Residual and ovicidal efficacy of essential oil‐based formulations in vitro against the donkey chewing louse Bovicola ocellatus

Essential oils have shown good experimental potential as novel veterinary ectoparasiticides. However, if they are to be used as veterinary products, they must be available in formulations that are suitable for practical application against specific ectoparasites. Here, the efficacies of formulations containing 5% (v/v) lavender or tea tree oil, in combination with two emulsifiers [a surfactant, 5% (w/v) N‐lauroylsarcosine sodium salt (SLS), and a soluble polymer, 5% (w/v) polyvinylpyrrolidone (PVP)], with or without 10% coconut oil, were tested in contact bioassays against the donkey chewing louse Bovicola ocellatus (Piaget) (Phthiraptera: Trichodectidae). Residual activity was quantified in open and closed containers; ovicidal efficacy was also examined. Exposure to either of 5% (v/v) lavender or tea tree oils with SLS or PVP resulted in louse mortality of 100%, but when coconut oil was included as an excipient, significantly lower efficacy was recorded. However, the formulations became significantly less effective after 2 h in open containers and 40 h in closed containers. The results confirm that the residual activity of essential oils is relatively transitory and the addition of 10% coconut oil does not prolong the period of insecticidal activity by slowing essential oil evaporation. Too short a period of residual activity is likely to be a significant impediment to the effective practical use of essential oils. However, unlike many synthetic pediculicides, the essential oils tested here were highly ovicidal, which suggests that prolonged residual activity may not be essential to kill newly hatched nymphs after treatment.     

Plant essential oils synergize various pyrethroid insecticides and antagonize malathion in Aedes aegypti

Pyrethroid resistance is a significant threat to agricultural, urban and public health pest control activities. Because economic incentives for the production of novel active ingredients for the control of public health pests are lacking, this field is particularly affected by the potential failure of pyrethroid‐based insecticides brought about by increasing pyrethroid resistance. As a result, innovative approaches are desperately needed to overcome insecticide resistance, particularly in mosquitoes that transmit deadly and debilitating pathogens. Numerous studies have demonstrated the potential of plant essential oils to enhance the efficacy of pyrethroids. The toxicity of pyrethroids combined with plant oils is significantly greater than the baseline toxicity of either oils or pyrethroids applied alone, which suggests there are synergistic interactions between components of these mixtures. The present study examined the potential of eight plant essential oils applied in one of two concentrations (1% and 5%) to enhance the toxicity of various pyrethroids (permethrin, natural pyrethrins, deltamethrin and β‐cyfluthrin). The various plant essential oils enhanced the pyrethroids to differing degrees. The levels of enhancement provided by combinations of plant essential oils and pyrethroids in comparison with pyrethroids alone were calculated and synergistic outcomes characterized. Numerous plant essential oils significantly synergized a variety of pyrethroids; type I pyrethroids were synergized to a greater degree than type II pyrethroids. Eight plant essential oils significantly enhanced 24‐h mortality rates provided by permethrin and six plant essential oils enhanced 24‐h mortality rates obtained with natural pyrethrins. By contrast, only three plant essential plants significantly enhanced the toxicity of deltamethrin and β‐cyfluthrin. Of the plant essential oils that enhanced the toxicity of these pyrethroids, some produced varying levels of synergism and antagonism. Geranium, patchouli and Texas cedarwood oils produced the highest levels of synergism, displaying co‐toxicity factors of > 100 in some combinations. To assess the levels of enhancement and synergism of other classes of insecticide, malathion was also applied in combination with the plant oils. Significant antagonism was provided by a majority of the plant essential oils applied in combination with this insecticide, which suggests that plant essential oils may act to inhibit the oxidative activation processes within exposed adult mosquitoes.     

Antimicrobial activity of Pelargonium essential oils added to a quiche filling as a model food system

Eight essential oils obtained by steam distillation from the scented leaves of Pelargonium species and cultivars were added at 250, 500 and 1000 ppm to a quiche filling, inoculated with either Saccharomyces ludwigii or Zygosaccharomyces bailii (at 10⁸ cfu g⁻¹), Salmonella enteriditis or Listeria innocua (at 10⁹ cfu g⁻¹). The quiche fillings were then kept at 25 °C for 24 h and the residual number of micro-organisms determined using the pour plate technique. There was an effective antimicrobial activity by the Pelargonium essential oils at 250 ppm, comparable with that of commercial thyme oil, an excellent antimicrobial agent, against Saccharomyces ludwigii and Zygosaccharomyces bailii , and a lesser inhibition compared with commercial thyme against Salm. enteriditis. There was a greater diversity of activity against L. innocua, which was in some cases more effective than commercial thyme oil. At 500 ppm, there was a greatly increased inhibition of microbial growth using the Pelargonium essential oils, which was comparable with that of commercial thyme, clove, geranium and coriander oils. As there is no evidence for the toxicity of any of these novel Pelargonium oils, and their odour does not make the delicately flavoured quiche filling unpalatable, there is a strong potential for their use in food processing.     

Essential oils as spatial repellents for the brown marmorated stink bug,Halyomorpha halys (Stål) (Hemiptera: Pentatomidae)

The brown marmorated stink bug (BMSB), Halyomorpha halys (Stål), native to Northeastern Asia, is a serious invasive pest in the United States, Canada, Switzerland, Germany and France. Several common essential oils and their compositions were tested against BMSBs as potential repellents. All the tested individual essential oils and a ternary oil blend showed significant repellency to both BMSB nymphs and adults. Clove oil, lemongrass oil, spearmint oil, ylang‐ylang oil, and the ternary oil mixture (clove, lemongrass and spearmint) almost completely blocked attraction of BMSBs to the stink bug attractant‐baited traps; whereas wintergreen oil, geranium oil, pennyroyal oil and rosemary oil resulted in 60–85% trap catch reductions. Over 20 BMSB antennally active compounds were identified from SPME headspace samples of the eight repellent essential oils using GC‐EAD and GC‐MS techniques. Among the synthetic EAD‐active compounds tested in the field, eugenol, l‐carvone, p/l‐menthone, pulegone, methyl salicylate, trans/cis‐citral, methyl benzoate and β‐caryophyllene significantly reduced trap catches of BMSBs by 72–99%; these compounds are likely responsible for the repellency of their corresponding essential oils. Surprisingly, a synthetic mixture of the predacious spined soldier bug (SSB) [Podisus maculiventris (Say)] aggregation pheromone (trans‐2‐hexenal, α‐terpineol and benzyl alcohol) also showed a significant inhibition of BMSB response to its attractants. These repellent essential oils and their active compounds, as well as the synthetic SSB pheromone, are potentially useful as part of an efficient, environmentally sound semiochemical‐based IPM programme to combat this serious invasive stink bug.     

Suppression of Powdery Mildew on Flax by Foliar Application of Essential Oils

Six essential oils were evaluated as to their efficiency in controlling powdery mildew (PM) of flax when they were applied as foliar sprays in an outdoor pot experiment. Onion, flax and fenugreek oils did not affect PM severity ratings – that is, they were ineffective in controlling the disease. On the other hand, black cumin, jojoba and coriander oil showed variable levels of efficiency in controlling the disease. Black cumin was moderately effective in controlling the disease because it reduced disease severity by 32.87%, while jojoba and coriander oils were highly effective as they reduced disease severity by 66.24 and 68.64%, respectively. Essential oils did not affect seed weight; however, coriander oil was a notable exception as it reduced seed weight by 55%. Straw weight was not affected by any oil. Foliar application of essential oils resulted in significant changes in the levels of protein, phenols, ascorbic acid and malondialdehyde and in activities of peroxidase and polyphenol oxidase. The lack of significant correlation between levels and activities of these biochemical components and PM severity demonstrate that these components are not involved in the suppression of PM by essential oils. Therefore, direct toxicity of essential oils to the causal pathogen Oidium lini is the most likely explanation for the disease suppression.     

Toxicity of plant essential oils to Tetranychus urticae (Acari: Tetranychidae) and Phytoseiulus persimilis (Acari: Phytoseiidae)

Fifty-three plant essential oils were tested for their toxicity against eggs and adults of Tetranychus urticae Koch as well as adults of Phytoseiulus persimilis Athias-Henriot, by using a filter paper diffusion bioassay without allowing direct contact. Responses varied according to oil type and dose, and mite species. In a plastic container (4.5 by 9.5 cm) bioassay at 14 x 10(-3) microl/ml air, caraway seed, citronella java, lemon eucalyptus, pennyroyal, and peppermint oils gave > 90% mortality against adult T. urticae, whereas 82 and 81% mortality was observed with sage and spearmint oils, respectively. With the exception of sage oil, the other six essential oils were highly effective against T. urticae eggs at 9.3 x 10(-3) microl/ml air. Against adult P. persimilis, these six test oils caused > 90% mortality at 7.1 x 10(-3) microl/ml air. Particularly peppermint oil at 4.7 x 10(-3) microl/ml air was highly toxic. In an acrylic cage (30 by 30 by 40 cm ) test, lemon eucalyptus, pennyroyal, peppermint, and spearmint oils were highly effective against adult T. urticae at 1.4 x 10(-3) microl/ml air. These results indicate that the mode of delivery of these essential oils was largely a result of action in the vapor phase via the respiratory system. The essential oils described herein merit further study as potential fumigants for T. urticae control.     

Toxicity of some terpenoids of essential oils of Xylopia aethiopica from Cameroon against Sitophilus zeamais Motschulsky

Abstract:  The acute toxicity of essential oils from the whole fruit (EF) or from the fibres of the fruit (FF) of the local aromatic plants Xylopia aethiopica Dunal (Annonaceae) collected in north Cameroon was evaluated on Sitophilus zeamais adults. A concentration of 1 ml of essential oil per 100 g of maize seeds was tested to determine weevil mortality after 24 h of exposure. Under these conditions, the essential oil derived from both EF and FF of X. aethiopica led to 100% mortality. In a second step, proportions of active compounds present in the oil of both EF and FF of X. aethiopica were quantified. The toxicity of the four main compounds was tested against S. zeamais : α -pinene, β -pinene, Δ-3-carene and terpinen-4-ol according to their proportion in the essential oil of the concerned plant part. β -pinene and terpinen-4-ol were responsible for 50% of the mortality at the proportion found in EF and FF essential oils respectively. When mixed, a synergic effect of the compounds was observed that restored the mortality percentage observed for the crude oil. It appears that X. aethiopica essential oil could be a potential source of natural and low-cost insecticide to control storage pests.     

Vapor phase toxicity of plant essential oils to Cadra cautella (Lepidoptera: Pyralidae)

The toxicities of 44 plant essential oils against larvae of Cadra cautella (Walker) were examined using direct contact and vapor phase toxicity bioassays and compared with the lethal activity of chlorpyrifos-methyl, diazinon, dichlorvos, and fenthion, four widely used organophosphorus insecticides. Responses varied according to plant material used and exposure dose and time. In a filter paper contact toxicity bioassay, potent toxicity was produced from buchu leaf, niaouli, and rosemary oils at 2.4 mg/cm2 and armoise, cypress, galbanum, and mace oils at 4.7 mg/cm2. In vapor phase toxicity bioassays with larvae, cypress, galbanum, niaouli, and rosemary oils were much more effective in closed containers than in open containers, indicating that the lethal effects of these oils were largely because of action in the vapor phase. As judged by 24-h LC50 values, potent fumigant action was observed with niaouli oil (64.7 mg/liter air) and rosemary oil (64.6 mg liter/air). Cypress and galbanum oils exhibited weak fumigant activity. These essential oils were less active than dichlorvos (0.86 mg/liter air). Little or no fumigant action was observed with chlorpyrifos-methyl, diazinon, and fenthion. Essential oils described herein, particularly niaouli and rosemary oils, merit further study as potential larvicides for the control of C. cautella.     

41种植物精油对淡色库蚊的熏蒸活性

为发现具有较高杀蚊活性的精油, 推动植物精油类卫生杀虫剂的创制, 本研究采用三角瓶熏蒸法测定了17科41种植物精油对淡色库蚊Culex pipiens pallens雌成蚊的熏蒸活性, 并进一步采用密闭圆筒法验证其杀虫毒力大小。三角瓶熏蒸法测定表明, 在12 μL/L浓度下, 留兰香油（spearmint oil）、 薰衣草油（lavender oil）、 山苍子油（Litsea cubeba oil）等26种精油均有较强的熏蒸作用, KT₅₀小于15 min。该26种精油用密闭圆筒熏蒸法进一步测定表明, 在浓度为10 μL/L时, 冬青油（wintergreen oil）、 艾叶油（blumea oil）、 薄荷油（peppermint oil）、 桉叶油（Eucalyptus robusta oil）和蓝桉油（E. globulus oil）等植物精油熏蒸活性较强, 其KT₅₀分别为16.91, 21.20, 22.57, 18.43和19.48 min。结果证明冬青油、 艾叶油、 薄荷油、 桉叶油和蓝桉油等5种精油对淡色库蚊具有较强的熏蒸活性, 具备作为淡色库蚊防控剂开发的潜力, 值得进一步研究。     

Acaricidal properties of essential oils from agro‐industrial waste products from citric fruit against Tetranychus urticae

Tetranychus urticae is a major agricultural pest with worldwide distribution that has caused considerable damage to vegetable crops in north‐eastern Brazil. The aim of the present study was to investigate the chemical and lethal/sublethal effects of essential oils from the peels of the lime (Citrus aurantiifolia), lemon (C. limon), mandarin orange (C. reticulata) and (C. reticulata × C. sinensis) as well as selected constituents (linalool, α‐terpineol, α‐pinene, β‐pinene, terpinolene and limonene) against T. urticae. The greatest yield was achieved with the mandarin and tangerine peel oils. The chemical analysis (gas chromatography‐mass spectrometry) of the essential oils from the Citrus fruit peels enabled the identification of 127 compounds, revealing a predominance of monoterpenes. Limonene was the major constituent, and α‐pinene, β‐pinene, linalool and α‐terpineol were found in substantial quantities. Regarding the susceptibility of T. urticae, the Citrus oils and selected constituents were more effective by fumigation than residual contact. The C. reticulata oil was the most toxic by fumigation, and the C. limon oil was the most toxic by residual contact. The constituent α‐terpineol exhibited the highest toxicity with both methods. At a sublethal concentration, the oils and selected constituents had significant effects on the fecundity, feeding preference and oviposition of the mite. Citrus oils and their constituents are potentially useful for the future integrated management of T. urticae due to their lethal and sublethal properties. However, further studies are needed to evaluate the action of these essential oils against non‐target organisms and determine the cost–benefit ratio for the formulation of an acaricide harvested from agro‐industrial waste from citric fruit processing activities for use in the integrated control of T. urticae.     

Efficacy and repellency of some essential oils and their blends against larval and adult house flies,Musca domestica L. (Diptera: Muscidae)

House flies are global pests and notoriously difficult to control. Essential oils of vetiver, cinnamon, and lavender and their blends were tested for toxic and repellent effects against larval and adult flies. All of the oils had moderate toxicity for eggs. Mortality of 2^nd instar larvae was 57–78% in dipping assays, 38–100% in contact assays, and 94–100% in treated media. Lavender was less effective (38% mortality) than the others (91–100%) in contact bioassays. Oil blends were not more effective against larvae than individual oils. Vetiver and cinnamon oils were strongly repellent (84 and 78%, respectively) for larvae in treated media. None of the oils were repellent for adult house flies in olfactometer assays, but testing of additional products demonstrated significant repellency for neem oil, p‐menthane‐3,8‐diol (PMD), and vanillin. Contact/fumigant toxicity of vetiver, cinnamon, and lavender oils was 100%, significantly higher than mortality from sunflower oil (67%). Blends of oils were not more effective against adults than the individual oils, but blends diluted with sunflower oil were as effective as the individual oils. Essentials oils of vetiver and cinnamon may have potential for fly management in situations where conventional insecticides cannot be used.     

Fumigant Toxicity of Plant Essential Oils to Plutella xylostella (Lepidoptera: Yponomeutidae) and Cotesia glomerata (Hymenoptera: Braconidae)

The fumigant toxicity of 66 plant essential oils to Plutella xylostella (L.) larvae and Cotesia glomerata (L.) adults was examined using a vapor-phase toxicity bioassay and compared with that of dichlorvos. Responses varied according to oil and insect species used. Based on 24 h LD₅₀ values, pennyroyal oil [10.77 mg/filter paper (4.25 cm diameter)] was the most toxic fumigant, followed by rosemary and sage (Dalmatin) oils (15.15 mg/paper). Potent fumigant toxicity was also produced from armoise, buchu leaf, cedarleaf, coriander, eucalyptus, howood, lavender, myrtle, niaouli, peppermint, and rosewood oils (LD₅₀, 21.29–27.31 mg/paper). All essential oils were less effective than dichlorvos (LD₅₀, 0.52 mg/paper). Against adult C. glomerata, dichlorvos (LD₅₀, 0.03 mg/paper) was the most toxic fumigant, whereas the LD₅₀ values of the 14 essential oils ranged from 1.59 to 8.51 mg/paper. Based on selective toxicity ratio (STR, P. xylostella LD₅₀/C. glomerata LD₅₀), the 14 essential oils (STR, 2.5–14.5) are more selective than dichlorvos (STR, 17.3). The essential oils tested merit further study as potential fumigants for the control of P. xylostella in greenhouses because of their selective toxicity to adult C. glomerata and their much greater activity as a fumigant.     

Essential oils: effects of application rate and modality on potential for combating northern fowl mite infestations

The northern fowl mite (NFM), Ornithonyssus sylviarum (Mesostigmata: Macronyssidae), is the primary blood‐feeding ectoparasite found on poultry in the U.S.A. Three experiments were conducted in vitro to test the acaricidal properties of cade, garlic, lavender, lemongrass, pine and thyme essential oils against NFM, and to evaluate whether these effects are altered by adjusting oil application rates and application modality (direct vs. vapour contact). Applied at the rate of 0.21 mg/cm², the essential oils of cade, thyme, lemongrass and garlic resulted in higher NFM mortality at 24 h post‐application than lavender and pine oils, and the untreated and ethanol‐treated controls. Cade and thyme were the most consistent and fast‐acting of the essential oils in terms of toxicity to NFM. Cade applied at 0.21 mg/cm² and 0.11 mg/cm² and thyme applied at 0.21 mg/cm² were effective in eliminating NFM within 2 h through direct contact. The modality of application did not affect the efficacy of cade and thyme essential oils. The results suggest that essential oils may be utilized as alternatives to chemical pesticides and could be used as fumigants for the control of NFM.     

Environmental interactions with the toxicity of plant essential oils to the poultry red mite Dermanyssus gallinae

The toxicity of a range of plant essential oils to the poultry red mite, Dermanyssus gallinae (De Geer) (Acari: Dermanyssidae), a serious ectoparasitic pest of laying hens throughout Europe and elsewhere, was assessed in the laboratory. Dermanyssus gallinae may cause losses in egg production, anaemia and, in extreme cases, death of hens. With changes in legislation and consumer demand, alternatives to synthetic acaricides are needed to manage this pest. Fifty plant essential oils were selected for their toxicity to arthropods reported in the literature. Twenty-four of these essential oils were found to kill > 75% of adult D. gallinae in contact toxicity tests over a 24-h period at a rate of 0.21 mg/cm². Subsequent testing at lower rates showed that the essential oils of cade, manuka and thyme were especially toxic to adult D. gallinae . The toxicity of the seven most acaricidal essential oils was found to be stable at different temperatures likely to be encountered in commercial poultry housing (15°C, 22°C and 29°C), although results suggest that humidity and dust might influence the toxicity of some of the oils tested. The toxicity of clove bud essential oil to D. gallinae , for example, was increased at high humidity and dust levels compared with ambient levels. The results suggest that certain essential oils may make effective botanical pesticides for use against D. gallinae , although it is likely that issues relating to the consistency of the toxic effect of some oils will determine which oils will be most effective in practice.     

Toxicity of citrus essential oils against Ceratitis capitata (Diptera: Tephritidae) larvae

Citrus peel essential oils are considered to constitute the most important resistance factor of citrus fruits against fruit flies. Essential oils were obtained from three sweet orange varieties, one bitter orange and one lemon variety. Yield, chemical composition and toxicity against neonates of the Mediterranean fruit fly were determined. Based on chemical analysis, the toxicity of commercially purchased major and minor components (monoterpenes and sesquiterpenes) of essential oils was determined. In addition, fractions were prepared to evaluate the role of minor components in the toxicity of crude essential oils. Limonene was by far the most abundant ingredient (96.2–97.4%) in all sweet orange varieties and in bitter orange, while the concentration of limonene was much lower in lemon essential oils (74.3%). Orange and bitter orange essential oils were more toxic than lemon essential oils. The toxicity of orange and bitter orange essential oils was similar to that of their major component limonene. In tests of commercially purchased chemicals, the oxygenated components of essential oils were more toxic than hydrocarbons but their low concentration in citrus essential oils could not affect the toxic activity of essential oils. The presence of α-pinene and β-pinene seems to account for the lower toxicity of lemon essential oils in relation to other citrus essential oils. The importance of understanding the toxicity of essential oils in relation to their composition and their role regarding the resistance of citrus fruits to Ceratitis capitata infestation is discussed.     

Composition and Antimicrobial Activity of the Essential Oils of Laserpitium latifolium L. and L. ochridanum Micevski (Apiaceae)

The chemical composition and antimicrobial activity of essential oils of Laserpitium latifolium and L. ochridanum were investigated. The essential oils were isolated by steam distillation and characterized by GC‐FID and GC/MS analyses. All essential oils were distinguished by high contents of monoterpenes, and α‐pinene was the most abundant compound in the essential oils of L. latifolium underground parts and fruits (contents of 44.4 and 44.0%, resp.). The fruit essential oil was also rich in sabinene (26.8%). Regarding the L. ochridanum essential oils, the main constituents were limonene in the fruit oil (57.7%) and sabinene in the herb oil (25.9%). The antimicrobial activity of these essential oils as well as that of L. ochridanum underground parts, whose composition was reported previously, was tested by the broth‐microdilution method against four Gram‐positive and three Gram‐negative bacteria and two Candida albicans strains. Except the L. latifolium underground‐parts essential oil, the other investigated oils showed a high antimicrobial potential against Staphylococcus aureus, S. epidermidis, Micrococcus luteus, or Candida albicans (minimal inhibitory concentrations of 13.0–73.0 μg/ml), comparable to or even higher than that of thymol, which was used as reference compound.     

Blend effects in the toxicity of the essential oil constituents of Ocimum kilimandscharicum and Ocimum kenyense (Labiateae) on two post-harvest insect pests

The lethal toxicity of major components of the essential oils of Ocimium kilimandscharicum and O. kenyense and of selected blends of these against Sitophilus zeamais and Rhyzopertha dominica were compared with those of the full blends of the essential oils. The compounds were assayed in amounts and proportions present in the minimum 100% lethal dose of the oils. Whereas a major component of O. kilimandscharicum was found to be largely responsible for the toxic action of its essential oil against R. dominica, the results with the other treatments indicated that the toxic action of the essential oils were due to the combined effects of different components, either with or without significant individual toxic action of their own against the insects. The significance of the results and their implication in screening and using plants and their phytochemicals for pest and microbial control are highlighted.     

Insecticidal activity of polycaprolactone nanocapsules loaded with Rosmarinus officinalis essential oil in Tribolium castaneum (Herbst)

In this study, the opportunity to enhance the insecticidal activity of Rosmarinus officinalis essential oil was studied for effective management of the red flour beetle, Tribolium castaneum , as a stored product pest beetle. Nanoprecipitation method was used to prepare rosemary oil‐loaded nanocapsules. Bioassays were conducted at 27–30°C temperature and 70–75 % relative humidity in the dark. Fumigant toxicity of the non‐formulated oil and nanocapsules of R. officinalis were investigated at 13.20, 15.92, 19.12, 23.04, and 27.76 μL/L air after 24 and 72 h exposure and the contact toxicity of the non‐formulated oil and nanocapsules were investigated at 4.28, 3.55, 2.95, 2.45 and 2.36 μL/cm² after 24 h exposure. The major constituents of the essential oil of rosemary were α‐Pinene, 1,8‐cineol, camphor, and cis‐verbenone. Nanocapsules presented an average size (145 ± 15 nm) (± standard error [SE]) with a polydispersity index below 0.3, a negative zeta potential (?11.0 ± 0.5 mV), and a high encapsulation efficiency (78.20 ± 0.93 %). Scanning electron microscope photomicrograph of rosemary oil‐loaded nanocapsules showed the presence of spherical nanocapsules with regular and homogeneous surfaces. In fumigant and contact toxicity, there were significant differences between non‐formulated and rosemary oil‐loaded nanocapsules in all the concentrations and times. The results suggested that nanoencapsulated essential oils from R. officinalis can be used for effective control in T. castaneum . When this technique is used, it can produce pesticides that have controlled‐release properties and reduce the concentration of the applied doses and number of applications.     

The in vitro Antimicrobial Activity and Chemometric Modelling of 59 Commercial Essential Oils against Pathogens of Dermatological Relevance

This study reports on the inhibitory concentration of 59 commercial essential oils recommended for dermatological conditions, and identifies putative compounds responsible for antimicrobial activity. Essential oils were investigated for antimicrobial activity using minimum inhibitory concentration assays. Ten essential oils were identified as having superior antimicrobial activity. The essential oil compositions were determined using gas chromatography coupled to mass spectrometry and the data analysed with the antimicrobial activity using multivariate tools. Orthogonal projections to latent structures models were created for seven of the pathogens. Eugenol was identified as the main biomarker responsible for antimicrobial activity in the majority of the essential oils. The essential oils mostly displayed noteworthy antimicrobial activity, with five oils displaying broad‐spectrum activity against the 13 tested micro‐organisms. The antimicrobial efficacies of the essential oils highlight their potential in treating dermatological infections and through chemometric modelling, bioactive volatiles have been identified.     

四种植物精油成分对枸杞棉蚜的生物活性

【目的】研究植物精油4种成分丁香酚(eugenol)、α-松油醇(α-terpineol)、肉桂油(cinnamon oil)和香茅油(citronella oil)对枸杞棉蚜Aphis gossypii的生物活性以及马来酸二乙酯和水杨酸乙酯对这些化合物对枸杞棉蚜毒力的影响,为无公害防治枸杞(Lycium spp.)害虫奠定科学基础。【方法】采用二项选择法测定上述4种精油成分(1%)对枸杞棉蚜无翅成蚜的驱避作用;玻璃管药膜法进行生物测定,评估这4种化合物及其与马来酸二乙酯或水杨酸乙酯的混合液对枸杞棉蚜成蚜的毒力;采用生物化学方法分析这些化合物处理后枸杞棉蚜成蚜乙酰胆碱酯酶(AChE)和三磷酸腺苷酶(ATPase)的离体活性。【结果】α-松油醇(1%)对枸杞棉蚜无翅成蚜的驱避作用明显,1, 2和3 h的驱避率分别为58.1%, 58.6%和55.7%; 3 h时测试的4种化合物对枸杞棉蚜成蚜的驱避率由大到小依次为α-松油醇>香茅油>肉桂油>丁香酚。丁香酚对枸杞棉蚜成蚜的毒杀作用最强,处理4 h时的LC₅₀值为0.48 mL/L,肉桂油、α-松油醇、香茅油对枸杞棉蚜成蚜的LC₅₀值分别为1.23, 6.24和11.97 mL/L。对枸杞棉蚜成蚜的生物测定结果表明,马来酸二乙酯对香茅油、肉桂油、丁香酚和α-松油醇的增效比分别为2.75, 2.86, 1.78和1.56;水杨酸乙酯对香茅油、肉桂油、丁香酚和α-松油醇的增效比分别为3.41, 2.67, 2.00和1.89。毒力比结果表明,所测定的4种化合物对枸杞棉蚜的毒力相差49.9倍,丁香酚与马来酸二乙酯或水杨酸乙酯的混合液对枸杞棉蚜的触杀毒力最高。4种精油成分对枸杞棉蚜成蚜AChE和ATPase活性有不同的作用,丁香酚对AChE活性的抑制作用最强,但对ATPase活性表现为低浓度促进,高浓度抑制。【结论】α-松油醇对枸杞棉蚜驱避作用最好;丁香酚、α-松油醇、肉桂油和香茅油这4种精油成分对枸杞棉蚜的毒力相差很大;丁香酚与马来酸二乙酯或水杨酸乙酯混合后对枸杞棉蚜的毒力提高,具有进一步开发应用的潜力;所测精油成分对枸杞棉蚜离体AChE和ATPase活性有一定抑制作用。