Plant extracts for the control of bacterial growth: efficacy, stability and safety issues for food application

Plant antimicrobial polyphenols as potential natural food preservatives

BACKGROUND

The growing demand for natural food preservatives in the last decade has promoted investigations on their application for preserving perishable foods. In this context, the present review is focused on discussing the prospective application of plant extracts containing phenolics or isolated plant phenolics as natural antimicrobials in foods. Plant essential oils are outside the scope of this review since utilization of their antimicrobial activity for food preservation has been extensively reviewed.

RESULTS

Although the exact antimicrobial mechanisms of action of phenolic compounds are not yet fully understood, it is commonly acknowledged that they have diverse sites of action at the cellular level. Antimicrobial phenolics can be added directly to the formulation of perishable food products or incorporated into food-contact materials to release them in the immediate zone of perishable foods. Edible coatings or active food packaging materials can thus be used as carriers of plant bioactive compounds.

CONCLUSION

These materials could be an interesting delivery system to improve the stability of phenolics in foods and to improve the shelf life of perishable foods. This review will thus provide an overview of current knowledge of the antimicrobial activity of phenolic-rich plant extracts and of the promises and limits of their exploitation for the preservation of perishable foods. © 2018 Society of Chemical Industry.

Antibacterial Activity study of Musizin isolated from Rhamnus wightii Wight and Arn

The crude extracts and the compounds isolated from traditional medicinal plants are used to treat infectious diseases caused by bacteria, fungi, and viruses. An attempt has been made in the present investigation to evaluate the antibacterial activity of musizin isolated from Rhamnus wightii, (Family: Rhamnaceae) against Gram-positive (Bacillus cereus, Staphylococcus aureus, Streptococcus faecalis), and Gramnegative (Escherichia coli, Klebsiella pneumonia, and Pseudomonas aeruginosa) bacteria. The tested compound showed more pronounced antibacterial activity against the tested pathogens than the standard antibiotics like streptomycin and gentamycin with the lowest minimum inhibitory concentration (MIC). Molecular docking analysis was performed to study the effectiveness of musizin compared to the standard antibiotics; it showed a significant interaction with the target proteins such asalgR (P. arginosa), divIVA (E. faecalis), icaA (S. aureus), plcR(B. cereus), treC (K. pneumonia) and ftsl (E. coli) and found that musizin showed higher potential with least binding energy. It has also been found that musizin had better ADMET properties than the standard drugs. Thus,musizin acts as an inhibitor of bacterial growth for consideration as a drug to treat bacterial infections.

Artemisia campestris L.: review on taxonomical aspects, cytogeography, biological activities and bioactive compounds

Artemisia campestris L. (Asteraceae) is a polymorphic species that consists of many subspecies and varieties. It is known for its medicinal, pharmacological, and culinary properties. This review is undertaken with the aim to highlight some aspects of this plant, specifically the taxonomy, the cytogeography, the phytochemistry with an emphasis on the structure-activity relationship (SAR) of the main bioactive compounds of A. campestris L. in addition to its biological properties and the food control properties. The bibliographic data compiled in this review allowed the revision of 146 papers, by using different databases and scientific engines, such as Scopus, ScienceDirect, Pubmed, and google scholar. The taxonomic analysis has embedded A. campestris L. in the tribe Anthemideae, and the genus Artemisia L. Also many subtaxa have been identified, and a subspecific classification of this species has been established on the basis of its botanical characters. The cytogenetic findings evidenced that A.campestris L. is prevailed by the chromosome number x = 9, with a polyploidization degree ranging from diploidy to hexaploidy according to the geographical distribution of the plant populations, while the genome size seems to be proportional to the ploidy level, suggesting an adaptive trait of the cytotypes to new environments. This plant is rich in polyphenols, flavonoids, and terpenic compounds, which substantiate the bioactivities attributed to its extracts and essential oil. Hence, the SAR of the main bioactive compounds of A. campestris L., mainly the prominent flavonoids, phenolic acids, and terpenes revealed a tight link between specific chemical entities of the bioactive compound and the respective biological activity. Many biological activities were approached in this review, mainly the antioxidant, antivenom, antidiabetic, antihyperlipidemic, anti-inflammatory, antihypertensive, anti-leishmaniasis, antinociceptive, wound healing, and analgesic activities in addition to the hepatoprotective, nephroprotective, neuroprotective, and gastroprotective actions. Finally, the food preservative ability of the extracts and essential oil obtained from A.campestris L. have been fully discussed. The present review contributes to the literature, by bringing more clarifications about the different aspects of A.campestris L., like taxonomy, cytogeography and biological interests of this species. The SAR approach of some constituents that occur in A.campestris L., gives a solid support that can be used to explore the bioactivity of components isolated from this species, while the preservative properties of this plant can be usefully exploited for the agrifood sector.

Pomegranate extract specifically inhibits Clostridium difficile growth and toxin production without disturbing the beneficial bacteria in vitro

Objective

The aim of this study was to assess the pomegranate juice against the growth and toxin production of multidrug-resistant Clostridium difficile hypervirulent strain NAP1/027/BI and also against the growth of beneficial bacteria to prevent or suppress C. difficile infection (CDI).

Materials and methods

Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were taken as parameters for the assessment of antimicrobial property of the pomegranate juice. Four different C. difficile hypervirulent strains NAP1/027/BI, Lactococcus lactis spp., Lactobacillus casei, and Bifidobacterium animalis were subjected to the broth dilution method to determine the MIC and MBC. Enzyme-linked immunosorbent assay (ELISA) was performed to determine clostridial toxin B (TcdB) production in the presence of pomegranate juice.

Results

The MIC and MBC of pomegranate juice containing punicalagin were found to be 390 µg/mL for all C. difficile hypervirulent strain NAP1/027/BI, and the growth of L. lactis spp., L. casei, and B. animalis was not inhibited. Pomegranate juice reduced TcdB production in C. difficile hypervirulent strain NAP1/027/BI.

Conclusion

This study highlights the potential of pomegranate juice to reduce CDI without affecting the beneficial bacteria. Pomegranate juice may be a useful antimicrobial agent to prevent or suppress CDI, avoiding the use of antibiotics.

Comparison of Single and Combined Use of Catechin, Protocatechuic, and Vanillic Acids as Antioxidant and Antibacterial Agents against Uropathogenic Escherichia Coli at Planktonic and Biofilm Levels

The objective of this study was to evaluate the effect of combining catechin, protocatechuic, and vanillic acids against planktonic growing, adhesion, and biofilm eradication of uropathogenic Escherichia coli (UPEC), as well as antioxidant agents. The minimum inhibitory concentrations (MIC) of protocatechuic, vanillic acids and catechin against the growth of planktonic bacteria were 12.98, 11.80, and 13.78 mM, respectively. Mixing 1.62 mM protocatechuic acid + 0.74 mM vanillic acid + 0.05 mM catechin resulted in a synergistic effect acting as an MIC. Similarly, the minimum concentrations of phenolic compounds to prevent UPEC adhesion and biofilm formation (MBIC) were 11.03 and 7.13 mM of protocatechuic and vanillic acids, respectively, whereas no MBIC of catechin was found. However, combinations of 1.62 mM protocatechuic acid + 0.74 mM vanillic acid + 0.05 mM catechin showed a synergistic effect acting as MBIC. On the other hand, the minimum concentrations to eradicate biofilms (MBEC) were 25.95 and 23.78 mM, respectively. The combination of 3.20 mM protocatechuic acid, 2.97 mM vanillic acid, and 1.72 mM catechin eradicated pre-formed biofilms. The antioxidant capacity of the combination of phenolics was higher than the expected theoretical values, indicating synergism by the DPPH^•, ABTS, and FRAP assays. Effective concentrations of catechin, protocatechuic, and vanillic acids were reduced from 8 to 1378 times when combined. In contrast, the antibiotic nitrofurantoin was not effective in eradicating biofilms from silicone surfaces. In conclusion, the mixture of phenolic compounds was more effective in preventing cell adhesion and eradicating pre-formed biofilms of uropathogenic E. coli than single compounds and nitrofurantoin, and showed antioxidant synergy.

The influence of the essential oil extracted from hops on monolayers and bilayers imitating plant pathogen bacteria membranes

Many plant-derived compounds possess antimicrobial, antioxidant and even anticancer activities. Therefore, they are considered as substances that can be used instead of synthetic compounds in various applications. In this work, the essential oil from hop cones was extracted and analyzed, and then its effects on model bacteria membranes were studied to verify whether the hop essential oils could be used as ecological pesticides. The experiments involved surface pressure-area measurements, penetration studies and Brewster angle microscopy (BAM) imaging of lipid monolayers as well as hydrodynamic diameter, zeta potential, steady-state fluorescence anisotropy and Cryo-Transmission Electron Microscopy (cryo-TEM) measurements of liposomes. Finally the bactericidal tests on plant pathogen bacteria Pseudomonas syringae pv. lachrymans PCM 1410 were performed. The obtained results showed that the components of the essential oils from hop cones incorporate into lipid monolayers and bilayers and alter their fluidity. However, the observed effect is determined by the system composition, its condensation and the oil concentration. Interestingly, at a given dose, the effect of the essential oil on membranes was found to stabilize. Moreover, BAM images proved that hop oil prevents the formation of a large fraction of a condensed phase at the interface. Both the studies on model membranes as well as the in vitro tests allow one to conclude that the hop essential oil could likely be considered as the candidate to be used in agriculture as a natural pesticide.

Predicting heat process efficiency in thermal processes when bacterial inactivation is not log-linear

The food industry widely uses the F-value which considers microbial log-linear inactivation, while microbial heat inactivation may result in a non-log-linear inactivation pattern due to genetic or phenotypical heterogeneity. This may yield discrepancies in predicting microbial heat inactivation under dynamic conditions of heat treatment. In this paper, we suggest the calculation of the equivalent time of heat treatment at a given temperature to overcome these constraints. To validate our proposal, the heat inactivation of Bacillus pumilus, showing non-log-linear behavior, was predicted for 4 different heat inactivation profiles and bacterial enumeration was performed to determine whether prediction errors were acceptable. When the proportion of residuals in an acceptable zone from 1 log (fail safe) to 0.5 log (fail dangerous) was greater or equal to 70%, the model was considered as acceptable for predictions of the tested data. The new approach gave four different temperature profiles, with 96, 85, 85 and 100% of the residuals in the acceptable zone, indicating satisfactory prediction. Thus the proposed practical alternative to simulate microbial heat inactivation kinetics is able to extend the F-value to non-log-linear inactivation patterns.

Time-Kill Kinetics of Lipid Fractions Isolated from Condiments against Foodborne Pathogens

Lipid fractions that are extracted from condiments have a wide array of biological potential and are commonly utilized for medicinal and culinary applications. This investigation aims at determining the antimicrobial potential of lipid fractions isolated using two different solvent systems against five foodborne pathogens. The antibacterial efficacy was tested after 0, 1, 2, 3 and 24 h of incubation with the active agent. The leakage of cellular content was assessed at 1 and 2 h of incubation. Scanning electron microscope (SEM) images were obtained after 18 h of contact time with lipid fractions at their minimum inhibitory concentration (MIC). From the results obtained from time-kill and cell constituents release tests, it could be concluded that during 3 and 1 h of incubation, the lipid fractions were more potent against Gram-negative isolates (Escherichia coli ATCC 8739). However, prolonged incubation with the active agent inhibited Gram-positive isolate, i.e. Listeria monocytogenes ATCC 13932. SEM images of treated microorganisms also confirmed the inhibitory action of selected lipid fractions against all the tested pathogens. The cellular morphology of the bacteria was completely altered after 18 h of incubation with the lipid fractions. The results of the present study corroborate significant inhibitory effects and disruption in bacterial cell integrity following prolonged incubation with these lipid fractions. The results also affirm the use of the tested lipid fractions in food systems.

Plants of Genus Mentha: From Farm to Food Factory

Genus Mentha, a member of Lamiaceae family, encompasses a series of species used on an industrial scale and with a well-described and developed culture process. Extracts of this genus are traditionally used as foods and are highly valued due to the presence of significant amounts of antioxidant phenolic compounds. Many essential oil chemotypes show distinct aromatic flavor conferred by different terpene proportions. Mint extracts and their derived essential oils exert notable effects against a broad spectrum of bacteria, fungi or yeasts, tested both in vitro or in various food matrices. Their chemical compositions are well-known, which suggest and even prompt their safe use. In this review, genus Mentha plant cultivation, phytochemical analysis and even antimicrobial activity are carefully described. Also, in consideration of its natural origin, antioxidant and antimicrobial properties, a special emphasis was given to mint-derived products as an interesting alternative to artificial preservatives towards establishing a wide range of applications for shelf-life extension of food ingredients and even foodstuffs. Mentha cultivation techniques markedly influence its phytochemical composition. Both extracts and essential oils display a broad spectrum of activity, closely related to its phytochemical composition. Therefore, industrial implementation of genus Mentha depends on its efficacy, safety and neutral taste.

Mechanisms of Nα-lauroyl arginate ethyl ester against Penicillium digitatum and Pectobacterium carotovorum subsp. carotovorum

The purpose of this study was to investigate the antimicrobial activity and mechanisms of Nα-lauroyl arginate ethyl ester (LAE) against Penicillium digitatum and Pectobacterium carotovorum subsp. carotovorum. The minim inhibitory concentrations of LAE against P. digitatum and P. carotovorum were found to be 400 and 25 μg/ml, respectively. Loss of intracellular protein and nucleic acid increased significantly, and membrane permeability reached 76.28, 54.29 and 85.20%, respectively, when 400 μg/ml of LAE was applied to the hyphae and spores of P. digitatum and to P. carotovorum. Flow cytometry showed that LAE reduced the membrane potential, and the depolarization ratios of P. digitatum and P. carotovorum were 98.19 and 97.25% (P < 0.05), respectively. Transmission electron microscopy photos revealed that LAE caused a rough surface, irregular cellular organelles, protoplast shrinkage, intracytoplasmic coagulation and empty cavities in all three cell types. These results showed that LAE had notable ability to damage the structure of fungal and bacterial cells, making it a possible alternative chemical for use in the preservation of fruits and vegetables.

Using Sensory Evaluation to Determine the Highest Acceptable Concentration of Mango Seed Extract as Antibacterial and Antioxidant Agent in Fresh-Cut Mango

Plant extracts have the potential to be used as food additives; however, their use have been limited by causing undesirable changes in the sensory attributes of foods. We characterized the mango seed extract as a preserving agent for fresh-cut mangoes. We established the maximum concentration of extract that, while increasing the antioxidant activity, and limiting microbial contamination of the fruit, did not negatively affect fruit sensory acceptability. The extract contained 277.4 g gallic acid equivalent (GAE)/kg dw (dry weight) of polyphenols and 143.7 g quercetin equivalent (QE)/kg dw of flavonoids. Antioxidant capacity values were 2034.1 and 4205.7 μmol Trolox equivalent (TE)/g against 2,2-diphenyl-1-picryl-hydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radicals, respectively. Chromatographic analysis revealed the presence of gallic and chlorogenic acids. The extract (16 g/L) inhibited the growth of Escherichia coli, Salmonella Typhimurium, Staphylococcus aureus and Listeria monocytogenes. The highest concentration with sensory acceptability was 6.25 g/L. At such concentration, the extract preserved fresh-cut fruits, increasing polyphenols (0.427 g GAE/kg fw (fresh weight)), flavonoid content (0.234 g QE/kg fw) and antioxidant activity (DPPH = 2.814 and ABTS = 0.551 mol TE/kg fw). It also reduced inoculated bacteria (range: 5.50 × 10³ to 1.44 × 10⁵ colony forming units (CFU)/g). These results showed the importance of considering consumer acceptability to determine the effective concentration of plant extracts as additives.

Use of Tunisian flavored olive oil as anisakicidal agent in industrial anchovy marinating process

BACKGROUND

Natural compounds are more frequently used against Anisakis, responsible for the important fish-borne disease anisakidosis. The aim of the study was to evaluate the effectiveness of enriched Tunisian olive oil with different spices (cumin, turmeric, clove, thyme, and lemon) against Anisakis larvae type 1.

RESULTS

In vitro experiment: larvae were submerged separately in the aforementioned oils and then examined to check viability. For each oil, LT50 and LT100 were calculated. Turmeric and cumin oils are the most effective against the parasites; followed by lemon, thyme and clove oils. For the in vivo experiment, turmeric and cumin oils were tested in anchovy fillets previously artificially parasitized with L3 larvae. Cumin was the most effective against parasites (dead after 5 days) compared with turmeric (8 days). For the two oils, the resulting odor was pleasant, as was the taste, while changes in color were much more evident in turmeric fillets.

CONCLUSION

All the flavored oils demonstrated a good nematodical action against Anisakis. Cumin oil was the most effective against encysted larvae. Turmeric oil showed the best activity in the in vitro experiment. The use of flavored oils in the marinating process could represent an efficient strategy to devitalize Anisakis. © 2017 Society of Chemical Industry.

Extraction of bioactive compounds and essential oils from mediterranean herbs by conventional and green innovative techniques: A review

Market interest in aromatic plants from the Mediterranean is continuously growing mainly due to their medicinal and bioactive compounds (BACs) with other valuable constituents from essential oils (EOs). From ancient times, these plants have been important condiments for traditional Mediterranean cuisine and remedies in folk medicine. Nowadays, they are considered as important factors for food quality and safety, due to prevention of various deteriorative factors like oxidations and microbial spoilage. EOs have different therapeutic benefits (e.g. antioxidant, anti-inflammatory, antimicrobial, and antifungal), while BACs mostly affect nutritive, chemical, microbiological, and sensory quality of foods. Currently, many plant extracts are used for functional (healthy) foods, which additionally fuels consumer and industrial interest in sustainable and non-toxic routes for their production. EO yields from dried plants are below 5%. Their extraction is strongly dependent on the hydrophobic or lipophilic character of target molecules, hence the common use of organic solvents. Similarly, BACs encompass a wide range of substances with varying structures as reflected by their different physical/chemical qualities. Thus, there is a need to identify optimal non-toxic extraction method(s) for isolation/separation of EO/BCs from plants. Various innovative non-thermal extractions (e.g. ultrasound-, high-pressure-, pulsed electric fields assisted extraction, etc.) have been proposed to overcome the above mentioned limitations. These techniques are "green" in concept, as they are shorter, avoid toxic chemicals, and are able to improve extract yields and quality with reduced consumption of energy and solvents. This research provides an overview of such extractions of both BAC and EOs from Mediterranean herbs, sustained by innovative and non-conventional energy sources.

Chemical Composition, Characteristics Profiles and Bioactivities of Tunisian Phalaris canariensis Seeds: a Potential Source of ω-6 and ω-9 Fatty Acids

Seeds oils of Phalaris canariensis extracted by ultrasonication and cold maceration were evaluated for their physical characteristics, total phenol contents, fatty acid and sterol compositions as well as for their antioxidant, antibacterial and acetylcholinesterase activities. The physicochemical properties of ultrasonication and cold maceration oils respectively were: acid values (4.00 and 3.25) mg KOH/g, peroxide values (5.53 and 4.41) meq O2 Kg^-1, iodine values (88.83 and 95.17) g/100 g of oil, saponification values (119.21 and 98.17) mg KOH/g, phenolic content (36.40 and 53.00) mg GAE/g extract, chlorophylls (0.52 and 0.60) mg/kg oil and carotenoids contents (1.92 and 1.88) mg/kg oil. Gas chromatography analysis revealed that linoleic (52.03 and 52.2%), oleic (31.75 and 31.84%) and palmitic (11.09 and 11.34 %) acids were the major fatty acids in the two oils. Specific extinctions at 232 nm (K₂₃₂) and 270 nm (K₂₇₀) were (0.58 and 0.44) and (0.42 and 0.33), respectively. The DSC melting curve showed that their melting points and melting enthalpies were (-28.05°C and 76.8 J/g) and (-27.47°C and 62.3 J/g), respectively. On the other hand, the evaluation of their DPPH radical scavenging, total antioxidant capacity, antibacterial and acetylcholinesterase activities showed interesting results. Thus, Phalaris canariensis seeds oils could deserve further consideration and investigation as a potentially new multi-purpose product for agro-food, medicinal and cosmetic uses.

Time-Kill Kinetics of Lipid Fractions Isolated from Condiments against Foodborne Pathogens

Lipid fractions that are extracted from condiments have a wide array of biological potential and are commonly utilized for medicinal and culinary applications. This investigation aims at determining the antimicrobial potential of lipid fractions isolated using two different solvent systems against five foodborne pathogens. The antibacterial efficacy was tested after 0, 1, 2, 3 and 24 h of incubation with the active agent. The leakage of cellular content was assessed at 1 and 2 h of incubation. Scanning electron microscope (SEM) images were obtained after 18 h of contact time with lipid fractions at their minimum inhibitory concentration (MIC). From the results obtained from time-kill and cell constituents release tests, it could be concluded that during 3 and 1 h of incubation, the lipid fractions were more potent against Gram-negative isolates (Escherichia coli ATCC 8739). However, prolonged incubation with the active agent inhibited Gram-positive isolate, i.e. Listeria monocytogenes ATCC 13932. SEM images of treated microorganisms also confirmed the inhibitory action of selected lipid fractions against all the tested pathogens. The cellular morphology of the bacteria was completely altered after 18 h of incubation with the lipid fractions. The results of the present study corroborate significant inhibitory effects and disruption in bacterial cell integrity following prolonged incubation with these lipid fractions. The results also affirm the use of the tested lipid fractions in food systems.

Shelf-life enhancement of whole rainbow trout (Oncorhynchus mykiss) treated with Reshgak ice coverage

The effect of ice coverage comprised of Reshgak extract and Reshgak essential oil on shelf-life extension of chilled whole rainbow trout (Oncorhynchus mykiss) was evaluated. Chemical (peroxide value (PV), thiobarbituric acids (TBA), total volatile nitrogen base (TVB-N), and free fatty acids (FFA)), microbiological (total viable count (TVC) and psychrotrophic viable count (PVC)), and sensory evaluations (texture, color, flavor, and general acceptance) were investigated every 4 days during a 20-day storage period. Results revealed that the effect of both icing systems led to considerably lower bacterial counts and chemical indices in comparison with the traditional ice coverage without such phytogenic. According to sensory analyses, fish stored in ice containing Reshgak essential oil had a longer shelf-life (>16 days) and those stored in ice medium included with Reshgak extract possessed a shelf-life of 16 days, whereas lot stored in traditional ice showed a shorter shelf-life of 12 days.

Lipids, pH, and Their Interaction Affect the Inhibitory Effects of Carvacrol against Salmonella Typhimurium PT4 and Escherichia coli O157:H7

Although carvacrol (CAR) is considered an alternative antimicrobial for use in food, few is known about the influence of food-related parameters on its inhibitory effects against pathogens. This study assessed the influence of different amounts of proteins, using beef extract (BE) as a protein-rich source, lipids (LIP), using sunflower oil as a LIP-rich source, and pH values or their interaction on the inhibitory effects of CAR against Salmonella Typhimurium PT4 (ST) and Escherichia coli O157:H7 (EC). The specific maximum growth rate (μmax) and lag phase duration (λ) of the test pathogens when exposed to CAR in media with different amounts of BE (4, 6, and 8 g/100 mL), LIP (3.75, 5, and 6.25 mL/100 mL), and pH values (5, 5.5, and 6) were determined. The viable counts of the tested pathogens in media that promoted the highest and lowest μmax in the presence of CAR were monitored during 24 h. The lowest μmax of ST and EC exposed to 2.4 μL/mL (-1.29 and -0.82 log CFU/mL/h, respectively) or 4.8 μL/mL CAR (-1.44 and -2.17 log CFU/mL/h, respectively) were observed in media with the highest LIP amount (6.25 mL/100 mL) and pH value (pH 6). For both SE and EC, the longest λ (> 2 h) was verified in media where these pathogens showed the lowest μmax. These data indicate that the concomitant increase in LIP amounts and pH values affected positively the CAR inhibitory effects against the target pathogens. CAR (2.4 or 4.8 μL/mL) failed to inhibit the increase in ST and EC counts in media where the highest μmax values were previously observed. On the contrary, CAR inhibited the increase of ST counts (final counts 5 log CFU/mL) and decreased the EC counts (final counts 3.5 log CFU/mL) in media where the lowest μmax values were observed. These results show that the inhibitory effects of CAR on ST and EC in food matrices could be affected as a function of the interaction of LIP amounts and pH values.

Effect of pH and Mexican Oregano (Lippia berlandieri Schauer) Essential Oil Added to Carboxymethyl Cellulose and Starch Edible Films on Listeria monocytogenes and Staphylococcus aureus

The aim of this work was to evaluate the effect of pH and Mexican oregano essential oil (MOEO) added to carboxymethyl cellulose (CMC) and starch (S) edible films on Listeria monocytogenes and Staphylococcus aureus. CMC and S edible films were formulated with different concentrations (0%, 0.25%, 0.50%, 0.75%, and 1%) of MOEO at different pH (5, 6, or 7). Antimicrobial assay was performed. Inhibition curves were fitted to the Fermi model. Significant differences (p<0.05) were found in tc (time to reduce 50% of microbial population) and a (slope of the curve around tc), being lower at acidic pH. For L. monocytogenes, CMC films exhibited a higher antimicrobial effectiveness (0.50% of MOEO) compared to S films which need a higher concentration of MOEO (0.75%). S. aureus was inhibited with CMC films at 0.50% MOEO and pH 5 and 6. Microbial modeling has allowed estimating key intrinsic factors as pH and MOEO concentration with the synergistic effect against two important food-borne pathogens.

Antimicrobial efficacy of Syzygium antisepticum plant extract against Staphylococcus aureus and methicillin-resistant S. aureus and its application potential with cooked chicken

For the past decades, there has been a growing demand for natural antimicrobials in the food industry. Plant extracts have attracted strong research interests due to their wide-spectrum antimicrobial activities, but only a limited number have been investigated thoroughly. The present study aimed at identifying a novel anti-staphylococcal plant extract, to validate its activity in a food model, and to investigate on its composition and antimicrobial mechanism. Four plant extracts were evaluated against Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) in vitro, with Syzygium antisepticum leaf extract showing the strongest antimicrobial activity (MIC = 0.125 mg/mL). Relatively high total phenolic content (276.3 mg GAE/g extract) and antioxidant activities (90.2-138.0 mg TE/g extract) were measured in S. antisepticum extract. Food validation study revealed that higher extract concentration (32 mg/mL) was able to inhibit or reduce staphylococcal growth in cooked chicken, but caused color change on meat surface. By GC-MS, β-caryophyllene (12.76 area%) was identified as the dominant volatile compound in extract. Both crude extract and pure β-caryophyllene induced membrane damages in S. aureus. These results suggested good anti-staphylococcal properties of S. antisepticum plant extract, identified its major volatile composition and its membrane-damaging antimicrobial mechanism.

An overview of natural antimicrobials role in food

The present paper aims to review the natural food preservatives with antimicrobial properties emphasizing their importance for the future of food manufacturing and consumers' health. The extraction procedures applied to natural antimicrobials will be considered, followed by the description of some natural preservatives' antimicrobial mechanism of action, including (i) membrane rupture with ATP-ase activity inhibition, (ii) leakage of essential biomolecules from the cell, (iii) disruption of the proton motive force and (iiii) enzyme inactivation. Moreover, a provenance-based classification of natural antimicrobials is discussed by considering the sources of origin for the major natural preservative categories: plants, animals, microbes and fungi. As well, the structure influence on the antimicrobial potential is considered. Natural preservatives could also constitute a viable alternative to address the critical problem of microbial resistance, and to hamper the negative side effects of some synthetic compounds, while meeting the requirements for food safety, and exerting no negative impact on nutritional and sensory attributes of foodstuffs.

Antibacterial activity and stability of microencapsulated lemon grass essential oil in feeds for broiler chickens

SUMMARY The antibacterial effect of microencapsulated lemon grass (Cymbopogon citratus) essential oil on strains of Escherichia coli (ATCC8739), Staphylococcus aureus (ATCC 6538) and Salmonella enterica subsp. enterica (ATCC 6017), and the stability of this oil in feeds for broiler chickens were evaluated. The Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) were determined by the macrodilution method, using the microencapsulated lemon grass essential oil at concentrations of 160 μL mL−1, 80 μL mL−1, 40 μL mL−1, 20 μL mL−1, and 10 μL mL−1. The oil concentration of 80 μL mL−1 presented the best results against the three bacteria evaluated. Samples of 200 g of feed mixed with 120 μL g−1 of the microencapsulated lemon grass essential oil was stored to evaluate the oil stability. Feed without microencapsulated lemon grass essential oil was prepared as control. The oil remained active for seven days, with significant reduction of S. aureus (3.08 CFU), E. coli (3.01 CFU), and S. enterica (3.10 CFU). The microencapsulated lemon grass essential oil at concentration of 80 μL mL−1 had antibacterial effect against the E. coli, S. enterica and S. aureus, and maintained stability of the feed for seven days, even with presence of organic matter, which is source of nutrients for pathogens.

Phytosterols on growth performance, antioxidant enzymes and intestinal morphology in weaned piglets

BACKGROUND

Plant extracts have been used widely to improve growth, lower cholesterol, and exert antioxidative defense and antimicrobial activities in animal production. The present study aimed to investigate the effects of dietary phytosterols (PS) on growth performance, antioxidant enzymes and intestinal morphology in weaned piglets.

RESULTS

A total of 120 crossbred piglets, weighing 9.58 ± 0.26 kg, were randomly allocated to three treatments: control, PS (0.2 g kg^-1 ) and polymyxin E (0.04 g kg^-1 , antibiotic control). Compared to the control, PS or polymyxin E supplementation decreased diarrhea rate, serum cholesterol and malondialdehyde (MDA) of the piglets (P < 0.05). Liver MDA was significantly decreased in PS-fed piglets compared to the control (P < 0.05), although there was no difference between the control and polymyxin E-fed piglets. PS increased the villous height/crypt depth ratio of the duodenum and jejunum compared to the control (P < 0.05). Polymyxin E supplementation in piglets did not alter the villous height/crypt depth ratio but raised the villous height and crypt depth of the duodenum compared to the control (P < 0.05).

CONCLUSION

The results of the present study indicated that PS could decrease diarrhea rate, lower serum cholesterol, reduce lipid peroxidation and ameliorate intestinal morphology in weaned piglets. In addition, PS exerted better amelioration on intestinal morphology than polymyxin E in piglets. © 2017 Society of Chemical Industry.

Antibacterial and antifungal activities of the polyphenolic fractions isolated from the seed coat of Abrus precatorius and Caesalpinia crista

Crude seed coat extracts from Abrus precatorius and Caesalpinia crista were purified into four different fractions namely phenolic acids, flavonols, flavanols and anthocyanin which were then examined for their polyphenol contents and antimicrobial potentials. The fractions derived from seed coat of A. precatorius were found more potent with high phenolic and flavonoid contents as compared to C. crista fractions. The significant antibacterial activity was observed against all strain tested by the fractions of both samples apart from anthocyanin fraction. It was interesting to note that the phenolic acid fractions of both samples was found more active against gram-negative bacteria, while gram-positive bacteria were found to be more sensitive towards flavonol fractions. The phenolic acid and flavonol fractions being potent antibacterial were selected to demonstrate the antifungal capacity of two samples. Among them, phenolic acid fraction of both samples was found active towards all the fungal strain.

Phytosterols improve immunity and exert anti-inflammatory activity in weaned piglets

BACKGROUND

Phytosterols (PS), plant-derived natural steroid compounds, are novel feed additives to regulate immune function and promote pig growth. This study was conducted to determine the effects of PS on the immune response of weaned piglets.

RESULTS

One hundred and twenty crossbred (Duroc × Landrace × Yorkshire) piglets with an average initial weight of 9.58 ± 0.26 kg were randomly allotted to three treatments. Treatments consisted of a control, PS (0.2 g kg^-1 ) and polymyxin E (0.04 g kg^-1 , antibiotic control) treatment. The results showed that PS or polymyxin E supplementation remarkably decreased diarrhea rate and elevated CD3⁺ CD4⁺ /CD3⁺ CD8⁺ ratio in piglets compared with the control (P < 0.05). PS increased basophil and serum interleukin-4, and caused a shift towards Th2 profile by decreasing Th1/Th2 ratios in piglets compared with control (P < 0.05). Polymyxin E contributed to an increase in interleukin-10 compared with the control (P < 0.05). No significant difference was observed in the amount of Lactobacillus, Bifidobacterium or Escherichia coli of jejunum among the three treatments (P > 0.05).

CONCLUSION

These results suggest that PS supplementation has no significant effect on growth but could remarkably decrease diarrhea rate, and improve immunity and anti-inflammatory activity in weaned piglets. In addition, PS supplementation had similar effects on growth, anti-inflammation and intestinal microorganisms as supplementation with polymyxin E in piglets. © 2017 Society of Chemical Industry.

Chemical composition and antifungal activity of the essential oil of Zhumeria majdae, Heracleum persicum and Eucalyptus sp. against some important phytopathogenic fungi

Application of essential oils of medicinal plants is considered a safe and acceptable method for plant disease management to protect plants from pathogenic microorganisms. Thus, in recent study, essential oils (EOs) from Zhumeria majdae, Heracleum persicum (two Iranian endemic plants) and Eucalyptus sp. were assayed for their antifungal potential against ten phytopathogenic fungi, including Fusarium graminearum, Fusarium asiaticum, Fusarium redolens f.sp. dianthus, Fusarium verticillioides, Fusarium oxysporum f.sp. lentis, Sclerotinia sclerotiorum, Aspergillus flavus, Aspergillus tubingensis, Botrytis cinerea and Cladosporium cladosporioides. Chemical composition of these oils was identified by GC-MS analysis. Based on our results, Z. majdae essential oil exhibited the best antifungal activity among tested essential oils, completely inhibiting growth of five fungal species. EOs of Eucalyptus sp. and H. persicum showed moderate and poor antifungal capacity, respectively. GC-MS analysis demonstrated that linalool and camphor were the main components of the essential oils of Z. majdae; furthermore, 1,8-cineole and hexyl ester formed the major portions of Eucalyptus sp. and H. persicum EOs. Due to the significant inhibition of some EOs, additional research about their use for control of plant diseases caused by these fungi is recommended.

Evaluating water deficit and glyphosate treatment on the accumulation of phenolic compounds and photosynthesis rate in transgenic Codonopsis lanceolata (Siebold & Zucc.) Trautv. over-expressing γ-tocopherol methyltransferase (γ-tmt) gene

The effect of water stress and herbicide treatment on the phenolic compound concentration and photosynthesis rate in transgenic Codonopsis lanceolata plants over-expressing the γ-tmt gene was investigated and compared to that in control non-transgenic C. lanceolata plants. The total phenolic compound content was investigated using high-performance liquid chromatography combined with diode array detection in C. lanceolata seedlings 3 weeks after water stress and treatment with glyphosate. Changes in the composition of phenolic compounds were observed in leaf and root extracts from transformed C. lanceolata plants following water stress and treatment with glyphosate. The total concentration of phenolic compounds in the leaf extracts of transgenic samples after water stress ranged from 3455.13 ± 40.48 to 8695.00 ± 45.44 µg g-1 dry weight (DW), whereas the total concentration phenolic compound in the leaf extracts of non-transgenic control samples was 5630.83 ± 45.91 µg g-1 DW. The predominant phenolic compounds that increased after the water stress in the transgenic leaf were (+) catechin, benzoic acid, chlorogenic acid, ferulic acid, gallic acid, rutin, vanillic acid, and veratric acid. The total concentration of phenolic compounds in the leaf extracts of transgenic samples after glyphosate treatment ranged from 4744.37 ± 81.81 to 12,051.02 ± 75.00 µg g-1 DW, whereas the total concentration of the leaf extracts of non-transgenic control samples after glyphosate treatment was 3778.28 ± 59.73 µg g-1 DW. Major phenolic compounds that increased in the transgenic C. lanceolata plants after glyphosate treatment included kaempherol, gallic acid, myricetin, p-hydroxybenzjoic acid, quercetin, salicylic acid, t-cinnamic acid, catechin, benzoicacid, ferulic acid, protocatechuic acid, veratric acid, and vanillic acid. Among these, vanillic acid showed the greatest increase in both leaf and root extracts from transgenic plants relative to those from control C. lanceolata plants following treatment with glyphosate, which could affect the 5-enol-pyruvyl shikimate-3-phosphate (EPSP) synthase, an enzyme in the shikimate pathway. We observed enhanced stomatal conductance (gs) and photosynthesis rate (A) in the transgenic plants treated with water stress and glyphosate treatment. The results of this study demonstrated large variations in the functioning of secondary metabolites pathway in response glyphosate and water stress in transgenic C. lanceolata.