Inhibition ofStaphylococcus aureusby Phenolic Phytochemicals of Selected Clonal Herbs Species ofLamiaceaeFamily and Likely Mode of Action through Proline Oxidation

Pistacia vera L. as natural source against antimicrobial and antiviral resistance

Increased global research is focused on the development of novel therapeutics to combat antimicrobial and antiviral resistance. Pistachio nuts represent a good source of protein, fiber, monounsaturated fatty acids, minerals, vitamins, and phytochemicals (carotenoids, phenolic acids, flavonoids and anthocyanins). The phytochemicals found in pistachios are structurally diverse compounds with antimicrobial and antiviral potential, demonstrated as individual compounds, extracts and complexed into nanoparticles. Synergistic effects have also been reported in combination with existing drugs. Here we report an overview of the antimicrobial and antiviral potential of pistachio nuts: studies show that Gram-positive bacterial strains, such as Staphylococcus aureus, are the most susceptible amongst bacteria, whereas antiviral effect has been reported against herpes simplex virus 1 (HSV-1). Amongst the known pistachio compounds, zeaxanthin has been shown to affect both HSV-1 attachment penetration of human cells and viral DNA synthesis. These data suggest that pistachio extracts and derivatives could be used for the topical treatment of S. aureus skin infections and ocular herpes infections.

Enhancing Milk Quality and Antioxidant Status in Lactating Dairy Goats through the Dietary Incorporation of Purple Napier Grass Silage

Oxidative stress resulting from an imbalance between oxidants and antioxidants can cause damage to certain cellular components. Purple Napier grass, a semi-dwarf variety, is characterized by its purple leaves and contains anthocyanins, which provide it with antioxidant properties. This study examined the effects of feeding purple Napier grass ("Prince") silage to lactating dairy goats on blood antioxidant activity, milk yield, and milk quality. Eighteen female Saanen crossbred goats, weighing 52.34 ± 2.86 kg and producing milk for 14 ± 2 days, were systematically divided into three groups based on their lactation period in the previous cycle as follows: early, mid, and late lactation. In a randomized complete block design (RCBD), treatments were randomly allocated to six animals in each block. The dairy goats were fed a total mixed ration (TMR) consisting of the three following treatments: control (100% Napier Pakchong 1 grass silage), 50% (a 50% replacement of the control with purple Napier grass silage), and 100% (100% purple Napier grass silage). The results show that goats who were fed a diet including 100% purple Napier grass silage showed higher levels of certain milk contents, especially with regard to lactose, when compared to those who were fed a control diet, as well as a diet with a 50% replacement of purple Napier grass silage. The somatic cell count (SCC) of these goats was reduced. In terms of antioxidant activity, dairy goats who were fed 100% purple Napier grass silage showed higher levels of enzymes in both plasma and milk, including glutathione s-transferase, total antioxidant capacity, superoxide dismutase, and 2,2-diphenyl-1-picrylhydrazyl radical, compared to the control group and the 50% replacement group. The plasma and milk of these goats showed lower levels of malondialdehyde. The dairy goats who were fed a 100% purple Napier grass silage diet showed higher concentrations of anthocyanins, including C3G, P3G, Peo3G, M3G, Cya, Pel, and total anthocyanins in milk, when compared to the control group and the 50% replacement group. The increased replacement of purple Napier grass silage led to significant differences in lactose levels, somatic cell count, glutathione S-transferase, total antioxidant capacity, superoxide dismutase, 2,2-diphenyl-1-picrylhydrazyl radical, and the composition of anthocyanins. This study provides evidence to support the use of purple Napier grass silage as a beneficial source of roughage for lactating dairy goats.

Novel Biodegradable Nanoparticulate Chain-End Functionalized Polyhydroxybutyrate-Caffeic Acid with Multifunctionalities for Active Food Coatings

The bioactivities of polyhydroxyalkanoates have been curtailed owing to the lack of bioactive functional groups in their backbones. In this regard, polyhydroxybutyrate (PHB) produced from new locally isolated Bacillus nealsonii ICRI16 was chemically modified for enhancing its functionality, stability as well as solubility. First, PHB was transformed to PHB-diethanolamine (PHB-DEA) by transamination. Subsequently, for the first time, the chain ends of the polymer were substituted by caffeic acid molecules (CafA), generating novel PHB-DEA-CafA. The chemical structure of such a polymer was confirmed by Fourier-transform infrared (FTIR) spectroscopy and proton nuclear magnetic resonance (¹H NMR). The modified polyester demonstrated improved thermal behavior compared to PHB-DEA as was shown by thermogravimetric analysis, derivative thermogravimetry, and differential scanning calorimetry analyses. Interestingly, 65% of PHB-DEA-CafA was biodegraded in a clay soil environment after 60 days at 25 °C, while 50% of PHB was degraded within the same period. On another avenue, PHB-DEA-CafA nanoparticles (NPs) were successfully prepared with an impressive mean particle size of 223 ± 0.12 nm and high colloidal stability. The nanoparticulate polyester had powerful antioxidant capacity with an IC₅₀ of 32.2 mg/mL, which was the result of CafA loading in the polymer chain. More importantly, the NPs had a considerable effect on the bacterial behavior of four food pathogens, inhibiting 98 ± 0.12% of Listeria monocytogenes DSM 19094 after 48 h of exposure. Finally, the raw polish sausage coated with NPs had a significantly lower bacterial count of 2.11 ± 0.21 log cfu/g in comparison to other groups. When all these positive features are recognized, the polyester described herein could be considered as a good candidate for commercial active food coatings.

Prospecting Plant Extracts and Bioactive Molecules with Antimicrobial Activity in Brazilian Biomes: A Review

Antimicrobial resistance is currently one of the greatest threats to global health, food security, and development. In this aspect, medicinal plants have been studied to support the development of viable alternatives to prevent and treat infectious diseases. This study aimed to perform a review of the literature comprising the antimicrobial activity of vegetable species from Brazilian biomes. We selected 67 original scientific publications about extracts, fractions, or isolated molecules from plants in the Brazilian biomes, published between 2016 and 2020 in Pubmed, ScienceDirect, and Scielo. Data demonstrated that 98 plant species, especially collected in the Cerrado, Atlantic Forest, and Caatinga biomes, were tested against 40 fungi and 78 bacterial strains. Bioactive fractions of Eucalyptus globulus methanolic stump wood extract were active against Candida albicans and C. tropicalis (MIC 2.50 µg/mL). The catechin purified from Banisteriopsis argyrophylla leaves had activity against C. glabrata (MIC 2.83 µg/mL) and ethanolic extract obtained from Caryocar coriaceum bark and fruit pulp exhibited MIC of 4.1 µg/mL on Microsporum canis. For bacteria, compounds isolated from the dichloromethane extract of Peritassa campestris, lectin extracted from a saline extract of Portulaca elatior and essential oils of Myrciaria pilosa exhibited significant effect against Bacillus megaterium (MIC 0.78 µg/mL), Pseudomonas aeruginosa (MIC 4.06 µg/mL) and Staphylococcus aureus strains (MIC 5.0 µg/mL), respectively. The findings support the antimicrobial and bioeconomic potential of plants from Brazilian biodiversity and their promising health applications.

Microbiological stability and sensorial valorization of thyme and oregano essential oils alone or combined with ethanolic pomegranate extracts in wine marinated pork meat

In the present study, wine-based marinades containing ethanolic extract from pomegranate (Punica granatum L.), alone or in combination with two Essential Oils (Thyme & Oregano), were used for pork fillets marination and their antimicrobial activity, as well as their sensorial impact were evaluated. Likewise, the marinades exhibited promising results concerning their recorded antimicrobial activity versus Enterobacteriaceae, Total Mesophilic Bacteria, Yeasts/molds, Staphylococcus spp., Pseudomonas spp. & Lactic Acid Bacteria (LAB). The outcome demonstrated that pork fillets marinated with wine containing ethanolic extract of pomegranate and Oregano Essential Oil were more resistant to spoilage compared to all other samples; thus, their shelf-life was significantly extended (4 days in some cases). Triterpenes (maslinic, oleanolic and betulinic acid), monoterpenes (p-cymene, carvacrol, thymol, limonene), organic acids (citric & malic acid) and phenols, were the main constituents found in the plant extract, the wine and Essential Oils applied, as determined through LC-QTOF/MS and HPLC analysis. Additionally, the sensorial properties (color, tenderness, flavor and juiciness) of the marinated meat samples were not negatively influenced. Consequently, marinades of this type could be used as natural preservatives in meat products, with satisfying antimicrobial and organoleptic results.

Valorisation of Three Underutilised Native Australian Plants: Phenolic and Organic Acid Profiles and In Vitro Antimicrobial Activity

Tasmannia lanceolata, Diploglottis bracteata and Syzygium aqueum are understudied native Australian plants. This study aimed to characterise the non-anthocyanin phenolic and organic acid profiles of the aqueous extracts obtained from the leaves of T. lanceolata and fruits of D. bracteata and S. aqueum by UHPLC-Q-Orbitrap-MS/MS and UHPLC-TQ-MS/MS. A total of 39, 22, and 27 non-anthocyanin polyphenols were tentatively identified in T. lanceolata, D. bracteata, and S. aqueum extracts, respectively. Furthermore, sugars and ascorbic acid contents as well as in vitro antioxidant and antimicrobial activities of the extracts were determined. Response surface methodology was applied to achieve an extract blend with a strong inhibitory effect against Pseudomonas viridiflava, the main cause of soft rot in vegetables, Bacillus subtilis, Rhodotorula diobovata and Alternaria alternata. The identified compounds including organic acids (e.g., quinic, citric and malic acids) and polyphenols (e.g., catechin, procyanidins, and ellagitannins) might contribute to the observed antimicrobial activity. Furthermore, this study provides the most comprehensive phenolic profiles of these three underutilised native Australian plants to date.

Antibacterial activity and metabolomic analysis of linalool against bovine mastitis pathogen Streptococcus agalactiae

Streptococcus agalactiae is among the major causative pathogens of bovine mastitis, as well as crucial pathogen leading to human morbidity and mortality. Being a promising natural antibacterial agent, linalool has been broadly applied in medicine and food processing. However, its antibacterial effect against S. agalactiae has barely been elucidated. This study is the first to investigate the antibacterial activity and action mechanism of linalool against S. agalactiae causing bovine mastitis. Linalool exhibited significant antibacterial activity against S. agalactiae, with an inhibition zone diameter of 23 mm and a minimum inhibitory concentration of 1.875 μL/mL. In addition, linalool damaged cell structural integrity of S. agalactiae, leading to the leakage of intracellular components (alkaline phosphatase, nucleic acids and protein). Linalool also exhibited a scavenging effect on biofilm. Moreover, untargeted metabolomics analysis revealed that linalool stress substantially disrupted intracellular metabolism of S. agalactiae. Linalool caused energy metabolism disorder, and obstructed nucleic acid synthesis in S. agalactiae. Furthermore, downregulation of amino acids (e.g., proline, alanine) and upregulation of saturated fatty acids provide strong evidence for linalool induced cell wall and membrane damage. Overall, linalool exhibited strong antibacterial activity against S. agalactiae by destroying the cell structure and disrupting intracellular metabolism. This study provides a new insight and theoretical foundation for linalool application in preventing S. agalactiae infection.

Antimicrobial effect of phenolic-rich jaboticaba peel aqueous extract on Staphylococcus aureus and Escherichia coli

Abstract Jaboticaba peels are an important source of health-benefit and antimicrobial compounds. The present work aims to evaluate concentration of polyphenolics and the mode of action of aqueous extract from jaboticaba peels against Staphylococcus aureus and Escherichia coli. Jaboticaba peel extract showed minimum inhibitory concentration and minimum bactericidal concentration against S. aureus of 5.1 g L-1 and 10.1 g L-1, respectively; meanwhile, against E. coli the parameters were 2.0 g L-1 and 3.4 g L-1. Kinetics of viable cell counts indicated a bacteriolytic action against both bacteria and Scanning Electron Microscopy (SEM) showed that jaboticaba peel extract causes subtle morphological changes in bacterial cells. Concentration of total polyphenols in the extract was 1535.04±36.05 mg of gallic acid equivalent (GAE) mL-1, monomeric anthocyanins was 14.52 ± 0.98 mg of cyanidin 3-glucoside mL-1, condensed tannins was 0.49 ± 0.05 mg of epicatechin equivalent mL-1 and phenolic acids was 80.04 ± 4.11 mg of caffeic acid equivalent (CAE) mL-1, which have demonstrated well-documented antibacterial activity. In conclusion, jaboticaba peel aqueous extract may be an interesting natural preservative to control Gram-positive and Gram-negative bacteria growth when interacting with the bacteria cell wall.

Study on the inhibition mechanism of eucalyptus tannins against Microcystis aeruginosa

Microcystis aeruginosa is the competitively dominant algal species in eutrophic waters and poses a serious threat to the aquatic ecological environment. To investigate the effects of eucalyptus tannins (TFL) and black water in eucalyptus plantations on M. aeruginosa, this study exposed M. aeruginosa to different concentrations (0 (control), 20, 50, 80, 110, and 140 mg L-1) of tannic acid (TA; hydrolyzed tannins, HT; reagent tannin), epigallocatechin gallate (EGCG; condensed tannins, CT; reagent tannin), eucalyptus tannins (TFL, complex tannin) and mixed TFL + Fe3+ solution (tannin: Fe3+ molar ratio = 1:10). The cell density, chlorophyll-a (Chl-a) content, superoxide dismutase (SOD) activity, malondialdehyde (MDA) and soluble protein (SP) contents of algae under tannin stress were determined, and the algal cell density treated with under the combination of TFL and Fe3+ was determined. The results showed a reduction in the Chl-a content of algal cells, which inhibited photosynthesis; leading to membrane lipid peroxidation; and the complexation of soluble proteins resulting in blocked protein synthesis were the main mechanisms by which tannins inhibited the growth of M. aeruginosa. TFL achieved the same inhibition of algal cells as the tannin reagent at the same concentration. At 4 d, TFL at 80 mg L-1 and above could achieve more than 54.87 % algal density inhibition. The inhibition rate of 80 mg L-1 and above TFL + Fe3+ on algal density was more than 75 %, indicating that TFL + Fe3+ had a stronger inhibitory effect on algal density. The results may facilitate the resource utilization of eucalyptus harvesting residues, explorations of the potential application of eucalyptus tannins in the control of M. aeruginosa, and provide new ideas for ecological algal inhibition in eucalyptus plantations.

Synthesis of sustainable eugenol/hydroxyethylmethacrylate-based polymers with antioxidant and antimicrobial properties

Eugenol is a phenolic monoterpenoid, emplyed in this study to obtain bio-based antimicrobial and antioxidant methacrylate polymers.

Caffeic Acid and Diseases-Mechanisms of Action

Caffeic acid belongs to the polyphenol compounds we consume daily, often in the form of coffee. Even though it is less explored than caffeic acid phenethyl ester, it still has many positive effects on human health. Caffeic acid can affect cancer, diabetes, atherosclerosis, Alzheimer's disease, or bacterial and viral infections. This review focuses on the molecular mechanisms of how caffeic acid achieves its effects.

Polyphenols: Bioavailability, Microbiome Interactions and Cellular Effects on Health in Humans and Animals

Polyphenolic compounds have a variety of functions in plants including protecting them from a range of abiotic and biotic stresses such as pathogenic infections, ionising radiation and as signalling molecules. They are common constituents of human and animal diets, undergoing extensive metabolism by gut microbiota in many cases prior to entering circulation. They are linked to a range of positive health effects, including anti-oxidant, anti-inflammatory, antibiotic and disease-specific activities but the relationships between polyphenol bio-transformation products and their interactions in vivo are less well understood. Here we review the state of knowledge in this area, specifically what happens to dietary polyphenols after ingestion and how this is linked to health effects in humans and animals; paying particular attention to farm animals and pigs. We focus on the chemical transformation of polyphenols after ingestion, through microbial transformation, conjugation, absorption, entry into circulation and uptake by cells and tissues, focusing on recent findings in relation to bone. We review what is known about how these processes affect polyphenol bioactivity, highlighting gaps in knowledge. The implications of extending the use of polyphenols to treat specific pathogenic infections and other illnesses is explored.

The Response Surface Optimization of Supercritical CO2 Modified with Ethanol Extraction of p-Anisic Acid from Acacia mearnsii Flowers and Mathematical Modeling of the Mass Transfer

A widely disseminated native species from Australia, Acacia mearnsii, which is mainly cultivated in Brazil and South Africa, represents a rich source of natural tannins used in the tanning process. Many flowers of the Acacia species are used as sources of compounds of interest for the cosmetic industry, such as phenolic compounds. In this study, supercritical fluid extraction was used to obtain non-volatile compounds from A. mearnsii flowers for the first time. The extract showed antimicrobial activity and the presence of p-anisic acid, a substance with industrial and pharmaceutical applications. The fractionation of the extract was performed using a chromatographic column and the fraction containing p-anisic acid presented better minimum inhibitory concentration (MIC) results than the crude extract. Thus, the extraction process was optimized to maximize the p-anisic acid extraction. The response surface methodology and the Box–Behnken design was used to evaluate the pressure, temperature, the cosolvent, and the influence of the particle size on the extraction process. After the optimization process, the p-anisic acid yield was 2.51% w/w and the extraction curve was plotted as a function of time. The simulation of the extraction process was performed using the three models available in the literature.

Caffeic Acid and Its Derivatives: Antimicrobial Drugs toward Microbial Pathogens

Caffeic acid is a plant-derived compound that is classified as hydroxycinnamic acid which contains both phenolic and acrylic functional groups. Caffeic acid has been greatly employed as an alternative strategy to combat microbial pathogenesis and chronic infection induced by microbes such as bacteria, fungi, and viruses. Similarly, several derivatives of caffeic acid such as sugar esters, organic esters, glycosides, and amides have been chemically synthesized or naturally isolated as potential antimicrobial agents. To overcome the issue of water insolubility and poor stability, caffeic acid and its derivative have been utilized either in conjugation with other bioactive molecules or in nanoformulation. Besides, caffeic acid and its derivatives have also been applied in combination with antibiotics or photoirradiation to achieve a synergistic mode of action. The present review describes the antimicrobial roles of caffeic acid and its derivatives exploited either in free form or in combination or in nanoformulation to kill a diverse range of microbial pathogens along with their mode of action. The chemistry employed for the synthesis of the caffeic acid derivatives has been discussed in detail as well.

Antioxidant, antimicrobial, and cytotoxic activities of extracts from the seed and pulp of Jujube (Ziziphus jujuba) grown in Iran

The aim of the present study was to investigate the biological activities of the ultrasound-assisted extracts obtained from pulp and seed of jujube (Ziziphus jujuba) fruits. To reach this purpose, total phenolic content (TPC), total flavonoid content (TFC), total pro-anthocyanin, DPPH radical scavenging activity, rancimat test, as well as antimicrobial activity and cytotoxicity test of both jujube pulp and seed extracts were evaluated. Total phenolic content (TPC), total flavonoid content (TFC), and total pro-anthocyanin in pulp extract were higher than those obtained from seed extract. In addition, DPPH radical scavenging activity of pulp extract (IC50 = 53.97 µg/ml) was higher than that of seed extract (IC50 = 88.68 µg/ml). Furthermore, the highest antimicrobial activity was observed against Escherichia coli and Staphylococcus aureus (MIC = 20 mg/ml) for both seed and pulp extracts. In vitro cytotoxicity evaluation on seven cell lines revealed that pulp and seed extracts of jujube had no cytotoxic activity. The present results suggested the promising antioxidant properties of jujube, which can be used in the fabrication of functional bioactive ingredients for different purposes.

Role of Antioxidant Molecules and Polymers in Prevention of Bacterial Growth and Biofilm Formation

Background:

Antioxidants are multifaceted molecules playing a crucial role in several cellular functions. There is by now a well-established knowledge about their involvement in numerous processes associated with aging, including vascular damage, neurodegenerative diseases and cancer. An emerging area of application has been lately identified for these compounds in relation to the recent findings indicating their ability to affect biofilm formation by some microbial pathogens, including Staphylococcus aureus, Streptococcus mutans, and Pseudomonas aeruginosa.

Methods:

A structured search of bibliographic databases for peer-reviewed research literature was performed using a focused review question. The quality of retrieved papers was appraised using standard tools.

Results:

One hundred sixty-five papers extracted from pubmed database and published in the last fifteen years were included in this review focused on the assessment of the antimicrobial and antibiofilm activity of antioxidant compounds, including vitamins, flavonoids, non-flavonoid polyphenols, and antioxidant polymers. Mechanisms of action of some important antioxidant compounds, especially for vitamin C and phenolic acids, were identified.

Conclusion:

The findings of this review confirm the potential benefits of the use of natural antioxidants as antimicrobial/antibiofilm compounds. Generally, gram-positive bacteria were found to be more sensitive to antioxidants than gram-negatives. Antioxidant polymeric systems have also been developed mainly derived from functionalization of polysaccharides with antioxidant molecules. The application of such systems in clinics may permit to overcome some issues related to the systemic delivery of antioxidants, such as poor absorption, loss of bioactivity, and limited half-life. However, investigations focused on the study of antibiofilm activity of antioxidant polymers are still very limited in number and therefore they are strongly encouraged in order to lay the foundations for application of antioxidant polymers in treatment of biofilm-based infections.

Action mode of cranberry anthocyanin on physiological and morphological properties of Staphylococcus aureus and its application in cooked meat

This study researched the action mode of cranberry anthocyanin (CA) against Staphylococcus aureus and the effect of CA on the counts of S. aureus and the quantity of cooked meat during storage. The antibacterial effect was assessed by minimum inhibitory concentration (MIC) and survival populations of S. aureus strains after CA treatments. The changes in intracellular adenosine 5'-triphosphate (ATP) concentration, cell membrane potential, content of bacterial protein and cell morphology were analyzed to reveal possible action mode. Application potentials of CA as antimicrobial agent were assessed during storage of cooked pork and beef. The result showed that the MIC of CA against S. aureus strains was 5 mg/mL. Approximately 8 log CFU/mL of S. aureus strains can be completely inhibited after treatment with 2.0 MIC of CA for 0.5 h. Treatments of CA resulted in lower intracellular ATP and soluble protein levels, damaged membrane structure and leakage of cytoplasmic. Application of CA on cooked pork and beef caused a significant decrease in S. aureus counts and pH values, and color-darkening compared with control samples. These findings demonstrated that CA played an effective antimicrobial against S. aureus and had a potential as natural preservative to inhibit the growth of food pathogens.

Antimicrobial Capacity of Plant Polyphenols against Gram-positive Bacteria: A Comprehensive Review

BACKGROUND

Multi-drug-resistant bacteria such as Methicillin-Resistant Staphylococcus aureus (MRSA) disseminate rapidly amongst patients in healthcare facilities and suppose an increasingly important cause of community-associated infections and associated mortality. The development of effective therapeutic options against resistant bacteria is a public health priority. Plant polyphenols are structurally diverse compounds that have been used for centuries for medicinal purposes, including infections treatment and possess, not only antimicrobial activity, but also antioxidant, anti-inflammatory and anticancer activities among others. Based on the existing evidence on the polyphenols' antibacterial capacity, polyphenols may be postulated as an alternative or complementary therapy for infectious diseases.

OBJECTIVE

To review the antimicrobial activity of plant polyphenols against Gram-positive bacteria, especially against S. aureus and its resistant strains. Determine the main bacterial molecular targets of polyphenols and their potential mechanism of action.

METHODOLOGY

The most relevant reports on plant polyphenols' antibacterial activity and their putative molecular targets were studied. We also performed virtual screening of thousand different polyphenols against proteins involved in the peptidoglycan biosynthesis to find potential valuable bioactive compounds. The bibliographic information used in this review was obtained from MEDLINE via PubMed.

RESULTS

Several polyphenols: phenolic acids, flavonoids (especially flavonols), tannins, lignans, stilbenes and combinations of these in botanical mixtures, have exhibited significant antibacterial activity against resistant and non-resistant Gram-positive bacteria at low μg/mL range MIC values. Their mechanism of action is quite diverse, targeting cell wall, lipid membrane, membrane receptors and ion channels, bacteria metabolites and biofilm formation. Synergic effects were also demonstrated for some combinations of polyphenols and antibiotics.

CONCLUSION

Plant polyphenols mean a promising source of antibacterial agents, either alone or in combination with existing antibiotics, for the development of new antibiotic therapies.

In Vitro Antibacterial and Synergistic Effect of Chitosan-Phytochemical Conjugates Against Antibiotic Resistant Fish Pathogenic Bacteria

Chitosan-phytochemical conjugates exhibited significant antibacterial effect with minimum inhibitory concentration (MIC) ranging from 128 to 2048 µg/ml against antibiotic-resistant fish pathogenic bacteria such as Edwardseilla tarda, Vibrio harveyi and Photobacterium damselaewhich were isolated from Korean cultured fish. Furthermore, the MIC values of old-fashioned antibiotics such as erythromycin and oxytertacycline drastically reduced in combination with chitosan-phytochemical conjugates against the fish pathogenic bacteria. The combination of conjugates with erythromycin and oxytetracycline gave median ∑FIC results ranging from 0.281 to 0.625 and 0.312 to 0.625, respectively. This result indicates the synergistic antibacterial effects and an increased susceptibility against the antibiotics.

Rapid Screening of Natural Plant Extracts with Calcium Diacetate for Differential Effects Against Foodborne Pathogens and a Probiotic Bacterium

This study focused on advancing a rapid turbidimetric bioassay to screen antimicrobials using specific cocktails of targeted foodborne bacterial pathogens. Specifically, to show the relevance of this rapid screening tool, the antimicrobial potential of generally recognized as safe calcium diacetate (DAX) and blends with cranberry (NC) and oregano (OX) natural extracts was evaluated. Furthermore, the same extracts were evaluated against beneficial lactic acid bacteria. The targeted foodborne pathogens evaluated were Escherichia coli O157:H7, Salmonella spp., Listeria monocytogenes, and Staphylococcus aureus using optimized initial cocktails (∼10⁸ colony-forming unit/mL) containing strains isolated from human food outbreaks. Of all extracts evaluated, 0.51% (w/v) DAX in ethanol was the most effective against all four pathogens. However, DAX when reduced to 0.26% and with added blends from ethanol extractions consisting of DAX:OX (3:1), slightly outperformed or was equal to same levels of DAX alone. Subculture of wells in which no growth occurred after 1 week indicated that all water and ethanol extracts were bacteriostatic against the pathogens tested. All the targeted antimicrobials had no effect on the probiotic organism Lactobacillus plantarum. The use of such rapid screening methods combined with the use of multistrain cocktails of targeted foodborne pathogens from outbreaks will allow rapid large-scale screening of antimicrobials and enable further detailed studies in targeted model food systems.

Use of Antimicrobial Food Additives as Potential Dipping Solutions to Control Pseudomonas spp. Contamination in the Frankfurters and Ham

This study evaluated the effect of sodium diacetate and sodium lactate solutions for reducing the cell count of Pseudomonas spp. in frankfurters and hams. A mixture of Pseudomonas aeruginosa (NCCP10338, NCCP10250, and NCCP11229), and Pseudomonas fluorescens (KACC10323 and KACC10326) was inoculated on cooked frankfurters and ham. The inoculated samples were immersed into control (sterile distilled water), sodium diacetate (5 and 10%), sodium lactate (5 and 10%), 5% sodium diacetate + 5% sodium lactate, and 10% sodium diacetate + 10% sodium lactate for 0-10 min. Inoculated frankfurters and ham were also immersed into acidified (pH 3.0) solutions such as acidified sodium diacetate (5 and 10%), and acidified sodium lactate (5 and 10%) in addition to control (acidified distilled water) for 0-10 min. Total aerobic plate counts for Pseudomonas spp. were enumerated on Cetrimide agar. Significant reductions (ca. 2 Log CFU/g) in Pseudomonas spp. cells on frankfurters and ham were observed only for a combination treatment of 10% sodium lactate + 10% sodium diacetate. When the solutions were acidified to pH 3.0, the total reductions of Pseudomonas spp. were 1.5-4.0 Log CFU/g. The order of reduction amounts of Pseudomonas spp. cell counts was 10% sodium lactate > 5% sodium lactate ≥ 10% sodium diacetate > 5% sodium diacetate > control for frankfurters, and 10% sodium lactate > 5% sodium lactate > 10% sodium diacetate > 5% sodium diacetate > control for ham. The results suggest that using acidified food additive antimicrobials, as dipping solutions, should be useful in reducing Pseudomonas spp. on frankfurters and ham.

Caffeic acid loading wound dressing: physicochemical and biological characterization

Aim: Caffeic acid has been described as active against bacteria commonly isolated from wound infections. However, its low stability and poor solubility reduce caffeic acid applicability as a pharmaceutical product. These parameters can be enhanced by complexation with cyclodextrin. The main goal of the present work was to incorporate caffeic acid on cyclodextrin-based hydrogels capable of controlled delivery, in order to be used as antibacterial wound dressing. Materials & methods: Cyclodextrin-based hydrogels were prepared by direct crosslinking of β-cyclodextrin or hydroxypropyl-β-cyclodextrin with 1,4-butanediol diglycidyl ether in the presence of hydroxypropyl methylcellulose. Results: The hydrogels obtained combine good physicochemical properties (viscoelasticity, superabsorbency and high ability to retain and deliver caffeic acid) with the preservation of caffeic acid’ antibacterial activity and effect on fibroblasts, with gel–β-cyclodextrin the most suited. Conclusion: The hydrogels obtained could be useful as caffeic acid delivery-system devices for the treatment of wound infections.

Antibacterial activities of Ligaria cuneifolia and Jodina rhombifolia leaf extracts against phytopathogenic and clinical bacteria

Six plant extracts prepared from Ligaria cuneifolia and Jodina rhombifolia were screened for their potential antimicrobial activities against phytopathogens and clinically standard reference bacterial strains. Bioautography and broth microdilution methods were used to study samples antibacterial activities against 7 bacterial strains. The minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of samples were attained. An antibacterial activity guided isolation and identification of active compounds was carried out for L. cuneifolia methanolic extract (LCME). Both methanolic and aqueous extracts from L. cuneifolia showed inhibitory activities against phytopathogenic bacteria, with MICs ranging from 2.5 to 156 μg mL(-1) for LCME and 5 mg mL(-1) for the aqueous extract. None of the three J. rhombifolia extracts showed significant antibacterial activities against phytopathogenic strains (MIC > 5 mg mL(-1)), except for the aqueous extracts against Pseudomonas syringae (MIC = 312 μg mL(-1)). Only LCME showed bactericidal activities against phytopathogenic strains (MBCs = 78 μg mL(-1)). The LCME exhibited significant inhibitory activity against reference clinical strains: Escherichia coli (MIC = 156 μg mL(-1)) and Staphylococcus aureus (MIC = 78 μg mL(-1), MBC = 312 μg mL(-1)). LCME active compounds were identified as flavonol mono and diglycosides, and gallic acid. The antibacterial activity of purified compounds was also evaluated. A synergistic effect against S. aureus was found between gallic acid and a quercetin glycoside. Hence, anti-phytopathogenic bacteria potential compounds isolated from L. cuneifolia could be used as an effective source against bacterial diseases in plants.

Antibacterial potential of northeastern Portugal wild plant extracts and respective phenolic compounds

The present work aims to assess the antibacterial potential of phenolic extracts, recovered from plants obtained on the North East of Portugal, and of their phenolic compounds (ellagic, caffeic, and gallic acids, quercetin, kaempferol, and rutin), against bacteria commonly found on skin infections. The disk diffusion and the susceptibility assays were used to identify the most active extracts and phenolic compounds. The effect of selected phenolic compounds on animal cells was assessed by determination of cellular metabolic activity. Gallic acid had a higher activity, against gram-positive (S. epidermidis and S. aureus) and gram-negative bacteria (K. pneumoniae) at lower concentrations, than the other compounds. The caffeic acid, also, showed good antibacterial activity against the 3 bacteria used. The gallic acid was effective against the 3 bacteria without causing harm to the animal cells. Gallic and caffeic acid showed a promising applicability as antibacterial agents for the treatment of infected wounds.

Antistaphylococcal and biofilm inhibitory activities of gallic, caffeic, and chlorogenic acids

Staphylococcus aureus is a Gram-positive pathogen which is able to form biofilms, exhibiting a more pronounced resistance to antibiotics and disinfectants. The hurdles posed in eradicating biofilms have driven the search for new compounds able to fight these structures. Phenolic compounds constitute one of the most numerous and ubiquitous group of plant secondary metabolites with many biological activities. The aim of the present work was to study the potential antimicrobial and antibiofilm properties of gallic, caffeic, and chlorogenic acids against S. aureus as well to elucidate its mechanism of action. It was concluded that the phenolic acids studied in this work have antistaphylococcal properties. For instance, gallic acid is able to influence the adhesion properties of S. aureus. The phenolic acids tested were also able to inhibit the production of α-hemolysin by this microorganism, with the exception of chlorogenic acid. Regarding its mechanism of action, caffeic acid interferes with the stability of the cell membrane and with the metabolic activity of the cells of S. aureus.

Phytochemicals in lowbush wild blueberry inactivate Escherichia coli O157:H7 by damaging its cell membrane

The antimicrobial activity and model of action of polyphenolic compounds extracted from lowbush wild blueberries (LWB) were studied against Escherichia coli O157:H7. Polyphenols in LWB were extracted using 80% vol/vol methanol and designated as total blueberry phenolics (TBP). The fraction was further separated by a C-18 Sep-Pak cartridge into monomeric phenolics acids (MPA) and anthocyanins plus proanthocyanidins (A&P). The A&P fraction was further separated into anthocyanins and proanthocyanidins using a LH-20 Sephadex column. Each fraction was diluted in 0.85% wt/vol NaCl, inoculated with E. coli O157:H7 to achieve 8 log colony-forming units (CFU)/mL, and incubated at 25 °C for 1 h. The survival populations of E. coli O157:H7 in the phenolic fractions were determined by a viable cell counts method. The permeability of the cell membrane of E. coli O157:H7 was determined using LIVE/DEAD viability assay, and the damage was visualized by using transmission electron microscopy (TEM). Significant (p<0.05) reductions of 5 log CFU/mL of E. coli O157:H7 were observed for MPA at 0.4 g/L gallic acid equivalents (GAE), A&P at 0.9 g/L GAE, and anthocyanins at 0.65 g/L GAE. Reductions of 6-7 CFU/mL were observed for MPA at 0.8 g/L GAE, A&P at 1.8 g/L GAE, and anthocyanins at 1.3 g/L GAE compared to the control. The cell membrane of E. coli O157:H7 exhibited a significantly increased permeability when treated with proanthocyanidins (0.15 g/L GAE), A&P (0.45 g/L GAE), anthocyanins (0.65 g/L GAE), and TBP (0.14 g/L GAE). TEM confirmed the inactivation and increased membrane permeability of E. coli O157:H7. This study demonstrated the antimicrobial effect of polyphenols from LWB against E. coli O157:H7 and the probable mode of action.

The antimicrobial effects of cranberry against Staphylococcus aureus

The antimicrobial effects of the American cranberry ( Vaccinium macrocarpon) on a major food-borne pathogen, Staphylococcus aureus, were investigated using commercially obtained Lakewood® organic cranberry juice and Ocean Spray® cranberry juice cocktail and four other berry fruit extracts (acai berry, strawberry, raspberry, and blueberry). The results showed that cranberry is a potent antimicrobial against S. aureus and the most potent among the berries studied. The order of percentage inhibition of bacterial growth at the same concentration of phenolic materials as gallic acid equivalents was Lakewood cranberry juice > Ocean Spray cranberry juice ≫ blueberry > acai berry ≫ raspberry ≫ strawberry. The antimicrobial effect was not due to the acidity of the berries as NaOH-neutralized samples were almost as effective in terms of percentage inhibition of viable cell growth. Solid-phase extraction of cranberry juice using C18 solid phase showed that the antimicrobial effects reside exclusively with the C18-bound materials.

Inhibitory potential of tea polyphenolics and influence of extraction time against Helicobacter pylori and lack of inhibition of beneficial lactic acid bacteria

Tea polyphenolics such as catechins are known to have the potential to inhibit many bacterial pathogens. Helicobacter pylori has been identified as an etiologic agent in the development of gastric ulcer, peptic ulcer, gastritis, and many other stomach-related diseases. In this study, we investigated the effect of 9 tea extracts--3 different brands representing 4 different processed types (white, green, oolong, and black)--on the inhibition of H. pylori. Extraction times of 2 and 5 minutes were compared. Most 5-minute extracts showed H. pylori inhibition, whereas 2-minute extracts only of Choice darjeeling black and Tazo white showed inhibition. No recovery was observed after the addition of 0.5 and 5 mM proline, indicating that tea polyphenols do not inhibit H. pylori by inhibition of proline oxidation via proline dehydrogenase. Extracts that showed inhibition were further evaluated for their effect on beneficial lactic acid bacteria. None of the samples showed inhibition, suggesting that tea might be able to inhibit H. pylori without affecting the beneficial lactic acid bacteria. High-performance liquid chromatography indicated the presence of gallic acid, quercetin, caffeine, and tea catechins (including catechin, epicatechin, and epigallocatechin) in all the tea samples. Our study indicates that tea can be potentially used as a low-cost dietary support to combat H. pylori-linked gastric diseases without affecting the beneficial intestinal bacteria.

Lycopersicon esculentum seeds: an industrial byproduct as an antimicrobial agent

Lycopersicon esculentum (tomato) fruit is a widely studied matrix. However, only few works focus their attention on its seeds, which constitute a major byproduct of the tomato processing industry. In this study the antimicrobial potential of ten different tomato seed extracts from "Bull's heart" and "Cherry" varieties were analyzed against Gram-positive (Staphylococcus aureus, Staphylococcus epidermidis, Micrococcus luteus, Enterococcus faecalis and Bacillus cereus) and Gram-negative (Proteus mirabilis, Escherichia coli, Pseudomonas aeruginosa and Salmonella typhimurium) bacteria and fungi (Candida albicans, Aspergillus fumigatus and Trichophyton rubrum). Regarding antibacterial capacity, the different extracts were revealed to be active only against Gram-positive bacteria, E. faecalis being the most susceptible one (MIC: 2.5-10 mg/mL). Concerning antifungal activity, "Bull's heart" extracts were the most active. In a general way C. albicans was the most susceptible species (MIC: 5-10 mg/mL). The chemical composition of the extracts was also pursued, concerning organic acids, phenolics and fatty acids, in order to establish a possible relationship with the observed antimicrobial effect.