the medical, food, and cosmetic industries.

Dietary phenolic-type Nrf2-activators: implications in the control of toxin-induced hepatic disorders

Numerous studies have exemplified the importance of nuclear factor erythroid 2-related factor 2 (Nrf2) activation in the alleviation of toxin-induced hepatic disorders primarily through eliminating oxidative stress. Whereafter, increasingly more efforts have been contributed to finding Nrf2-activators, especially from dietary polyphenols. The present review summarized the phenolic-type Nrf2-activators published in the past few decades, analyzed their effectiveness based on their structural characteristics and outlined their related mechanisms. It turns out that flavonoids are the largest group of phenolic-type Nrf2-activators, followed by nonflavonoids and phenolic acids. When counting on subgroups, the top three types are flavonols, flavones, and hydroxycinnamic acids, with curcuminoids having the highest effective doses. Moreover, most polyphenols work through the phosphorylation of Nrf2. Besides, mitogen-activated protein kinases (MAPKs) and protein kinase B (Akt) are the frequent targets of these Nrf2-activators, which indirectly mediate the behavior of Nrf2. However, current data are not sufficient to conclude any structure-activity relationship.

A review on polyphenols and their potential application to reduce food allergenicity

This review summarized recent studies about the effects of polyphenols on the allergenicity of allergenic proteins, involving epigallocatechin gallate (EGCG), caffeic acid, chlorogenic acid, proanthocyanidins, quercetin, ferulic acid and rosmarinic acid, etc. Besides, the mechanism of polyphenols for reducing allergenicity was discussed and concluded. It was found that polyphenols could noncovalently (mainly hydrophobic interactions and hydrogen bonding) and covalently (mainly alkaline, free-radical grafting, and enzymatic method) react with allergens to induce the structural changes, resulting in the masking or/and destruction of epitopes and the reduction of allergenicity. Oral administration in murine models showed that the allergic reaction might be suppressed by regulating immune cell function, changing the levels of cytokines, suppressing of MAPK, NF-κb and allergens-presentation pathway and improving intestine function, etc. The outcome of reduced allergenicity and suppressed allergic reaction was affected by many factors such as polyphenol types, polyphenol concentration, allergen types, pH, oral timing and dosage. Moreover, the physicochemical and functional properties of allergenic proteins were improved after treatment with polyphenols. Therefore, polyphenols have the potential to produce hypoallergenic food. Further studies should focus on active concentrations and bioavailability of polyphenols, confirming optimal intake and hypoallergenic of polyphenols based on clinical trials.

Gallnut Tannic Acid Exerts Anti-stress Effects on Stress-Induced Inflammatory Response, Dysbiotic Gut Microbiota, and Alterations of Serum Metabolic Profile in Beagle Dogs

Stress exposure is a potential threat to humans who live or work in extreme environments, often leading to oxidative stress, inflammatory response, intestinal dysbiosis, and metabolic disorders. Gallnut tannic acid (TA), a naturally occurring polyphenolic compound, has become a compelling source due to its favorable anti-diarrheal, anti-oxidative, anti-inflammatory, and anti-microbial activities. Thus, this study aimed to evaluate the anti-stress effects of gallnut TA on the stress-induced inflammatory response, dysbiotic gut microbiota, and alterations of serum metabolic profile using beagle models. A total of 13 beagle dogs were randomly divided into the stress (ST) and ST + TA groups. Dietary supplementation with TA at 2.5 g/kg was individually fed to each dog in the ST + TA group for 14 consecutive days. On day 7, all dogs were transported for 3 h from a stressful environment (days 1–7) to a livable site (days 8–14). In our results, TA relieved environmental stress-induced diarrheal symptoms in dogs and were shown to protect from myocardial injury and help improve immunity by serum biochemistry and hematology analysis. Also, TA inhibited the secretion of serum hormones [cortisol (COR), glucocorticoid (GC), and adrenocorticotropic hormone (ACTH)] and the expression of heat shock protein (HSP) 70 to protect dogs from stress-induced injury, thereby relieving oxidative stress and inflammatory response. Fecal 16S rRNA gene sequencing revealed that TA stimulated the growth of beneficial bacteria (Allobaculum, Dubosiella, Coriobacteriaceae_UCG-002, and Faecalibaculum) and suppressed the growth of pathogenic bacteria (Escherichia-Shigella and Streptococcus), thereby increasing fecal butyrate levels. Serum metabolomics further showed that phytosphingosine, indoleacetic acid, arachidonic acid, and biotin, related to the metabolism of sphingolipid, tryptophan, arachidonic acid, and biotin, respectively, could serve as potential biomarkers of stress exposure. Furthermore, Spearman’s correlation analysis showed strong relationships between the four potential serum biomarkers and differential bacteria. Overall, gallnut TA may be a potential prebiotic for the prevention and treatment of stress-induced metabolic disorders by targeting intestinal microbiota.

Morais L. Convergent pathways of the gut microbiota-brain axis and neurodegenerative disorders

Recent research has been uncovering the role of the gut microbiota for brain health and disease. These studies highlight the role of gut microbiota on regulating brain function and behavior through immune, metabolic, and neuronal pathways. In this review we provide an overview of the gut microbiota axis pathways to lay the groundwork for upcoming sessions on the links between the gut microbiota and neurogenerative disorders. We also discuss how the gut microbiota may act as an intermediate factor between the host and the environment to mediate disease onset and neuropathology. Based on the current literature, we further examine the potential for different microbiota-based therapeutic strategies to prevent, to modify, or to halt the progress of neurodegeneration.

Bioaccessibility and movement of phenolic compounds from tomato (Solanum lycopersicum) during in vitro gastrointestinal digestion and colonic fermentation

Tomatoes (Solanum lycopersicum) are highly involved in diets consumed worldwide, and are rich in bioactive compounds including phenolics, carotenoids and vitamins. In this study, four different varieties of fresh tomato pulp (Oxheart, Green Zebra, Kumato and Roma) were used to estimate the bioaccessibility of target phenolic compounds during in vitro gastrointestinal digestion and colonic fermentation, and to determine their antioxidant capacity. The production of short chain fatty acids (SCFAs) was also estimated during colonic fermentation. Among these, Roma displayed relatively higher total phenolic content (TPC) and free radical scavenging (2,2'-diphenyl-1-picrylhydrazyl (DPPH) assay) values after gastrointestinal digestion of 0.31 mg gallic acid equivalents (GAE) per g and 0.12 mg Trolox equivalents (TE) per g. Kumato exhibited the highest total flavonoid content (TFC) of 2.47 mg quercetin equivalents (QE) per g after 8 hours of colonic fermentation. Oxheart and Roma showed similar ferric reducing antioxidant power (FRAP) values of around 4.30 mg QE per g after 4 hours of faecal reaction. Catechin was the most bioaccessible phenolic compound in all fresh tomatoes, and could be completely decomposed after intestinal digestion, whereas the release of some bonded phenolic compounds required the action of gut microflora. Kumato and Green Zebra showed higher production of individual and total SCFAs for 16 hours of fermentation, which would provide more gut health benefits.

The Role of Gut Microbiota in the Immunopathology of Atherosclerosis: focus on immune cells

Gut microbiota (GM) play important roles in multiple organ function, homeostasis and several diseases. More recently, increasing evidences have suggested that the compositional and functional alterations of GM play a crucial role in the accumulation of foam cells and the formation of atherosclerotic plaque in atherosclerosis. In particular, the effects of bacterial components and metabolites on innate and adaptive immune cells have been explored as the underlying mechanisms. Understanding the effects of GM and metabolites on immunoregulation are important for clinical therapy for atherosclerosis. Herein, we summarize the potential role of the GM (such as bacterial components lipopolysaccharide and peptidoglycan) and GM-derived metabolites (such as short-chain fatty acids, trimethylamine N-oxide and bile acids) in the immunopathology of atherosclerosis. Based on that, we further discuss the anti-atherosclerotic effects of GM-directed dietary bioactive factors such as dietary fibers, dietary polyphenols and probiotics. Because of drug-induced adverse events in anti-inflammatory therapies, personalized dietary interventions would be potential therapies for atherosclerosis, and the interactions between GM-derived products and immune cells should be studied further.

(Poly)phenolic compounds and gut microbiome: new opportunities for personalized nutrition

For decades, (poly)phenols have been linked to cardiometabolic health, but population heterogeneity limits their apparent efficacy and the development of tailored, practical protocols in dietary interventions. This heterogeneity is likely determined by the existence of different metabotypes, sub-populations of individuals metabolizing some classes of (poly)phenols differently. The gut microbiota plays a major role in this process. The impact of microbiota-related phenolic metabotypes on cardiometabolic health is becoming evident, although the picture is still incomplete, and data are absent for some classes of (poly)phenols. The lack of a complete understanding of the main microbial actors involved in the process complicates the picture. Elucidation of the mechanisms behind phenolic metabotypes requires novel experimental designs that can dissect the inter-individual variability. This paper, in addition to providing an overview on the current state-of-the-art, proposes wider metabotyping approaches as a means of paving the way towards effective personalized nutrition with dietary (poly)phenols.

Food-Derived Bioactive Molecules from Mediterranean Diet: Nanotechnological Approaches and Waste Valorization as Strategies to Improve Human Wellness

The beneficial effects of the Mediterranean diet (MedDiet), the most widely followed healthy diet in the world, are principally due to the presence in the foods of secondary metabolites, mainly polyphenols, whose healthy characteristics are widely recognized. However, one of the biggest problems associated with the consumption of polyphenols as nutraceutical adjuvant concerns their bioavailability. During the last decades, different nanotechnological approaches have been developed to enhance polyphenol bioavailability, avoiding the metabolic modifications that lead to low absorption, and improving their retention time inside the organisms. This review focuses on the most recent findings regarding the encapsulation and delivery of the bioactive molecules present in the foods daily consumed in the MedDiet such as olive oil, wine, nuts, spice, and herbs. In addition, the possibility of recovering the polyphenols from food waste was also explored, taking into account the increased market demand of functional foods and the necessity to obtain valuable biomolecules at low cost and in high quantity. This circular economy strategy, therefore, represents an excellent approach to respond to both the growing demand of consumers for the maintenance of human wellness and the economic and ecological exigencies of our society.

Effects of Grape Pomace Polyphenols and In Vitro Gastrointestinal Digestion on Antimicrobial Activity: Recovery of Bioactive Compounds

Grape pomace (GP), a major byproduct obtained from the winemaking process, is characterized by a high amount of phenolic compounds and secondary plant metabolites, with potential beneficial effects on human health. Therefore, GP is a source of bioactive compounds with antioxidant, antimicrobial, and anti-inflammatory activity. As people are paying more attention to sustainability, in this work, we evaluate two different extractions (aqueous and hydroalcoholic) of GP bioactive compounds. In vitro simulated gastrointestinal digestion of the GP extracts was performed to improve the bioavailability and bioaccessibility of polyphenols. The antioxidant activity (ABTS and DPPH assays) and the phenolic characterization of the extracts by UHPLC-DAD were evaluated. The antimicrobial effects of GP antioxidants in combination with a probiotic (Lactiplantibacillus plantarum) on the growth of pathogenic microorganisms (Escherichia coli, Bacillus megaterium, and Listeria monocytogenes) were evaluated. As a result, an increase of antioxidant activity of aqueous GP extracts during the gastrointestinal digestion, and a contextual decrease of hydroalcoholic extracts, were detected. The main compounds assessed by UHPLC-DAD were anthocyanins, phenolic acids, flavonoids, and stilbenes. Despite lower antioxidant activity, due to the presence of antimicrobial active compounds, the aqueous extracts inhibited the growth of pathogens.

Tamarillo Polyphenols Encapsulated-Cubosome: Formation, Characterization, Stability during Digestion and Application in Yoghurt

Tamarillo extract is a good source of phenolic and anthocyanin compounds which are well-known for beneficial antioxidant activity, but their bioactivity maybe lost during digestion. In this study, promising prospects of tamarillo polyphenols encapsulated in cubosome nanoparticles prepared via a top-down method were explored. The prepared nanocarriers were examined for their morphology, entrapment efficiency, particle size and stability during in vitro digestion as well as potential fortification of yoghurt. Tamarillo polyphenol-loaded cubosomes showed cubic shape with a mean particle size of 322.4 ± 7.27 nm and the entrapment efficiency for most polyphenols was over 50%. The encapsulated polyphenols showed high stability during the gastric phase of in vitro digestion and were almost completely, but slowly released in the intestinal phase. Addition of encapsulated tamarillo polyphenols to yoghurt (5, 10 and 15 wt% through pre- and post-fermentation) improved the physicochemical and potential nutritional properties (polyphenols concentration, TPC) as well as antioxidant activity. The encapsulation of tamarillo polyphenols protected against pH changes and enzymatic digestion and facilitated a targeted delivery and slow release of the encapsulated compounds to the intestine. Overall, the cubosomal delivery system demonstrated the potential for encapsulation of polyphenols from tamarillo for value-added food product development with yoghurt as the vehicle.

The Importance of Nitrate Reduction for Oral Health

Salivary glands concentrate plasma nitrate into saliva, leading to high nitrate concentrations that can reach the millimolar range after a nitrate-rich vegetable meal. Whereas human cells cannot reduce nitrate to nitrite effectively, certain oral bacteria can. This leads to an increase in systemic nitrite that can improve conditions such as hypertension and diabetes through nitric oxide availability. Apart from systemic benefits, it has been proposed that microbial nitrate reduction can also promote oral health. In this review, we discuss evidence associating dietary nitrate with oral health. Oral bacteria can reduce nitrite to nitric oxide, a free radical with antimicrobial properties capable of inhibiting sensitive species such as anaerobes involved in periodontal diseases. Nitrate has also been shown to increase resilience against salivary acidification in vivo and in vitro, thus preventing caries development. One potential mechanism is proton consumption during denitrification and/or bacterial reduction of nitrite to ammonium. Additionally, lactic acid (organic acid involved in oral acidification) and hydrogen sulfide (volatile compound involved in halitosis) can act as electron donors for these processes. The nitrate-reducing bacteria Rothia and Neisseria are consistently found at higher levels in individuals free of oral disease (vs. individuals with caries, periodontitis, and/or halitosis) and increase when nitrate is consumed in clinical studies. Preliminary in vitro and clinical evidence show that bacteria normally associated with disease, such as Veillonella (caries) and Prevotella (periodontal diseases and halitosis), decrease in the presence of nitrate. We propose nitrate as an ecologic factor stimulating eubiosis (i.e., an increase in health-associated species and functions). Finally, we discuss the preventive and therapeutic potential, as well as safety issues, related to the use of nitrate. In vivo evidence is limited; therefore, robust clinical studies are required to confirm the potential benefits of nitrate reduction on oral health.

Dietary proanthocyanidins on gastrointestinal health and the interactions with gut microbiota

Many epidemiological and experimental studies have consistently reported the beneficial effects of dietary proanthocyanidins (PAC) on improving gastrointestinal physiological functions. This review aims to present a comprehensive perspective by focusing on structural properties, interactions and gastrointestinal protection of PAC. In brief, the main findings of this review are summarized as follows: (1) Structural features are critical factors in determining the bioavailability and subsequent pharmacology of PAC; (2) PAC and/or their bacterial metabolites can play a direct role in the gastrointestinal tract through their antioxidant, antibacterial, anti-inflammatory, and anti-proliferative properties; (3) PAC can reduce the digestion, absorption, and bioavailability of carbohydrates, proteins, and lipids by interacting with them or their according enzymes and transporters in the gastrointestinal tract; (4). PAC showed a prebiotic-like effect by interacting with the microflora in the intestinal tract, and the enhancement of PAC on a variety of probiotics, such as Bifidobacterium spp. and Lactobacillus spp. could be associated with potential benefits to human health. In conclusion, the potential effects of PAC in prevention and alleviation of gastrointestinal diseases are remarkable but clinical evidence is urgently needed.

Effect of Dietary Protein and Processing on Gut Microbiota-A Systematic Review

The effect of diet on the composition of gut microbiota and the consequent impact on disease risk have been of expanding interest. The present review focuses on current insights of changes associated with dietary protein-induced gut microbial populations and examines their potential roles in the metabolism, health, and disease of animals. Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) protocol was used, and 29 highly relevant articles were obtained, which included 6 mouse studies, 7 pig studies, 15 rat studies, and 1 in vitro study. Analysis of these studies indicated that several factors, such as protein source, protein content, dietary composition (such as carbohydrate content), glycation of protein, processing factors, and protein oxidation, affect the digestibility and bioavailability of dietary proteins. These factors can influence protein fermentation, absorption, and functional properties in the gut and, consequently, impact the composition of gut microbiota and affect human health. While gut microbiota can release metabolites that can affect host physiology either positively or negatively, the selection of quality of protein and suitable food processing conditions are important to have a positive effect of dietary protein on gut microbiota and human health.

Beneficial Effects of Laurel (Laurus nobilis L.) and Myrtle (Myrtus communis L.) Extract on Rat Health

Polyphenols of Laurel and Myrtle exhibit structural diversity, which affects bioavailability, metabolism, and bioactivity. The gut microbiota plays a key role in modulating the production, bioavailability and, thus the biological activities of phenolic metabolites, particularly after the intake of food containing high-molecular-weight polyphenols. The aim of this study was to investigate whether the polyphenolic components of Laurel and Myrtle aqueous extract have beneficial effects on rat health. The growth of lactic acid bacteria (LAB), β-glucuronidase, β-glucosidase, β-galactosidase activity, pH value, body weight change and food efficacy ratio after intragastric treatment of rats with Laurel and Myrtle extract at doses of 50 and 100 mg/kg for two weeks were investigated. The endogenous populations of colonic probiotic bacteria (Lactobacilli and Bifidobacteria) were counted on selective media. According to the obtained data, Laurel extract in the applied dose of 50 and 100 and Myrtle extract (100 mg/kg) positively affects the rats health by increasing the number of colonies of Lactobacilli and Bifidobacteria compared to the control group, causes changes in glycolytic enzymatic activity and minor change in antioxidative tissue activity. In addition, high doses of Laurel increase food efficiency ratio, while Myrtle has the same effect at a lower dose.

Plant-Based Polyphenols: Anti-Helicobacter pylori Effect and Improvement of Gut Microbiota

Helicobacter pylori (H. pylori) infection affects more than half of the world’s population, and thus, about 10 to 20% of people with H. pylori suffer from peptic ulcers, which may ultimately lead to gastric cancer. The increase in antibiotic resistance and susceptibility has encouraged the search for new alternative therapies to eradicate this pathogen. Several plant species are essential sources of polyphenols, and these bioactive compounds have demonstrated health-promoting properties, such as the gut microbiota stimulation, inflammation reduction, and bactericidal effect. Therefore, this review aims to discuss the potential effect of plant-based polyphenols against H. pylori and their role in the gut microbiota improvement.

Polyphenols-Gut Microbiota Interrelationship: A Transition to a New Generation of Prebiotics

The present review summarizes the studies carried out on this topic in the last five years. According to the new definitions, among all the compounds included in the group of prebiotics, polyphenols are probably the most important secondary metabolites produced by the plant kingdom. Many of these types of polyphenols have low bioavailability, therefore reaching the colon in unaltered form. Once in the colon, these compounds interact with the intestinal microbes bidirectionally by modulating them and, consequently, releasing metabolites. Despite much research on various metabolites, little is known about the chemistry of the metabolic routes used by different bacteria species. In this context, this review aims to investigate the prebiotic effect of polyphenols in preclinical and clinical studies, highlighting that the consumption of polyphenols leads to an increase in beneficial bacteria, as well as an increase in the production of valuable metabolites. In conclusion, there is much evidence in preclinical studies supporting the prebiotic effect of polyphenols, but further clinical studies are needed to investigate this effect in humans.

Impact of solid-state fermentation on factors and mechanisms influencing the bioactive compounds of grains and processing by-products

Cereal and legume grains and their processing by-products are rich sources of bioactives such as phenolics with considerable health potential, but these bioactives suffer from low bioaccessibility and bioavailability, resulting in limited use. Several studies have demonstrated that solid-state fermentation (SSF) with food-grade microorganisms is effective in releasing bound phenolic compounds in cereal and legume products. In this review, we discuss the effect of SSF on cereal and legume grains and their by-products by examining the role of specific microorganisms, their hydrolytic enzymes, fermentability of agri-food substrates, and the potential health benefits of SSF-enhanced bioactive compounds. SSF with fungi (Aspergillus spp. and Rhizopus spp.), bacteria (Bacillus subtilis and lactic acid bacteria (LAB) spp.) and yeast (Saccharomyces cerevisiae) significantly increased the bioactive phenolics and antioxidant capacities in cereal and legume grains and by-products, mainly through carbohydrate-cleaving enzymes. Increased bioactive phenolic and peptide contents of SSF-bioprocessed cereal and legume grains have been implicated for improved antioxidant, anti-inflammatory, anti-carcinogenic, anti-diabetic, and angiotensin-converting-enzyme (ACE) inhibitory effects in fermented agri-food products, but these remain as preliminary results. Future research should focus on the microbial mechanisms, suitability of substrates, and the physiological health benefits of SSF-treated grains and by-products.