Chemical composition and antimicrobial activity of the essential oil of Lippia grandis Schauer (Verbenaceae) from the western Amazon

Antifungal Activity of Essential Oil and Plant-Derived Natural Compounds against Aspergillus flavus

Aspergillus flavus is a facultative parasite that contaminates several important food crops at both the pre- and post-harvest stages. Moreover, it is an opportunistic animal and human pathogen that causes aspergillosis diseases. A. flavus also produces the polyketide-derived carcinogenic and mutagenic secondary metabolite aflatoxin, which negatively impacts global food security and threatens human and livestock health. Recently, plant-derived natural compounds and essential oils (EOs) have shown great potential in combatting A. flavus spoilage and aflatoxin contamination. In this review, the in situ antifungal and antiaflatoxigenic properties of EOs are discussed. The mechanisms through which EOs affect A. flavus growth and aflatoxin biosynthesis are then reviewed. Indeed, several involve physical, chemical, or biochemical changes to the cell wall, cell membrane, mitochondria, and related metabolic enzymes and genes. Finally, the future perspectives towards the application of plant-derived natural compounds and EOs in food protection and novel antifungal agent development are discussed. The present review highlights the great potential of plant-derived natural compounds and EOs to protect agricultural commodities and food items from A. flavus spoilage and aflatoxin contamination, along with reducing the threat of aspergillosis diseases.

Antifungal Activities of Different Essential Oils and Their Electrospun Nanofibers against Aspergillus and Penicillium Species Isolated from Bread

Mold growth, especially Aspergillus spp. and Penicillium spp., deteriorates the quality of bakery products. Essential oils (EOs) have been categorized as good natural antimicrobials. Hereby, this study aimed to evaluate the antifungal activity of six EOs, ginger, cumin, cinnamon, black pepper, origanum, and clove, and their volatile compounds against fungal strains isolated from bread: Penicillium carneum DDS4, Aspergillus flavus DDS6, and Aspergillus niger DDS7 by disc diffusion and disc volatilization methods, respectively. Among EOs, cumin, cinnamon, origanum, and clove were found to be effective against fungal strains, and their minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) were determined. The observed lowest MIC value of EOs was obtained at 1000 μg/mL concentration, and the lowest MFC value was obtained from the results of clove at a concentration of 1000 μg/mL. Based on the MIC and MFC values, clove and cinnamon EOs were found to be more effective at lower concentrations. Electrospun nanofiber films of clove and cinnamon were produced with 6% poly(vinyl alcohol) (PVA), 2% β-cyclodextrin (β-CD), and 2% EO to overcome the unfavorable sensory impact of EOs on food products. The inhibitory activity of cinnamon EO film (2.64-2.51 log(CFU/mg)) was considerably lower than clove EO film (3.18-3.24 log(CFU/mg)) against P. carneum DDS4 and A. niger DDS7. Furthermore, these nanofiber films prevented fungal growth on bread samples visibly and were shown to be an alternative application for active food packaging.

Essential Oil of the Plants Growing in the Brazilian Amazon: Chemical Composition, Antioxidants, and Biological Applications

Essential oils are biosynthesized in the secondary metabolism of plants, and in their chemical composition, they can be identified different classes of compounds with potential antioxidant and biological applications. Over the years in the Amazon, several species of aromatic plants were discovered and used in traditional medicine. The literature has shown that essential oils extracted from amazon species have several biological activities, such as antioxidant, antibacterial, antifungal, cytotoxic, and antiprotozoal activities. These activities are related to the diversified chemical composition found in essential oils that, by synergism, favors its pharmacological action. In light of this vital importance, this study aimed at performing a review of the literature with particular emphasis on the chemical composition and biological activities in studies conducted with species collected in the Amazon, taking into consideration in particular the last 10 years of collection and research.

Piper aduncum essential oil: a promising insecticide, acaricide and antiparasitic. A review

Several studies have assessed the potential of essential oils as substitutes for synthetic pesticides, in order to counter insect resistance to commercial pesticides. Piper aduncum L. is a very common shrub in the Amazon Rainforest and in other subtropical areas. The objective of this review was to analyse the existing information on P. aduncum essential oil as a raw material for new bioproducts for sustainable pest disease management. With this review, we collected and critically analysed 59 papers, representing all the studies that aimed to evaluate the essential oil properties of this species as an insecticide, acaricide and antiparasitic. The chemical composition differs depending on the origin, although phenylpropanoid dillapiole is the most cited component, followed by myristicin, 1,8-cineole and β-ocimene. Between the acaricidal, antiparasitic and synergistic activities, the insecticidal effects are highly promising, with optimal results against the malaria vector Aedes aegypti, with an LC50 that ranges between 57 and 200μg/mL. Acaricidal activity has mainly been reported against Tetranychus urticae, showing an LC50 that ranges between 5.83 and 7.17μg/mL. Antiparasitic activity has predominately been found on Leishmania amazonensis, and antipromastigote activity has been found to be between 23.8 and 25.9μg/mL. Concerning the synergistic effect between dillapiole and synthetic insecticides, four studies on Spodoptera frugiperda found promising results with cypermethrin. In this review, we highlighted the potential of P. aduncum essential oil as a biopesticide, also focusing on the lack of information about applied research. We also provide suggestions for future investigations.

Botanical and chemical fungicides in the treatment of commercial seeds of Brachiaria brizantha and Panicum maximum

Brazil is the largest producer, consumer, and exporter of forage seeds in the world. However, the high incidence of pathogens threatens the seed production system, resulting in decreases in production and quality. Currently, the emphasis has been placed on the use of alternative products as a way of maintaining productivity and environmental sustainability. Thus, the objective of this study was to evaluate the mycoflora associated with the commercial seeds of Brachiaria brizantha and Panicum maximum treated with chemical and alternative fungicide. To test with chemical and alternative treatments, seeds were subjected to fluazinam + thiophanate-methyl, fludioxonil + metalaxyl-M, noni essential oil, rosemary pepper essential oil, sulfuric acid. There was also an untreated control. The most efficient products in the control of incident fungi were, in decreasing order, fluazinam + thiophanate-methyl, fludioxonil + metalaxyl-M, noni essential oil, rosemary pepper essential oil, and sulfuric acid. Fungicides mainly controlled the genera Alternaria, Aspergillus, Bipolaris, Chaetomium, Cladosporium, Colletotrichum, Curvularia, Fusarium, Penicillium, Phoma and Rhizopus. Essential oils showed positive effects in controlling Bipolaris, Curvularia, and Fusarium. Sulfuric acid reduced the incidence of Bipolaris, Colletotrichum, Curvularia, Fusarium, Phoma, and Rhizopus. Seed treatment is one of the promising strategies for obtaining seeds of a healthy quality. As a result, the fungicides and botanical components listed above were promising in reducing fungi associated with forage seeds and can be used for seed treatments and in the development of new products with a natural base through essential oils.

Chemical compositions and antimicrobial activities of the essential oil from Pterocarya stenoptera C. DC

The present study investigated the chemical compositions and antimicrobial activities of essential oil from Pterocarya stenoptera. The essential oil obtained by hydrodistillation from the dried leaves of P. stenoptera was analysed by GC-MS and 39 constituents accounting for the total 90.44% of the oil were identified. The main constituents were δ-cadinene (24.83%), caryophyllene oxide (9.10%), α-cadinol (7.48%) and β-elemene (6.24%). The antimicrobial activity of the oil was evaluated by disc diffusion and broth microdilution methods. The essential oil was found to show broad-spectrum antimicrobial activities against all the tested microorganisms. Bacillus subtilis was the most sensitive strain with the minimum inhibitory concentration of 0.23 mg/mL. The results suggested that the essential oil was a potential source of natural antimicrobials in food preservation and pharmaceutical industry.

Lippia gracilis Schauer essential oil as a growth promoter for Japanese quail

The use of antibiotics as performance enhancers in animal feeding is declining, so Lippia gracilis Schauer essential oil (LGSEO) could be used as a potential substitute for the conventionally used growth promoters. The LGSEO contains components such as carvacrol and thymol, which kill and/or control pathogenic bacteria, increase population of beneficial organisms, act against oxidative processes and onto nutrient digestibility and absorption. The aim of this study was to investigate the action and the effects of LGSEO as a growth promoter in the diet of Japanese quail by examining their productive performance, intestinal microbiology, blood biochemical parameters, hepatic thiobarbituric acid reactive substances (TBARS) content and intestinal gene expression. A total of 252 two-day-old quail (Coturnix coturnix japonica) were assigned to 3 treatments in 7 replicates, using 12 birds per experimental unit. The treatments consisted of a basal diet, basal diet + LGSEO at 400 mg/kg of diet and basal diet + chemical antimicrobial (bacitracin methylene disalicylate) at 500 mg/kg of diet. The experimental period was 34 days. The highest feed intake (P < 0.01) was found in the group receiving the conventional antimicrobial, whereas the best feed conversion (P < 0.01) was shown by the animals receiving LGSEO. Escherichia coli growth was restricted in the quail receiving the growth promoters. Salmonella spp. growth was controlled by the treatment containing the conventional antimicrobial. There was no difference between the treatments (P > 0.05) for the concentration of aspartate aminotransferase and alanine aminotransferase enzymes in the blood or hepatic TBARS content. Birds receiving negative-control treatment exhibited a higher expression of sodium-glucose cotransporter (SGLT1), while those receiving the treatment with essential oil showed lower catalase (CAT) and glutathione peroxidase (GPX7) expressions compared to the conventional antimicrobial and control groups, respectively. Lippia gracilis Schauer essential oil is a powerful performance enhancer for Japanese quail by virtue of its abilities to improve their intestinal environment, balance the microbial population and reduce energy expenditure for oxidative processes.

In vitro antioxidant, antibacterial, in vivo immunomodulatory, antitumor and hematological potential of exopolysaccharide produced by wild type and mutant Lactobacillus delbureckii subsp. bulgaricus

Biological evaluation of exopolysaccharides (EPS) produced by wild type and mutant Lactobacillus delbureckii (EPSWLD and EPSMLD) was investigated. Varying degrees of functional groups associated with polysaccharides were present thus confirming the EPS. The EPSs had strong antioxidant potential in a dose dependent (0.5–10 mg/mL) manner. EPSWLD and EPSMLD exhibited the highest 1,1-diphemy 1-2-picryl-hydrazyl (DPPH) activity (73.4 % and 65.6 %), total antioxidant activity (1.80 % and 1.42 %), H₂O₂ scavenging activity (88.5 % and 78.6 %) and Ferric Reducing Antioxidant Power (FRAP) (1.89 % and1.81 %) at 10 mg/mL respectively. WLD and MLD were highly susceptible to chloramphenicol, cotrimoxazole, tetracycline, erythromycin and ceftazidine and resistant to cefuroxime, gentamicin and cloxacillin. The EPSs had antibacterial activity against the test pathogens. B. subtilis and S. aureus had the highest susceptibility (26.0 mm and 23.0 mm). EPSMLD modulate the highest IgG, IgA and IgM production (68–126 mg/dL and 67–98 mg/dL and 64–97 mg/dL) in the treated tumor induced mice (TTIM). EPSWLD and EPSMLD exhibited reduction capability on the CEA level (3.99–4.35 ng/L and 4.12–4.23 ng/L) of the TTIM. EPSWLD TTIM had the highest amount of RBC, WBC and PCV (5.6 × 10¹²%, 68000% and 42%). The EPS increased the lifespan of TTIM. In conclusion EPSWLD and EPSMLD had strong biological potential with pharmacological and neutraceutical activity.

Improving the Efficacy of Essential Oils as Antimicrobials in Foods: Mechanisms of Action

The consumer preference for clean-label products is requiring the food industry to reformulate their products by replacing artificial additives with natural alternatives. Essential oils are natural antimicrobials isolated from plant sources that have the potential to combat many foodborne pathogens and spoilage organisms. This review begins by discussing the antimicrobial properties of essential oils, the relationships between their chemical structure and antimicrobial efficacy, and their potential limitations for commercial applications (such as strong flavor, volatility, and chemical instability). We then review the commonly used methods for screening the antimicrobial efficacy of essential oils and elucidating their mechanisms of action. Finally, potential applications of essential oils as antimicrobials in foods are reviewed and the major types of food-grade delivery systems available for improving their efficacy are discussed.

Antimicrobial Activity and Chemical Composition of Essential Oils from Verbenaceae Species Growing in South America

The Verbenaceae family includes 2600 species grouped into 100 genera with a pantropical distribution. Many of them are important elements of the floras of warm-temperature and tropical regions of America. This family is known in folk medicine, and its species are used as digestive, carminative, antipyretic, antitussive, antiseptic, and healing agents. This review aims to collect information about the essential oils from the most reported species of the Verbenaceae family growing in South America, focusing on their chemical composition, antimicrobial activity, and synergism with commercial antimicrobials. The information gathered comprises the last twenty years of research within the South American region and is summarized taking into consideration the most representative species in terms of their essential oils. These species belong to Aloysia, Lantana, Lippia, Phyla, and Stachytarpheta genera, and the main essential oils they contain are monoterpenes and sesquiterpenes, such as β-caryophyllene, thymol, citral, 1,8-cineole, carvone, and limonene. These compounds have been found to possess antimicrobial activities. The synergism of these essential oils with antibiotics is being studied by several research groups. It constitutes a resource of interest for the potential use of combinations of essential oils and antibiotics in infection treatments.

Computational tool for optimizing the essential oils utilization in inhibiting the bacterial growth

Day after day, the importance of relying on nature in many fields such as food, medical, pharmaceutical industries, and others is increasing. Essential oils (EOs) are considered as one of the most significant natural products for use as antimicrobials, antioxidants, antitumorals, and anti-inflammatories. Optimizing the usage of EOs is a big challenge faced by the scientific researchers because of the complexity of chemical composition of every EO, in addition to the difficulties to determine the best in inhibiting the bacterial activity. The goal of this article is to present a new computational tool based on two methodologies: reduction by using rough sets and optimization with particle swarm optimization. The developed tool dubbed as Essential Oil Reduction and Optimization Tool is applied on 24 types of EOs that have been tested toward 17 different species of bacteria.

Antibacterial and Antifungal Activities of Spices

Infectious diseases caused by pathogens and food poisoning caused by spoilage microorganisms are threatening human health all over the world. The efficacies of some antimicrobial agents, which are currently used to extend shelf-life and increase the safety of food products in food industry and to inhibit disease-causing microorganisms in medicine, have been weakened by microbial resistance. Therefore, new antimicrobial agents that could overcome this resistance need to be discovered. Many spices-such as clove, oregano, thyme, cinnamon, and cumin-possessed significant antibacterial and antifungal activities against food spoilage bacteria like Bacillus subtilis and Pseudomonas fluorescens, pathogens like Staphylococcus aureus and Vibrio parahaemolyticus, harmful fungi like Aspergillus flavus, even antibiotic resistant microorganisms such as methicillin resistant Staphylococcus aureus. Therefore, spices have a great potential to be developed as new and safe antimicrobial agents. This review summarizes scientific studies on the antibacterial and antifungal activities of several spices and their derivatives.

Essential Oils of Oregano: Biological Activity beyond Their Antimicrobial Properties

Essential oils of oregano are widely recognized for their antimicrobial activity, as well as their antiviral and antifungal properties. Nevertheless, recent investigations have demonstrated that these compounds are also potent antioxidant, anti-inflammatory, antidiabetic and cancer suppressor agents. These properties of oregano essential oils are of potential interest to the food, cosmetic and pharmaceutical industries. The aim of this manuscript is to review the latest evidence regarding essential oils of oregano and their beneficial effects on health.

Chemical Composition and Cytotoxic and Antibacterial Activities of the Essential Oil of Aloysia citriodora Palau Grown in Morocco

The aim of this work is to investigate the in vitro cytotoxic and antibacterial effects of the essential oils of Aloysia citriodora Palau, harvested in different regions of Morocco. The chemical profile was established using gas chromatography-mass spectrometry analysis. The cytotoxic activity against P815, MCF7, and VERO cell lines as well as the normal human peripheral blood mononuclear cells (PBMCs) was evaluated using the MTT assay. Standard, ATCC, strains of bacteria (Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa) were cultivated in Muller Hinton media. Then, agar disc diffusion, minimum inhibitory concentrations (MICs), and minimal bactericidal concentrations (MBCs) were determined using microdilution method. The essential oils obtained were predominantly composed of β-spathulenol (15.61%), Ar-curcumene (14.15%), trans-caryophyllene oxide (14.14%), and neral (10.02%). The results of the assays showed that the cytotoxic effect of the essential oil of A. citriodora was high on P815 and moderate on MCF7 and on VERO cell lines. However, no cytotoxic effect was observed on PBMCs. On the other hand, essential oils showed a significant antimicrobial activity against both Gram-negative and Gram-positive bacteria. MICs ranged between 2.84 and 8.37 mg/ml. Essential oil of A. citriodora leaves possesses significant antibacterial effect and cytotoxic activity against tumor cell lines.

Differential Cytotoxic Activity of Essential Oil of Lippia citriodora from Different Regions in Morocco

The aim of this work was to investigate the cytotoxic effect of the essential oil of dried leaves of Lippia citriodora (H.B. & K.) harvested in different regions of Morocco. This effect was evaluated against the P815 murine mastocytoma cell line using the MTT assay. Interestingly, this work demonstrated for the first time that these essential oils exhibited a strong cytotoxic activity against the P815 cell line, with IC₅₀ values ranging from 7.75 to 13.25 μg/ml. This cytotoxicity began early and increased in a dose- and time-dependent manner. The chemical profile of these essential oils was analyzed by gas chromatography coupled to mass spectrometry. Importantly, the difference in terms of major components' contents was not significant suggesting probably that the differential cytotoxicity between these essential oils could be attributed to the difference in the content of these essential oils in minor compounds, which could interact with each other or with the main molecules. Finally, this study demonstrated for the first time that essential oils of L. citriodora from different regions in Morocco induced apoptosis against P815 tumor cell line.

Experimental Paper. Activity of essential oils against Staphylococcus aureus strains isolated from skin lesions in the course of staphylococcal skin infections

Introduction: Staphylococcus aureus is an important etiological agent of skin and soft tissue infections. Due to the increasing resistance of this bacterium to antimicrobial agents, treatment of staphylococcal infections remains a great challenge for clinicians and requires an alternative treatment options. Objective: The aim of the study was to determine the antimicrobial activity of essential oils: caraway (CEO), patchouli (PEO) and geranium (GEO) against S. aureus strains isolated from skin lesions in the course of staphylococcal skin infections. Methods: The antibacterial activity of essential oils was tested using the dilution method in Mueller-Hinton broth. Results: The antimicrobial effect of CEO, PEO and GEO was observed. The highest antimicrobial activity showed PEO (MIC = 1.7±0.8 µl/ml), the lower was observed for GEO (MIC = 5.4±2.0 µl/ml) and CEO (MIC = 18.8±10.3 µl/ml). Conclusion: All tested essential oils showed antibacterial activity against S. aureus strains isolated from skin lesions of patients with staphylococcal skin infections. Application of the CEO, PEO and GEO can become an alternative method of treatment of staphylococcal infections, but further microbiological tests and clinical trials should be assessed.

Chemical composition and some biological activities of the essential oils from basil Ocimum different cultivars

Background

The plants belonging to the Ocimum genus of the Lamiaceae family are considered to be a rich source of essential oils which have expressed biological activity and use in different area of human activity. There is a great variety of chemotypes within the same basil species. Essential oils from three different cultivars of basil, O. basilicum var. purpureum, O. basilicum var. thyrsiflora, and O. citriodorum Vis. were the subjects of our investigations.

Methods

The oils were obtained by steam distillation in a Clevenger-type apparatus. The gas chromatography mass selective analysis was used to determine their chemical composition. The antioxidant activities of these essential oils were measured using 1,1-diphenyl-2-picrylhydrazyl assays; the tyrosinase inhibition abilities of the given group of oils were also assessed spectophotometrically, and the antimicrobial activity of the essential oils was determined by the agar diffusion method, minimal inhibitory concentrations were expressed.

Results

According to the results, the qualitative and quantitative composition of essential oils was quite different: O. basilicum var. purpureum essential oil contained 57.3% methyl-chavicol (estragol); O. basilicum var. thyrsiflora oil had 68.0% linalool. The main constituents of O. citriodorum oil were nerol (23.0%) and citral (20.7%). The highest antioxidant activity was demonstrated by O. basilicum var. thyrsiflora essential oil. This oil has also exhibited the highest tyrosinase inhibition level, whereas the oil from O. citriodorum cultivar demonstrated the highest antimicrobial activity.

Conclusions

The results obtained indicate that these essential oils have antioxidant, antibacterial and antifungal activity and can be used as natural antioxidant and antimicrobial agents in medicine, food industry and cosmetics.

Antimicrobial and antibiofilm activity of Baccharis psiadioides essential oil against antibiotic-resistant Enterococcus faecalis strains

CONTEXT

Baccharis psiadioides (Less.) Joch. Müller (Asteraceae) is considered as a producer of bioactive essential oils and is used in south Brazilian folk medicine for its proprieties as stimulant, antipyretic, anti-inflammatory and as an antidote for snake bites.

OBJECTIVE

To verify the antimicrobial and antibiofilm activities of the essential oil of B. psiadioides (EOBP) against antibiotic-resistant Enterococcus faecalis.

MATERIALS AND METHODS

The initial evaluation of EOBP activity was conducted by the agar and microdilution methods against 13 antibiotic-resistant E. faecalis strains. The antibiofilm effect was determined by the application of EOBP in the earlier adherent cells or to the stabilized biofilm for 24 h and was evaluated by crystal violet, viability and scanning electron microscopy (SEM) assays. Chemical composition of EOBP was determined by gas chromatography (GC/FID - GC/MS).

RESULTS

The MIC values for EOBP were at least 1.25% and 4-16% for agar and microdilution assays, respectively. The EOBP reduced the microbial adherence and the viability of the cells, but did not cause the complete disruption of biofilms. SEM images indicate that EOBP influences the adherence of cells to a surface. The monoterpene β-pinene was the major constituent identified in EOBP.

CONCLUSION

This research shows the ability of EOBP to control resistant E. faecalis strains and to reduce the biofilm amount attached to abiotic surfaces, indicating its role as a promising new natural antimicrobial agent. Moreover, these results further contribute to the growing number of studies of plant natural products which suggest that these compounds can combat resistant microorganisms.

Atividade antisséptica do óleo essencial de Lippia origanoides Cham. (Alecrim-pimenta) na presença de leite bovino

Resumo: Objetivou-se determinar atividade antisséptica do óleo essencial de Lippia origanoides na presença de leite bovino. A composição química do óleo essencial de alecrim pimenta foi determinada por cromatografia gasosa acoplada à espectrometria de massas (CG-EM), sendo detectados 53 compostos, dos quais 16 foram identificados (>0,1% área total). O carvacrol (32,7%), p-cimeno (23%), timilmetil éter, cariofileno (7,98%) e o γ-terpineno (5,40%) foram os componentes mais abundantes. A concentração inibitória mínima para Staphylococcus aureus ATCC 25923 e E. coli ATCC 8739 foi de 60μL/mL, enquanto para Salmonella Choleraesuis ATCC 35640 foi de 90μL/mL. A concentração bactericida mínima foi de 120μL/mL para as três bactérias. Avaliou-se a atividade antisséptica do óleo essencial na concentração de 120μL/mL na presença de leite bovino sobre as mesmas cepas bacterianas. O óleo em estudo apresentou efeito inibitório do crescimento das cepas em diferentes tempos de ação (p<0,05). S. aureus apresentou maiores índices de inibição após 5 min de contato e Escherichia coli e Salmonella Choleraesuis após 15 min. O óleo essencial de alecrim-pimenta revelou ser um potencial antimicrobiano natural, mesmo na presença de matéria orgânica constituída de uma matriz nutricional complexa que é o leite bovino.

The Chemical Featuring, Toxicity, and Antimicrobial Activity of Psidium cattleianum (Myrtaceae) Leaves

It is known that the phytochemical identification and assessment of biological effects caused by the constituent species Psidium cattleianum, which belongs to family Myrtaceae, are poorly held in the literature. The aim of the current study is to investigate the composition of secondary metabolites, the toxicity, and the antimicrobial activity of P. cattleianum leaves. The crude ethanolic extract of the plant was obtained through maceration and fractionated with hexane, dichloromethane, and ethyl acetate. The crude ethanol extract and the fractions were subjected to phytochemical screening and tested against the microcrustacean Artemia salina for toxicological assessment. Antimicrobial tests with crude ethanol extract and the fractions were carried out through the agar diffusion method using broth microdilution against Staphylococcus aureus, S. epidermidis, Burkholderia cepacia, and Escherichia coli strains. A variety of secondary metabolite groups such as catechins, steroids, phenolic compounds, flavonoids, and saponins was detected. Regarding toxicity, hexane and dichloromethane fractions were considered nontoxic, whereas the crude ethanol extract and the ethyl acetate fraction showed low toxicity. The crude ethanol extract and the fractions, except for the hexane fraction, showed activity against the tested strains. Therefore, the composition of the secondary metabolites, the low toxicity, and the antimicrobial activity suggest that this species is promising in the search and development of new drugs.

Antimicrobial and seasonal evaluation of the carvacrol-chemotype oil from Lippia origanoides kunth

This study evaluated the influence of seasonal variation on the yield and composition of essential oil of Lippia origanoides occurring in the Middle Rio Amazonas, Brazil, and the impact on its antimicrobial potential. The average oil yield was 1.7% ± 0.2% in the rainy season and 1.6% ± 0.3% in the dry season. Some correlations with climatic parameters were observed. The major components were carvacrol (rainy, 43.5% ± 1.9%; dry, 41.4% ± 2.04%), thymol (rainy, 10.7% ± 1.1%; dry, 10.6% ± 0.9%), p-cymene (rainy, 9.8% ± 0.7%; dry, 10.0% ± 1.4%) and p-methoxythymol (rainy, 9.6% ± 0.8%; dry, 10.4% ± 1.4%). It was found that the antibacterial activity of L. origanoides against Staphylococcus aureus and Escherichia coli was little influenced by the changes in oil composition due to seasonal variation. Against S. aureus, the oil Minimum Inhibitory Concentration (MIC) value was 1.25 μL/mL over ten months. Against E. coli, the oil MIC values ranged from 0.15 μL/mL to 0.31 μL/mL in different months of the year. The Minimum Bactericidal Concentration (MBC) value was 2.5 μL/mL against S. aureus and 1.25 μL/mL against E. coli. The results suggest that the antimicrobial activity identified in the oil remain unchanged for the full year, allowing its medicinal use without any risk of loss or absence of the active principles of the plant.

Antimicrobial activity of the essential oil of Glossogyne tenuifolia against selected pathogens

BACKGROUND

Glossogyne tenuifolia (GT) is a perennial herb widely distributed in the areas from south Asia to Australia. Many biological effects of G. tenuifolia have been reported; however, the information about antimicrobial activity of the essential oil (EO) of the herb remains unavailable. Therefore, the aims of this study were to investigate the antimicrobial activity of the GT-EO in vitro and food systems, the antimicrobial impact (AI) of its individual compounds, and interactive effects of major active compounds (linalool, 4-terpineol, α-terpineol, ρ-cymene) on selected Gram-positive (S. aureus, L. monocytogenes, S. mutans and S. sanguinis) and Gram-negative (E. coli O157:H7, V. parahaemolyticus and S. enterica) pathogens.

RESULTS

The minimal microbicidal concentration (MMC) of the GT-EO ranged from 0.75 to 12 mg mL(-1) against the test bacteria in vitro. Except for L. monocytogenes, the GT-EO exhibited more inhibitory effect on the selected Gram positive than against the Gram negative bacteria at the GT-EO concentrations ≤ 12 mg mL(-1) . The interactive effects of major active compounds (linalool, 4-terpineol, α-terpineol, ρ-cymene) are additive instead of synergistic via the checkerboard analysis. The bacteria with a microbial load of ca. 10(2) CFU mL(-1) in the milk tea could be completely inactivated by the GT-EO with the MMC of 1.5 mg mL(-1) .

CONCLUSION

ρ-Cymene is the largest component in the GT-EO; however, it is not the compound predominantly affecting the entire antimicrobial activity of the EO. Instead, 4-terpineol is the most influential among the test compounds that contribute to the antimicrobial activity of the GT-EO.

Entomopathogenic nematodes associated with essential oil of Lippia sidoides for control of Rhipicephalus microplus (Acari: Ixodidae)

In vitro effect of the association of the entomopathogenic nematodes Heterorhabditis bacteriophora HP88 and Heterorhabditis indica LPP1 with the essential oil of Lippia sidoides on engorged females of Rhipicephalus microplus was assessed. Engorged females with homogeneous weights (p >0.05) were divided into six groups of ten ticks each (each female = an experimental unit). In the treated groups, the ticks were exposed to the oil (40 μl/ml=4%) and nematodes (300 entomopathogenic nematodes (EPNs/tick) separately and also to the nematodes together with the oil, while in the control group, the females were immersed in Tween 80 (3%). All the treatments caused a significant reduction in the egg mass weight (p <0.05). The hatching percentage of larvae was reduced (p <0.05) in the groups treated with H. bacteriophora HP88, H. indica LPP1, and H. bacteriophora HP88 associated with the oil, but in the group treated only with the oil, the hatching of percentage of larvae rate was similar to that of the control group (p >0.05). The percentage of control in the group exposed only to the oil was 50.7%, while in the other treated groups, the percentage of control was greater than 95 %, reaching 100 %in the group treated with H. indica LPP1 associated with the oil. The results of the L. sidoides essential oil in the concentrations tested in association with both H. bacteriophora HP88 and H. indica LPP1 indicate that these combinations can be used to control R. microplus.

Antimicrobial activity of Thymus longicaulis C. Presl essential oil against respiratory pathogens

Thymus longicaulis C. Presl is a small aromatic perennial herb used as a traditional remedy for cold, flu and cough. Composition of the essential oil of T. longicaulis from Croatia and its in vitro antimicrobial activity against the most common respiratory pathogens were evaluated. The yield of essential oil obtained by hydrodistillation from aerial plant parts was 1.2%. According to the GC-MS analysis, a total of forty one compounds (99%) were identified. Thymol (46.3%), γ-terpinene (16.2%), thymyl methyl ether (11.4%), and p-cymene (9.4%) were the main components. Antimicrobial activity of the essential oil against six clinically isolated bacterial and yeast strains was determined using standard disc agar diffusion method and microdilution broth assay. The essential oil exhibited antimicrobial activity towards all tested respiratory pathogens. The most sensitive strains were Haemophilus influenzae and Streptococcus pneumoniae(MIC=0.78 mg/mL), while Staphylococcus aureus was the most resistant (MIC>25.00 mg/mL). Our results indicate that T. longicaulis essential oil could be effective against clinically relevant respiratory pathogens which have the ability to develop resistance to antimicrobial drugs.