Novel strategies of essential oils,chitosan, and nano- chitosan for inhibition of multi-drug resistant: E. coli O157:H7 and Listeria monocytogenes

Despite the wide range of available antibiotics, food borne bacteria demonstrate a huge spectrum of resistance. The current study aims to use natural components such as essential oils (EOs), chitosan, and nano-chitosan that have very influential antibacterial properties with novel technologies like chitosan solution/film loaded with EOs against multi-drug resistant bacteria. Two strains of Escherichia coli O157:H7 and three strains of Listeria monocytogenes were used to estimate antibiotics resistance. Ten EOs and their mixture, chitosan, nano-chitosan, chitosan plus EO solutions, and biodegradable chitosan film enriched with EOs were tested as antibacterial agents against pathogenic bacterial strains. Results showed that E. coli O157:H7 51,659 and L. monocytogenes 19,116 relatively exhibited considerable resistance to more than one single antibiotic. Turmeric, cumin, pepper black, and marjoram did not show any inhibition zone against L. monocytogenes; Whereas, clove, thyme, cinnamon, and garlic EOs exhibited high antibacterial activity against L. monocytogenes with minimum inhibitory concentration (MIC) of 250–400 μl 100^?1 ml and against E. coli O157:H7 with an MIC of 350–500 μl 100^?1 ml, respectively. Among combinations, clove, and thyme EOs showed the highest antibacterial activity against E. coli O157:H7 with MIC of 170 μl 100^?1 ml, and the combination of cinnamon and clove EOs showed the strongest antibacterial activity against L. monocytogenes with an MIC of 120 μl 100^?1 ml. Both chitosan and nano-chitosan showed a promising potential as an antibacterial agent against pathogenic bacteria as their MICs were relatively lower against L. monocytogenes than for E. coli O157:H7. Chitosan combined with each of cinnamon, clove, and thyme oil have a more effective antibacterial activity against L. monocytogenes and E. coli O157:H7 than the mixture of oils alone. Furthermore, the use of either chitosan solution or biodegradable chitosan film loaded with a combination of clove and thyme EOs had the strongest antibacterial activity against L. monocytogenes and E. coli O157:H7. However, chitosan film without EOs did not exhibit an inhibition zone against the tested bacterial strains.     

Comparative study of the antioxidant activity of the essential oils of five plants against the H2O2 induced stress in Saccharomyces cerevisiae

The purpose of this work was to investigate the protective effect of five essential oils (EOs); Rosmarinus officinalis, Thymus vulgaris, Origanum compactum Benth., Eucalyptus globulus Labill. and Ocimum basilicum L.; against oxidative stress induced by hydrogen peroxide in Saccharomyces cerevisiae. The chemical composition of the EOs was analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS). The in vitro antioxidant activity was evaluated and the protective effect of EOs was investigated. Yeast cells were pretreated with different concentrations of EOs (6.25–25 µg/ml) for an hour then incubated with H₂O₂ (2 mM) for an additional hour. Cell viability, antioxidants (Catalase, Superoxide dismutase and Glutathione reductase) and metabolic (Succinate dehydrogenase) enzymes, as well as the level of lipid peroxidation (LPO) and protein carbonyl content (PCO) were evaluated. The chemical composition of EOs has shown the difference qualitatively and quantitatively. Indeed, O. compactum mainly contained Carvacrol, O. basilicum was mainly composed of Linalool, T. vulgaris was rich in thymol, R. officinalis had high α-Pinene amount and for E. globulus, eucalyptol was the major compound. The EOs of basil, oregano and thyme were found to possess the highest amount of total phenolic compounds. Moreover, they have shown the best protective effect on yeast cells against oxidative stress induced by H₂O₂. In addition, in a dose dependent manner of EOs in yeast medium, treated cells had lower levels of LPO, lower antioxidant and metabolic enzymes activity than cells exposed to H₂O₂ only. The cell viability was also improved. It seems that the studied EOs are efficient natural antioxidants, which can be exploited to protect against damages and serious diseases related to oxidative stress.     

Phytochemical Variation within Aerial Parts of Ferula cupularis Populations,an Endangered Medicinal Plant from Iran

Ferula cupularis (Boiss.) Spalik et S. R. Downie is an endangered endemic Iranian medicinal plant with occurrence restricted to Fars and Kohkilooyeh Boyerahmad provinces, Iran. F. cupularis is cited for strong antibacterial activity, usages in foodstuffs preservation, and has long been used by local peoples for ulcer treatment. In this research, the aerial parts of F. cupularis wild populations were collected from three natural habitats: Eqlid-Kaftar (FC1), Kakan (FC2), and Sepidan-Komohr (FC3), to assess phytochemical diversity and antioxidant activity. The quantity of essential oil (EO) ranged remarkably from 0.42 to 0.72 % v/w among the populations. Results obtained from the EO analysis by GC-FID and GC/MS detected up to 56 compounds. α-Pinene (21.65–31.53 %), sabinene (4.74–11.39 %), phellandrene (1.78–5.1 %), δ-3-carene (1.85–7.18 %), limonene (4.12–7.45 %), (Z)-β-ocimene (9.08–17.64 %), and elemicin (0.23–5.74 %) were the major compounds of EOs varied significantly among the populations. Moreover, total phenol content (250.54 to 387.45 mg gallic acid/100 g dry weight (DW)) and flavonoids (34.38 to 41.12 mg quercetin/100 g DW) of methanolic extracts varied substantially among the populations. Antioxidant activities of F. cupularis EOs and extracts were assessed by DPPH (2,2,1-diphenyl-1-picrylhydrazyl) radical scavenging method. EOs exhibited EC₅₀ values ranging from 8.88 to 9.67 μg mL⁻¹ and the EC₅₀ values for the extract ranged from 941.36 to 1335.96 μg mL⁻¹ within the populations. Results demonstrated significantly different levels of antioxidant capacities among the studied populations. Monitoring the data, the population collected from Eqlid-Kaftar (FC1) was selected as the most potent population concerning the highest EO content and antioxidant activity level. The obtained data provided new insights for an initial source of breeding plans and ultimately massive production for food and pharmaceutical industries.     

The Effect of Some Natural Essential Oils Against Bovine Mastitis Caused by <Emphasis Type="Italic">Prototheca zopfii</Emphasis> Isolates In Vitro

The aim of the study was to evaluate the effect of essential oils obtained from Thymus vulgaris L., Origanum vulgare L., Origanum majerana L., Mentha × piperita L. and Allium ursinum L. against Prototheca zopfii strains that cause inflammation of the udder (mastitis) in cows. The study was conducted on ten strains derived from milk samples. The microdilution method was used to determine the sensitivity of P. zopfii strains to the studied essential oils, and the disk diffusion method was used to determine the sensitivity to antifungal chemotherapeutics. The plates were incubated for 48 h at 37 °C under aerobic conditions. All strains of algae were sensitive to the essential oils marjoram, thyme and oregano and resistant to mint and garlic oils. MIC values ranged from 0.25 to 1 μl/ml. Marjoram oil demonstrated the greatest activity, and oregano oil the weakest. Among the antifungal agents tested, 90% of strains showed sensitivity to nystatin. One of the tested strains (71/IV) was resistant to all investigated antifungal agents. The tested essential oils are known to have anti-algae activity and can be used as natural agents for prophylaxis in animals, particularly in mastitis-affected cows.     

Insecticidal properties of Pimpinella anisum essential oils against the Culex quinquefasciatus and the non-target organism Daphnia magna

The efficacy of an essential oil obtained from Pimpinella anisum fruits and its major compound, trans-Anethole, was tested on the eggs, larvae and adults of Culex quinquefasciatus. While causing no significant mortality on eggs, other tested stages were very sensitive to the essential oil and trans-Anethole. LC₅₀ for the 2nd to 4th instar larvae was estimated as 26–27 μL·L^− 1 and 15–19 μL·L^− 1 for the essential oil and trans-Anethole, respectively. As for the essential oil applied on adults, LC(LD)₅₀ was estimated as 9.3 μL mL^− 1 (spray test), 1.9 μL L^− 1 (fumigation test) and 0.6 μg cm^− 2 (tarsal test), and for trans-Anethole as 8.1 μL mL^− 1 (spray test), 2.1 μL L^− 1 (fumigation test) and 0.4 μg cm^− 2 (tarsal test). The time needed to achieve 50% mortality after application of LC(LD)₉₉ of the essential oil was significantly different; for example, in larvicidal assays it ranged from 15 to 235 min depending on the larval instar, and from 9 to 180 min when applied to adults, depending on the mode of application. It was also found that temperature had an important effect on the larvicidal efficacy of the essential oil, and oviposition deterrent activity was studied.The essential oil and trans-Anethole were toxic for Daphnia magna (62–92% mortality) and significantly reduced its fertility at high concentrations (35–50 μL mL^− 1) and long exposure (48 h). However, no negative effect on Daphnia mortality or fertility was found at shorter exposure times (6 h) and/or lower concentrations (20 μL mL^− 1).Based on the results of this study, we can recommend the essential oil from P. anisum as a suitable active substance for potential botanical insecticides.     

Effective biodegradation of 2,4,6-trinitrotoluene using a novel bacterial strain isolated from TNT-contaminated soil

In this environmental-sample based study, rapid microbial-mediated degradation of 2,4,6-trinitrotoluene (TNT) contaminated soils is demonstrated by a novel strain, Achromobacter spanius STE 11. Complete removal of 100 mg L⁻¹ TNT is achieved within only 20 h under aerobic conditions by the isolate. In this bio-conversion process, TNT is transformed to 2,4-dinitrotoluene (7 mg L⁻¹), 2,6-dinitrotoluene (3 mg L⁻¹), 4-aminodinitrotoluene (49 mg L⁻¹) and 2-aminodinitrotoluene (16 mg L⁻¹) as the key metabolites. A. spanius STE 11 has the ability to denitrate TNT in aerobic conditions as suggested by the dinitrotoluene and NO₃ productions during the growth period. Elemental analysis results indicate that 24.77 mg L⁻¹ nitrogen from TNT was accumulated in the cell biomass, showing that STE 11 can use TNT as its sole nitrogen source. TNT degradation was observed between pH 4.0–8.0 and 4–43 °C; however, the most efficient degradation was at pH 6.0–7.0 and 30 °C.     

Antibacterial effect of essential oils and interaction with food components

The antibacterial effect of essential oils (EOs) derived from Citrus lemon, Juniperus communis, Origanum majorana, and Salvia sclarea, was investigated either alone or in combination, on 2 food related bacteria (Bacillus cereus and Escherichia coli). The influence of food ingredients — hydrolyzed proteins originating from animal and plant (meat extract and soy peptone) and sucrose — on the antibacterial effect of EOs was also tested. The most effective antibacterial activities were obtained with marjoram and clary sage oil, alone and in combination. High concentration of meat extract protected the bacteria from the growth inhibiting effect of marjoram oil, while soy peptone had no such effect. Sucrose intensified the lag phase lengthening by marjoram oil in a dose-independent manner.     

Investigation of Heavy Metal Level and Mineral Nutrient Status in Widely Used Medicinal Plants’ Leaves in Turkey: Insights into Health Implications

The use of plants in treatments has been as old as humanity and it has preserved its popularity for centuries til now because of their availability, affordability and safeness. However, despite their widespread use, safety and quality issues have been major concerns in the world due to industrial- and anthropogenic-based heavy metal contamination risks. Thus, this study was attempted to analyze the heavy metal levels and mineral nutrient status of widely used medicinal plants in Turkey to have insights about their health implications on humans. The plant concentrations of B, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb and Zn were analyzed by ICP-OES in the leaves of 44 medical plants purchased from herbal markets of three different districts of Istanbul/Turkey. The measured lowest to highest concentrations were 0.065–79.749 mg kg⁻¹ B, 921.802–12,854.410 mg kg⁻¹ Ca, 0.020–0.558 mg kg⁻¹ Cd, 0.015–4.978 mg kg⁻¹ Cr, 0.042–8.489 mg kg⁻¹ Cu, 34.356–858.446 mg kg⁻¹ Fe, 791.323–15,569.349 mg kg⁻¹ K, 102.236–2837.836 mg kg⁻¹ Mg, 4.915–91.519 mg kg⁻¹ Mn, 10.224–3213.703 mg kg⁻¹ Na, 0.001–5.589 mg kg⁻¹ Ni, 0.003–3.636 mg kg⁻¹ Pb and 2.601–36.102 mg kg⁻¹ Zn. Those levels in plants were in acceptable limits though some elements in some plants have high limits which were not harmful. Variations (above acceptable limits) in element concentrations also indicated that these plants could be contaminated with other metals and that genetic variations may influence accumulation of these elements at different contents. Overall, analyzed medicinal plants are expected not to pose any serious threat to human health.

     

Antimicrobial activity of essential oils of Thymus vulgaris and Origanum vulgare on phytopathogenic strains isolated from soybean

The aim of this work was to study the antimicrobial activity of essential oils obtained from Thymus vulgaris (thyme) and Origanum vulgare (oregano) on phytopathogenic Pseudomonas species isolated from soybean. Strains with characteristics of P. syringae were isolated from leaves of soybean plants with blight symptoms. Ten of these could be identified in Group Ia of LOPAT as P. syringae. Six of these were confirmed as P. syringae using 16S rRNA, indicating the presence of these phytopathogenic bacteria in east and central Argentina. All the phytopathogenic bacteria were re‐isolated and identified from the infected plants. MIC values for thyme were 11.5 and 5.7 mg·ml^?1 on P. syringae strains, while oregano showed variability in the inhibitory activity. Both essential oils inhibited all P. syringae strains, with better inhibitory activity than the antibiotic streptomycin. The oils were not bactericidal for all pseudomonads. Both oils contained high carvacrol (29.5% and 19.7%, respectively) and low thymol (1.5%). Natural products obtained from aromatic plants represent potential sources of molecules with biological activity that could be used as new alternatives for the treatment of phytopathogenic bacteria infections.     

Mycoremediation of oil contaminant by Pleurotus florida (P.Kumm) in liquid culture

This study investigated the potential functions of Pleurotus florida (an edible mushroom) in the biodegradation of gas oil at concentrations of 0 (control), 2.5, 5, and 10% (V: V) for 30 days. The gas oil increased dry weight and protein concentration in all treatments (by an average of 19.5 and 108%, respectively). Moreover, the pH, surface tension (ST), and interfacial tension (IFT) were reduced by the mushroom supplementation. The lowest surface tension (31.9 mN m⁻¹) and the highest biosurfactant production belonged to the 10% gas oil treatment (0.845 ± 0.03 mg mL⁻¹). The results demonstrated that the adsorption isotherm agreed well with the Langmuir isotherm. The maximum Langmuir adsorption capacity was calculated at 0.743 mg g⁻¹ wet biomass of P. florida. The fungal supplementation efficiently remedied the total petroleum hydrocarbons (TPHs) by an average of 55% after 30 days. Gas chromatography (GC) analysis revealed that P. florida effectively detoxified C₁₃–C₂₈ hydrocarbons, Pristane, and Phytane, implying its high mycoremediation function. The toxicity test showed that mycoremediation increased the germination by an average of 35.82% ± 8.89 after 30 days. Laccase activity increased significantly with increasing gas oil concentration in the treatments. The maximum laccase activity was obtained in the 10% gas oil treatment (142.25 ± 0.72 U L⁻¹). The presence of pollutants was also associated with induction in the tyrosinase activity when compared to the control. These results underline the high mycoremediation capacity of P. florida through the involvement of biosurfactants, laccase, and tyrosinase.     

Antiradical properties of oregano, thyme, and savory essential oils

In model reactions with the stable free 2,2-diphenyl-1-picrylhydrazyl radical, the antiradical properties of essential oils of thyme (Thymus vulgare), oregano (Origanum vulgare), and savory (Satureja hortensis) that are similar in the qualitative composition, but differ in the quantitative content of the main components, were studied and compared with the properties of synthetic antioxidant ionol. The reaction rates of components of essential oils with the radical were almost identical for all essential oils and were twice the reaction rate of ionol. The antiradical efficiency values were close to each other for all essential oils and by an order of magnitude smaller than for ionol.     

Triacontanol Protects Mentha arvensis L. from Nickel-Instigated Repercussions by Escalating Antioxidant Machinery,Photosynthetic Efficiency and Maintaining Leaf Ultrastructure and Root Morphology

Nickel (Ni), an essential micronutrient and a prime component of the plant enzyme urease, has an indispensable role in plants. Triacontanol (TRIA) is a conspicuous plant growth regulator in agriculture, which proved advantageous in enhancing the overall production of plants. Therefore, an experiment was laid down to understand the effects of Ni toxicity on the menthol mint (Mentha arvensis L.) and its mitigation by exogenously applied TRIA. The different treatments applied to the plants were 0 (control), TRIA (10⁻⁶ M), Ni (60 mg kg⁻¹), Ni (80 mg kg⁻¹), TRIA (10⁻⁶ M) + Ni (60 mg kg⁻¹), and TRIA (10⁻⁶ M) + Ni (80 mg kg⁻¹). This work was evaluated on the basis of various growth, biochemical, physiological, yield and quality parameters. Nickel applied at 80 mg kg⁻¹ of soil exhibited maximum inhibition in the parameters studied. Application of TRIA improved all the growth parameters such as plant height, fresh and dry weights as well as herbage yield under non stress and stressed conditions. The levels of carbonic anhydrase (CA) activity, photosynthetic parameters (chlorophyll and carotenoids), and chlorophyll fluorescence of the plants were also stimulated by TRIA under Ni stress. Exogenous TRIA also displayed positive effects on the cellular antioxidant defense mechanism of Ni-affected plants as it increased the levels of proline (PRO), electrolytic leakage (EL), and activities of antioxidant enzymes, viz. superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX), therefore, restrained the triggering of the oxidative burst (reactive oxygen species) in the plant cells. Moreover, TRIA improved the overall production (in terms of yield and content) of EO in the plants and maintained the leaf ultrastructure and root morphology under Ni treatment. GC–MS analysis revealed that TRIA upregulated the level of menthone and menthyl acetate over their respective controls and under Ni-stressed condition.

     

Toxicity and repellency of origanum essential oil and its components against Tribolium castaneum (Coleoptera: Tenebrionidae) adults

The components of Origanum vulgare L. essential oil showing insecticidal activity and repellency against red flour beetle, Tribolium castaneum (Coleoptera: Tenebrionidae), adults were analysed by GC-MS. All constituents were identified, and the main components were carvacrol (67.2%), p-cymene (16.2%), γ-terpinene (5.5%), thymol (4.9%), and linalool (2.1%). In a vapor phase fumigant assay, the origanum oil was more effective in closed conditions (LD₅₀ = 0.055 mg/cm³) than in open conditions (LD₅₀ > 0.353 mg/cm³). This suggests that toxicity is exerted largely in the vapor phase. Based on 24-h LD₅₀ values, the toxicity of caryophyllene oxide (0.00018 mg/cm³) was comparable with that of dichlorvos (0.00007 mg/cm³). In addition, thymol, camphene, α-pinene, p-cymene, and γ-terpinene showed good insecticidal activity (LD₅₀ = 0.012–0.195 mg/cm³). In repellency tests using 9 constituents of origanum oil, caryophyllene oxide showed complete repellency at 0.03 mg/cm². Hydrogenated monoterpenoids, such as thymol, α-pinene, carvacrol, and myrcene, elicited strong repellency at 0.03 and 0.006 mg/cm². Repellency depended on both time and concentration. These results indicate that origanum oil and its components could be potential candidates as a fumigant and repellent for managing T. castaneum adults.     

Effects of selected plant essential oils on the growth and development of mouse preimplantation embryos in vivo

Plant essential oils (EOs) have been reported to have health benefit properties and their preventive and therapeutic use in animals is expected to increase in the future. We evaluated the influence of five essential oils obtained from plant species which are known to have positive antimicrobial, antioxidative and anti-inflammatory effects--sage EO from Salvia officinalis L. (Lamiaceae), oregano EO from Origanum vulgare L. (Lamiaceae), thyme EO from Thymus vulgaris L. (Lamiaceae), clove EO from Syzygium aromaticum L. (Myrtaceae) and cinnamon EO from Cinnamomum zeylanicum Blume (Lauraceae) on the growth and development of mouse preimplantation embryos in vivo. Essential oils were added to commercial diet at concentrations of 0.25% for sage EO, thyme EO, clove EO, cinnamon EO and 0.1% for oregano EO, and fed to ICR female mice for 2 weeks ad libitum. Females were then mated with males of the same strain. Embryos obtained on Day 4 of pregnancy at the blastocyst stage were stained by morphological triple staining (Hoechst, PI, Calcein-AM) and evaluated using fluorescent microscopy. The effects of essential oils were estimated by the viability of embryos, number of nuclei and distribution of embryos according to nucleus number. Cinnamon EO significantly decreased the number of nuclei and the distribution of embryos according to nucleus number was significantly altered. Sage EO negatively influenced the distribution of embryos according to nucleus number. Clove and oregano EOs induced a significantly increased rate of cell death. Only thyme EO had no detectable effects on embryo development. In conclusion, none of the essential oils had any positive effect on embryo development, but some of them reduced the number of cells and increased the incidence of cell death.     

Anti-Barnacle Activities of Isothiocyanates Derived from β-Citronellol and Their Structure–Activity Relationships

Antifouling agents with low toxicity are in high demand for sustaining marine industries and the environment. This study aimed to synthesize 15 isothiocyanates derived from β-citronellol and evaluate their antifouling activities and toxicities against cypris larvae of the barnacle Amphibalanus amphitrite. The synthesized isothiocyanates exhibited effective antifouling activities (EC₅₀=0.10–3.33 μg mL⁻¹) with high therapeutic ratios (LC₅₀/EC₅₀ >30). Four isothiocyanates with an amide or isocyano group showed great potential as effective antifouling agents (EC₅₀=0.10–0.32 μg mL⁻¹, LC₅₀/EC₅₀=104–833). The enantiomers of the isothiocyanates only slightly differed in their antifouling activities. These results may serve as a basis for further research and development of β-citronellol-derived isothiocyanates as effective low-toxic antifouling agents. To the best of our knowledge, this study is the first to report the antifouling activities of isothiocyanates derived from accessible natural products.     

Morpho-physiological and phytochemical traits of (<Emphasis Type="Italic">Thymus daenensis</Emphasis> Celak.) in response to deficit irrigation and chitosan application

Thymus daenensis Celak. is an aromatic herb used as a popular medicine and its natural products in the form of extracts and essential oil have significant economic values in Iran. We hypothesized that spraying plants grown under deficit irrigation system with chitosan can be considered as an applicable method to enhance essential oil and antioxidant activity in thyme. Response of thyme to three irrigation regimes including well-watered, moderate stress, and severe stress along with three levels of chitosan application rates 0, 200, and 400 μL L^?1 was evaluated in a 2-year study in 2014 and 2015. Drought stress condition significantly shortened phenologic stages, more specifically in the first (establishment) year. All growth parameters were reduced dramatically as drought stress intensified. Imposing even moderate stress reduced leaf area as much as 59 and 44% in the first year and the second year, respectively. Biomass yield of plants grown under severe drought stress decreased substantially, whereas essential oil content and the share of thymol in thyme oil which possesses the greatest degree of biological activity improved. Maximum oil yield (1.50 g plant^?1) was obtained from plants under mild drought stress when sprayed with 400 μL L^?1 chitosan in the second year when plants were well-established. Foliar applications of chitosan reduced the adverse effect of water deficit on oil yield and improved thymol content of the essential oil. Chitosan also increased secondary metabolites including α-terpinene, p-cymene, γ-terpinene, thymol, carvacrol and β-caryophyllene. Leaf flavonoid reduced under deficit irrigation while more phenol was found in plants grown under deficit irrigation. The essential oil of thyme exhibited antioxidant property when the plants were sprayed with 400 μL L^?1 chitosan. The results of this study indicated that thyme can be grown successfully under moderate stress and that application of chitosan elicitor can to some degree compensate the negative impact of deficit irrigation on its biomass and essential oil yield.     

Effect of two plant extracts and Lactobacillus fermentum on colonization of gastrointestinal tract by Salmonella enterica var. Düsseldorf in chicks

According to published data, it is well known that essential oils from plants possess antimicrobial activity against a wide range of pathogens, including Salmonella strains. The influence of the administration of essential oils from oregano (Origanum vulgare) and thyme (Thymus vulgaris) as well as Lactobacillus fermentum on crop, caecum, liver and spleen colonization by Salmonella enterica var. Düsseldorf in chicks was investigated in this study. For the experiment, one hundred 1-day old chicks were used, and they were divided into four groups: (i) untreated (C); (ii) treated with L. fermentum (L); (iii) treated with a mixture of oregano and thyme essential oils (OT); and (iv) treated with a combination of L. fermentum and a mixture of oregano and thyme essential oils (LOT). Essential oils from oregano and thyme were mixed with commercial poultry diet, which was offered ad libitum to chicks in appertaining groups. L. fermentum was added daily to drinking water. After 3 days all the chicks were challenged orally with S. enterica var. Düsseldorf. The crops, ceca, spleens and livers of the birds were examined for S. enterica var. Düsseldorf colonization 5 days after the challenge. Our results showed that a combined administration of L. fermentum and essential oils (oregano and thyme) in group with combined application of essential oils and lactobacillus strain reduced the percentage of colonized crops and ceca when compared to the control group without any treatment. Presented at the Second Probiotic Conference, Košice, 15–19 September 2004, Slovakia.     

Application of natural products as insecticide candidates: Semisynthesis and biological evaluation of some novel osthole-based esters

Natural products are very important sources for the development of new pesticides. Osthole, derived from many medical plants such as Cnidium, Angelica and Citrus plants, is a naturally occurring coumarin compound. To discover the new natural products-based insecticides, thirty-one osthole-based esters containing O-acyl-hydroxylamine groups were prepared, and their structures were identified by different spectral analysis methods. Derivatives A7, A17, A20 and A25 displayed more potent growth inhibitory (GI) activity than the botanical insecticide, toosendanin. Over half of target osthole derivatives had more effective larvicidal effect on P. xylostella than toosendanin. Among all title derivatives, compound A18 displayed more pronounced larvicidal activity (LC₅₀ = 0.64 μmol mL⁻¹) when compared with toosendanin (LC₅₀ = 0.94 μmol mL⁻¹). Some interesting results of structure–activity relationships (SARs) of these osthole derivatives were also discussed. In addition, the hemolysis and cytotoxicity assays indicated that these osthole derivatives showed very low toxicity toward normal mammalian cells.     

Anti-bacterial,anti-scavenging and cytotoxic activity of garden cress polysaccharides

Plants polysaccharides are an infinite stock of drug composites with varying pharmacological and biological activities. The present investigation aimed to examine the antibacterial, anti-scavenging and cytotoxic potential of garden cress (GC) polysaccharides. The antibacterial effects vs Escherichia coli and as well as Staphylococcus aureus of GC polysaccharides were examined by means of agar diffusion assay, minimum inhibitory concentration (MIC), outer and inner cell membrane permeability. Antioxidant potential of the GC polysaccharides were performed by free radical DPPH scavenging, superoxide anion scavenging, hydroxyl radical scavenging, reducing power potential assay, and hydrogen peroxide method. Cytotoxicity potential of GC polysaccharides were evaluated by MTT assay in human cervical (HeLa) and liver carcinoma (HepG2) cell lines. The findings showed that GC polysaccharides MIC were 1.06 and 0.56 mg mL⁻¹ against E. coli and S. aureus, respectively. Compared to the standard inhibitor, the GC polysaccharides showed essential inhibitor assays in a very dose dependent approach, and notable actions to scavenge reactive oxygen species (ROS) are also due to the large quantities of hydrophilic polyphenols. The IC₅₀ values of all tested parameters were measured against standard ascorbic acid antioxidant agent. The GC polysaccharides diminish the cell viability percentage of HeLa and HepG2 in a concentration dependent manner. GC polysaccharides at a dose of 500 µg ml⁻¹ exhibited higher anti-tumor activity in both HeLa (65.33 ± 3.75%) and HepG2 (60.33 ± 3.48%). The findings obtained in this study indicate that GC polysaccharides has antibacterial and has a possible source of natural antioxidant and also has cytotoxic effect on different carcinoma cell lines.     

Inhibitory effect of Thymus vulgaris and Origanum vulgare essential oils on virulence factors of phytopathogenic Pseudomonas syringae strains

• Pseudomonas syringae is a phytopathogenic bacterium that causes lesions in leaves during the colonisation process. The damage is associated with production of many virulence factors, such as biofilm and phytotoxins. The essential oils of Thymus vulgaris (thyme) and Origanum vulgare (oregano) have been demonstrated to inhibit P. syringae. The aim of this study was to investigate the effects of T. vulgaris and O. vulgare essential oils on production of virulence factors of phytopathogenic P. syringae strains, including anti‐biofilm and anti‐toxins activities.
• The broth microdilution method was used for determination of MIC and biofilm inhibition assays. Coronatine, syringomycin and tabtoxin were pheno‐ and genotypically evaluated.
• Both oils showed good inhibitory activity against P. syringae, with MIC values from 1.43 to 11.5 mg·ml^?1 for thyme and 5.8 to 11.6 mg·ml^?1 for oregano. Biofilm formation, production of coronatine, syringomycin and tabtoxin were inhibited by thyme and oregano essential oil in most strains.
• The results presented here are promising, demonstrating the bactericidal activity and reduction of virulence factor production after treatment with thyme and oregano oil, providing insight into how they exert their antibacterial activity. These natural products could be considered in the future for the control of diseases caused by P. syringae.