Anti-quorum sensing activity of phenolic extract from Eugenia brasiliensis (Brazilian cherry)

Emerging berries from the Brazilian Amazon and Atlantic Forest biomes: new sources of bioactive compounds with potential health benefits

Brazil has a broad geographic biodiversity spread across its six different biomes. However, it has been suffering from the abusive exploitation of its resources, which poses a threat to the local fauna and flora. The Amazon and Atlantic Forest, for example, are birthplaces to rare and edible native species, such as bacaba (Oenocarpus bacaba, Arecaceae) and camu-camu (Myrciaria dubia, Myrtaceae), and cereja-do-Rio Grande (Eugenia involucrata, Myrtaceae) and grumixama (Eugenia brasiliensis, Myrtaceae), respectively. These plants produce fruits which are sources of macro and micronutrients, including sugars, dietary fibers, vitamins, minerals, and/or lipids. Nutritionally, their consumption have the ability to reach partially or totally the daily recommendations for adults of some nutrients. More recently, these fruits have also been exposed as interesting sources of minor bioactive compounds, such as carotenoids, terpenes, and/or polyphenols, the latter which include anthocyanins, phenolic acids, and tannins. Particularly, bacaba stands out for being a rich source of polyunsaturated fatty acids (around 22%, dry weight) and dietary fibers (6.5-21%, dry weight); camu-camu has very high contents of vitamin C (up to 5000 mg per 100 g of pulp, dry basis); and cereja-do-Rio-Grande and grumixama are abundant sources of anthocyanins. Although they are still underexplored, several in vitro and in vivo studies with different parts of the fruits, including the peel, seed, and pulp, indicate their health potential through anti-oxidative, anti-obesity, antihyperglycemic, antidyslipidemic, antimicrobial, and/or anticancer effects. All things considered, the focus of this research was to highlight the bioactive potential and health impact of native fruits from the Amazon and Atlantic Forest biomes.

Potential of Selected African Medicinal Plants as Alternative Therapeutics against Multi-Drug-Resistant Bacteria

Antimicrobial resistance is considered a "One-Health" problem, impacting humans, animals, and the environment. The problem of the rapid development and spread of bacteria resistant to multiple antibiotics is a rising global health threat affecting both rich and poor nations. Low- and middle-income countries are at highest risk, in part due to the lack of innovative research on the surveillance and discovery of novel therapeutic options. Fast and effective drug discovery is crucial towards combatting antimicrobial resistance and reducing the burden of infectious diseases. African medicinal plants have been used for millennia in folk medicine to cure many diseases and ailments. Over 10% of the Southern African vegetation is applied in traditional medicine, with over 15 species being partially or fully commercialized. These include the genera Euclea, Ficus, Aloe, Lippia. And Artemisia, amongst many others. Bioactive compounds from indigenous medicinal plants, alone or in combination with existing antimicrobials, offer promising solutions towards overcoming multi-drug resistance. Secondary metabolites have different mechanisms and modes of action against bacteria, such as the inhibition and disruption of cell wall synthesis; inhibition of DNA replication and ATP synthesis; inhibition of quorum sensing; inhibition of AHL or oligopeptide signal generation, broadcasting, and reception; inhibition of the formation of biofilm; disruption of pathogenicity activities; and generation of reactive oxygen species. The aim of this review is to highlight some promising traditional medicinal plants found in Africa and provide insights into their secondary metabolites as alternative options in antibiotic therapy against multi-drug-resistant bacteria. Additionally, synergism between plant secondary metabolites and antibiotics has been discussed.

Quorum sensing in human gut and food microbiomes: Significance and potential for therapeutic targeting

Human gut and food microbiomes interact during digestion. The outcome of these interactions influences the taxonomical composition and functional capacity of the resident human gut microbiome, with potential consequential impacts on health and disease. Microbe-microbe interactions between the resident and introduced microbiomes, which likely influence host colonisation, are orchestrated by environmental conditions, elements of the food matrix, host-associated factors as well as social cues from other microorganisms. Quorum sensing is one example of a social cue that allows bacterial communities to regulate genetic expression based on their respective population density and has emerged as an attractive target for therapeutic intervention. By interfering with bacterial quorum sensing, for instance, enzymatic degradation of signalling molecules (quorum quenching) or the application of quorum sensing inhibitory compounds, it may be possible to modulate the microbial composition of communities of interest without incurring negative effects associated with traditional antimicrobial approaches. In this review, we summarise and critically discuss the literature relating to quorum sensing from the perspective of the interactions between the food and human gut microbiome, providing a general overview of the current understanding of the prevalence and influence of quorum sensing in this context, and assessing the potential for therapeutic targeting of quorum sensing mechanisms.

Antimicrobial and Antioxidant Activity of Apricot (Mimusopsis comersonii) Phenolic-Rich Extract and Its Application as an Edible Coating for Fresh-Cut Vegetable Preservation

Edible coatings have several advantages in preserving foods, such as avoiding water loss, controlling microbial growth, and reducing the need for preservatives added directly to the product. Antimicrobial action can be obtained by adding antimicrobial substances including phenolic compounds commonly found in plant extracts. This study evaluated the phenolic compounds content, antioxidant and antimicrobial activity of pulp, and seed extracts of Mimusopsis comersonii (popularly known in Brazil as abrico), besides the phenolic compounds were identified and quantified in the pulp extract. Edible coatings were incorporated with pulp extract in order to evaluate the preservation of minimally processed apples and baroa potatoes against foodborne bacteria, and enzymatic browning was also determined. Myricetin-3-glucoside, quercetin-3-glucoside, and kaempferol-3-glucoside were identified as major flavonoids in the apricot pulp extract. The seed and pulp extracts inhibited all tested microorganisms, especially Staphylococcus aureus and Salmonella Typhimurium. Edible coatings added with 9% of phenolic extract showed in vitro antimicrobial activity, in addition to being effective in preventing enzymatic browning in minimally processed apples and baroa potatoes for up to 15 days of storage. They were also effective in reducing up to 2 log CFU/g of aerobic mesophiles after 15 days of storage for apples, even though no microbial inhibition in baroa potatoes was observed under the same conditions. The addition of pulp phenolic extract in edible coatings proved to be an alternative in the preservation of apples and in the antibrowning activity of minimally processed baroa potatoes.

Secondary Metabolites with Biomedical Applications from Plants of the Sarraceniaceae Family

Carnivorous plants have fascinated researchers and hobbyists for centuries because of their mode of nutrition which is unlike that of other plants. They are able to produce bioactive compounds used to attract, capture and digest prey but also as a defense mechanism against microorganisms and free radicals. The main purpose of this review is to provide an overview of the secondary metabolites with significant biological activity found in the Sarraceniaceae family. The review also underlines the necessity of future studies for the biochemical characterization of the less investigated species. Darlingtonia, Heliamphora and Sarracenia plants are rich in compounds with potential pharmaceutical and medical uses. These belong to several classes such as flavonoids, with flavonol glycosides being the most abundant, monoterpenes, triterpenes, sesquiterpenes, fatty acids, alkaloids and others. Some of them are well characterized in terms of chemical properties and biological activity and have widespread commercial applications. The review also discusses biological activity of whole extracts and commercially available products derived from Sarraceniaceae plants. In conclusion, this review underscores that Sarraceniaceae species contain numerous substances with the potential to advance health. Future perspectives should focus on the discovery of new molecules and increasing the production of known compounds using biotechnological methods.

Chemical Approach to the Optimization of Conditions Using HS-SPME/GC–MS for Characterization of Volatile Compounds in Eugenia brasiliensis Fruit

Grumixama (Eugenia brasiliensis Lam.) is a native fruit of the Brazilian Atlantic Forest, belonging to the Myrtaceae family, which designatesthe most significant number of species with food potential. It stands out due to its phytochemical characteristics because of the presence of polyphenols and volatile organic compounds. Volatile compounds are substances released by foods that give off an aroma and influence flavor. Solid-phase microextraction is a technique that allows for low-cost, fast, and solvent-free extraction, has an affinity for numerous analytes, and is easily coupled to gas chromatography. The objectives of this work were to evaluate the efficiency of different fibers of SPME (solid-phase microextraction) in the extraction of volatile organic compounds from grumixama pulp; optimize a method for extraction time, temperature, and sample weight; and to determine the characteristic volatile profile of this fruit. For the extraction of volatile compounds, three fibers of different polarities were used: polar polyacrylate (PA) fibers, divinylbenzene/carboxyne/polydimethylsiloxane (DVB/CAR/PDMS) semipolar fibers, and polydimethylsiloxane/divinylbenzene (PDMS/DVB). Fourteen volatile organic compounds (VOCs) were identified by DVB/CAR/PDMS, six by PA, and seven by PDMS/DVB through solid-phase microextraction in the headspace mode (SPME-HS). Considering the total number of compounds identified, regardless of the fiber used, and the optimization of the method, Eugenia brasiliensis presented sesquiterpene fractions (85.7%, 83.3%, and 85.7% of total VOCs) higher than the monoterpene fractions (14.3%, 16.7%, and 14.3%) for DVB/CAR/PDMS, PA, and PDMS/DVB, respectively in its composition. In addition, it was possible to verify that the fiber DVB/CAR/PDMS presented a better efficiency due to the larger chromatographic area observed when the grumixama pulp was subjected to conditions of 75 °C, 2.0 g, and an adsorption time of 20 min.

Impact of Quercetin against Salmonella Typhimurium Biofilm Formation on Food-Contact Surfaces and Molecular Mechanism Pattern

Quercetin is an active nutraceutical element that is found in a variety of foods, vegetables, fruits, and other products. Due to its antioxidant properties, quercetin is a flexible functional food that has broad protective effects against a wide range of infectious and degenerative disorders. As a result, research is required on food-contact surfaces (rubber (R) and hand gloves (HG)) that can lead to cross-contamination. In this investigation, the inhibitory effects of quercetin, an antioxidant and antibacterial molecule, were investigated at sub-MIC (125; 1/2, 62.5; 1/4, and 31.25; 1/8 MIC, μg/mL) against Salmonella Typhimurium on surfaces. When quercetin (0−125 μg/mL) was observed on R and HG surfaces, the inhibitory effects were 0.09−2.49 and 0.20−2.43 log CFU/cm2, respectively (p < 0.05). The results were confirmed by field emission scanning electron microscopy (FE-SEM), because quercetin inhibited the biofilms by disturbing cell-to-cell connections and inducing cell lysis, resulting in the loss of normal cell morphology, and the motility (swimming and swarming) was significantly different at 1/4 and 1/2 MIC compared to the control. Quercetin significantly (p < 0.05) suppressed the expression levels of virulence and stress response (rpoS, avrA, and hilA) and quorum-sensing (luxS) genes. Our findings imply that plant-derived quercetin could be used as an antibiofilm agent in the food industry to prevent S. Typhimurium biofilm formation.

Interactive effects of dietary quercetin nanoparticles on growth, flesh antioxidant capacity and transcription of cytokines and Aeromonas hydrophila quorum sensing orchestrating genes in Nile tilapia (Oreochromis niloticus)

Recently, the concept of incorporating natural products into nanocarriers has been intended to promote fish growth and health via modulating their stability and bioavailability. In this concern, the potential role of reformulated quercetin into nanocarriers was examined, for the first time, on Nile tilapia's performance and immunity, flesh quality and antioxidant indices and disease resistance. Five hundred fish assigned into five experimental groups with formulated diets containing quercetin nanoparticles (QT-NPs) at levels of 0, 100, 200, 300 and 400 mg/kg were challenged with Aeromonas hydrophila (A. hydrophila) after 12 weeks feeding trial. Fish final body weight gain and feed efficiency were significantly maximized in groups enriched with 300 and 400 mg/kg of QT-NPs. Significant reduction in total saturated fatty acids and an elevation in polyunsaturated fatty acids' contents were noticed in fish fed higher QT-NPs doses. The levels of Hydrogen peroxide, reactive oxygen species and malondialdehyde, the markers of meat antioxidant capacity, were reduced by higher inclusion levels of QT-NPs. Accordingly, serum activities and transcriptional levels of GSH-Px, CAT and SOD genes were increased with elevated QT-NPs levels. Immune responses mediated by upregulation of IL-10 and TGF-β and downregulation of IL-1β, IL-8 and TNF-α mRNA levels were found to be positively affected by QT-NPs. Dietary QT-NPs downregulated the expression of ahyI and ahyR quorum sensing genes conferring protection against A. hydrophila challenge. This study concluded that supplementation of quercetin in encapsulated nanoparticles could improve its efficacy making it as a compelling approach to improve fish performance and as a promising drug candidate against A. hydrophila virulence.

Identification and Characterization of Polyphenols from Carissa spinarum Fruit and Evaluation of Their Antioxidant and Anti-quorum Sensing Activity

Quorum sensing controls bacterial virulence through signaling molecules, which plays a vital role in managing foodborne pathogens that cause food spoilage and human infections. Though many synthetic compounds have been used to control infection, antibiotic resistance has become a global issue. Targeting the bacterial quorum sensing using the bioactive compounds could be an alternative strategy to combat their resistance. In this context, polyphenols from an unexplored unripe and ripe fruits of Carissa spinarum were evaluated for anti-quorum sensing activity. The study aimed at determining nutritional, phytochemical composition, and polyphenol profiling to evaluate their antioxidant potential of the fruit. Furthermore, the violacein inhibition, anti-biofilm, and effect on the motility of foodborne pathogens were also studied. The phytochemical content of C. spinarum fruit showed the phenolic and flavonoid content 273.20 mg GAE/100 g and 453.78 mg QE/100 g fresh weight , respectively, in ripe fruit. HPLC characterization of fruit extracts showed high content of syringic acid, resveratrol, and quercetin in ripe, whereas it showed epicatechin and gentisic acid in unripe fruit. The antioxidant activity of the ripe fruit extract exhibited a higher potential to scavenge DPPH radicals with IC₅₀ 4.69 mg/mL. Further, the anti-quorum sensing activity was higher in ripe fruit extract at 1.8 mg/mL inhibited with 78.65% violacein production in Chromobacterium violaceum, swimming motility, and biofilm formation in Pseudomonas aeruginosa and Yersinia enterocolitica (66.25% and 59.36% respectively at 1.2 mg/mL). Hence C. spinarum fruit bioactive could be a natural plant source for anti-quorum sensing activity to manage foodborne pathogens over synthetic compounds.

Anti-quorum Sensing and Protective Efficacies of Naringin Against Aeromonas hydrophila Infection in Danio rerio

It is now well known that the quorum sensing (QS) mechanism coordinates the production of several virulence factors and biofilm formation in most pathogenic microorganisms. Aeromonas hydrophila is a prime pathogen responsible for frequent outbreaks in aquaculture settings. Recent studies have also continuously reported that A. hydrophila regulates virulence factor production and biofilm formation through the QS system. In addition to the presence of antibiotic resistance genes, biofilm-mediated antibiotic resistance increases the severity of A. hydrophila infections. To control the bacterial pathogenesis and subsequent infections, targeting the QS mechanism has become one of the best alternative methods. Though very few compounds were identified as QS inhibitors against A. hydrophila, to date, the screening and identification of new and effective natural QS inhibitors is a dire necessity to control the infectious A. hydrophila. The present study endorses naringin (NA) as an anti-QS and anti-infective agent against A. hydrophila. Initially, the NA showed a concentration-dependent biofilm reduction against A. hydrophila. Furthermore, the results of microscopic analyses and quantitative virulence assays displayed the promise of NA as a potential anti-QS agent. Subsequently, the downregulation of ahh1, aerA, lip and ahyB validate the interference of NA in virulence gene expression. Furthermore, the in vivo assays were carried out in zebrafish model system to evaluate the anti-infective potential of NA. The outcome of the immersion challenge assay showed that the recovery rate of the zebrafish has substantially increased upon treatment with NA. Furthermore, the quantification of the bacterial load upon NA treatment showed a decreased level of bacterial counts in zebrafish when compared to the untreated control. Moreover, the NA treatment averts the pathogen-induced histoarchitecture damages in vital organs of zebrafish, compared to their respective controls. The current study has thus analyzed the anti-QS and anti-infective capabilities of NA and could be employed to formulate effective treatment measures against A. hydrophila infections.

Quorum sensing system: Target to control the spread of bacterial infections

Quorum Sensing (QS) systems regulate the gene expression of different types of virulence factors in accordance with the cell population density. A literature search was performed, including electronic databases such as MEDLINE/PubMed, SciELO, and LILACS, as well as other databases not indexed, such as Google Scholar. The search was conducted between July 2018 and April 2019, through online research. Antimicrobial resistance is one of the biggest threats to global health and the dissemination of resistant microbes in the environment is a major public health problem. Therefore, it is important to develop new therapies to control the spread of resistant bacteria to humans. Thus, interference in the chemical signal (autoinducers) of the QS system has been postulated as a good alternative, technically known as "Quorum Quenching" or QS inhibitors. Inhibition of QS signaling is not intended to kill the microorganism, but to block the expression of the target genes, making the cells less virulent and more vulnerable to host immune response. Anti-virulence therapy by agents that interfere with this system in pathogenic bacteria is a well-studied strategy, including medicinal plants and their bioactive constituents, and presents good prospects. This review aims to provide an overview of the QS system in bacteria and describe the main inhibitors of the system.

Effect of Capsicum Frutescens Extract, Capsaicin, and Luteolin on Quorum Sensing Regulated Phenotypes

Capsicum peppers have not been investigated as sources of quorum sensing (QS) inhibitors. This study aimed to identify compounds in pimenta-malagueta (Capsicum frutescens) and red pepper (Capsicum annuum) extracts and to evaluate their effect on violacein production in Chromobacterium violaceum ATCC 12472 and C. violaceum CV026, as well as biofilm formation (BF) in Pseudomonas aeruginosa PAO1 and Serratia marcescens MG1. Among the extracts, pimenta-malagueta methanolic extract (PMME) was chosen because it contained capsaicin, dihydrocapsaicin, and luteolin in greater amount than the other extracts. In general, PMME partially inhibited bacterial growth at 2.5 and 5.0 mg/mL, as well as capsaicin at 100 µg/mL and luteolin at 62.5, 125, and 250 µg/mL. At lower concentrations, PMME and luteolin reduced violacein production in C. violaceum ATCC 12472 without affecting growth, a result that was not observed with capsaicin. We show that violacein inhibition by PMME is likely due to luteolin. In silico docking evaluation showed that luteolin binds to the CviR QS regulator. Crystal violet staining and confocal microscopy revealed that BF was increased by PMME and capsaicin, being remarkably superior for P. aeruginosa PAO1 at 30 °C. Capsaicin is not an effective QS inhibitor, while luteolin should be further investigated for its potential effects in QS regulated phenotypes. PRACTICAL APPLICATION: Quorum sensing (QS) is a form of bacterial communication targeted for studies aiming to inhibit bacterial virulence. QS regulates phenotypes that influence microbial activities across many areas, including Food Science. Capsicum frutescens is a type of chili pepper consumed in Brazil, rich in bioactive compounds such as capsaicin (which gives its pungency) and luteolin (a phenolic compound). We show that C. frutescens extract and luteolin inhibit QS in a model bacterium, along with the possible molecular mechanism of inhibition. Capsaicin did not inhibit QS neither biofilm formation. Luteolin should be further investigated for its QS inhibition properties and biotechnological applications.

Effect of Quercetin Rich Onion Extracts on Bacterial Quorum Sensing

Quorum sensing (QS) regulates bacterial gene expression and studies suggest quercetin, a flavonol found in onion, as a QS inhibitor. There are no studies showing the anti-QS activity of plants containing quercetin in its native glycosylated forms. This study aimed to evaluate the antimicrobial and anti-QS potential of organic extracts of onion varieties and its representative phenolic compounds quercetin aglycone and quercetin 3-β-D-glucoside in the QS model bacteria Chromobacterium violaceum ATCC 12472, Pseudomonas aeruginosa PAO1, and Serratia marcescens MG1. Three phenolic extracts were obtained: red onion extract in methanol acidified with 2.5% acetic acid (RO-1), white onion extract in methanol (WO-1) and white onion extract in methanol ammonium (WO-2). Quercetin 4-O-glucoside and quercetin 3,4-O-diglucoside were identified as the predominant compounds in both onion varieties using HPLC-DAD and LC-ESI-MS/MS. However, quercetin aglycone, cyanidin 3-O-glucoside and quercetin glycoside were identified only in RO-1. The three extracts showed minimum inhibitory concentration (MIC) values equal to or above 125 μg/ml of dried extract. Violacein production was significantly reduced by RO-1 and quercetin aglycone, but not by quercetin 3-β-D-glucoside. Motility in P. aeruginosa PAO1 was inhibited by RO-1, while WO-2 inhibited S. marcescens MG1 motility only in high concentration. Quercetin aglycone and quercetin 3-β-D-glucoside were effective at inhibiting motility in P. aeruginosa PAO1 and S. marcescens MG1. Surprisingly, biofilm formation was not affected by any extracts or the quercetins tested at sub-MIC concentrations. In silico studies suggested a better interaction and placement of quercetin aglycone in the structures of the CviR protein of C. violaceum ATCC 12472 than the glycosylated compound which corroborates the better inhibitory effect of the former over violacein production. On the other hand, the two quercetins were well placed in the AHLs binding pockets of the LasR protein of P. aeruginosa PAO1. Overall onion extracts and quercetin presented antimicrobial activity, and interference on QS regulated production of violacein and swarming motility.

Anti-Candida and anti-quorum sensing activity of airborne microorganisms detected by a rapid method

INTRODUCTION

Introducing new antibiotics to the clinic is critical.

METHODS

We adapted a plate method described by Kawaguchi and coworkers in 20131 for detecting inhibitory airborne microorganisms.

RESULTS

We obtained 51 microbial colonies antagonist to Chromobacterium violaceum, purified and retested them, and of these, 39 (76.5%) were confirmed. They comprised 24 bacteria, 13 fungi, and 2 yeasts. Among the fungi, eight (61.5%) produced active extracts. Among the bacterial, yeast, and fungal strains, 17 (44.7%) and 12 (31.6%) were active against Candida albicans and Candida parapsilosis, respectively.

CONCLUSIONS

The proposed screening method is a rapid strategy for discovering potential antibiotic producers.

Influence of pitanga leaf extracts on lipid and protein oxidation of pork burger during shelf-life

The effect of pitanga leaf extracts, as source of natural antioxidants, on physicochemical properties as well as lipid and protein oxidation of pork burgers during storage at 2 ± 1 °C, packed under modified atmosphere, was assessed. Formerly, the in vitro antioxidant and antimicrobial activities as well as the phenolic profile of pitanga leaf extracts were also studied. Thereafter, five samples were prepared, including control (without antioxidants), commercial synthetic antioxidant (BHT at 200 mg/kg) and three concentrations of pitanga leaf extracts: PLL (at 250 mg/kg), PLM (at 500 mg/kg) and PLH (at 1000 mg/kg). The predominant phenolic compounds identified in pitanga leaf extracts were hydroxycinnamic acids, followed by tyrosol and other phenolics (alkylmethoxyphenols, hydroxycoumarins and hydroxyphenylpropenes). Pitanga leaf extracts showed a high antioxidant and antimicrobial in vitro activity. The addition of pitanga leaf extracts improved the redness of pork burgers during the whole display. On the other hand, the addition of natural antioxidants decreased the lipid oxidation from day 7 till the end of storage period. Burgers with antioxidant showed a similar protein oxidation level, observing an inhibition between 36% and 49% compared to control treatment. From the results, it can be concluded that pitanga leaf extract is a good alternative to commercial synthetic antioxidants to improve the quality and extend the shelf-life of pork burgers.

The Effects of Chinese Herbal Medicines on the Quorum Sensing-Regulated Virulence in Pseudomonas aeruginosa PAO1

The quorum sensing (QS) system has been used by many opportunistic pathogenic bacteria to coordinate their virulence determinants in relation to cell-population density. As antibiotic-resistant bacteria are on the rise, interference with QS has been regarded as a novel way to control bacterial infections. As such, many plant-based natural products have been widely explored for their therapeutic roles. These natural products may contain anti-QS compounds that could block QS signals generation or transmission to combat QS pathogens. In this study, we report the anti-QS activities of four different Chinese herbal plant extracts: Poria cum Radix pini, Angelica dahurica, Rhizoma cibotii and Schizonepeta tenuifolia, on Pseudomonas aeruginosa PAO1. All the plants extracted using hexane, chloroform and methanol were tested and found to impair swarming motility and pyocyanin production in P.aeruginosa PAO1, particularly by Poria cum Radix pini. In addition, all the plant extracts also inhibited violacein production in C.violaceum CV026 up to 50% while bioluminescence activities were reduced in lux-based E. coli biosensors, pSB401 and pSB1075, up to about 57%. These anti-QS properties of the four medicinal plants are the first documentation that demonstrates a potential approach to attenuate pathogens’ virulence determinants.