Plant polyphenols inhibit VacA, a toxin secreted by the gastric pathogen Helicobacter pylori

Polyphenolic Compounds: Orchestrating Intestinal Microbiota Harmony during Aging

In the aging process, physiological decline occurs, posing a substantial threat to the physical and mental well-being of the elderly and contributing to the onset of age-related diseases. While traditional perspectives considered the maintenance of life as influenced by a myriad of factors, including environmental, genetic, epigenetic, and lifestyle elements such as exercise and diet, the pivotal role of symbiotic microorganisms had been understated. Presently, it is acknowledged that the intestinal microbiota plays a profound role in overall health by signaling to both the central and peripheral nervous systems, as well as other distant organs. Disruption in this bidirectional communication between bacteria and the host results in dysbiosis, fostering the development of various diseases, including neurological disorders, cardiovascular diseases, and cancer. This review aims to delve into the intricate biological mechanisms underpinning dysbiosis associated with aging and the clinical ramifications of such dysregulation. Furthermore, we aspire to explore bioactive compounds endowed with functional properties capable of modulating and restoring balance in this aging-related dysbiotic process through epigenetics alterations.

Fermented foods and gastrointestinal health: underlying mechanisms

Although fermentation probably originally developed as a means of preserving food substrates, many fermented foods (FFs), and components therein, are thought to have a beneficial effect on various aspects of human health, and gastrointestinal health in particular. It is important that any such perceived benefits are underpinned by rigorous scientific research to understand the associated mechanisms of action. Here, we review in vitro, ex vivo and in vivo studies that have provided insights into the ways in which the specific food components, including FF microorganisms and a variety of bioactives, can contribute to health-promoting activities. More specifically, we draw on representative examples of FFs to discuss the mechanisms through which functional components are produced or enriched during fermentation (such as bioactive peptides and exopolysaccharides), potentially toxic or harmful compounds (such as phytic acid, mycotoxins and lactose) are removed from the food substrate, and how the introduction of fermentation-associated live or dead microorganisms, or components thereof, to the gut can convey health benefits. These studies, combined with a deeper understanding of the microbial composition of a wider variety of modern and traditional FFs, can facilitate the future optimization of FFs, and associated microorganisms, to retain and maximize beneficial effects in the gut.

The synergistic effects of polyphenols and intestinal microbiota on osteoporosis

Osteoporosis is a common metabolic disease in middle-aged and elderly people. It is characterized by a reduction in bone mass, compromised bone microstructure, heightened bone fragility, and an increased susceptibility to fractures. The dynamic imbalance between osteoblast and osteoclast populations is a decisive factor in the occurrence of osteoporosis. With the increase in the elderly population in society, the incidence of osteoporosis, disability, and mortality have gradually increased. Polyphenols are a fascinating class of compounds that are found in both food and medicine and exhibit a variety of biological activities with significant health benefits. As a component of food, polyphenols not only provide color, flavor, and aroma but also act as potent antioxidants, protecting our cells from oxidative stress and reducing the risk of chronic disease. Moreover, these natural compounds exhibit anti-inflammatory properties, which aid in immune response regulation and potentially alleviate symptoms of diverse ailments. The gut microbiota can degrade polyphenols into more absorbable metabolites, thereby increasing their bioavailability. Polyphenols can also shape the gut microbiota and increase its abundance. Therefore, studying the synergistic effect between gut microbiota and polyphenols may help in the treatment and prevention of osteoporosis. By delving into how gut microbiota can enhance the bioavailability of polyphenols and how polyphenols can shape the gut microbiota and increase its abundance, this review offers valuable information and references for the treatment and prevention of osteoporosis.

Antibacterial and Antihemolytic Activity of New Biomaterial Based on Glycyrrhizic Acid and Quercetin (GAQ) against Staphylococcus aureus

The goal of this study is to obtain and characterize the complex of quercetin with glycyrrhizic acid, which is known to serve as a drug delivery system. Quercetin is a flavonoid with a wide range of biological activities, including an antimicrobial effect. However, quercetin instability and low bioavailability that limits its use in medical practice makes it necessary to look for new nanoformulations of it. The formation of the GAQ complex (2:1) was confirmed by using UV and FT-IR spectroscopies. It was found that the GAQ exhibited antimicrobial and antihemolytical activities against S. aureus bacteria and its main virulent factor-α-hemolysin. The IC₅₀ value for the antihemolytical effect of GAQ was 1.923 ± 0.255 µg/mL. Using a fluorescence method, we also showed that the GAQ bound tightly to the toxin that appears to underlie its antihemolytic activity. In addition, another mechanism of the antihemolytic activity of the GAQ against α-hemolysin was shown, namely, its ability to increase the rigidity of the outer layer of the erythrocyte membrane and thus inhibit the incorporation of α-hemolysin into the target cells, increasing their resistance to the toxin. Both of these effects of GAQ were observed at concentrations below the MIC value for S. aureus growth, indicating the potential of the complex as an antivirulence agent.

Antimicrobial Activity of Quercetin, Naringenin and Catechin: Flavonoids Inhibit Staphylococcus aureus-Induced Hemolysis and Modify Membranes of Bacteria and Erythrocytes

Search for novel antimicrobial agents, including plant-derived flavonoids, and evaluation of the mechanisms of their antibacterial activities are pivotal objectives. The goal of this study was to compare the antihemolytic activity of flavonoids, quercetin, naringenin and catechin against sheep erythrocyte lysis induced by α-hemolysin (αHL) produced by the Staphylococcus aureus strain NCTC 5655. We also sought to investigate the membrane-modifying action of the flavonoids. Lipophilic quercetin, but not naringenin or catechin, effectively inhibited the hemolytic activity of αHL at concentrations (IC₅₀ = 65 ± 5 µM) below minimal inhibitory concentration values for S. aureus growth. Quercetin increased the registered bacterial cell diameter, enhanced the fluidity of the inner and surface regions of bacterial cell membranes and raised the rigidity of the hydrophobic region and the fluidity of the surface region of erythrocyte membranes. Our findings provide evidence that the antibacterial activities of the flavonoids resulted from a disorder in the structural organization of bacterial cell membranes, and the antihemolytic effect of quercetin was related to the effect of the flavonoid on the organization of the erythrocyte membrane, which, in turn, increases the resistance of the target cells (erythrocytes) to αHL and inhibits αHL-induced osmotic hemolysis due to prevention of toxin incorporation into the target membrane. We confirmed that cell membrane disorder could be one of the direct modes of antibacterial action of the flavonoids.

Ethnobotanical study of Hakka traditional medicine in Ganzhou, China and their antibacterial, antifungal, and cytotoxic assessments

Background

Traditional herbs played a crucial role in the health care of the Hakka people. However, studies to identify these traditional herbs are few. Here we document and assess the potential of these plants for treating microbial infections. Many herbs used by the Hakka people could potentially be a novel medicinal resource.

Methods

Local herb markets were surveyed via semi-structured interviews, complemented by direct observations to obtain information on herbal usage. For each herb selected for this study, extracts in four different solvents were prepared, and tested for activity against 20 microorganisms, as well as cancerous and noncancerous cells. All data were subjected to cluster analysis to discover relationships among herbs, plant types, administration forms, solvents, microorganisms, cells, etc., with the aim to discern promising herbs for medicine.

Results

Ninety-seven Hakka herbs in Ganzhou were documented from 93 plants in 62 families; most are used for bathing (97%), or as food, such as tea (32%), soup (12%), etc. Compared with the Chinese Pharmacopoeia and Chinese Materia Medica, 24 Hakka medicines use different plant parts, and 5 plants are recorded here for the first time as traditional medicines. The plant parts used were closely related with the life cycle: annual and perennial herbs were normally used as a whole plant, and woody plants as (tender) stem and leaf, indicating a trend to use the parts that are easily collected. Encouragingly, 311 extracts (94%) were active against one or more microorganisms. Most herbs were active against Gram-positive bacteria, such as Staphylococcus aureus (67%), Listeria innocua (64%), etc. Cytotoxicity was often observed against a tumor cell, but rarely against normal cells. Considering both antimicrobial activity and cytotoxicity, many herbs reported in this study show promise as medicine.

Conclusion

Hakka people commonly use easily-collected plant parts (aerial parts or entire herb) as medicine. External use of decoctions dominated, and may help combating microbial infections. The results offer promising perspectives for further research since little phytopharmacology and phytochemistry has been published to date.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-022-03712-z.

Flavonoids-Rich Plant Extracts Against Helicobacter pylori Infection as Prevention to Gastric Cancer

Gastric cancer is the fifth most common and fourth type to cause the highest mortality rates worldwide. The leading cause is related to Helicobacter pylori (H. pylori) infection. Unfortunately, current treatments have low success rates, highlighting the need for alternative treatments against carcinogenic agents, specifically H. pylori. Noteworthy, natural origin products contain pharmacologically active metabolites such as flavonoids, with potential antimicrobial applications.

Objective: This article overviews flavonoid-rich extracts’ biological and pharmacological activities. It focuses on using these substances against Helicobacter pylori infection to prevent gastric cancer. For this, PubMed and Science Direct databases were searched for studies that reported the activity of flavonoids against H. pylori, published within a 10-year time frame (2010 to August 2020). It resulted in 1,773 publications, of which 44 were selected according to the search criteria. The plant family primarily found in publications was Fabaceae (9.61%). Among the flavonoids identified after extraction, the most prevalent were quercetin (19.61%), catechin (13.72), epicatechin (11.76), and rutin (11.76). The potential mechanisms associated with anti-H. pylori activity to the extracts were: inhibition of urease, damage to genetic material, inhibition of protein synthesis, and adhesion of the microorganism to host cells.

Conclusion: Plant extracts rich in flavonoids with anti-H. pylori potential proved to be a promising alternative therapy source, reinforcing the relevance of studies with natural products.

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.

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.

Higher dietary total antioxidant capacity is inversely associated with Helicobacter pylori infection among adults: A case-control study

INTRODUCTION

Antioxidants appear to hinder the actions of Helicobacter pylori (H. pylori). The aim of this research was to evaluate the association between dietary total antioxidant capacity (DTAC) and H. pylori infection.

METHODS

A case-control study was carried out among 200 patients with  H. pylori infection and 402 healthy subjects (18-55 years). Dietary data were collected using a validated 168-item quantitative food frequency questionnaire. DTAC was calculated based on the oxygen radical absorbance capacity of each food (except for coffee) reported by the US Department of Agriculture.

RESULTS

Compared with participants in the lowest tertile of DTAC, those in the highest tertile had a significantly lower odds ratio (OR) in the crude model (OR, 0.29; 95% CI, 0.14-0.61; p for trend = 0.001), model 1 (adjustment for age and sex) (OR, 0.37; 95% CI, 0.24-0.58; p for trend < 0.001), and model 2 (adjustment for model 1 plus body mass index, waist circumference, physical activity, smoking, dietary intake of energy and fat) (OR, 0.20; 95% CI, 0.10-0.40; p for trend ≤ 0.001).

CONCLUSIONS

A high DTAC is associated with a reduced risk of H. pylori infection in adults. Further studies are mandatory to elucidate the mechanisms and a dose-effect relationship.

High-polyphenol extracts from Sorghum bicolor attenuate replication of Legionella pneumophila within RAW 264.7 macrophages

Polyphenols derived from a variety of plants have demonstrated antimicrobial activity against diverse microbial pathogens. Legionella pneumophila is an intracellular bacterial pathogen that opportunistically causes a severe inflammatory pneumonia in humans, called Legionnaires' Disease, via replication within macrophages. Previous studies demonstrated that tea polyphenols attenuate L. pneumophila intracellular replication within mouse macrophages via increased tumor necrosis factor (TNF) production. Sorghum bicolor is a sustainable cereal crop that thrives in arid environments and is well-suited to continued production in warming climates. Sorghum polyphenols have anticancer and antioxidant properties, but their antimicrobial activity has not been evaluated. Here, we investigated the impact of sorghum polyphenols on L. pneumophila intracellular replication within RAW 264.7 mouse macrophages. Sorghum high-polyphenol extract (HPE) attenuated L. pneumophila intracellular replication in a dose-dependent manner but did not impair either bacterial replication in rich media or macrophage viability. Moreover, HPE treatment enhanced both TNF and IL-6 secretion from L. pneumophila infected macrophages. Thus, polyphenols derived from sorghum enhance macrophage restriction of L. pneumophila, likely via increased pro-inflammatory cytokine production. This work reveals commonalities between plant polyphenol-mediated antimicrobial activity and provides a foundation for future evaluation of sorghum as an antimicrobial agent.

Evolving Interplay Between Dietary Polyphenols and Gut Microbiota-An Emerging Importance in Healthcare

Polyphenols are natural plant compounds and are the most abundant antioxidants in the human diet. As the gastrointestinal tract is the primary organ provided to diet sections, the diet may be regarded as one of the essential factors in the functionality, integrity, and composition of intestinal microbiota. In the gastrointestinal tract, many polyphenols remain unabsorbed and may accumulate in the large intestine, where the intestinal microbiota are most widely metabolized. When assuming primary roles for promoting host well-being, this intestinal health environment is presented to the effect of external influences, including dietary patterns. A few different methodologies have been developed to increase solvency and transport across the gastrointestinal tract and move it to targeted intestinal regions to resolve dietary polyphenols at the low bioavailability. Polyphenols form a fascinating community among the different nutritional substances, as some of them have been found to have critical biological activities that include antioxidant, antimicrobial, or anticarcinogenic activities. Besides, it affects metabolism and immunity of the intestines and has anti-inflammatory properties. The well-being status of subjects can also benefit from the development of bioactive polyphenol-determined metabolites, although the mechanisms have not been identified. Even though the incredible variety of health-advancing activities of dietary polyphenols has been widely studied, their effect on intestinal biology adaptation, and two-way relationship between polyphenols and microbiota is still poorly understood. We focused on results of polyphenols in diet with biological activities, gut ecology, and the influence of their proportional links on human well-being and disease in this study.

Antibacterial green tea catechins from a molecular perspective: mechanisms of action and structure-activity relationships

This review summarizes the mechanisms of antibacterial action of green tea catechins, discussing the structure-activity relationship (SAR) studies for each mechanism. The antibacterial activity of green tea catechins results from a variety of mechanisms that can be broadly classified into the following groups: (1) inhibition of virulence factors (toxins and extracellular matrix); (2) cell wall and cell membrane disruption; (3) inhibition of intracellular enzymes; (4) oxidative stress; (5) DNA damage; and (6) iron chelation. These mechanisms operate simultaneously with relative importance differing among bacterial strains. In all SAR studies, the highest antibacterial activity is observed for galloylated compounds (EGCG, ECG, and theaflavin digallate). This observation, combined with numerous experimental and theoretical evidence, suggests that catechins share a common binding mode, characterized by the formation of hydrogen bonds and hydrophobic interactions with their target.

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

The beneficial health roles of dietary polyphenols in preventing oxidative stress related chronic diseases have been subjected to intense investigation over the last two decades. As our understanding of the role of gut microbiota advances our knowledge of the antioxidant and anti-inflammatory functions of polyphenols accumulates, there emerges a need to examine the prebiotic role of dietary polyphenols. This review focused onthe role of different types and sources of dietary polyphenols on the modulation of the gut microbiota, their metabolites and how they impact on host health benefits. Inter-dependence between the gut microbiota and polyphenol metabolites and the vital balance between the two in maintaining the host gut homeostasis were discussed with reference to different types and sources of dietary polyphenols. Similarly, the mechanisms behind the health benefits by various polyphenolic metabolites bio-transformed by gut microbiota were also explained. However, further research should focus on the importance of human trials and profound links of polyphenols-gut microbiota-nerve-brain as they provide the key to unlock the mechanisms behind the observed benefits of dietary polyphenols found in vitro and in vivo studies.

Curcumin, Quercetin, Catechins and Metabolic Diseases: The Role of Gut Microbiota

Polyphenols (PPs) are the naturally occurring bioactive components in fruits and vegetables, and they are the most abundant antioxidant in the human diet. Studies are suggesting that ingestion of PPs might be helpful to ameliorate metabolic syndromes that may contribute in the prevention of several chronic disorders like diabetes, obesity, hypertension, and colon cancer. PPs have structural diversity which impacts their bioavailability as they accumulate in the large intestine and are extensively metabolized through gut microbiota (GM). Intestinal microbiota transforms PPs into their metabolites to make them bioactive. Interestingly, not only GM act on PPs to metabolize them but PPs also modulate the composition of GM. Thus, change in GM from pathogenic to beneficial ones may be helpful to ameliorate gut health and associated diseases. However, to overcome the low bioavailability of PPs, various approaches have been developed to improve their solubility and transportation through the gut. In this review, we present evidence supporting the structural changes that occur after metabolic reactions in PPs (curcumin, quercetin, and catechins) and their effect on GM composition that leads to improving overall gut health and helping to ameliorate metabolic disorders.

Effect of Feijoa Sellowiana Acetonic Extract on Proliferation Inhibition and Apoptosis Induction in Human Gastric Cancer Cells

Gastric cancer (GC) still represents a relevant health problem in the world for both incidence and mortality rates. Many studies underlined that natural products consumption could reduce GC risk, indicating flavonoids as responsible for the beneficial effects through the modulation of several biological processes, such as the inhibition of cancer antioxidant defense and induction of apoptosis. Since Feijoa sellowiana fruit is known to contain high amounts of flavonoids, among which is flavone, we evaluated the antiproliferative and proapoptotic effects of F. sellowiana acetonic extract on GC cell lines through MTS and Annexin-V FITC assays. Among three GC cell lines tested, SNU-1 results being sensitive to both the F. sellowiana acetonic extract and synthetic flavone, which was used as the reference treatment. Moreover, we evaluated their antioxidant effects, assessing the activity of the antioxidant enzymes supeoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) in polymorphonuclear cells. We found a significant increase of their activity after exposure to both F. sellowiana acetonic extract and flavone, supporting the idea that a diet that includes flavone-rich fruits could be of benefit for health. In addition to this antioxidant effect on normal cells, this study indicates, for the first time, an anticancer effect of F. sellowiana acetonic extract in GC cells.

Roles of the Polyphenol-Gut Microbiota Interaction in Alleviating Colitis and Preventing Colitis-Associated Colorectal Cancer

Accumulating evidence indicates that the gut microbiota can promote or inhibit colonic inflammation and carcinogenesis. Promotion of beneficial gut bacteria is considered a promising strategy to alleviate colonic diseases including colitis and colorectal cancer. Interestingly, dietary polyphenols, which have been shown to attenuate colitis and inhibit colorectal cancer in animal models and some human studies, appear to reach relatively high concentrations in the large intestine and to interact with the gut microbial community. This review summarizes the modulatory effects of polyphenols on the gut microbiota in humans and animals under healthy and diseased conditions including colitis and colitis-associated colorectal cancer (CAC). Existing human and animal studies indicate that polyphenols and polyphenol-rich whole foods are capable of elevating butyrate producers and probiotics that alleviate colitis and inhibit CAC, such as Lactobacillus and Bifidobacterium. Studies in colitis and CAC models indicate that polyphenols decrease opportunistic pathogenic or proinflammatory microbes and counteract disease-induced dysbiosis. Consistently, polyphenols also change microbial functions, including increasing butyrate formation. Moreover, polyphenol metabolites produced by the gut microbiota appear to have anticancer and anti-inflammatory activities, protect gut barrier integrity, and mitigate inflammatory conditions in cells and animal models. Based on these results, we conclude that polyphenol-mediated alteration of microbial composition and functions, together with polyphenol metabolites produced by the gut microbiota, likely contribute to the protective effects of polyphenols on colitis and CAC. Future research is needed to validate the causal role of the polyphenol-gut microbiota interaction in polyphenols' anti-colitis and anti-CAC effects, and to further elucidate mechanisms underlying such interaction.

Inhibition of interaction between Staphylococcus aureus α-hemolysin and erythrocytes membrane by hydrolysable tannins: structure-related activity study

The objective of the study was a comparative analysis of the antihemolytic activity against two Staphylococcus aureus strains (8325-4 and NCTC 5655) as well as α-hemolysin and of the membrane modifying action of four hydrolysable tannins with different molecular mass and flexibility: 3,6-bis-O-di-O-galloyl-1,2,4-tri-O-galloyl-β-d-glucose (T1), 1,2,3,4,5-penta-O-galloyl-β-d-glucose (T2), 3-O-galloyl-1,2-valoneoyl-β-d-glucose (T3) and 1,2-di-O-galloyl-4,6-valoneoyl-β-d-glucose (T4). We showed that all the compounds studied manifested antihemolytic effects in the range of 5–50 µM concentrations. However, the degree of the reduction of hemolysis by the investigated tannins was not uniform. A valoneoyl group—containing compounds (T3 and T4) were less active. Inhibition of the hemolysis induced by α-hemolysin was also noticed on preincubated with the tannins and subsequently washed erythrocytes. In this case the efficiency again depended on the tannin structure and could be represented by the following order: T1 > T2 > T4 > T3. We also found a relationship between the degree of antihemolytic activity of the tannins studied and their capacity to increase the ordering parameter of the erythrocyte membrane outer layer and to change zeta potential. Overall, our study showed a potential of the T1 and T2 tannins as anti-virulence agents. The results of this study using tannins with different combinations of molecular mass and flexibility shed additional light on the role of tannin structure in activity manifestation.

Effect of β-caryophyllene from Cloves Extract on Helicobacter pylori Eradication in Mouse Model

New antibacterial treatments against Helicobacter pylori are needed as H. pylori is acquiring antibiotic resistance. β-caryophyllene is a natural bicyclic sesquiterpene, with anti-inflammatory and antimicrobial effects. This study investigates the effects of H-002119-00-001 from β-caryophyllene on the eradication of H. pylori in a mouse model, and its effects on the inflammation of the gastric mucosa. To evaluate the anti-H.pylori efficacy of β-caryophyllene, a total of 160 mice were divided into eight groups (n = 10 each) and were administered different treatments for 2 and 4 weeks. H. pylori eradication was assessed using a Campylobacter-like organism (CLO) test and H. pylori qPCR of the gastric mucosa. The levels of inflammation of gastric mucosa were assessed using histology and immunostaining. H-002119-00-001 decreased bacterial burden in vitro. When H-002119-00-001 was administered to mice once daily for 2 weeks, cure rates shown by the CLO test were 40.0%, 60.0%, and 70.0% in groups 6, 7, and 8, respectively. H. pylori levels in gastric mucosa decreased dose-dependently after H-002119-00-001 treatment. H-002119-00-001 also reduced levels of inflammation in gastric mucosa. H-002119-00-001 improved inflammation and decreased bacterial burden in H. pylori-infected mouse models. H-002119-00-001 is a promising and effective therapeutic agent for the treatment of H. pylori infection.

Beneficial Effects of Dietary Polyphenols on Gut Microbiota and Strategies to Improve Delivery Efficiency

The human intestine contains an intricate ecological community of dwelling bacteria, referred as gut microbiota (GM), which plays a pivotal role in host homeostasis. Multiple factors could interfere with this delicate balance, including genetics, age, antibiotics, as well as environmental factors, particularly diet, thus causing a disruption of microbiota equilibrium (dysbiosis). Growing evidences support the involvement of GM dysbiosis in gastrointestinal (GI) and extra-intestinal cardiometabolic diseases, namely obesity and diabetes. This review firstly overviews the role of GM in health and disease, then critically reviews the evidences regarding the influence of dietary polyphenols in GM based on preclinical and clinical data, ending with strategies under development to improve efficiency of delivery. Although the precise mechanisms deserve further clarification, preclinical and clinical data suggest that dietary polyphenols present prebiotic properties and exert antimicrobial activities against pathogenic GM, having benefits in distinct disorders. Specifically, dietary polyphenols have been shown ability to modulate GM composition and function, interfering with bacterial quorum sensing, membrane permeability, as well as sensitizing bacteria to xenobiotics. In addition, can impact on gut metabolism and immunity and exert anti-inflammatory properties. In order to overcome the low bioavailability, several different approaches have been developed, aiming to improve solubility and transport of dietary polyphenols throughout the GI tract and deliver in the targeted intestinal regions. Although more research is still needed, particularly translational and clinical studies, the biotechnological progresses achieved during the last years open up good perspectives to, in a near future, be able to improve the use of dietary polyphenols modulating GM in a broad range of disorders characterized by a dysbiotic phenotype.

Gut microbiota, dietary phytochemicals and benefits to human health

Purpose of the review

In this review, we discuss the roles of the gut microbiota, dietary phytochemicals in improving human health. Recent studies have reported that the human gut microbiota can be altered by dietary phytochemicals including phenolics, carotenoids, and dietary fibers. In addition, both pathogenic and nonpathogenic bacteria show regulatory effects with phytochemicals, suggesting potential synergistic effects in the improvement of human gut health and prevention of chronic diseases.

Recent findings

Numerous studies have been conducted on gut microbial alterations induced by phytochemicals, such as phenolics and carotenoids. Butyrate, a short-chain fatty acid produced via bacterial fermentation in the colon, also shows a significantly beneficial effect in the maintenance of gut microbial homeostasis. However, the molecular mechanisms underlying the effects of diets and the interactions of the gut microorganisms remain poorly understood. The gut microbiome profile changes have been observed in chronic inflammation-induced diseases including colitis, Crohn's disease, immune dysfunction, colon cancer, obesity and diabetes. The anti-inflammatory effects of dietary phytochemicals against these diseases may be partially mediated by regulation of microbial profiles. Latest advances in biomedical technology such as the next-generation sequencing (NGS), and continuous cost reduction associated with these technologies, enabled researchers to perform ever-increasing number of large-scale, high-throughput computational analyses to elucidate the potential mechanism of phytochemical-microbiome interactions.

Summary

Information obtained from these studies may provide valuable insights to guide future clinical research for the development of therapeutics, botanicals and drug efficacy testing, many of which will be discussed in this review.

Syk: a new target for attenuation of Helicobacter pylori-induced gastric mucosal inflammatory responses

The magnitude of gastric mucosal inflammatory response to H. pylori relies primarily on the extent of its key endotoxin, LPS, engagement of Toll-like receptor-4 (TLR4) and the initiation of signal transduction events converging on mitogen-activated protein kinase (MAPK) and IκB complex (IKK) cascades. These cascades, in turn, exert their control over the assembly of transcription factors, NFκB and AP1, implicated in the induction of the expression of iNOS and COX-2 proinflammatory genes. The LPS-induced TLR4 activation and the ensuing phosphorylation of its intracellular tyrosine domain by Src-family kinases not only leads to recruitment to the cytoplasmic domain of TLR4 of adaptor molecules directly involved in propagation of the signaling cascades converging on MAPK and IKK, but also provides a propitious docking site for a non-receptor tyrosine kinase, spleen tyrosine kinase (Syk), the activation of which apparently leads to upregulation in the expression of proinflammatory genes. Here, we review the pathways engaged by H. pylori in the recruitment and interaction of Syk with TLR4 in gastric mucosa, and discuss the cascades involved in Syk-mediated amplification in proinflammatory signaling. We focus, moreover, on the potential role of drugs targeting Syk and TLR4 in the treatment of H. pylori-related gastric disease.

Inhibition of bacterial toxin recognition of membrane components as an anti-virulence strategy

Over recent years, the development of new antibiotics has not kept pace with the rate at which bacteria develop resistance to these drugs. For this reason, many research groups have begun to design and study alternative therapeutics, including molecules to specifically inhibit the virulence of pathogenic bacteria. Because many of these pathogenic bacteria release protein toxins, which cause or exacerbate disease, inhibition of the activity of bacterial toxins is a promising anti-virulence strategy. In this review, we describe several approaches to inhibit the initial interactions of bacterial toxins with host cell membrane components. The mechanisms by which toxins interact with the host cell membrane components have been well-studied over the years, leading to the identification of therapeutic targets, which have been exploited in the work described here. We review efforts to inhibit binding to protein receptors and essential membrane lipid components, complex assembly, and pore formation. Although none of these molecules have yet been demonstrated in clinical trials, the in vitro and in vivo results presented here demonstrate their promise as novel alternatives and/or complements to traditional antibiotics.

Catechin-mediated restructuring of a bacterial toxin inhibits activity

BACKGROUND

Catechins, polyphenols derived from tea leaves, have been shown to have antibacterial properties, through direct killing of bacteria as well as through inhibition of bacterial toxin activity. In particular, certain catechins have been shown to have bactericidal effects on the oral bacterium, Aggregatibacter actinomycetemcomitans, as well as the ability to inhibit a key virulence factor of this organism, leukotoxin (LtxA). The mechanism of catechin-mediated inhibition of LtxA has not been shown.

METHODS

In this work, we studied the ability of six catechins to inhibit LtxA-mediated cytotoxicity in human white blood cells, using Trypan blue staining, and investigated the mechanism of action using a combination of techniques, including fluorescence and circular dichroism spectroscopy, confocal microscopy, and surface plasmon resonance.

RESULTS

We found that all the catechins except (-)-catechin inhibited the activity of this protein, with the galloylated catechins having the strongest effect. Pre-incubation of the toxin with the catechins increased the inhibitory action, indicating that the catechins act on the protein, rather than the cell. The secondary structure of LtxA was dramatically altered in the presence of catechin, which resulted in an inhibition of toxin binding to cholesterol, an important initial step in the cytotoxic mechanism of the toxin.

CONCLUSIONS

These results demonstrate that the catechins inhibit LtxA activity by altering its structure to prevent interaction with specific molecules present on the host cell surface.

GENERAL SIGNIFICANCE

Galloylated catechins modify protein toxin structure, inhibiting the toxin from binding to the requisite molecules on the host cell surface.

In Vitro Inhibition of Helicobacter pylori Growth by Redox Cycling Phenylaminojuglones

Infection by Helicobacter pylori increases 10 times the risk of developing gastric cancer. Juglone, a natural occurring 1,4-naphthoquinone, prevents H. pylori growth by interfering with some of its critical metabolic pathways. Here, we report the design, synthesis, and in vitro evaluation of a series of juglone derivatives, namely, 2/3-phenylaminojuglones, as potential H. pylori growth inhibitors. Results show that 5 out of 12 phenylaminojuglones (at 1.5 μg/mL) were 1.5-2.2-fold more active than juglone. Interestingly, most of the phenylaminojuglones (10 out of 12) were 1.1-2.8 fold more active than metronidazole, a known H. pylori growth inhibitor. The most active compound, namely, 2-((3,4,5-trimethoxyphenyl)amino)-5-hydroxynaphthalene-1,4-dione 7, showed significant higher halo of growth inhibitions (HGI = 32.25 mm) to that of juglone and metronidazole (HGI = 14.50 and 11.67 mm). Structural activity relationships of the series suggest that the nature and location of the nitrogen substituents in the juglone scaffold, likely due in part to their redox potential, may influence the antibacterial activity of the series.

Use of dark chocolate for diabetic patients: a review of the literature and current evidence

Dietary changes are a major lifestyle factor that can influence the progression of chronic diseases such as diabetes. Recently, flavanols, a subgroup of plant-derived phytochemicals called flavonoids, have gained increasing attention, due to studies showing an inverse correlation between dietary intake of flavanols and incidence of diabetes. Flavanoids in the cocoa plant may ameliorate insulin resistance by improving endothelial function, altering glucose metabolism, and reducing oxidative stress. Oxidative stress has been proposed as the main culprit for insulin resistance. The well-established effects of cocoa on endothelial function also points to a possible effect on insulin sensitivity. The relationship between insulin resistance and endothelial function is a reciprocal one. Overall, the evidence from these studies suggests that cocoa may be useful in slowing the progression to type 2 diabetes and ameliorating insulin resistance in metabolic syndrome. Additionally, results from several small studies indicate that cocoa may also have therapeutic potential in preventing cardiovascular complications in diabetic patients. Studies highlighting the potential of cocoa-containing diets, in large-randomized controlled trials should be performed which might give us a better opportunity to analyze the potential health-care benefit for reducing the risk of complications in diabetic patients at molecular level.

Phytochemicals for human disease: An update on plant-derived compounds antibacterial activity

In recent years, many studies have shown that phytochemicals exert their antibacterial activity through different mechanisms of action, such as damage to the bacterial membrane and suppression of virulence factors, including inhibition of the activity of enzymes and toxins, and bacterial biofilm formation. In this review, we summarise data from the available literature regarding the antibacterial effects of the main phytochemicals belonging to different chemical classes, alkaloids, sulfur-containing phytochemicals, terpenoids, and polyphenols. Some phytochemicals, besides having direct antimicrobial activity, showed an in vitro synergistic effect when tested in combination with conventional antibiotics, modifying antibiotic resistance. Review of the literature showed that phytochemicals represent a possible source of effective, cheap and safe antimicrobial agents, though much work must still be carried out, especially in in vivo conditions to ensure the selection of effective antimicrobial substances with low side and adverse effects.

Anti-Helicobacter pylori activity of crude N-acetylneuraminic acid isolated from glycomacropeptide of whey

Helicobacter pylori colonizes the gastric mucosa of about half of the world's population, causing chronic gastritis and gastric cancer. An increasing emergence of antibiotic-resistant H. pylori arouses demand on alternative non-antibiotic-based therapies. In this study, we freshly prepared crude N-acetylneuraminic acid obtained from glycomacropeptide (G-NANA) of whey through a neuraminidase-mediated reaction and evaluated its antibacterial ability against H. pylori and H. felis. Overnight cultures of the H. pylori were diluted with fresh media and different concentrations (1-150 mg/mL) of crude G-NANA were added directly to the culture tube. Bacterial growth was evaluated by measuring the optical density of the culture medium and the number of viable bacteria was determined by a direct count of the colony forming units (CFU) on agar plates. For the in vivo study, mice were orally infected with 100 µL (5×10(8) cfu/mL) of H. felis four times at a day's interval, accompanied by a daily administration of crude G-NANA or vehicle. A day after the last infection, the mice were daily administered the crude G-NANA (0, 75, and 300 mg/mL) for 10 days and euthanized. Their stomachs were collected and bacterial colonization was determined by quantitative real-time PCR. Crude G-NANA inhibited H. pylori's growth and reduced the number of viable bacteria in a dose-dependent manner. Furthermore, crude G-NANA inhibited bacterial colonization in the mice. These results showed that crude G-NANA has antibacterial activity against Helicobacter and demonstrated its therapeutic potential for the prevention of chronic gastritis and gastric carcinogenesis induced by Helicobacter infection in humans.

Antibacterial Flavonoids from Medicinal Plants Covalently Inactivate Type III Protein Secretion Substrates

Traditional Chinese Medicines (TCMs) have been historically used to treat bacterial infections. However, the molecules responsible for these anti-infective properties and their potential mechanisms of action have remained elusive. Using a high-throughput assay for type III protein secretion in Salmonella enterica serovar Typhimurium, we discovered that several TCMs can attenuate this key virulence pathway without affecting bacterial growth. Among the active TCMs, we discovered that baicalein, a specific flavonoid from Scutellaria baicalensis, targets S. Typhimurium pathogenicity island-1 (SPI-1) type III secretion system (T3SS) effectors and translocases to inhibit bacterial invasion of epithelial cells. Structurally related flavonoids present in other TCMs, such as quercetin, also inactivated the SPI-1 T3SS and attenuated S. Typhimurium invasion. Our results demonstrate that specific plant metabolites from TCMs can directly interfere with key bacterial virulence pathways and reveal a previously unappreciated mechanism of action for anti-infective medicinal plants.

Challenges to the Treatment and New Perspectives for the Eradication of Helicobacter pylori

Helicobacter pylori (H. pylori) is one of the leading causes of gastric diseases such as chronic gastritis, peptic ulcer, and gastric adenocarcinoma. The current treatment of H. pylori infection with antibiotics and proton pump inhibitors has several limitations, including poor adherence and intrinsic patient-related factors, drug resistance, and the absence of adequate treatments. This review summarizes the current therapeutic approaches to eradicating H. pylori, the difficulties associated with its treatment, and several new perspectives aimed at improving existing treatment strategies.

In vitro effect of bergamot (Citrus bergamia) juice against cagA-positive and-negative clinical isolates of Helicobacter pylori

Background

Helicobacter pylori infection has been associated with chronic gastritis, peptic ulcer and gastric carcinoma as over half of the world's population is colonized with this gram-negative bacterium. Due to the increasing antibiotic resistance, its eradication rates fails in a great portion of patients. A number of studies showed that molecules largely distributed in commonly consumed fruits and vegetables may have antimicrobial activity. The aim of the present study was to investigate the effect of bergamot juice (BJ) against Helicobacter pylori in vitro. The potential therapeutic combination between BJ and the antibiotics amoxicillin (AMX), clarithromycin (CLA) and metronidazole (MTZ) has also been evaluated.

Methods

The minimum inhibitory concentration (MIC) of BJ, AMX, CLA and MTZ against 2 ATCC and 32 clinical isolates of H. pylori was assayed according to CLSI. The checkerboard method was used to determine the efficacy of the association BJ with the three reference antibiotics.

Killing curves were performed on the two cagA-positive ATCC strains of H. pylori (ATCC 43504 and ATCC 49503), on the clinical isolate cagA-positive HP6 strain of H. pylori and on the clinical isolate cagA-negative HP61 strain of H. pylori.

Results

BJ (2.5 %, v/v) inhibited the growth of 50 % of the H. pylori clinical isolates, whereas 5 % (v/v) inhibited 90 %. AMX was the most effective antibiotic against the reference strains and the clinical isolates, followed by CLA and MTZ. In the combination assays, synergism was observed between BJ and AMX and between BJ and MTZ against both the reference strains and the clinical isolates. Indifference was observed between BJ and CLA.

Conclusions

BJ was effective in vitro against H. pylori and the genotype status of the clinical strains may have an impact on its susceptibility. The synergistic combination of BJ and antibiotics could be used to prevent or treat resistance.

Resveratrol antibacterial activity against Escherichia coli is mediated by Z-ring formation inhibition via suppression of FtsZ expression

Resveratrol exhibits a potent antimicrobial activity. However, the mechanism underlying its antibacterial activity has not been shown. In this study, the antibacterial mechanism of resveratrol was investigated. To investigate induction of the SOS response, a strain containing the lacZ⁺gene under the control of an SOS-inducible sulA promoter was constructed. DNA damage was measured by pulse-field gel electrophoresis (PFGE). After resveratrol treatment, the cells were observed by confocal microscopy. For the RNA silencing assay, ftsZ-specific antisense peptide nucleic acid (PNA) was used. Reactive oxygen species (ROS) production increased in Escherichia coli after resveratrol treatment; however, cell growth was not recovered by ROS quenching, indicating that, in this experiment, ROS formation and cell death following resveratrol treatment were not directly correlated. Resveratrol treatment increased DNA fragmentation in cells, while SOS response-related gene expression levels increased in a dose-dependent manner. Cell elongation was observed after resveratrol treatment. Elongation was induced by inhibiting FtsZ, an essential cell-division protein in prokaryotes, and resulted in significant inhibition of Z-ring the formation in E. coli. The expression of ftsZ mRNA was suppressed by resveratrol. Our results indicate that resveratrol inhibits bacterial cell growth by suppressing FtsZ expression and Z-ring formation.

Nontraditional therapies to treat Helicobacter pylori infection

The Gram-negative pathogen Helicobacter pylori is increasingly more resistant to the three major antibiotics (metronidazole, clarithromycin and amoxicillin) that are most commonly used to treat infection. As a result, there is an increased rate of treatment failure; this translates into an overall higher cost of treatment due to the need for increased length of treatment and/or the requirement for combination or sequential therapy. Given the rise in antibiotic resistance, the complicated treatment regime, and issues related to patient compliance that stem from the duration and complexity of treatment, there is clearly a pressing need for the development of novel therapeutic strategies to combat H. pylori infection. As such, researchers are actively investigating the utility of antimicrobial peptides, small molecule inhibitors and naturopathic therapies. Herein we review and discuss each of these novel approaches as a means to target this important gastric pathogen.

Exploring alternative treatments for Helicobacter pylori infection

Helicobacter pylori (H. pylori) is a successful pathogen that can persist in the stomach of an infected person for their entire life. It provokes chronic gastric inflammation that leads to the development of serious gastric diseases such as peptic ulcers, gastric cancer and Mucosa associated lymphoid tissue lymphoma. It is known that these ailments can be avoided if the infection by the bacteria can be prevented or eradicated. Currently, numerous antibiotic-based therapies are available. However, these therapies have several inherent problems, including the appearance of resistance to the antibiotics used and associated adverse effects, the risk of re-infection and the high cost of antibiotic therapy. The delay in developing a vaccine to prevent or eradicate the infection has furthered research into new therapeutic approaches. This review summarises the most relevant recent studies on vaccine development and new treatments using natural resources such as plants, probiotics and nutraceuticals. In addition, novel alternatives based on microorganisms, peptides, polysaccharides, and intragastric violet light irradiation are presented. Alternative therapies have not been effective in eradicating the bacteria but have been shown to maintain low bacterial levels. Nevertheless, some of them are useful in preventing the adverse effects of antibiotics, modulating the immune response, gastroprotection, and the general promotion of health. Therefore, those agents can be used as adjuvants of allopathic anti-H. pylori eradication therapy.

Benefits of polyphenols on gut microbiota and implications in human health

The biological properties of dietary polyphenols are greatly dependent on their bioavailability that, in turn, is largely influenced by their degree of polymerization. The gut microbiota play 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. In addition, evidence is emerging on the activity of dietary polyphenols on the modulation of the colonic microbial population composition or activity. However, although the great range of health-promoting activities of dietary polyphenols has been widely investigated, their effect on the modulation of the gut ecology and the two-way relationship "polyphenols ↔ microbiota" are still poorly understood. Only a few studies have examined the impact of dietary polyphenols on the human gut microbiota, and most were focused on single polyphenol molecules and selected bacterial populations. This review focuses on the reciprocal interactions between the gut microbiota and polyphenols, the mechanisms of action and the consequences of these interactions on human health.

Antibacterial activities of almond skins on cagA-positive and-negative clinical isolates of Helicobacter pylori

BACKGROUND

Helicobacter pylori is known to be a gastric pathogen of humans. Eradication regimens for H. pylori infection have some side effects, compliance problems, relapses, and antibiotic resistance. Therefore, the need for alternative therapies for H. pylori infections is of special interest. We have previously shown that polyphenols from almond skins are active against a range of food-borne pathogens. The aim of this study was to evaluate the antibacterial effects of natural almond skins before and after simulated human digestion and the pure flavonoid compounds epicatechin, naringenin and protocatechuic acid against H. pylori.

RESULTS

H. pylori strains were isolated from gastric biopsy samples following standard microbiology procedures. Also, cagA and vacA genes were identified using PCR. Susceptibility studies on 34 strains of H. pylori, including two reference strains (ATCC 43504, ATCC 49503), were performed by the standard agar dilution method.

CONCLUSIONS

Polyphenols from almond skins were effective in vitro against H. pylori, irrespective of genotype status and could therefore be used in combination with antibiotics as a novel strategy for antibiotic resistance.

Activities of muscadine grape skin and polyphenolic constituents against Helicobacter pylori

AIMS

To identify active phenolic constituents in muscadine grape skin (MGS) extracts and determine interactions among compounds while further exploring their anti-Helicobacter pylori potential in vitro.

METHODS AND RESULTS

The inhibitory effects of quercetin and resveratrol, active polyphenols identified in MGS extracts, against H. pylori were investigated. Quercetin and resveratrol significantly (P < 0.05) reduced H. pylori counts regardless of pH with minimal bactericidal concentrations of 256 and 128 μg ml(-1), respectively. MGS extracts displayed the highest efficacy, suggesting additional unidentified compounds not determined in this study. Time-course viability experiments showed a dose-dependent anti-H. pylori response to quercetin and resveratrol. Interestingly, neither quercetin nor resveratrol affected H. pylori outer membrane (OM) integrity as determined by 1-N-phenylnaphthylamine (NPN) uptake assays. However, treatment with MGS extract did increase NPN uptake, indicating OM destabilization possibly by additional unknown components. Furthermore, quercetin was found to enter H. pylori as measured by HPLC supporting intracellular drug accumulation.

CONCLUSIONS

Quercetin and resveratrol possess strong anti-H. pylori activity in vitro and are independent of pH. Our results also suggest that these compounds do not affect H. pylori OM integrity as previously hypothesized and that the primary antimicrobial activity of quercetin may be linked to interactions with intracellular components.

SIGNIFICANCE AND IMPACT OF THE STUDY

The anti-H. pylori effects of quercetin and resveratrol suggest that these compounds may be useful in the dietary prevention and/or treatment of H. pylori infection.

Tannins, peptic ulcers and related mechanisms

This review of the current literature aims to study correlations between the chemical structure and gastric anti-ulcer activity of tannins. Tannins are used in medicine primarily because of their astringent properties. These properties are due to the fact that tannins react with the tissue proteins with which they come into contact. In gastric ulcers, this tannin-protein complex layer protects the stomach by promoting greater resistance to chemical and mechanical injury or irritation. Moreover, in several experimental models of gastric ulcer, tannins have been shown to present antioxidant activity, promote tissue repair, exhibit anti Helicobacter pylori effects, and they are involved in gastrointestinal tract anti-inflammatory processes. The presence of tannins explains the anti-ulcer effects of many natural products.

Recent advances in understanding the antibacterial properties of flavonoids

Antibiotic resistance is a major global problem and there is a pressing need to develop new therapeutic agents. Flavonoids are a family of plant-derived compounds with potentially exploitable activities, including direct antibacterial activity, synergism with antibiotics, and suppression of bacterial virulence. In this review, recent advances towards understanding these properties are described. Information is presented on the ten most potently antibacterial flavonoids as well as the five most synergistic flavonoid-antibiotic combinations tested in the last 6 years (identified from PubMed and ScienceDirect). Top of these respective lists are panduratin A, with minimum inhibitory concentrations (MICs) of 0.06-2.0 μg/mL against Staphylococcus aureus, and epicatechin gallate, which reduces oxacillin MICs as much as 512-fold. Research seeking to improve such activity and understand structure-activity relationships is discussed. Proposed mechanisms of action are also discussed. In addition to direct and synergistic activities, flavonoids inhibit a number of bacterial virulence factors, including quorum-sensing signal receptors, enzymes and toxins. Evidence of these molecular effects at the cellular level include in vitro inhibition of biofilm formation, inhibition of bacterial attachment to host ligands, and neutralisation of toxicity towards cultured human cells. In vivo evidence of disruption of bacterial pathogenesis includes demonstrated efficacy against Helicobacter pylori infection and S. aureus α-toxin intoxication.

Effect of resveratrol and quercetin in experimental infection by Salmonella enterica serovar Typhimurium

Flavonoids are phenolic compounds widely distributed in almost every plant and act as pharmacologically active constituents in many herbal medicines. They have multiple biological, pharmacological, and medicinal properties including anti-inflammatory and cytoprotective effects. In the present study, the experiments were performed to evaluate the effect of resveratrol and quercetin on proliferation, viability, nitric oxide (NO) production, and apoptosis in Salmonella enterica serovar Typhimurium-infected U937 cells and monocytes (MN). The results showed in a time- and dose-dependent manner that both resveratrol and quercetin reduced S. enterica serovar Typhimurium-induced NO production. In addition, the vegetable extracts resveratrol and quercetin inhibited cell viability and proliferation in S. enterica serovar Typhimurium-infected cells. S. enterica serovar Typhimurium-induced apoptosis was also blocked by resveratrol and quercetin. The results obtained indicate that flavonoids modulate the host response during salmonellosis by protecting the host cells from the toxic effects of bacterial infection and also by decreasing programmed cell death. Hence, these polyphenols can be considered potential candidates against S. enterica serovar Typhimurium-related gastric pathogenic processes, and further attention should be given to their application as a treatment for infectious diseases.

Activities of muscadine grape skin and quercetin against Helicobacter pylori infection in mice

AIMS

To explore the preventative potential of muscadine grape skin (MGS) and the single flavonoid, quercetin, as an alternative means for ameliorating Helicobacter pylori infection and/or the H. pylori-induced inflammatory response in mice.

METHODS AND RESULTS

The antimicrobial and anti-inflammatory properties of MGS and quercetin, a major phenolic constituent, were evaluated against H. pylori in vitro and in vivo. The antimicrobial activity of quercetin was evaluated against 11 H. pylori strains in vitro with inhibition of all strains at 128-64 μg ml(-1) . In vivo studies showed a moderate reduction in H. pylori counts following treatment with 5 and 10% MGS or quercetin (25 mg kg(-1) body weight) in addition to significantly reduced inflammatory cytokines (TNF-α, IL-1β and IFN-γ) when compared with untreated mice.

CONCLUSIONS

MGS and quercetin did not significantly reduce H. pylori growth in a mouse model. However, these products were effective in regulating the inflammatory response to H. pylori infection.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our results suggest that H. pylori infection may be reduced or prevented via the consumption of fruits rich in certain phenolic compounds (e.g. quercetin) such as muscadine grapes.

Phenolic compounds responsible for the superoxide dismutase-like activity in high-Brix apple vinegar

High-Brix apple vinegar (HBAV) with palatable drinking qualities has been developed using a greater amount of apple ingredients. In HBAV and in regular apple vinegar (RAV), constituents of 4 kinds of organic acids, 20 kinds of amino acids, 3 kinds of sugars, 4 kinds of minerals, and phenols were determined. These constituents, except for acetic acid, in HBAV are of higher abundance than in RAV. HBAV had a 7.1 times greater superoxide dismutase (SOD)-like activity compared with RAV. Those constituents, except for phenols, had very low SOD-like activity, and total phenol levels in HBAV were comparable to 181 mg of gallic acid equivalents/100 mL, which was 6.0 times more abundant than in RAV. Nine kinds of phenols including two kinds of hydroxycinnamates, two kinds of hydroxybenzoates, and five kinds of hydroxycinnamoyl quinates, originating from raw material were determined, but there were no ascorbic acid and flavonoids in HBAV. Chlorogenic acid, 4-p-coumaroylquinic acid, and caffeic acid were the three major phenols, and their content levels were 19.6, 13.5, and 0.76 mg in 100 mL of HBAV, respectively. Sum of contents of chlorogenic acid and the isomers was 24.0 mg/100 mL, and the percentage was 56.9% in the total identified phenols in HBAV. In RAV, only chlorogenic acid was determined as phenols, and the content was 3.1 mg/100 mL. SOD-like activities of the constituents of HBAV were obtained through high-accuracy assays using vinegar reconstitutions, and each contribution to the total SOD-like activity was found. As a result, 77.2% for all SOD-like activity of HBAV was reconstituted using the determined nine phenols and other constituents. Chlorogenic acids were the most effective, and the contribution to the total activity was 41.7%. The most abundant phenols, chlorogenic acids, were the most important contributors to the SOD-like activity. These SOD-active phenols originated from raw material and remained through the acetic acid fermentation processes. In the fermentation process of HBAV, the active constituents were well maintained, providing an advantage in the production of a phenol-rich product.

In vitro and in vivo effects of apple peel polyphenols against Helicobacter pylori

The inhibitory effects of a standarized apple peel polyphenol-rich extract (APPE) against Helicobacter pylori infection and vacuolating bacterial toxin (VacA) induced vacuolation were investigated. Apple peel polyphenols significantly prevented vacuolation in HeLa cells with an IC(50) value of 390 microg of gallic acid equivalents (GAE)/mL. APPE also displayed an in vitro antiadhesive effect against H. pylori. A significant inhibition was observed with a 20-60% reduction of H. pylori attachment at concentrations between 0.250 and 5 mg of GAE/mL. In a short-term infection model (C57BL6/J mice), two levels of APPE doses (150 and 300 mg/kg/day) showed an inhibitory effect on H. pylori attachment. Orally administered apple peel polyphenols also showed an anti-inflammatory effect on H. pylori-associated gastritis, lowering malondialdehyde levels and gastritis scores.