Molecular binding of black tea theaflavins to biological membranes: relationship to bioactivities

Molecular insights into the interactions of theaflavin and epicatechin with different lipid bilayer membranes by molecular dynamics simulation

At present, consumers increasingly favored the natural food preservatives with fewer side-effects on health. The green tea catechins and black tea theaflavins attracted considerable interest, and their antibacterial effects were extensively reported in the literature. Epicatechin (EC), a green tea catechin without a gallate moiety, showed no bactericidal activity, whereas the theaflavin (TF), also lacking a gallate moiety, exhibited potent bactericidal activity, and the antibacterial effects of green tea catechins and black tea theaflavins were closely correlated with their abilities to disrupt the bacterial cell membrane. In our present study, the mechanisms of membrane interaction modes and behaviors of TF and EC were explored by molecular dynamics simulations. It was demonstrated that TF exhibited markedly stronger affinity for the POPG bilayer compared to EC. Additionally, the hydrophobic interactions of tropolone/catechol rings with the acyl chain part could significantly contribute to the penetration of TF into the POPG bilayer. It was also found that the resorcinol/pyran rings were the key functional groups in TF for forming hydrogen bonds with the POPG bilayer. We believed that the findings from our current study could offer useful insights to better understand the stronger antibacterial effects of TF compared to EC.

Molecular Interactions Between Egg White Peptides and Giant Unilamellar Vesicle Membranes: Effect of Peptide Localization on Membrane Fluidity

Bioactive peptides have been shown to affect cell membrane fluidity, which is an important indicator of the cell membrane structure and function. However, the underlying mechanism of egg white-derived bioactive peptide regulation of cell membrane fluidity has not been elucidated yet. The cell membrane fluidity was investigated by giant unilamellar vesicles in the present study. The results showed that peptides TCNW, ADWAK, ESIINF, VPIEGII, LVEEY, and WKLC connect to membranes through intermolecular interactions, such as hydrogen bonding and regulated membrane fluidity, in a concentration-dependent way. In addition, peptides prefer to localize in the hydrophobic core of the bilayers. This study provides a theoretical basis for analyzing the localization of egg white bioactive peptides in specific cell membrane regions and their influence on the cell membrane fluidity.

Lowering glycemic levels via gastrointestinal tract factors: the roles of dietary fiber, polyphenols, and their combination

Dietary fiber (DF) and polyphenols (DP) are typical blood sugar-lowering components, and both play distinct yet interconnected roles in exerting their blood sugar-lowering effects. We comprehensively summarized the single and combined effects of DF and DP on blood glucose homeostasis through regulating the relevant factors in the upper gastrointestinal tract (UGT) and lower gastrointestinal tract (LGT). In the UGT, DF slowed down glucose metabolism by enhancing digesta viscosity and hindering enzyme-substrate interaction. DP primarily targeted enzymes and substrates. When combined, DP enhanced the adsorption capacity of DF for glucose. DF weakened DP's inhibitory effect on enzymes. Both DF and DP disrupted glucose intestinal uptake via physical or genomic modulation, but the co-consumption of DF and DP demonstrated a lower inhibitory effect on glucose uptake than DP alone. In the LGT, DF and DP showed synergistic or antagonistic effects on gut microbiota. Remarkably, whole foods exhibited potent prebiotic effects due to their compound-rich matrix, potentially enhancing glucose homeostasis and expanding dietary options for glucose regulation research.

Effects of Tea Polyphenols and Theaflavins on Three Oral Cariogenic Bacteria

In order to investigate the antibacterial mechanism of tea polyphenols and theaflavins against oral cariogenic bacteria, the pH value of the culture medium, the number of bacteria adhering to the smooth glass tube wall, and the electrical conductivity value within 10 h were measured, respectively. The effects of four concentrations of tea polyphenols and theaflavins below the MIC value were studied on acid production, adhesion, and electrical conductivity of oral cariogenic bacteria. The live/dead staining method was used to observe the effects of four concentrations of tea polyphenols and theaflavins below the MIC value on the biofilm formation of oral cariogenic bacteria under a laser scanning confocal microscope. With the increase in concentrations of tea polyphenols and theaflavins, the acid production and adhesion of the cariogenic bacteria gradually decreased, and the conductivity gradually increased. However, the conductivity increase was not significant (p < 0.05). Compared with the control group, the 1/2MIC and 1/4MIC tea polyphenols and theaflavins treatments significantly reduced the biomass of the cariogenic biofilm (p < 0.05). The confocal laser scanning microscope showed that the integrated optical density of green fluorescence of the cariogenic biofilm gradually decreased with the increase in agent concentration after the action of tea polyphenols and theaflavins.

Dietary supplementation of black rice bran to colon carcinogen-induced mice: Examining the development of colorectal cancer by improving environmental colon conditions

This research aims to identify the effects of the administration of a black rice bran diet on colorectal cancer in dextran sodium sulfate and azoxymethane-induced BALB/c mice. The research was conducted on three groups consisting of eight Balb/c mice: two groups were fed with carcinogens, and the third group, referred to as the normal group, was supplied with Isotonic NaCl 0.9% intraperitoneally. One group fed with carcinogens was supplied a standard AIN 1993 M diet modified with black rice bran as a substitute of fibre source, while the other two mice groups were fed the standard diet (AIN-93M) containing cellulose fibre. At the 17th week, all mice were euthanized; their colonic sections were taken for histopathological evaluation, and cecum for short-chain fatty acids concentration, total lactic acid bacteria, pH and β-glucuronidase activity evaluations. The results show an increase in the total lactic acid bacteria and short-chain fatty acids in the mice group fed with rice bran. Consequently, pH value and β-glucuronidase activity had decreased. Histopathological evaluation of mucosal tissue exhibited inhibition of the tumor growth rate in the mice groups fed rice bran compared to the group supplied with the standard diet. Furthermore, the proliferating cell nuclear antigen expression had decreased significantly, while expression of caspase-8 and caspase-3 had increased notably, in the group fed with a rice bran diet. These results suggest that black rice bran can effectively inhibit colon carcinogenesis. The potential of black rice bran as a source of fibre has not been studied in detail regarding the inhibition mechanism of colorectal cancer cells; further investigation in this field could provide valuable information about new strategies to prevent colorectal cancer. This strand of research is very important to developing preventive methods against cancer and promoting the concept of healthy products, including functional foods.

Anticariogenic Activity of Black Tea: An In Vivo Study

BACKGROUND

The prevention of dental caries has always remained a challenge. Caries prevention through dietary intervention holds promise. Studies have revealed that several constituents present in tea have anticariogenic properties. Tea is a widely consumed beverage and hence could be utilized as a suitable caries preventive agent. The purpose of this study was to determine the effect of black tea on caries progression in experimental animals.

MATERIALS AND METHODS

This study was carried out in 17-day-old albino rat pups. The animals were divided into three groups, with eight animals in each group. They were fed on a cariogenic diet (MIT 200) and inoculated with Streptococcus mutans. Group I was given MIT 200 with water, Group II was placed on MIT 200 with black tea, and Group III was placed on MIT 200 with fluoridated water for a period of 45 days. After 45 days, the animals were killed under ether anesthesia, and their teeth were examined for caries.

RESULTS

The carious lesions were scored for the first two molars in each quadrant. In each group, a total of 64 teeth were examined. The caries score between the upper and lower jaws was compared using ANOVA.

CONCLUSION

From this study, it may be inferred that drinking black tea reduced the development of dental caries in young rats fed on a cariogenic diet. The tea used for this study was prepared using fluoride-free water, so we can assume that besides fluoride, certain components are present in tea leaves that possess anticariogenic properties.

Polyphenol Mechanisms against Gastric Cancer and Their Interactions with Gut Microbiota: A Review

The lack of new drugs and resistance to existing drugs are serious problems in gastric cancer(GC) treatment. The research found polyphenols possess anti-Helicobacter pylori(Hp) and antitumor activities and may be used in the research and development of drugs for cancer prevention and treatment. However, polyphenols are affected by their chemical structures and physical properties, which leads to relatively low bioavailability and bioactivity in vivo. The intestinal flora can improve the absorption, utilization, and biological activity of polyphenols, whereas polyphenol compounds can increase the richness of the intestinal flora, reduce the activity of carcinogenic bacteria, stabilize the proportion of core flora, and maintain homeostasis of the intestinal microenvironment. Our review summarizes the gastrointestinal flora-mediated mechanisms of polyphenol against GC.

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.

Theaflavin and its derivatives exert antibacterial action against Bacillus coagulans through adsorption to cell surface phospholipids

AIMS

To investigate the antibacterial effects of tea theaflavins and catechins against Bacillus coagulans and the underlying mechanism of antibacterial action.

METHODS AND RESULTS

Bactericidal activities of theaflavin and its analogs were evaluated and compared with that of epigallocatechin gallate. Theaflavin derivatives exhibited high bactericidal activity at 50 μmol L^-1 , whereas epigallocatechin gallate did not, even at 500 μmol L^-1 . Further, we investigated the adsorption of theaflavins to model phospholipid membranes and corresponding effects on membrane fluidity to reveal their effects on the B. coagulans cell surface. Cell membrane fluidity was decreased after treatment with theaflavin derivatives with one or more galloyl moieties. Quartz-crystal microbalance analysis showed strong affinity of the membrane phosphatidyl glycerol (PG) bilayers for theaflavin derivatives, correlating their bactericidal activity.

CONCLUSION

These findings suggest that theaflavins could effectively inhibit B. coagulans by decreasing cell membrane fluidity.

SIGNIFICANCE AND IMPACT

B. coagulans is a spore-forming heat-resistant bacterium responsible for spoilage in low-acidic beverages. Natural antimicrobial components in tea-based beverages are central to reducing microbial contamination and product quality deterioration, although mechanisms underlying their antimicrobial action remain obscure. This study highlights the inhibitory action of theaflavins on B. coagulans and their potential application in food and beverage industries.

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.

Effects of theaflavin-gallate in-silico binding with different proteins of SARS-CoV-2 and host inflammation and vasoregulations referring an experimental rat-lung injury

Background SARS-CoV-2 claimed 5,209,104 lives, infected 260,997,910 individuals, globally. Infection is caused due to exposure or susceptibility; deaths occur due to age,comorbidity,higher-viral-load, immuno-suppression, inflammation, and multi-organ failure. Theaflavin-gallate, the major black tea component, showed previous evidence to inhibit HIV-1. Purpose As theaflavin-gallate prevents experimental rat-lung injury, the study of inhibitory effects of theaflavin-gallate was done, on SARS-CoV-2proteins and various host proteins related to some adverse effects in COVID-19 patients. Study Design Currently, some prospective phytochemical, black-tea (Camellia-sinensis) extract (BTE) was initially tested in vivo in strong oxidant-mutagen arsenic-induced model rat lung injury similar to that of COVID-19 manifestations like severe inflammation, oxidative stress, lung tissue degenerations, and apoptotic death. In silico, extensive bioinformatics and molecular docking experiments were performed on all catechin or theaflavin derivatives of C. sinensis, and finally theaflavin-3'-O-gallate (TFMG) were screened for blocking or inactivation of several proteins of SARS CoV-2 and host adversely-acting proteins or factors. Methods In vivo experiments in DNA stability (ladder, comet assay), free radicals attack (malondialdehyde; MDA, superoxide dismutase SOD, catalase gel-zymogram assay), extra cellular matrix damage (matrix metalloprotease; MMP2and9 zymogram assay) and inflammation (TNF-α, ELISA). In silico experiments- molecular docking by AutoDock-Patchdock analysis, Surface Topology Calculation by CASTp, Grid-value calculation, and Ramachandran Plot study. Results The BTE showed strong protection of lung DNA and cell-matrix by decreasing MMPs, TNF-α, and free radicals, the same factors affecting COVID-19 patients. In silico data suggest that TFMG significantly blocked the entry, exit, and amino acids at catalytic active-site of more than thirty proteins including viral (nsp1,nsp2,Mainpro,∼-9.0 kcal/mol) and host inflammatory, oxidants, apoptotic, vaso-destabilizer molecules (FAS, CD40R, BCL2, TLR2, ∼ -10 and ACE1or2 ∼ -9.0 and AT1or2∼ -7.5 kcal/mol and more). When the binding energy of TFMG ranged from -7 to -11.7 kcal/mol(average -9.0) the same for hydroxy‑Chloroquine ranged (-2.5 to -7 average -4.5) and dexamethasone (-3.0 to -6.0, average -4.0 kcal/mol). Conclusions TFMG has some novel physicochemical or structural properties like (ACE values of binding to all tested proteins, -300 to -625), (for TFMG H-bond acceptor or donor: 15/10, for TFDG 20/13). Their topological-polar-surface-area (264Ų and 351Ų) and travel depth/height; 17.0/9.6 Å and 15.4/11.3 Å, respectively) were more potent than other compounds. Conclusively, the efficacy of TFMG may be further verified.

Interactions of chlorogenic acid and isochlorogenic acid A with model lipid bilayer membranes: Insights from molecular dynamics simulations

Because of the negative side-effects of synthetic preservatives, the naturally-occurring polyphenols aroused intense interest of researchers. It has been suggested that chlorogenic acid (CA) and isochlorogenic acid A (iso-CAA) were good candidates to replace the synthetic preservatives. Moreover, the bactericidal activity of iso-CAA was stronger than CA, and the anti-bacterial activities of iso-CAA and CA were highly membrane-dependent. However, the mechanisms were still unclear. Therefore, in the present study, we investigated the mechanisms of the interactions between the two polyphenols and lipid bilayers through molecular dynamics simulations. The results revealed that iso-CAA could be inserted much deeper into POPG lipid bilayer than CA. We also found that hydrophobic interactions and hydrogen bonds both contributed to the insertion of iso-CAA into the POPG lipid bilayer, and the quinic acid moiety was the key structure in iso-CAA to form hydrogen bonds with POPG lipid bilayer. We believed that these findings would provide more useful information to explain the stronger bactericidal activity of iso-CAA than CA at the atomic level.

Theaflavin-3'-O-gallate a Black-tea Constituent Blocked SARS CoV-2 RNA dependant RNA Polymerase Active-site with Better Docking Results than Remdesivir

BACKGROUND

Replication of SARS-CoV-2 depends on viral RNA-dependent RNA-polymerase (RdRp). Remdesivir, the broad-spectrum RdRp inhibitor acts as nucleoside-analogues (NAs). Remdesivir has initially been repurposed as a promising drug against SARS-CoV-2 infection with some health hazards like liver damage, allergic reaction, low blood-pressure, and breathing-shortness, throat-swelling. In comparison, theaflavin-3'-O-gallate (TFMG), the abundant black tea component has gained importance in controlling viral infection. TFMG is a non-toxic, non-invasive, antioxidant, anticancer and antiviral molecule.

RESULTS

Here, we analyzed the inhibitory effect of theaflavin-3'-O-gallate on SARS CoV-2 RdRp in comparison with remdesivir by molecular-docking study. TFMG has been shown more potent in terms of lower Atomic-Contact-Energy (ACE) and higher occupancy of surface area; -393.97 Kcal/mol and 771.90 respectively, favoured with lower desolvation-energy; -9.2:  Kcal/mol. TFMG forms more rigid electrostatic and H-bond than remdesivir. TFMG showed strong affinity to RNA primer and template and RNA passage-site of RdRp.

CONCLUSIONS

TFMG can block the catalytic residue, NTP entry site, cation binding site, nsp7-nsp12 junction with binding energy of -6. 72 Kcal/mol with Ki value of 11.79, and interface domain with binding energy of -7.72 and -6.16 Kcal/mol with Ki value of 2.21 and 30.71 µM. And most importantly, TFMG shows antioxidant/anti-inflammatory/antiviral effect on human studies.

Galloyl Group in B-type Proanthocyanidin Dimers Was Responsible for Its Differential Inhibitory Activity on 3T3-L1 Preadipocytes due to the Strong Lipid Raft-Perturbing Potency

The effects of three B-type proanthocyanidin (PA) dimers covering procyanidin B2 (B-0g), procyanidin B2 3'-O-gallate (B-1g), and procyanidin B2 3,3'-di-O-gallate (B-2g) on 3T3-L1 preadipocyte differentiation and the underlying mechanisms were investigated. The results showed that digalloylated B-type PA dimers (B-2g) strongly inhibited 3T3-L1 preadipocyte differentiation through disrupting the integrity of the lipid raft structure and inhibiting the expression of peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT/enhancer-binding protein alpha (C/EBPα) and then downregulating the expression of acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) factors, followed by B-1g, while B-0g had little effect. The different inhibitory effects were mainly due to the difference in the B-type PA dimer structure and the ability to interfere with lipid rafts. The greater the galloylation degree of B-type PA dimers, the stronger the ability to disrupt the lipid raft structure and oppose 3T3-L1 preadipocyte differentiation. In addition, galloylated B-type PA dimers had greater molecular hydrophobicity and topological polarity surface area and could penetrate into the lipid rafts to form multiple hydrogen bonds with the rafts by molecular dynamics simulation. These findings highlighted that the strong lipid raft-perturbing potency of galloylated B-type PA dimers was responsible for inhibition of 3T3-L1 preadipocyte differentiation.

Influence of the gallate moiety on the interactions between green tea polyphenols and lipid membranes elucidated by molecular dynamics simulations

Previous studies suggested that naturally occurring EGCG primarily acted on the bacterial cell membrane then damaged the membrane and the gallate moiety in EGCG was very important to its anti-bacterial activity. However, the detailed mechanisms were still poorly understood. In this paper, EGCG and EGC were selected to study the great contribution of gallate moiety on the anti-bacterial activities of polyphenols. The results indicated that EGCG could penetrate deeper into the POPG lipid bilayer and possess more potent structure-perturbing potency on the POPG lipid bilayer than EGC. We also found that EGCG had the ability to form hydrogen bonds with the deeper inside oxygen atoms in the POPG lipid bilayer and the gallate moiety was the key functional group for EGCG forming hydrogen bonds with the POPG lipid bilayer. Moreover, results from the binding free energy analysis demonstrated that the gallate moiety made great contribution to the high affinity between EGCG and the POPG lipid bilayer. We believed that these findings could yield useful insights into the influence mechanisms of gallate moiety on the anti-bacterial activities of polyphenols.

Changes in major catechins, caffeine, and antioxidant activity during CTC processing of black tea from North East India

Tea (Camellia sinensis L.) leaves undergo complex chemical transformations during black tea processing. However, the dynamic chemical changes during tea processing have not been explored in popular cultivars of North East India. In this study, changes in catechins, caffeine, total polyphenol (TP) and formation of theaflavins were examined throughout the different stages of CTC (curl, tear and crush) black tea processing based on UPLC metabolomic analysis along with antioxidant activity for eight cultivars viz. S.3A/3, TV1, TV7, TV9, TV17, TV22, TV23 and TV25. The results demonstrated that the most prolific changes were observed after complete maceration of tea leaves. The total catechin, (-)-epigallocatechin gallate and (-)-epicatechin gallate levels decreased by 96, 97 and 89%, respectively as the processing progressed from fresh leaves to black tea. The TP level decreased by 26 to 37% throughout the processing path. The caffeine content increased by 18% during processing. The total theaflavin reached the highest level at 20 min of fermentation and then decreased by 13 to 36% at 40 min. Cultivar TV23 and S.3A/3 had a high content of total theaflavin with 17.9 and 16.9 mg g-1, respectively. The antioxidant activity was observed to be decreased by 31% for the black tea as compared to fresh leaves. It is also observed that the total phenolic content exerted a greater effect on antioxidant activity rather than catechins and theaflavins. This study provides an insightful observation of black tea processing which will immensely help in improving the quality of processed tea.

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.

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.

Anti-trichomonad activities of different compounds from foods, marine products, and medicinal plants: a review

Human trichomoniasis, caused by the pathogenic parasitic protozoan Trichomonas vaginalis, is the most common non-viral sexually transmitted disease that contributes to reproductive morbidity in affected women and possibly to prostate cancer in men. Tritrichomonas foetus strains cause the disease trichomoniasis in farm animals (cattle, bulls, pigs) and diarrhea in domestic animals (cats and dogs). Because some T. vaginalis strains have become resistant to the widely used drug metronidazole, there is a need to develop alternative treatments, based on safe natural products that have the potential to replace and/or enhance the activity of lower doses of metronidazole. To help meet this need, this overview collates and interprets worldwide reported studies on the efficacy of structurally different classes of food, marine, and medicinal plant extracts and some of their bioactive pure compounds against T. vaginalis and T. foetus in vitro and in infected mice and women. Active food extracts include potato peels and their glycoalkaloids α-chaconine and α-solanine, caffeic and chlorogenic acids, and quercetin; the tomato glycoalkaloid α-tomatine; theaflavin-rich black tea extracts and bioactive theaflavins; plant essential oils and their compounds (+)-α-bisabolol and eugenol; the grape skin compound resveratrol; the kidney bean lectin, marine extracts from algae, seaweeds, and fungi and compounds that are derived from fungi; medicinal extracts and about 30 isolated pure compounds. Also covered are the inactivation of drug-resistant T. vaginalis and T. foetus strains by sensitized light; anti-trichomonad effects in mice and women; beneficial effects of probiotics in women; and mechanisms that govern cell death. The summarized findings will hopefully stimulate additional research, including molecular-mechanism-guided inactivations and human clinical studies, that will help ameliorate adverse effects of pathogenic protozoa.

Maysin plays a protective role against α-Synuclein oligomers cytotoxicity by triggering autophagy activation

Parkinson's disease (PD) is a widespread neurodegenerative disorder characterized by the progressive loss of neurons. The accumulation of aggregated forms of the α-Synuclein (Syn) protein is the main cause of neurotoxicity in PD by disrupting cellular homeostasis until neuronal death. Scientific research is constantly looking for natural products as preventive agents against the progression of several neurodisorders due their safety and non-toxic nature. Neuroprotective phytochemicals include Maysin (Mys), the most abundant C-glycosilflavone in corn silk. In this work, the Mys protective role against damage by Syn amyloid aggregates - oligomers and fibrils - was investigated in SH-SY5Y human neuroblastoma cells obtaining novel and interesting information concerning the Mys molecular mechanism of action. Mys showed effectiveness in preventing the typical toxic events induced by Syn amyloid aggregates, i.e. oxidative stress and imbalance of intracellular calcium homeostasis. Mys exhibited a cytoprotective role, especially against Syn oligomers injury, activating an autophagic degradative process, thus playing a key role on several features of amyloid neurotoxicity. Therefore, Mys could be proposed for the first time to the scientific community as an interesting novel natural compound that might allow to develop alternative strategies to prevent the damage of Syn oligomers involved in Parkinson's disease.

Nguyen D, A. Phan T, M. Hamada S, Panchel R, C. Tam C, H. Kim J, W. Cheng L, M. Land K. The Inhibitory Activity of Anthraquinones against Pathogenic Protozoa, Bacteria, and Fungi and the Relationship to Structure

Plant-derived anthraquinones were evaluated in cell assays for their inhibitory activities against the parasitic protozoa Trichomonas vaginalis human strain G3 that causes the sexually transmitted disease trichomoniasis in women, Tritrichomonas foetus bovine strain D1 that causes sexually transmitted diseases in farm animals (bulls, cows, and pigs), Tritrichomonas foetus-like strain C1 that causes diarrhea in domestic animals (cats and dogs), and bacteria and fungi. The anthraquinones assessed for their inhibitory activity were anthraquinone, aloe-emodin (1,8-dihydroxy-3-hydroxymethylanthraquinone), anthrarufin (1,5-dihydroxyanthraquinone), chrysazin (1,8-dihydroxyanthraquinone), emodin (1,3,8-trihydroxy-6-methylanthraquinone), purpurin (1,2,4-trihydroxyanthraquinone), and rhein (1,8-dihydroxy-3-carboxyanthraquinone). Their activities were determined in terms of IC₅₀ values, defined as the concentration that inhibits 50% of the cells under the test conditions and calculated from linear dose response plots for the parasitic protozoa, and zone of inhibition for bacteria and fungi, respectively. The results show that the different substituents on the anthraquinone ring seem to influence the relative potency. Analysis of the structure–activity relationships in protozoa indicates that the aloe-emodin and chrysazin with the highest biological activities merit further study for their potential to help treat the diseases in women and domestic and farm animals. Emodin also exhibited antifungal activity against Candida albicans. The suggested mechanism of action and the additional reported beneficial biological properties of anthraquinones suggest that they have the potential to ameliorate a broad spectrum of human diseases.

Difference in the antibacterial action of epigallocatechin gallate and theaflavin 3,3'-di-O-gallate on Bacillus coagulans

AIMS

To study the mechanism of the antibacterial action of tea polyphenols such as catechins and theaflavins against Bacillus coagulans, and the interaction of epigallocatechin gallate (EGCg) or theaflavin 3,3'-di-O-gallate (TFDG) with the surface of B. coagulans cells was investigated.

METHODS AND RESULTS

The antibacterial activities of EGCg and TFDG against B. coagulans cells were measured by counting of the viable cells after the mixing with each polyphenol. Bactericidal effect of TFDG was shown at the concentration of greater than or equal to 62·5 mg l^-1 ; however, at the same concentration, EGCg did not. According to the results of two dimensional (2D)-electrophoresis analysis, TFDG seemed to interact with cytoplasmic membrane proteins. The activity of the glucose transporters of the cells decreased 40% following the treatment with TFDG of 62·5 mg l^-1 ; however, this decrease was only slight in case of EGCg. This result was in accordance with the strength of their bactericidal activities.

CONCLUSION

Our results suggest that the direct interaction between membrane proteins and TFDG is an important factor in the antibacterial activity of polymerized catechins, affecting their functions and leading to cell death.

SIGNIFICANCE AND IMPACT OF THE STUDY

Tea polyphenols can effectively use the prevention of product spoilage in the food and beverage industry.

The Effects of Oxidation on the Antithrombotic Properties of Tea Lipids Against PAF, Thrombin, Collagen, and ADP

Tea provides health benefits, while oxidation is part of tea processing. The effect of oxidation on the antithrombotic properties of tea lipid extracts was evaluated for the first time. Total lipids (TL) extracted from fresh tea leaves and commercial tea powder, before and after 30–60 min of oxidation, were further fractionated into neutral lipids (NL) and polar lipids (PL). The antithrombotic bioactivities of tea TL, PL, and NL were assessed in human platelets against the inflammatory mediator platelet-activating factor. PL were further assessed against thrombin, collagen, and adenosine diphosphate, while their fatty acid composition was evaluated by GC-MS. PL exhibited the strongest antithrombotic effects against all platelet agonists and were rich in omega-3 polyunsaturated (ω3 PUFA) and monounsaturated (MUFA) fatty acids. A decline was observed in the antithrombotic activities, against all platelet agonists tested, for PL after 60 min of oxidation, and on their MUFA content, while their overall ω3 PUFA content and ω6/ω3 ratio remained unaffected. A synergistic effect between tea phenolic compounds and PL protects them against oxidation, which seems to be the rational for retaining the antithrombotic biofunctionalities of PL at a considerable favorable cardioprotective level, even after 60 min of tea oxidation. More studies are required to elucidate the mechanisms of the favorable synergism in tea PL extracts.

Omics Analyses of Gut Microbiota in a Circadian Rhythm Disorder Mouse Model Fed with Oolong Tea Polyphenols

Microbiome has been revealed as a key element involved in maintaining the circadian rhythms. Oolong tea polyphenols (OTP) has been shown to have potential prebiotic activity. Therefore, this study focused on the regulation mechanisms of OTP on host circadian rhythms. After 8 weeks of OTP administration, a large expansion in the relative abundance of Bacteroidetes with a decrease in Firmicutes was observed, which reflected the positive modulatory effect of OTP on gut flora. In addition, Kyoto Encyclopedia of Genes and Genomes pathways of ATP-binding cassette transporters, two-component system, and the biosynthesis of amino acids enriched the most differentially expressed genes after OTP treatment. Of the differentially expressed proteins identified, most were related to metabolism, genetic information processing, and environmental information processing. It underscores the ability of OTP to regulate circadian rhythm by enhancing beneficial intestinal microbiota and affecting metabolic pathways, contributing to the improvement of host microecology.

Systematic characterisation of the structure and radical scavenging potency of Pu'Er tea () polyphenol theaflavin

Resolving the functional 3D structural poses of Pu'Er tea antioxidant theaflavin.

Saliva and Flavor Perception: Perspectives

This paper reports the main trends and perspectives related to the current understanding of the relationships between saliva and flavor perception. Saliva is a key factor in flavor perception and controls the transport of flavor molecules to their receptors, their adsorption onto the mouth surfaces (i.e., oral mucosa), their metabolism by enzymatic modification, and the friction force in the oral cavity. The proteins in free saliva or in the mucosal pellicle contribute to flavor perception by interacting with or metabolizing flavor compounds. Most of these reactions were observed when using fresh whole saliva; however, they were absent or less frequently observed when using artificial saliva or depleted/frozen whole saliva. There is a need to better understand the role of protein aggregates in flavor perception. Within humans, there is great interindividual variation in salivary composition, which has been related to differences in flavor perception. However, the relative role of salivary proteins and the microbiota should be deeply investigated together with the impact of their composition on individual perception during life. Finally, future results must also consider cross-modal interactions at the brain level.

Molecular interactions of active constituents of essential oils in zwitterionic lipid bilayers

Eugenol and its related compounds are major active constituents of essential oils and have been extensively used as food flavoring agents with significant lipid peroxidation inhibition activity, highlighting the importance of understanding detailed molecular mechanisms behind their interactions with lipid bilayer. For this, we studied antioxidant activity of essential oils rich extract of Cinnamomum tamala leaves and molecular dynamics simulations of eugenol, isoeugenol, methyleugenol, acetyleugenol and eugenol oxide in POPC and PLPC lipid bilayers. All the compounds penetrated into bilayer however, isoeugenol showed highest affinity for the pure POPC and PLPC bilayers with lowest free energy profiles, formed more H-bonds with bilayer oxygen atoms and more pronounced changes in area per lipid and thickness of the bilayer, thus more efficient for scavenging radicals coming from outside as well as centrally located lipid peroxyl radicals. These molecular interactions rationalize the difference in inhibition activities of lipid peroxidation by eugenol and its related compounds.

Mechanisms of astringency: Structural alteration of the oral mucosal pellicle by dietary tannins and protective effect of bPRPs

The interaction of tannins with salivary proteins is involved in astringency. This paper focussed on saliva lining oral mucosae, the mucosal pellicle. Using a cell-based model, the impact of two dietary tannins (EgC and EgCG) on the mucosal pellicle structure and properties was investigated by microscopic techniques. The role of basic Proline-Rich-Proteins (bPRPs) in protecting the mucosal pellicle was also evaluated. At low (0.05 mM) tannin concentration, below the sensory detection threshold, the distribution of salivary mucins MUC5B on cells remained unaffected. At 0.5 and 1 mM, MUC5B-tannin aggregates were observed and their size increased with tannin concentration and with galloylation. In addition, 3 mM EgCG resulted in higher friction forces measured by AFM. In presence of bPRPs, the size distribution of aggregates was greatly modified and tended to resemble that of the "no tannin" condition, highlighting that bPRPs have a protective effect against the structural alteration induced by dietary tannins.

Mechanism of Antibacterial Activities of a Rice Hull Smoke Extract (RHSE) Against Multidrug-Resistant Salmonella Typhimurium In Vitro and in Mice

The present study tested antibacterial activity of a rice hull smoke extract (RHSE) against a multidrug-resistant strain of Salmonella Typhimurium and examined its mode of suppressive action in vitro and in mice. In vitro studies showed that the minimum inhibitory concentration (MIC) value of RHSE was 1.29% (v/v). The inactivation was confirmed by complete loss of cell viability in the range of 10⁴ to 10⁷ colony forming units of the resistant Salmonella Typhimurium strain. Agarose and sodium dodecyl sulfate-polyacrylamide gel electrophoreses were used to evaluate the integrities of bacterial genomic DNA and total cellular protein profiles. The antibacterial action of RHSE results from a leakage of intracellular macromolecules following rupture of bacterial cells. Scanning electron microscopy of the cells shows that RHSE also induced deleterious morphological changes in the bacterial cell membrane of the pathogens. In vivo antibacterial activity of RHSE at a 1 × MIC concentration was examined in a bacterial gastroenteritis model using Balb/c mice orally infected with the Salmonella Typhimurium. The results show greatly decreased excretion of the bacteria into the feces and suppressed translocation of the bacteria to internal organs (cecum, mesenteric lymph node, spleen, and liver) compared with the infected mice not subjected to the RHSE treatment. Collectively, the present findings indicate that the mechanism of the antibacterial activities both in vitro and in the gastroenteritis environment of the animal model is the result of the direct disruption of cell structure, leading to cell death. RHSE has the potential to serve as a multifunctional food additive that might protect consumers against infections by antibiotic-resistant microorganisms.

PRACTICAL APPLICATION

The rice hull derived liquid smoke has the potential to complement widely used wood-derived smoke as an antimicrobial flavor and health-promoting formulation for application in foods and feeds.

Phytochemical-rich foods inhibit the growth of pathogenic trichomonads

Background

Plants produce secondary metabolites that often possess widespread bioactivity, and are then known as phytochemicals. We previously determined that several phytochemical-rich food-derived preparations were active against pathogenic foodborne bacteria. Trichomonads produce disease (trichomoniasis) in humans and in certain animals. Trichomonads are increasingly becoming resistant to conventional modes of treatment. It is of interest to test bioactive, natural compounds for efficacy against these pathogens.

Methods

Using a cell assay, black tea, green tea, grape, pomegranate, and jujube extracts, as well as whole dried jujube were tested against three trichomonads: Trichomonas vaginalis strain G3 (found in humans), Tritrichomonas foetus strain D1 (found in cattle), and Tritrichomonas foetus-like organism strain C1 (found in cats). The most effective of the test substances was subsequently tested against two metronidazole-resistant Trichomonas vaginalis strains, and on normal mucosal flora.

Results

Black tea extract inhibited all the tested trichomonads, but was most effective against the T. vaginalis organisms. Inhibition by black tea was correlated with the total and individual theaflavin content of the two tea extracts determined by HPLC. Metronidazole-resistant Trichomonas vaginalis strains were also inhibited by the black tea extract. The response of the organisms to the remaining preparations was variable and unique. We observed no effect of the black tea extract on common normal flora bacteria.

Conclusions

The results suggest that the black tea, and to a lesser degree green tea, grape seed, and pomegranate extracts might present possible natural alternative therapeutic agents to treat Trichomonas vaginalis infections in humans and the related trichomonad infections in animals, without negatively affecting the normal flora.

Mechanisms of Antimicrobial Action of Cinnamon and Oregano Oils, Cinnamaldehyde, Carvacrol, 2,5-Dihydroxybenzaldehyde, and 2-Hydroxy-5-Methoxybenzaldehyde against Mycobacterium avium subsp. paratuberculosis (Map)

The antimicrobial modes of action of six naturally occurring compounds, cinnamon oil, cinnamaldehyde, oregano oil, carvacrol, 2,5-dihydroxybenzaldehyde, and 2-hydroxy-5-methoxybenzaldehyde, previously found to inhibit the growth of Mycobacterium avium subsp. paratuberculosis (Map) reported to infect food animals and humans and to be present in milk, cheese, and meat, were investigated. The incubation of Map cultures in the presence of all six compounds caused phosphate ions to leak into the extracellular environment in a time- and concentration-dependent manner. Cinnamon oil and cinnamaldehyde decreased the intracellular adenosine triphosphate (ATP) concentration of Map cells, whereas oregano oil and carvacrol caused an initial decrease of intracellular ATP concentration that was restored gradually after incubation at 37 °C for 2 h. Neither 2,5-dihydroxybenzaldehyde nor 2-hydroxy-5-methoxybenzaldehyde had a significant effect on intracellular ATP concentration. None of the compounds tested were found to cause leakage of ATP to the extracellular environment. Monolayer studies involving a Langmuir trough apparatus revealed that all anti-Map compounds, especially the essential oil compounds, altered the molecular packing characteristics of phospholipid molecules of model membranes, causing fluidization. The results of the physicochemical model microbial membrane studies suggest that the destruction of the pathogenic bacteria might be associated with the disruption of the bacterial cell membrane.

Theaflavins from black tea affect growth, development, and motility in Dictyostelium discoideum

Theaflavins, flavonoids found in black tea, exhibit a variety of health-promoting activities, but the mechanisms by which they act are not clear. Here, we assess the effects of black tea extract and isolated theaflavins on Dictyostelium discoideum, a model organism exhibiting an unusual life cycle relying on conserved pathways involved in human disease. Dictyostelium has been used to characterize the activities of numerous bioactive small molecules, including catechins, from which theaflavins are produced during the preparation of black tea. We show that theaflavins block growth, development, and motility in Dictyostelium, results that suggest catechins and theaflavins exert similar activities in this organism.

A-type ECG and EGCG dimers inhibit 3T3-L1 differentiation by binding to cholesterol in lipid rafts

The present study aimed to explore the underlying mechanisms of epicatechin-3-gallate-(4β→8, 2β→O→7)-epicatechin-3-gallate (A-type ECG dimer) and epigallocatechin-3-gallate-(4β→8, 2β→O→7)-epigallocatechin-3-gallate (A-type EGCG dimer) involved in their strong inhibitory effects on 3T3-L1 preadipocytes differentiation. In the synthetic "lipid raft-like" liposome, A-type ECG and EGCG dimers incorporated into the liposome with high affinity and decreased the fluidity of the liposome. In 3T3-L1 preadipocytes, A-type ECG and EGCG dimers possibly bonded to lipid rafts cholesterol and disrupted the integrity of lipid rafts, thus exerting their notable inhibitory effects on 3T3-L1 preadipocytes differentiation by suppressing mitotic clonal expansion process and mRNA levels of PPARγ, C/EBPα and SREBP1C. A highly positive correlation between the cholesterol binding capacity of the two dimers and their inhibitory effect on 3T3-L1 preadipocytes differentiation (R²=0.9328) was observed. Molecular dynamics simulation further verified that A-type ECG and EGCG dimers could bond to cholesterol via hydrogen bonding. The results of this study suggested that the disruption of A-type ECG and EGCG dimers on membrane lipid rafts by targeting cholesterol in the lipid rafts was involved in the underlying mechanisms of their strong inhibitory effects on 3T3-L1 preadipocytes differentiation. This broadens the understanding of the molecular mechanisms of polyphenols on modulating and controlling of metabolic dysregulation, particularly adipocyte differentiation, which is a significant risk factor associated with the development of cardiovascular disease.

Polyphenols protect mitochondrial membrane against permeabilization induced by HEWL oligomers: Possible mechanism of action

Increasing body of evidence suggests that polyphenols frequently interacting with amyloid aggregates and/or interfering with aggregate species to bind biomembranes may serve as a therapeutic approach for the treatment of amyloid-related diseases. Hence, in the present study, the possible effects of three naturally occurring polyphenols including Curcumin, Quercetin, and Resveratrol on mitochondrial membrane permeabilization induced by Hen Egg White Lysozyme (HEWL) oligomers were investigated. Our results indicated that pre-incubation of mitochondrial homogenate with polyphenols considerably inhibit membrane permeabilization in a concentration dependent manner. In parallel, HEWL oligomers, which were co-incubated with the polyphenols, showed less effectiveness on membrane permeabilization, suggesting that toxicity of oligomers was hindered. Using a range of techniques including fluorescence quenching, Nile red binding assay, zeta potential and size measurements, CD (far- and near-UV) spectroscopy, and molecular docking, we found that the polyphenols, structure-dependently, interact with and induce conformational changes in HEWL oligomers, thereby inhibit their toxicity. We proposed a mechanism by which selected polyphenols induce their protective effects through binding to mitochondria and interfering with HEWL oligomer-membrane interactions and/or by direct interaction with HEWL oligomers, induction of conformational changes, and generating far less toxic species. However, additional studies are needed to elucidate the detailed mechanisms involved.

Diet, microorganisms and their metabolites, and colon cancer

Colorectal cancer is one of the so-called westernized diseases and the second leading cause of cancer death worldwide. On the basis of global epidemiological and scientific studies, evidence suggests that the risk of colorectal cancer is increased by processed and unprocessed meat consumption but suppressed by fibre, and that food composition affects colonic health and cancer risk via its effects on colonic microbial metabolism. The gut microbiota can ferment complex dietary residues that are resistant to digestion by enteric enzymes. This process provides energy for the microbiota but culminates in the release of short-chain fatty acids including butyrate, which are utilized for the metabolic needs of the colon and the body. Butyrate has a remarkable array of colonic health-promoting and antineoplastic properties: it is the preferred energy source for colonocytes, it maintains mucosal integrity and it suppresses inflammation and carcinogenesis through effects on immunity, gene expression and epigenetic modulation. Protein residues and fat-stimulated bile acids are also metabolized by the microbiota to inflammatory and/or carcinogenic metabolites, which increase the risk of neoplastic progression. This Review will discuss the mechanisms behind these microbial metabolite effects, which could be modified by diet to achieve the objective of preventing colorectal cancer in Western societies.

Molecular Insight into Affinities of Gallated and Nongallated Proanthocyanidins Dimers to Lipid Bilayers

Experimental studies have proved the beneficial effects of proanthocyanidins (Pas) relating to interaction with the cell membrane. But the detailed mechanisms and structure-function relationship was unclear. In present study, molecular dynamics (MD) simulations were used to study the interactions of four PA dimers with a lipid bilayer composed of 1:1 mixed 1-palmitoyl-2-oleoyl phosphatidylcholine (POPC) and 1-palmitoyl-2-oleoyl phosphatidylethanolamine (POPE). The results showed that the gallated PA dimers had much higher affinities to the bilayer with lower binding free energies compared with nongallated PA dimers. The gallated PA dimers penetrated deeper into the bilayer and formed more hydrogen bonds (H-bonds) with bilayer oxygen atoms, especially the deeper oxygen atoms of the lipids simultaneously, thus inducing stronger lateral expansion of the membrane and lipid tails disorder. The present results provided molecular insights into the interactions between PA dimers and bio-membranes and agreed with our experimental results well. These molecular interactions helped to elucidate the structure-function relationship of the PA dimers and provided a foundation for a better understanding of the underlying mechanisms of the bioactivities of PA oligomers.

Structure-Dependent Membrane-Perturbing Potency of Four Proanthocyanidin Dimers on 3T3-L1 Preadipocytes

Proanthocyanidins (PAs) have been widely recognized for their broad spectrum of beneficial health effects, which are highly structure-dependent. It was found that PA dimers epicatechin-3-gallate-(4β→8,2β→O→7)-epicatechin-3-gallate (A-type ECG dimer) and epigallocatechin-3-gallate-(4β→,2β→O→7)-epigallocatechin-3-gallate (A-type EGCG dimer) inhibit the differentiation of 3T3-L1 cells significantly, whereas epicatechin-(4β→8,2β→O→7)-epicatechin (A-type EC dimer) and epicatechin-(4β→8)-epicatechin (B-type EC dimer) showed little effect in previous work. However, the underlying mechanisms are unclear. To test whether bilayer perturbation may underlie this diversity of actions, we examined the bilayer-modifying effects of the four dimers in both 3T3-L1 cell and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine liposome models by using scanning electron microscopy, fluorescent spectroscopy, differential scanning calorimetry, and molecular dynamics methods. Our results revealed that A-type ECG and EGCG dimers had a high affinity for the lipid bilayer and could form simultaneous hydrogen bonds (H-bond) with both the surface oxygen acceptors and the deeper inside lipid oxygen atoms. However, A-type and B-type EC dimers contacted only the surface oxygen atoms with limited and significantly fewer H-bonds. A-type ECG and EGCG dimers notably distorted the membrane morphology of 3T3-L1 cells. In the present study, we found there was a high positive correlation between the membrane-disturbing abilities of the four dimers and their 3T3-L1 cell differentiation inhibitory effects as previously reported. This indicated that the strong 3T3-L1 cell differentiation inhibitory effect of A-type ECG and EGCG dimers might be due to their strong bilayer-perturbing potency.

Black Tea Extract and Its Theaflavin Derivatives Inhibit the Growth of Periodontopathogens and Modulate Interleukin-8 and β-Defensin Secretion in Oral Epithelial Cells

Over the years, several studies have brought evidence suggesting that tea polyphenols, mostly from green tea, may have oral health benefits. Since few data are available concerning the beneficial properties of black tea and its theaflavin derivatives against periodontal disease, the objective of this study was to investigate their antibacterial activity as well as their ability to modulate interleukin-8 and human β-defensin (hBD) secretion in oral epithelial cells. Among the periodontopathogenic bacteria tested, Porphyromonas gingivalis was found to be highly susceptible to the black tea extract and theaflavins. Moreover, our data indicated that the black tea extract, theaflavin and theaflavin-3,3’-digallate can potentiate the antibacterial effect of metronidazole and tetracycline against P. gingivalis. Using lipopolysaccharide-stimulated oral epithelial cells, the black tea extract (100 μg/ml), as well as theaflavin and theaflavin-3,3’-digallate (50 μg/ml) reduced interleukin-8 (IL-8) secretion by 85%, 79%, and 86%, respectively, thus suggesting an anti-inflammatory property. The ability of the black tea extract and its theaflavin derivatives to induce the secretion of the antimicrobial peptides hBD-1, hBD-2 and hBD-4 by oral epithelial cells was then evaluated. Our results showed that the black tea extract as well as theaflavin-3,3’-digallate were able to increase the secretion of the three hBDs. In conclusion, the ability of a black tea extract and theaflavins to exert antibacterial activity against major periodontopathogens, to attenuate the secretion of IL-8, and to induce hBD secretion in oral epithelial cells suggest that these components may have a beneficial effect against periodontal disease.

Antibiotic-resistant bacteria: prevalence in food and inactivation by food-compatible compounds and plant extracts

Foodborne antibiotic-resistant pathogenic bacteria such as Campylobacter jejuni, Bacillus cereus, Clostridium perfringens, Escherichia coli, Salmonella enterica, Staphylococcus aureus, Vibrio cholerae, and Vibrio parahemolyticus can adversely affect animal and human health, but a better understanding of the factors involved in their pathogenesis is needed. To help meet this need, this overview surveys and interprets much of our current knowledge of antibiotic (multidrug)-resistant bacteria in the food chain and the implications for microbial food safety and animal and human health. Topics covered include the origin and prevalence of resistant bacteria in the food chain (dairy, meat, poultry, seafood, and herbal products, produce, and eggs), their inactivation by different classes of compounds and plant extracts and by the use of chlorine and physicochemical methods (heat, UV light, pulsed electric fields, and high pressure), the synergistic antimicrobial effects of combinations of natural antimicrobials with medicinal antibiotics, and mechanisms of antimicrobial activities and resistant effects. Possible areas for future research are suggested. Plant-derived and other safe natural antimicrobial compounds have the potential to control the prevalence of both susceptible and resistant pathogens in various environments. The collated information and suggested research will hopefully contribute to a better understanding of approaches that could be used to minimize the presence of resistant pathogens in animal feed and human food, thus reducing adverse effects, improving microbial food safety, and helping to prevent or treat animal and human infections.

Green tea extract and its major constituent epigallocatechin-3-gallate inhibit growth and halitosis-related properties of Solobacterium moorei

Background

Solobacterium moorei is a volatile sulfide compound (VSC)-producing Gram-positive anaerobic bacterium that has been associated with halitosis. The aim of this study was to investigate the effects of green tea extract and its major constituent epigallocatechin-3-gallate (EGCG) on growth and several halitosis-related properties of S. moorei.

Methods

A microplate dilution assay was used to determine the antibacterial activity of green tea extract and EGCG against S. moorei. Their effects on bacterial cell membrane integrity were investigated by transmission electron microscopy and a fluorescence-based permeability assay. Biofilm formation was quantified by crystal violet staining. Adhesion of FITC-labeled S. moorei to oral epithelial cells was monitored by fluorometry. The modulation of β-galactosidase gene expression in S. moorei was evaluated by quantitative RT-PCR.

Results

The green tea extract as well as EGCG inhibited the growth of S. moorei, with MIC values of 500 and 250 μg/ml, respectively. Transmission electron microscopy analysis and a permeabilization assay brought evidence that the bacterial cell membrane was the target of green tea polyphenols. Regarding the effects of green tea polyphenols on the S. moorei colonization properties, it was found that biofilm formation on EGCG-treated surfaces was significantly affected, and that green tea extract and EGCG can cause the eradication of pre-formed S. moorei biofilms. Moreover, both the green tea extract and EGCG were found to reduce the adherence of S. moorei to oral epithelial cells. The β-galactosidase activity of S. moorei, which plays a key role in VSC production, was dose-dependently inhibited by green tea polyphenols. In addition, EGCG at ½ MIC significantly decreased the β-galactosidase gene expression.

Conclusion

Our study brought evidence to support that green tea polyphenols possess a number of properties that may contribute to reduce S. moorei-related halitosis. Therefore, these natural compounds may be of interest to be used to supplement oral healthcare products.

Theaflavins inhibit pathogenic properties of P. gingivalis and MMPs production in P. gingivalis-stimulated human gingival fibroblasts

OBJECTIVES

Theaflavins, the main polyphenols in black tea, possesses a wide range of beneficial pharmacological properties. Porphyromonas gingivalis (P. gingivalis) is a major aetiological agent associated with periodontitis, a chronic inflammatory disease affecting tooth-supporting tissues. The aim of the present study is to investigate the effect of theaflavins on pathogenic properties of P. gingivalis and on periodontitis by inhibiting matrix metalloproteinases (MMPs) production induced by this oral pathogen.

METHODS

Microplate dilution assays were performed to determine the effect of theaflavins against planktonic culture and biofilm of P. gingivalis. The effect of theaflavins on gingipain and collagenase activities of P. gingivalis was evaluated using synthetic chromogenic peptides and fluorogenic substrate. Human gingival fibroblasts (HGFs) were stimulated with P. gingivalis in the presence or absence of theaflavins, and then MMP-1, -2 secretion and their mRNA expression were assessed using an enzyme-linked immunosorbent assay (ELISA) and real-time PCR analysis, respectively.

RESULTS

Theaflavins exhibited the antimicrobial effects against both planktonic culture and biofilm of P. gingivalis. Theaflavins also markedly inhibited the proteinase activities of P. gingivalis collagenase and gingipains in a dose-dependent manner. Lastly, theaflavins significantly inhibited the secretion and mRNA expression of MMP-1 and MMP-2 by HGFs stimulated with P. gingivalis.

CONCLUSION

Theaflavins can affect the virulent properties of P. gingivalis and attenuate the MMP-mediated inflammatory response induced by this pathogen, which suggests that theaflavins may be potentially valuable supplementary therapeutic agent for prevention and treatment of P. gingivalis-associated periodontal diseases.

Structure-dependent interactions of polyphenols with a biomimetic membrane system

Polyphenols are naturally-occurring compounds, reported to be biologically active, and through their interactions with cell membranes. Although association of the polyphenols with the bilayer has been reported, the detailed mechanism of interaction is not yet well elucidated. We report on spatio-temporal real-time membrane dynamics observed in the presence of polyphenols. Two distinct membrane dynamics, corresponding to the two classes of polyphenols used, were observed. Flavonoids (epi-gallocatechin-3-gallate, gallocatechin, theaflavin and theaflavin-3-gallate) caused lipid membrane aggregation and rigidification. As simple structural modification through opening of the aromatic C-ring into an olefin bond, present in trans-stilbenes (resveratrol and picead), completely changed the membrane properties, increasing fluidity and inducing fluctuation. There were differences in the membrane transformations within the same class of polyphenols. Structure-dependent classification of membrane dynamics may contribute to a better understanding of the physicochemical mechanism involved in the bioactivity of polyphenols. In general, an increase in the number of hydrophilic side chains (galloyl, hydroxyl, glucoside, gallate) increased the reactivity of the polyphenols. Most notable was the difference observed through a simple addition of the gallate group. Unraveling the importance of these polyphenols, at a functional group level further opens the key to tailored design of bioactive compounds as potential drug candidates.