Synergistic antimicrobial activities of natural essential oils with chitosan films

The synergistic antimicrobial activities of three natural essential oils (i.e., clove bud oil, cinnamon oil, and star anise oil) with chitosan films were investigated. Cinnamon oil had the best antimicrobial activity among three oils against Escherichia coli , Staphylococcus aureus , Aspergillus oryzae , and Penicillium digitatum . The chitosan solution exhibited good inhibitory effects on the above bacteria except the fungi, whereas chitosan film had no remarkable antimicrobial activity. The cinnamon oil-chitosan film exhibited a synergetic effect by enhancing the antimicrobial activities of the oil, which might be related to the constant release of the oil. The cinnamon oil-chitosan film had also better antimicrobial activity than the clove bud oil-chitosan film. The results also showed that the compatibility of cinnamon oil with chitosan in film formation was better than that of the clove bud oil with chitosan. However, the incorporated oils modified the mechanical strengths, water vapor transmission rate, moisture content, and solubility of the chitosan film. Furthermore, chemical reaction took place between cinnamon oil and chitosan, whereas phase separation occurred between clove bud oil and chitosan.     

Bioactivity of Backhousia citriodora: antibacterial and antifungal activity

Backhousia citriodora products are used as bushfoods and flavorings and by the aromatherapy industry. The antimicrobial activity of 4 samples of B. citriodora oil, leaf paste, commercial tea (0.2 and 0.02 g/mL), and hydrosol (aqueous distillate) were tested against 13 bacteria and 8 fungi. Little or no activity was found to be associated with the leaf tea and hydrosol, respectively. Leaf paste displayed antimicrobial activity against 7 bacteria including Clostridium perfringens, Pseudomonas aeruginosa, and a hospital isolate of methicillin resistant Staphylococcus aureus (MRSA). The 4 essential oils were found to be effective antibacterial and antifungal agents; however, variation was apparent between oils that did not correlate with citral content. The antimicrobial activity of B. citriodoraessential oils was found to be greater than that of citral alone and often superior to Melaleuca alternifolia essential oil. B. citriodora has significant antimicrobial activity that has potential as an antiseptic or surface disinfectant or for inclusion in foods as a natural antimicrobial agent.     

Chemical composition and antifungal activity of essential oils from different tissues of Japanese Cedar (Cryptomeria japonica)

In this study antifungal activities of essential oils from different tissues of Japanese cedar (Cryptomeria japonica D. Don) against four wood decay fungi and six tree pathogenic fungi were investigated. In addition, the yields of essential oils obtained by water distillation were compared and their constituents determined by GC-MS analyses. The yield of essential oils from four tissues of Japanese cedar is in the decreasing order of leaf (27.38 mL/kg) > bark (6.31 mL/kg) > heartwood (3.80 mL/kg) > sapwood (1.27 mL/kg). Results obtained from the antifungal tests demonstrate that the essential oil of Japanese cedar heartwood used against Laetiporus sulphureus and Trametes versicolor and sapwood essential oil used against L. sulphureus had strong antifungal activities at 500 mug/mL, with IC(50) values of 39, 91, and 94 microg/mL, respectively. Besides, the essential oils of Japanese cedar heartwood used against Rhizoctonia solani, Collectotrichum gloeosporioides, Fusarium solani, and Ganoderma australe had strong antifungal activities at 500 microg/mL, with IC(50) values of 65, 80, 80, and 110 microg/mL, respectively. GC-MS analyses showed that the sesquiterpene hydrocarbon compounds dominate in the essential oil from Japanese cedar heartwood, amounting to a total percentage of 82.56%, with the major compounds of delta-cadinene (18.60%), isoledene (12.41%), and gamma-muurolene (11.82%). It is proposed that the excellent antifungal activities of Japanese cedar heartwood essential oils might correlate with the presence of these compounds.     

Chemical composition of the essential oils of Juniperus from ripe and unripe berries and leaves and their antimicrobial activity

The composition of the essential oil from ripe and unripe berries and leaves of Juniperus oxycedrus L. ssp. oxycedrus, Juniperus phoenicea ssp. turbinata and Juniperus communis ssp. communis was analyzed by GC-MS, and microbiological assays were carried out. Samples were collected in different localities (Sardinia, Italy) and hydro distilled. The yields ranged between 2.54% +/- 0.21 (v\w dried weight) and 0.04% +/- 0.00. A total of 36 components were identified. The major compounds in the essential oils were alpha-pinene, beta-pinene, delta-3-carene, sabinene, myrcene, beta-phellandrene, limonene, and D-germacrene. Both qualitative and quantitative differences between species and between different parts of the plant were observed. The essential oils and their major compounds were tested against Candida albicans, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, and the minimum inhibitory concentration and minimum bactericidal concentration were determined. The results obtained led to a nonsignificant inhibitory effect, although all the essential oils from Juniperus phoenicea ssp. turbinata and the essential oil from leaves of Juniperus oxycedrus ssp. oxycedrus exhibited rather good or weak activity against Candida albicans and Staphylococcus aureus.     

Chemical compositions and antibacterial effects of essential oils of Turkish oregano (Origanum minutiflorum), bay laurel (Laurus nobilis), Spanish lavender (Lavandula stoechas L.), and fennel (Foeniculum vulgare) on common foodborne pathogens

Chemical compositions and inhibitory effects of essential oils of Turkish oregano (Origanum minutiflorum O. Schwarz & P. H. Davis), bay laurel (Laurus nobilis L.), Spanish lavender (Lavandula stoechas subsp. stoechas L.), and fennel (Foeniculum vulgare Mill.) on Escherichia coli O157:H7, Listeria monocytogenes, Salmonella typhimurium, and Staphylococcus aureus were determined. After the essential oils were applied on the foodborne pathogens at doses of 0 (control), 5, 10, 20, 30, 40, 50, and 80 microL/mL, the resultant numbers of cells surviving were counted. Results revealed that all essential oils exhibited a very strong antibacterial activity against the tested bacteria (P < 0.05). Gas chromatography-mass spectrophotometry analyses revealed that carvacrol (68.23%), 1,8-cineole (60.72%), fenchone (55.79%), and trans-anethole (85.63%) were the predominant constituents in Turkish oregano, bay laurel, Spanish lavender, and fennel essential oils, respectively.     

Acaricidal activity of pine essential oils and their main components against Tyrophagus putrescentiae,a stored food mite

Some essential oils obtained from the branches of four Pinus species (P. pinea L., P. halepensis Mill., P. pinaster Soil in Ait., and P. nigra Arnold) have been evaluated for their acaricidal activity by aerial diffusion against the stored food mite Tyrophagus putrescentiae (L.). All the essential oils showed a good efficacy, but P. pinea oil and its two constituents 1,8-cineole and limonene were the most effective compounds, showing 100% acaricidal activity at 8 microL; 1,8-cineole showed the same activity at 6 microL.     

Antibacterial and antioxidant activities of essential oils isolated from Thymbra capitata L. (Cav.) andOriganum vulgare L

Antilisterial activities of Thymbra capitata and Origanum vulgare essential oils were tested against 41 strains of Listeria monocytogenes. The oil of T. capitata was mainly constituted by one component, carvacrol (79%), whereas for O. vulgare three components constituted 70% of the oil, namely, thymol (33%), gamma-terpinene (26%), and p-cymene (11%). T. capitata essential oil had a significantly higher antilisterial activity in comparison to O. vulgare oil and chloramphenicol. No significant differences in L. monocytogenes susceptibilities to the essential oils tested were registered. The minimum inhibitory concentration values of T. capitata essential oil and of carvacrol were quite similar, ranging between 0.05 and 0.2 microL/mL. Antioxidant activity was also tested, the essential oil of T. capitata showing significantly higher antioxidant activity than that of O. vulgare. Use of T. capitata and O. vulgare essential oils can constitute a powerful tool in the control of L. monocytogenes in food and other industries.     

Composition and anti-insect activity of essential oils from Tagetes L. species (Asteraceae, Helenieae) on Ceratitis capitata Wiedemann and Triatoma infestans Klug

Essential oils from four species of the genus Tagetes L. (Asteraceae, Helenieae) collected in Tucuma?n province, Argentina, were evaluated for their chemical composition, toxicity, and olfactory activity on Mediterranean fruit fly Ceratitis capitata Wiedemann adults and for repellent properties on Triatoma infestans (Klug) (Chagas disease vector). Yields of essential oils range from 0.2 to 0.8% (v/w). The same main constituents among Tagetes minuta L., Tagestes rupestris Cabrera, and Tagetes terniflora Kunth, (cis-trans)-ocimenes, (cis-trans)-tagetones, and (cis-trans)-ocimenones showed important differences in their relative compositions. Tagetes filifolia Lag. was characterized by the recognized phenylpropanoids methylchavicol and trans-anethole as the main components. LD(50) was ≤20 μg/insect in topical bioassays. T. rupestris was the most toxic to C. capitata females, whereas the other oils presented similar toxicities against males and females. Tagetes rupestris oil attracted both sexes of C. capitata at 5 μg, whereas T. minuta showed opposite activities between males (attractant) and females (repellent). Oils from T. minuta and T. filifolia were the most repellent to T. infestans. The results suggest that compositions of essential oils influence their insecticidal and olfactory properties. The essential oils from Tagetes species show an important potential as infochemical agents on insects' behaviors. This study highlights the chemical variability of essential oils as a source of variation of anti-insect properties.     

Identification of the genotype from the content and composition of the essential oil of lemon verbena (Aloysia citriodora Palau)

Aloysia citriodora accessions from cultivated material, botanical collections, and wild populations were studied by means of their biomass and essential oil production and composition to assist the selection of the most promising genotype. The study was carried out through both field experiments during two year's time and laboratory processes. Data were evaluated by means of univariate and multivariate techniques. Aloysia citriodora intraspecific variation was accounted for by differences in both yield and chemical profiles of the essential oils, but no differences were found in the biomass production. Three chemotypes were identified according to qualitative and quantitative differences of the essential oils. For the higher contents of neral and geranial, Mendoza accession was the most promising to be encouraged for future crops.     

Effect of gamma and e-beam radiation on the essential oils of Thymus vulgaris thymoliferum, Eucalyptus radiata, and Lavandula angustifolia

The microbiological contamination of raw plant materials is common and may be adequately reduced by radiation processing. This study evaluated the effects of gamma- and e-beam ionizing radiations (25 kGy) on three plants used as food or as medicinal products (Thymus vulgaris L., Eucalyptus radiata D.C., and Lavandula angustifolia Mill.) as well as their effects on extracted or commercial essential oils and pure standard samples. Comparison between irradiated and nonirradiated samples was performed by GC/FID and GC/MS. At the studied doses, gamma and e-beam ionizing radiation did not induce any detectable qualitative or quantitative significant changes in the contents and yields of essential oils immediately after ionizing radiation of plants or commercial essential oils and standards. As the maximum dose tested (25 kGy) is a sterilizing dose (much higher than doses used for decontamination of vegetable drugs), it is likely that even decontamination with lower doses will not modify yields or composition of essential oils of these three plants.     

Effect of thyme essential oils (Thymus hyemalis and Thymus zygis) and monensin on in vitro ruminal degradation and volatile fatty acid production

The effect of the essential oils of thyme on the in vitro ruminal degradability of a barley seed/alfalfa hay substrate was studied. Two essential oils were used, one from Thymus hyemalis (TH), rich in carvacrol, and the other from Thymus zygis (TZ), rich in thymol. Four experimental treatments of in vitro degradability, using the Daisy II(200/220) incubator, were conducted including a negative control (CO), a positive control at 7.5 microg/mL of monensin (MO), and two treatments with essential oils (TH or TZ) at 1.35 microL/mL. The material was incubated at 39.5 degrees C for various lengths of time. At each time, the disappearance of dry matter, crude protein, and neutral detergent fiber was measured. Volatile fatty acids (VFAs) were determined after 48 h of incubation. CO and MO provided (p < 0.01) higher values of potential degradability (a + b) of DM than the TH and TZ treatments (72.6 and 70.8 vs 53.2 and 48.2%, respectively). Also, crude protein degradability was lowest in the essential oil treatments. The CO treatment showed the highest potential degradability of NDF. The values of VFA production obtained (p < 0.001) with CO and MO treatments were higher than those obtained with TH and TZ treatments (21.0 and 19.1 vs 11.2 and 10.1 mM). The essential oils decreased the molar proportion of propionate, increasing the acetate/propionate ratio. In conclusion, the effects of essential oils at assayed doses would not be nutritionally beneficial to the ruminal energetic metabolism.     

Insecticidal and acetylcholine esterase inhibition activity of apiaceae plant essential oils and their constituents against adults of German cockroach (Blattella germanica)

We evaluated the insecticidal and acetylcholine esterase (AChE) inhibition activity of 11 Apiaceae plant essential oils and their constituents in adult male and female Blattella germanica. Of the 11 Apiaceae plant essential oils tested, dill (Anethum graveolens), carvi (Carum carvi), and cumin (Cuminum cyminum) demonstrated >90% fumigant toxicity against adult male German cockroaches at a concentration of 5 mg/filter paper. In a contact toxicity test, dill (Anethum graveolens), carvi (Carum carvi), cumin (Cuminum cyminum), and ajowan (Trachyspermum ammi) produced strong insecticidal activity against adult male and female German cockroaches. Among the test compounds, (S)-(+)-carvone, 1,8-cineole, trans-dihydrocarvone, cuminaldehyde, trans-anethole, p-cymene, and γ-terpinene demonstrated strong fumigant toxicity against adult male and female B. germanica. In a contact toxicity test, carveol, cuminaldehyde, (S)-(+)-carvone, trans-anethole, thymol, and p-cymene showed strong contact toxicity against adult male and female B. germanica. IC(50) values of α-pinene, carvacrol, and dihydrocarvone against female AChE were 0.28, 0.17, and 0.78 mg/mL, respectively. The toxicity of the blends of constituents identified in 4 active oils indicated that carvone, cuminaldehyde, and thymol were major contributors to the fumigant activity or contact toxicity of the artificial blend.     

Antimicrobial and antioxidant properties of rosemary and sage (Rosmarinus officinalis L. and Salvia officinalis L., Lamiaceae) essential oils

The essential oils of rosemary ( Rosmarinus officinalis L.) and sage ( Salvia officinalis L.) were analyzed by means of gas chromatography-mass spectrometry and assayed for their antimicrobial and antioxidant activities. Antimicrobial activity was tested against 13 bacterial strains and 6 fungi, including Candida albicans and 5 dermatomycetes. The most important antibacterial activity of both essential oils was expressed on Escherichia coli, Salmonella typhi, S. enteritidis, and Shigella sonei. A significant rate of antifungal activity, especially of essential oil of rosemary, was also exhibited. Antioxidant activity was evaluated as a free radical scavenging capacity (RSC), together with the effect on lipid peroxidation (LP). RSC was assessed by measuring the scavenging activity of essential oils on 2,2-diphenyl-1-picrylhydrazil (DPPH) and hydroxyl radicals. Effects on LP were evaluated following the activities of essential oils in Fe(2+)/ascorbate and Fe(2+)/H2O2 systems of induction. Investigated essential oils reduced the DPPH radical formation (IC50 = 3.82 microg/mL for rosemary and 1.78 microg/mL for sage) in a dose-dependent manner. Strong inhibition of LP in both systems of induction was especially observed for the essential oil of rosemary.     

Plant extracts, spices, and essential oils inactivate Escherichia coli O157:H7 and reduce formation of potentially carcinogenic heterocyclic amines in cooked beef patties

Meats need to be heated to inactivate foodborne pathogens such as Escherichia coli O157:H7. High-temperature treatment used to prepare well-done meats increases the formation of carcinogenic heterocyclic amines (HCAs). We evaluated the ability of plant extracts, spices, and essential oils to simultaneously inactivate E. coli O157:H7 and suppress HCA formation in heated hamburger patties. Ground beef with added antimicrobials was inoculated with E. coli O157:H7 (10(7) CFU/g). Patties were cooked to reach 45 °C at the geometric center, flipped, and cooked for 5 min. Samples were then taken for microbiological and mass spectrometry analysis of HCAs. Some compounds were inhibitory only against E. coli or HCA formation, while some others inhibited both. Addition of 5% olive or apple skin extracts reduced E. coli O157:H7 populations to below the detection limit and by 1.6 log CFU/g, respectively. Similarly, 1% lemongrass oil reduced E. coli O157:H7 to below detection limits, while clove bud oil reduced the pathogen by 1.6 log CFU/g. The major heterocyclic amines 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) were concurrently reduced with the addition of olive extract by 79.5% and 84.3% and with apple extract by 76.1% and 82.1%, respectively. Similar results were observed with clove bud oil: MeIQx and PhIP were reduced by 35% and 52.1%, respectively. Addition of onion powder decreased formation of PhIP by 94.3%. These results suggest that edible natural plant compounds have the potential to prevent foodborne infections as well as carcinogenesis in humans consuming heat-processed meat products.     

Chemical composition and insecticidal activity of essential oils from Vanillosmopsis pohlii baker against Bemisia argentifolii

Essential oils from the heartwood and leaves of specimens of Vanillosmopsis pohlii collected in two different localities were analyzed by GC-MS. The major constituent of both heartwood essential oils was the sesquiterpene alpha-bisabolol. Essential oil composition from leaves was quite different for two specimens and showed beta-pinene and E-caryophyllene as principal constituents. The essential oil of heartwood and the pure sesquiterpene alpha-bisabolol were tested against Bemisia argentifolii, the white fly fruit plague, and pronounced insecticidal effects were observed.     

Characterization of the volatile composition of essential oils of some lamiaceae spices and the antimicrobial and antioxidant activities of the entire oils

The essential oils of Ocimum basilicum L., Origanum vulgare L., and Thymus vulgaris L. were analyzed by means of gas chromatography-mass spectrometry and assayed for their antioxidant and antimicrobial activities. The antioxidant activity was evaluated as a free radical scavenging capacity (RSC), together with effects on lipid peroxidation (LP). RSC was assessed measuring the scavenging activity of the essential oils on 2,2-diphenyl-1-picrylhydrazil (DPPH(*)) and OH(*) radicals. Effects on LP were evaluated following the activities of essential oils in Fe(2+)/ascorbate and Fe(2+)/H(2)O(2) systems of induction. Essential oils exhibited very strong RSCs, reducing the DPPH radical formation (IC(50)) in the range from 0.17 (oregano) to 0.39 microg/mL (basil). The essential oil of T. vulgaris exhibited the highest OH radical scavenging activity, although none of the examined essential oils reached 50% of neutralization (IC(50)). All of the tested essential oils strongly inhibited LP, induced either by Fe(2+)/ascorbate or by Fe(2+)/H(2)O(2). The antimicrobial activity was tested against 13 bacterial strains and six fungi. The most effective antibacterial activity was expressed by the essential oil of oregano, even on multiresistant strains of Pseudomonas aeruginosa and Escherichia coli. A significant rate of antifungal activity of all of the examined essential oils was also exhibited.     

Essential oils produced by in vitro shoots of sage (Salvia officinalis L.)

In vitro shoots of sage (Salvia officinalis L.) were established under eight different hormonal supplementations and proliferated by subculture of nodal shoot segments. The respective essential oils, obtained by hydrodistillation, were composed of more than 75 compounds, 65 of which were identified. The 10 major compounds were, by order of retention time, alpha-pinene (4.1-5.4%), camphene (6-7.1%), beta-pinene (9.3-14.5%), limonene (2-2.3%), 1,8-cineole (3.6-5.6%), (-)-thujone (13.2-16.1%), (+)-isothujone (6.6-7.4%), camphor (19.8-24%), alpha-humulene (5.1-6.8%), and manool (4.2-7.7%). Notwithstanding the eight different hormonal supplementations tested, the percentage composition of the shoot essential oils were kept in a narrow range of variation. However, the type and concentration of growth regulators apparently influenced the accumulation of essential oils. The highest accumulation of essential oils and the highest shoot biomass growth were obtained with 2.0 mg/L kinetin and 0.05 mg/L 2,4-dichlorophenoxyacetic acid.     

Characterization of the volatile pattern and antioxidant capacity of essential oils from different species of the genus Ocimum

The antioxidant capacity of essential oils obtained by steam hydrodistillation from five species of the genus Ocimum, namely Ocimum basilicum var. purpurascens, Ocimum basilicum, Ocimum gratissimum, Ocimum micranthum, and Ocimum tenuiflorum (syn. O. sanctum), were evaluated using a high-performance liquid chromatography-based hypoxanthine/xanthine oxidase and the DPPH assays. The yield of oils from the leaves of the five species was variable with the greater amount obtained from Ocimum gratissimum (3.5%) and the least from Ocimum basilicum var. purpurascens (0.5%). In the hypoxanthine/xanthine oxidase assay, strong antioxidant capacity was evident in all the oils but the greater was shown by that obtained from Ocimum tenuiflorum (syn. O. sanctum) (IC50 = 0.46 microL/mL) compared to Ocimum basilicum var. purpurascens (IC50 = 1.84 microL/mL). Antioxidant capacity was positively correlated (r = 0.92, p < 0.05) with a high proportion of compounds possessing a phenolic ring such as eugenol, while a strong negative correlation (r = -0.77, p > 0.1) with other major volatiles was observed. These correlations were confirmed to a large extent in the DPPH assay. The results of a 24 h experiment with Ocimum tenuiflorum (syn. O. sanctum) shows that the antioxidant capacity factor (amount of essential oil obtained x free radical scavenging capacity; mg x %/100) reaches a threshold between 10 and 12.00 h, corresponding to maximum sunlight intensity in Brasil and furthermore exhibits a clear diurnal variation. The data generated with Ocimum species indicates that essential oils obtained from various herbs and spices may have an important role to play in cancer chemoprevention, functional foods, and in the preservation of pharmacologic products.     

丁香精油对甜樱桃采后优势致腐真菌的控制及其抑菌机理

为探明植物精油对甜樱桃采后优势致病菌的抑菌效力及抑菌机理,以山东泰安地区主栽品种红灯为试验材料,从自然腐烂的甜樱桃果实上分离纯化优势致病菌,采用形态学方法并结合ITS序列法进行鉴定,选用丁香精油从体外熏蒸和接触2种作用方式研究其对主要病原真菌的抑菌效果。结果表明,甜樱桃采后的3种主要致腐真菌分别为灰葡萄孢菌(Botrytis cinerea)、链格孢菌(Alternaria alternata)和胶孢炭疽菌(Colletotrichum gloeosporioides);体外抑菌试验表明,一定浓度的丁香精油能显著抑制3种致病菌的菌丝生长和孢子萌发,熏蒸处理较接触效果更好,对B. cinerea、 A. alternata和C. gloeosporioides的最小抑菌浓度(MIC)分别为120、100和100 μL·L^-1;试验还表明丁香精油破坏了菌丝形态,其抑菌机理可能与精油疏水性造成的微生物膜系统结构破坏、及胞内主要内容物流失有关。综上所述,丁香精油作为甜樱桃贮藏前的熏蒸剂具有较好的应用潜力。     

Effect of essential oils on the growth of Fusarium verticillioides and fumonisin contamination in corn

Essential oils extracted by hydrodistillation from local plants in Benin, western Africa, and oil from seeds of the neem tree (Azadirachta indica) were evaluated in vitro and in vivo for their efficacy against Fusarium verticillioides infection and fumonisin contamination. Fumonisin in corn was quantified using a fluorometer and the Vicam method. Oils from Cymbopogon citratus, Ocimum basilicum, and Ocimum gratissimum were the most effective in vitro, completely inhibiting the growth of F. verticillioides at lower concentrations over 21 days of incubation. These oils reduced the incidence of F. verticillioides in corn and totally inhibited fungal growth at concentrations of 8, 6.4, and 4.8 microL/g, respectively, over 21 days. At the concentration of 4.8 microL/g, these oils did not affect significantly fumonisin production. However, a marked reduction of fumonisin level was observed in corn stored in closed conditions. The oils adversely affected kernel germination at 4.8 microL/g and therefore cannot be recommended for controlling F. verticillioides on stored corn used as seeds, when used at this concentration. The oil of neem seeds showed no inhibitory effect but rather accelerated the growth of F. verticillioides.