Antibacterial Effect of Eight Essential Oils against Bacteria Implicated in Bovine Mastitis and Characterization of Primary Action Mode of Thymus capitatus Essential Oil.

During the current investigation, eight essential oils (EOs) were tested for their antimicrobial activity against six species, belonging to the genus of staphylococcus, multi-resistant to antibiotics (S. epidermidis, S. cohni, S. wareneri, S. scuiri, S. chromogenes, S. pasteuri), three methicillin-resistant Staphylococcus aureus strains (MRSA) and two strains of Escherichia coli, producing extended-spectrum ß-lactamase (ESBL) responsible for bovine mastitis. Our results indicated that the antimicrobial activities of eight EOs varied significantly among the types of EOs and bacterial species. Thymus capitatus and Trachyspermum ammi EOs display important antibacterial activity against all tested strains, with the inhibition zone diameters situated between 20 and 45 mm, while EOs of Artemisia absinthium, Eucalyptus globulus, Eucalyptus camaldulensis, Myrtus communis and Mentha pulegium exerted an intermediate activity. For Cymbopogon citratus, this effect depends on bacteria species. In fact, an important effect was observed against S. warneri, S. epidermidis, S. cohenii, S. pasteuri and MRSA (EC 39+) strains. In addition, the important lytic effect was observed against MRSA strains, showing that Gram-positive bacteria were more sensitive to T. capitatus EO than Gram-negative ones. Concerning the characterization of the mode action of T. capitatus, experiments of kill-time, bacteriolytic, loss of salt tolerance and loss of cytoplasmic material showed that the used EO was able to destroy cell walls and membranes followed by the loss of vital intracellular materials. In addition, it inhibits the normal synthesis of DNA, causing the bacterial death of E. coli and MRSA strains. This study shows the potential of using of EOs, particularly T. capitaus, to inhibit the growth of Gram-positive and Gram-negative bacteria multi-resistant to antibiotics causing bovine mastitis.

HPLC analysis, mycochemical contents and biological activities of two edible hypogeous ascomycetes: Tirmania nivea and Terfezia boudieri.

Truffle, the hypogeous, ascomycetous macrofungus, has been recognized as a delicacy for centuries, and it is gaining elevated status in the culinary domain. The chemical composition and biological activities of aqueous extract and ground material of two desert Tunisian Tirmania nivea and Terfezia boudieri were studied for the first time. Using three assays antioxidant activity of the aqueous extract and ground material of the two truffles were investigated. Indeed, the aqueous extract and ground material of Terfezia boudieri showed the highest capacity for the DPPH scavenging test (IC50 = 0.18 mg/mL) and with regard to the chelating power of iron (IC50 = 0.22 mg/mL). At the same time, the highest capacity for iron reduction was recorded in the crude material of Tirmania nivea. Besides, the total phenolic, flavonoid, flavanol, tannin, and proanthocyanidin contents of both truffles extracts were determined. The ground material showed the best antibacterial activity for two ascomycetes against seven strains of bacteria. HPLC analysis of aqueous extracts showed that the predominant phenolic compounds in T. boudieri and T. nivea were gallic acid (33.25%) and myricetin (52.91%). Therefore, these truffles are a source of natural antioxidant and antimicrobial agents and could be used as a potential health food.

Phenolic Content, Antioxidant, Antibacterial, and Anti-Acetylcholinesterase Activities of Biosynthesized and Characterized Silver Nanoparticles from Tunisian Medicinal Lichen Species.

Lichens produce a myriad of bioactive compounds that can be exploited as reducing and capping agents in the green process of synthesizing nanoparticles. In this study, we exploit a simple, environmentally safe method for synthesizing silver nanoparticles (AgNPs), using aqueous extracts of three lichen species (Lobaria pulmonaria, Ramalina farinacea, and Evernia prunastri) for the first time. Characterization showed that the three lichen species selected could be perfectly suitable as reducing agents to produce AgNPs. First, ultraviolet-visible spectroscopy confirmed the presence of metallic silver with a maximum absorbance at 425 nm. Second, Fourier transform infrared spectroscopy analysis confirmed the chemical compounds involved in reduction. Third, the elemental composition of AgNPs was illustrated by energy dispersive X-ray spectroscopy. Finally, scanning electron microscopy images displayed the size and shape of biosynthesized particles. The prepared extracts containing AgNPs showed high contents of phenolic compounds and high antioxidant activities on three assays (DPPH, ferric reducing power, and chelating power). Moreover, since bacteria are developing resistance to many common antibiotics, AgNPs produced in an environmentally safe method are an interesting replacement. The antibacterial assessment revealed more effective activity against Gram-negative than Gram-positive bacteria and a bactericidal effect against all strains tested. In this study, we present a pioneering evaluation of acetylcholinesterase inhibition by lichen-based AgNPs. The three extracts exhibited strong enzyme inhibition, with IC50 values of 3.46 ± 0.09, 3.59 ± 0.02, and 4.34 ± 0.03 mg/mL for L. pulmonaria, R. farinacea, and E. prunastri, respectively. The green approach presented would encourage the nontoxic production of AgNPs, suggesting pharmaceutical applications.

Characterization of Primary Action Mode of Eight Essential Oils and Evaluation of Their Antibacterial Effect against Extended-Spectrum ß-Lactamase (ESBL)-Producing Escherichia coli Inoculated in Turkey Meat.

The current study aims to evaluate the antimicrobial activity of eight essential oils (EOs) against multidrug-resistant Escherichia coli strains, producing extended-spectrum ß-lactamase (ESBL) enzymes and isolated from foods. Disc-diffusion assay showed that the inhibition diameters generated by EOs varied significantly among the tested EOs and strains. In fact, EOs extracted from Thymus capitaus, Eucalyptus camaldulensis, Trachyspermum ammi and Mentha pulegium exerted an important antimicrobial effect against tested strains, with the diameters of inhibition zones varied between 20 and 27 mm. Moreover, minimal inhibition and bactericidal concentration (MIC and MBC) values demonstrated that T. capitatus EOs generate the most important inhibitory effect against E. coli strains, with MIC values ranging from 0.02 to 0.78%. Concerning the mode of action of T. capitatus EO, the obtained data showed that treatment with this EO at its MIC reduced the viability of E. coli strains, their tolerance to NaCl and promoted the loss of 260-nm-absorbing material. In addition, in the presence of T. capitatus EO, cells became disproportionately sensitive to subsequent autolysis. Moreover, the inhibitory effect of T. capitatus was evaluated against two E. coli strains, experimentally inoculated (105 CFU/g) in minced turkey meat, in the presence of two different concentrations of EO (MIC and 2 × MIC), and stored for 15 days. In both samples, EO exerted a bacteriostatic effect in the presence of concentrations equal to MIC. Interestingly, at 2 × CMI concentration, the bactericidal activity was pronounced after 15 days of storage. Our results highlighted that the use of essential oils, specially of T. capitatus, to inhibit or prevent the growth of extended-spectrum ß-lactamase (ESBL)-producing E. coli in food, may be a promising alternative to chemicals.

Tunisian Native Mentha pulegium L. Extracts: Phytochemical Composition and Biological Activities.

Mint species (Lamiaceae family) have been used as traditional remedies for the treatment of several diseases. In this work, we aimed to characterize the biological activities of the total phenolic and flavonoid contents of Mentha pulegium L. extracts collected from two different regions of Tunisia. The highest amounts of total phenols (74.45 ± 0.01 mg GAE/g DW), flavonoids (28.87 ± 0.02 mg RE/g DW), and condensed tannins (4.35 ± 0.02 mg CE/g DW) were found in the Bizerte locality. Methanolic leaf extracts were subjected to HPLC-UV analysis in order to identify and quantify the phenolic composition. This technique allowed us to identify seven phenolic compounds: two phenolic acids and five flavonoid compounds, such as eriocitrin, hesperidin, narirutin, luteolin, and isorhoifolin, which were found in both extracts with significant differences between samples collected from the different regions (p < 0.05). Furthermore, our results showed that the methanolic extract from leaves collected from Bizerte had the highest antioxidant activities (DPPH IC50 value of 16.31 µg/mL and 570.08 µmol Fe2+/g, respectively). Both extracts showed high radical-scavenging activity as well as significant antimicrobial activity against eight tested bacteria. The highest antimicrobial activities were observed against Gram-positive bacteria with inhibition zone diameters and MIC values ranging between 19 and 32 mm and 40 and 160 µg/mL, respectively. Interestingly, at 10 µg/mL, the extract had a significant effect on cell proliferation of U87 human glioblastoma cells. These findings open perspectives for the use of Mentha pulegium L. extract in green pharmacy, alternative/complementary medicine, and natural preventive therapies for the development of effective antioxidant, antibacterial, and/or antitumoral drugs.

Mycochemical Contents and Biological Activities of Three Wild Mushrooms from Tunisia.

The objective of the current study was to compare the mycochemical composition and biological activities of two extracts (aqueous extracts and ground materials prepared with the QUENCHER approach) of three wild Basidiomy-cetes, Agaricus vaporarius, Lactarius deliciosus, and Lycoperdon pyriforme, collected from a region located in the north of Tunisia. Mycochemical analysis in terms of total phenolic compounds, flavonoids, flavanols, proanthocyanidins, and tannin contents were determined. In addition, the antioxidant activities of the mushrooms were evaluated using three assays (2,2-di-phenyl-1-picrylhydrazyl free radical scavenging, ferric reducing antioxidant power assay, and metal chelating assay). Their antimicrobial activities were assessed against seven bacterial species. The obtained data revealed the presence of significant differences between secondary metabolites and the biological activities of the different tested extracts. Extracts of Basidiomy-cetes prepared with the QUENCHER approach had higher total phenolic content and antimicrobial activity against the evaluated strains. Antioxidant activity showed that the water extract had the greatest activity. The water extracts were analyzed with high-performance liquid chromatography, and the results showed that these three wild macromycetes contain a wide variety of antioxidant compounds in addition to many other bioactive compounds of nutritional and therapeutic interest.

Green Roccella phycopsis Ach. mediated silver nanoparticles: synthesis, characterization, phenolic content, antioxidant, antibacterial and anti-acetylcholinesterase capacities.

In this study, we develop here for the first time an easy, eco-friendly method for synthesizing silver nanoparticles (AgNPs) using the lichen Roccella phycopsis. AgNPs formation was first determined by a color change of the lichen filtrate to brown, subsequent to addition of AgNO3 solution, and confirmed by a maximum absorbance peak at 425 nm in UV-vis spectrum. Scanning electron microscope images showed a spherical shape with a size distribution between 11 and 18 nm, while the elemental composition was elucidated by the energy dispersive X-ray spectroscopy. The chemical compounds responsible for reduction and stabilization of silver nanoparticles were detected by Frourier transform infrared spectroscopy analysis. The synthesized R. phycopsis silver nanoparticles displayed a strong antioxidant activity. Further, the antibacterial activity was more effective against Gram-negative than Gram-positive bacteria. Besides, the R. phycopsis-AgNPs were potent in inhibiting acetylcholinesterase enzyme with IC50 value of 1.65 ± 0.07 mg/mL.

High pressure sensitization of heat-resistant and pathogenic foodborne spores to nisin.

Today, there is no effective non-thermal method to inactivate unwanted bacterial spores in foods. High-Pressure (HP) process has been shown to act synergistically with moderate heating and the bacteriocin nisin to inactivate spores but the mechanisms have not been elucidated. The purpose of the present work was to investigate in depth the synergy of HP and nisin on various foodborne spore species and to bring new elements of understandings. For this purpose, spores of Bacillus pumilus, B. sporothermodurans, B. licheniformis, B. weihenstephanensis, and Clostridium sp. were suspended in MES buffer, in skim milk or in a liquid medium simulating cooked ham brine and treated by HP at 500 MPa for 10 min at 50 °C or 20 °C. Nisin (20 or 50 IU/mL) was added at three different points during treatment: during HP, during and or in the plating medium of enumeration. In the latter two cases, a high synergy was observed with the inhibition of the spores of Bacillus spp. The evaluation of the germinated fraction of Bacillus spp. spores after HP revealed that this synergy was likely due to the action of nisin on HP-sensitized spores, rather than on HP-germinated spores. Thus, the combination of nisin and HP can lead to Bacillus spp. spore inhibition at 20 °C. And Nisin can act on HP-treated spores, even if they are not germinated. This paper provides new information about the inhibition of spores by the combination of HP and nisin. The high synergy observed at low temperature has not been reported yet and could allow food preservation without the use of any thermal process.

Determination of phenolic compounds by MALDI-TOF and essential oil composition by GC-MS during three development stages of Origanum majorana L.

This study aimed to investigate the effect of the maturation process of sweet marjoram (Origanum majorana L.) on essential oil composition, the phenolic profile of ethanolic extract and their antioxidant capacities. The essential oil composition was studied at three stages of maturity by GC-MS. Thirty compounds were detected representing 100% of the total essential oil. p-Menth-1-en-4-ol was the major compound (37.15-76.94%) followed by cyclohexanol-3,3,5 trimethyl (5.41-15.99%) and α-terpineol (0.94-11.34%). During the maturation process, an accumulation of oxygenated monoterpenes was observed. The phenolic composition was studied using matrix-assisted laser desorption/ionization time of flight. The analysis showed the presence of short flavonoid monomers at all stages of maturation. The antioxidant capacity of ethanolic extracts and essential oils was evaluated using the DPPH assay, iron chelating power and reducing power assay. The highest phenolic content and antioxidant capacity were found at flowering stage. These findings on essential oil composition, phenolic profile and antioxidant capacity of O. majorana at three different stages of development provide more information on how these secondary metabolites are accumulated.

Prevalence and Antibiotic Resistance Patterns of Campylobacter spp. Isolated from Broiler Chickens in the North of Tunisia.

The aim of the current study is to assess the prevalence of Campylobacter infection in broiler chickens, raised in intensive production conditions, and to evaluate the antimicrobial susceptibility of recovered Campylobacter isolates. A total of 590 cloacal swab samples were taken from 13 broiler chicken flocks in the North East of Tunisia. All samples were tested for the presence of thermophilic Campylobacter by culture and PCR, targeting the mapA and ceuE genes, respectively. Susceptibility to antimicrobial drugs was tested against 8 antibiotics. Prevalence of Campylobacter infection, relationship with geographic origins and seasons, antimicrobial resistance rates and patterns were analyzed. Total prevalence of Campylobacter infection in broiler flocks was in the range of 22.4%, with a predominance of C. jejuni (68.9%), followed by C. coli (31.1%). Positive association was highlighted between the infection level and the season (P < 0.001), but no link was emphasized considering the geographic origin. Antimicrobial susceptibility testing revealed very high resistance rates detected against macrolide, tetracycline, quinolones, and chloramphenicol, ranging from 88.6% to 100%. Lower resistance prevalence was noticed for ß-lactams (47% and 61.4%) and gentamicin (12.9%). 17 R-type patterns were observed, and a common pattern was found in 30.3% of isolates. This study provides updates and novel data on the prevalence and the AMR of broiler campylobacters in Tunisia, revealing the occurrence of high resistance to several antibiotics and emphasizing the requirement of better surveillance and careful regulation of antimicrobials use.

Screening of Bioactive Compounds of Medicinal Mushrooms Collected on Tunisian Territory.

This study is, to our knowledge, the first to investigate the pharmacological importance of wild Tunisian mushrooms. Ethanolic extracts of 5 Tunisian mushrooms-Phellinus torulosus, Fomes fomentarius, Trametes versicolor, Pisolithus albus, and Fomitopsis pinicola-were collected from the Kroumirie Region (North Tunisia). The dry basidomes of mushrooms were extracted using ethanol and evaluated for total polyphenol, flavonoid, flavonol, tannin, proanthocyanidin, and anthocyanin content. In addition, their antioxidant activities were determined using 3 assays (testing 2,2-diphenyl-1-picrylhydrazyl [DPPH] radical scavenging, the reducing power of iron, and the iron-chelating power). Their antimicrobial activities were assessed against 8 bacterial species. The results revealed the presence of significant differences between the secondary metabolites and biological activities of the different tested extracts. In addition, significant correlations were observed between antioxidant activities and phenolic contents. Crude ethanol extracts prepared from basidomes of F. fomentarius and Ph. torulosus have higher total phenolic content and antioxidant activity per the DPPH and metal-chelating activity assays. The reducing power assay showed that the ethanolic extract of F. pinicola had the highest activity. Ethanolic extracts of the 5 mushrooms have antibacterial activity against the evaluated strains.

Comparison of Phytochemical Composition and Biological Activities of Rubus ulmifolius Extracts Originating from Four Regions of Tunisia.

In the current study, the phenolic composition, antioxidant and antimicrobial activities of extracts from Rubus ulmifolius Schott leaves harvested in four localities (Sejnen, Tabarka, Faija and Ain drahem) in Tunisia were investigated for the first time. Great differences were found for the chemical composition, total phenol contents and biological activities among the evaluated extracts. HPLC analysis of methanolic extracts showed that the dominant compounds were kaempferol 3-O-rutinoside and naringenine. In addition, significant correlations were observed between antioxidant activities and phenolic contents. In fact, leaves collected from Sejnen presented higher total phenol content (53.32 mg GAE/g DW) and antioxidant activities (IC50 = 39.40 mg/l) than the others samples. All extracts showed significant antimicrobial activity against six used bacteria with the inhibition zones diameters and minimal inhibitory concentration values were in the range of 8 - 16 mm and 6.25 - 25 mg/ml, respectively. The highest antimicrobial activities were recorded in Sejnen extract against Gram-positive bacteria.

Phenolic content, antioxidant capacity and antimicrobial activity of leaf extracts from Pistacia atlantica.

The aim of this study was to investigate the secondary metabolites related to Pistacia atlantica Desf as well as their biological activities. Results show that using ethanol as a solvent exhibited the highest content of total phenolics and flavonoids (68.23 mg GAE g-1 of DW and 44 mg RE g-1 of DW), followed by aqueous one (20.07 mg GAE g-1 of DW and 15 mg RE g-1 of DW). Good correlation (Data not shown) was obtained between the DPPH radical-scavenging activities and total phenolics contents. Many similarities were observed between the results of the DPPH (IC50 = 32 and 200 µg mL-1) and ABTS (IC50 = 42 and 300 µg mL-1) assays. All tested extracts contained phenolic compounds exhibited an antimicrobial effect against Gram-positive and Gram-negative bacteria. Further, researches for identification and purification of phenolic compounds are required.

Evaluation of the anti-diarrheal activity of the hydromethanolic root extract of Rhus tripartita (Ucria) (Anacardiacae).

INTRODUCTION: Rhus tripartita (Anacardiacae) is a plant which is traditionally used for the treatment of ulcer and diarrhea in Tunisia. However, the scientific basis for this usage has not been well established. The core aim of the present study is to evaluate the antidiarrheal activity of Rhus tripartita root methanolic extract (RRE). MATERIAL AND METHODS: The antidiarrheal activity of RRE oral doses (50, 100, 200 and 300mg/kg) was evaluated using the castor oil-induced diarrhea, the intestinal fluid emptying method and the normal intestinal transit test. The antibacterial activity was tested against four pathogenic bacteria using two methods. The RRE was also phytochemical studied. RESULTS: Diarrhea experiments showed a protective effect of the RRE which produced a significant (p<0.05) and dose-dependent reduction of all the diarrhea parameters. It delayed the onset of diarrhea, produced a significant decrease in the frequency of defecation and the diarrhea score severity and decreased the volume of intestinal fluid induced by castor oil as well as the propulsion intestinal transit. The effect of the extract at the highest dose (300mg/kg) was similar to that of loperamide, the standard anti-diarrheal drug (10mg/kg). The anti-bacterial activity test showed that RRE exhibited a great inhibition activity against four pathogenic bacteria strains (Esherichia coli, Salmonella typhimurium, Salmonella argenosa, Staphylococcus aureus). Oral administration of the extract up to 3g/kg did not produce any acute toxicity in rats. The preliminary phytochemical screening of the RRE revealed the presence of flavonoids, tannins, and polyphenols. CONCLUSION: Results showed that RRE at 300mg/kg possesses the highest anti-diarrheal activity possibly mediated by the inhibitory effects on gastrointestinal propulsion and intestinal fluid accumulation.

Barks Essential Oil, Secondary Metabolites and Biological Activities of Four Organs of Tunisian Calligonum azel Maire.

This study is the first to investigate the chemical composition of barks essential oil (EO), secondary metabolites and biological activities of the MeOH and infusions extracts of seeds, leaves, barks and roots of Calligonum azel Maire (Polygonaceae) harvested from Tunisian desert. The gas chromatography/mass spectrometry (GC/MS) results showed the presence of fifty-four compounds in barks EO. The major components were: viridiflorol (14.6%), α-eudesmol (8.65%), trans-caryophyllene (6.72%), elemol (6.63%), ß-eudesmol (6.21%). The obtained results showed that C. azel is a very rich plant in secondary metabolites. High contents in polyphenols, flavonoids and tannins were observed in both extracts of all studied organs. Significant differences were found between both extracts of the four organs. Thus, polyphenols and tannins were more abundant in leaves infusion extract, while, flavonoids showed a high level in barks extract. The antioxidant activity data demonstrated that all extracts showed strong antioxidant and radical scavenging activities. The MeOH extracts presented potential for antibacterial and antifungal activities against all tested microorganisms. The inhibition zones diameters and minimal inhibitrice concentration values were in the range of 9 - 15 mm and 2.5 - 20 µg/ml, respectively. This study demonstrated that C. azel can be regarded as an excellent plant source for natural antimicrobial agents.

Comparison of antioxidant and antimicrobial activities of two cultivated Cistus species from Tunisia / Comparação das atividades antioxidante e antimicrobiana de duas espécies cultivada de Cistus da Tunísia

The secondary metabolite composition, antioxidant activities, and microbial inhibition properties of leaves of two Cistus species; C. monspeliensis and C. salvifolius were investigated using three solvent extracts (ethanol, hexane and distilled water). Ethanol extracts were most efficient at extracting phenolics, flavonoids and condensed tannins compared to hexane and distilled water for both Cistus species. A total antioxidant test (TAA) and two radical scavenging tests (DPPH and ABTS) indicated that the 70% ethanolic extract from C. salvifolius leaves had stronger antioxidant activity compared to the C. monspeliensis 70% ethanol extract, while the aqueous extract of C. monspeliensis was much stronger than the aqueous extract or the 70% ethanol extract of C. salvifolius. Overall, the polar extracts were more active in both species than the non-polar extracts. Thus aqueous ethanol extracts of the leaves of each Cistus species were tested for their ability to inhibit seven pathogenic microbial strains, including Escherichia coli ATCC 8739, Salmonella typhimurium NCTC 6017, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 29213, Enterococcus faecalis, Aspergillus niger, and Candida albicans. Leaf ethanol extracts from both species were active against each microbial species, but the C. monspeliensis leaf ethanolic extract was much more active against several microbial species than that of C. salvifolius. For example, the C. salvifolius 70% ethanol extract showed its highest antimicrobial activity against P. aeruginosa and A. niger (MIC 3.1 mg/ml and MBC 6.3 mg/ml for both), while the C. monspeliensis extract showed much higher overall activity against E. coli, P. aeruginosa and C. albicana. (MIC 6.25 mg/ml and MBC 12.5 mg/ml for all three). In conclusion, maceration with 70% ethanol was the most efficient method for extracting total polyphenols, flavonoids, and condensed tannins from the two Cistus species, and the aqueous-ethanol extracts displayed the highest antioxidant and antimicrobial activities. Hence, the aqueousethanolic extracts of both species may be considered as potential sources of natural antioxidants and antimicrobial agents.

A composição de metabólitos secundários, atividade antioxidante e propriedades de inibição microbiana de extratos das folhas de duas espécies de Cistus; C. monspeliensis e C. salvifolius foram investigados utilizando-se três solventes de extração (etanol, hexano e água destilada). A extração com etanol foi a mais eficiente na extração de compostos fenólicos, flavonóides e taninos condensados em comparação com hexano e água destilada para ambas as espécies de Cistus. Um teste antioxidante total (TAA) e dois testes de eliminação de radicais (DPPH e ABTS) indicaram que o extrato em etanol 70% das folhas de C. salvifolius teve maior atividade antioxidante em comparação com o extrato etanólico de C. monspeliensis, enquanto o extrato aquoso de C. monspeliensis teve maior atividade antioxidante que o respectivo extrato aquoso ou o extrato etanólico de C. salvifolius. Em geral, os extratos polares foram mais ativos em ambas as espécies do que os extratos não-polares. Assim, extratos etanólico e aquoso das folhas de cada uma das espécies de Cistus foram testados quanto à sua capacidade de inibir sete cepas microbianas patogênicas, incluindo Escherichia coli ATCC 8739, Salmonella typhimurium NCTC 6017, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 29213, Enterococcus faecalis, Aspergillus niger, e Candida albicans. Extratos etanólicos da folha de ambas as

Antidiarrhoeal, antimicrobial and antioxidant effects of myrtle berries (Myrtus communis L.) seeds extract.

OBJECTIVES: The present study was carried out to determine the antidiarrheal effects of myrtle (Myrtus communis L.) berries seeds aqueous extract (MBSAE) from Tunisia as well as the involvement of its antimicrobial and antioxidant properties in such protection. METHODS: Adult male wistar rats were used and divided into six groups of ten each: control, Castor oil, Castor oil + Loperamide and Castor oil + various doses of MBSAE. Animals were per orally (p.o.) pre-treated with MBSAE for one hour and intoxicated by castor oil acute oral administration. KEY FINDINGS: Our results demonstrated that the MBSAE is rich in total and condensed tannins and exhibited a broad spectrum of antibacterial activity. In vivo, we found that MBSAE administration induced a significant dose-dependent protection against diarrhoea and intestinal fluid accumulation. Castor oil-induced intestinal hypersecretion was accompanied by an oxidative stress status in the intestine. More importantly, we showed that acute diarrhoea was accompanied by an increase in intestinal mucosa hydrogen peroxide (H2 O2 ), calcium and free iron levels while MBSAE pre-treatment reversed all castor oil-induced intracellular mediators disturbances. CONCLUSIONS: We suggest that MBSAE had a potent protective effects against castor oil-induced acute diarrhoea due in part to its antioxidant and antimicrobial properties.

Inhibitory effects of nisin and potassium sorbate alone or in combination on vegetative cells growth and spore germination of Bacillus sporothermodurans in milk.

The inhibitory activities of nisin or/and potassium sorbate on spores and vegetative cells of Bacillus sporothermodurans LTIS27, which are known to be a contaminant of dairy products and to be extremely heat-resistant, were investigated. First, the tested concentrations of nisin or potassium sorbate inhibited vegetative cell growth; with the minimum inhibitory concentrations were 5 × 10(3) IU/ml and 2% (w/v), respectively. Then, the behaviour of vegetative cells and spores in presence of sub-lethal concentrations of nisin (50 UI/ml) or/and potassium sorbate (0.2%), in milk at 37 °C for 5 days, were evaluated. In the absence of inhibitors, strain grew and sporulated at the end of the exponential phase. Nisin (50 UI/ml) was able to inhibit spore outgrowth but didn't affect their germination. It induced an immediate and transitory reduction (1.6log(10) after 1 h and 2.8log(10) after 6 h of incubation) of vegetative cell growth which reappeared between 10 h and 24 h. Potassium sorbate (0.2%) had a durable bacteriostatic effect (1.1log(10) after 6 h), on vegetative cells, followed by a slower regrowth. It was able to inhibit both germination and outgrowth of spores. Association of nisin and potassium sorbate, at sub-lethal concentrations, showed a synergistic effect and resulted in a total inhibition of cells growth after 5 days. The results illustrate the efficacy of nisin and potassium sorbate in combination, and the commercial potential of applying such treatment to decontaminate any product that has a problem with persistence of bacterial spores.

Fatty acids composition of Tunisian Ziziphus lotus L. (Desf.) fruits and variation in biological activities between leaf and fruit extracts.

This study was conceived to evaluate the essential fatty acids, secondary metabolites, antiradical and antimicrobial activities of unexploited Tunisian Ziziphus lotus L. The obtained results indicated that the major components of fatty acids were oleic acid (88.12%) and elaidic acid (7.88%). Leaves contained higher amount of total phenols, flavonoids and tannins than fruits, although both methanolic extracts had significant antioxidant activities. Significant correlations were observed between the total phenol or flavonoid contents in methanolic extracts and antioxidant activity estimated by using both 2,2'-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic radical-scavenging methods. In addition, both methanolic extracts exhibited strong antibacterial and antifungal activities. The inhibition zone diameters and the minimal inhibition concentration values were in the range of 10-17 mm and 3.1-50 mg/mL, respectively.

Inactivation of Bacillus sporothermodurans spores by nisin and temperature studied by design of experiments in water and milk.

Spores of Bacillus sporothermodurans are known to be a contaminant of dairy products and to be extremely heat-resistant. A central composite experimental design with three factors using response surface methodology was used to evaluate the effect of nisin (50-150 UI/mL), temperature (80-100 °C), and temperature-holding time (10-20 min) on the inactivation of B. sporothermodurans LTIS27 spores in distilled water, in skim milk and in chocolate milk. The experimental values were shown to be significantly in good agreement with the values predicted by the quadratic equation since the adjusted determination coefficients (Radj(2)) were around 0.97. By analyzing the response surfaces plots, the inactivation was shown to be higher in distilled water than in skim milk under all the conditions tested. Five-log cycle reductions of B. sporothermodurans spores were obtained after a treatment at 95 °C for 12 min in presence of 125 UI of nisin/mL in distilled water or at 100 °C for 13 min in presence of 134 UI of nisin/mL in skim milk or at 100 °C for 15 min in presence of 135 UI of nisin/mL in chocolate milk. This study showed the efficiency of nisin (15-184 UI/mL) in combination with temperature (73-106 °C) to inactivate spores of B. sporothermodurans in milk.