Chemical composition and larvicidal activity of essential oils from Piper species

The larvicidal activity of essential oils of four species of Piper from the Amazon Forest was tested using third-instar larvae of Aedes aegypti. The oils were extracted by steam distillation and analyzed by GC and GC–MS. The main components isolated from each Piper species were as follows: viridiflorol (27.50%), aromadendrene (15.55%) and β-selinene (10.50%) from Piper gaudichaudianum; β-selinene (15.77%) and caryophyllene oxide (16.63%) from Piper humaytanum; dillapiol (54.70%) and myristicin (25.61%) from Piper permucronatum; and asaricin (27.37%) and myristicin (20.26%) from Piper hostmanianum. Amongst all essential oils tested, the most active against larvae of A. aegypti was the oil extracted from P. permucronatum, with a LC₅₀ = 36 μg/ml (LC₉₀ = 47 μg/ml), followed by the essential oil of P. hostmanianum, with a LC₅₀ = 54 μg/ml (LC₉₀ = 72 μg/ml). The oils with higher content of arylpropanoids were more active against larvae of A. aegypti.     

Effects of AeDNV infection on Aedes aegypti lifespan and reproduction

The effects of Aedes Densovirus (AeDNV) infections on survival, fertility, fecundity and vertical transmission in Aedes aegypti (Diptera: Culicidae) were measured in laboratories in Kiev, Ukraine and Colorado, USA and incorporated into a predictive model of the effects of AeDNV on vector capacity. Adult lifespan and daily survival were reduced in AeDNV infected mosquitoes. This effect was dependent on the dose of the virus. Infected females had decreased fecundity. The oviposition rate was less in infected females and the hatch rate declined in eggs laid by infected females. The amounts of AeDNV in infected females and the infection rate of their offspring were measured with real-time PCR. The average filial transmission rate was 70% and larval infection rates from infected females varied between 42 and 62%. Vertically infected larvae, and individual eggs contained 1 × 10⁵ AeDNV genome equivalents (geq). Modeling the effects of AeDNV infection on Ae. aegypti populations suggested a large decrease in the numbers of eggs, larvae, pupae, and adults arising from infected mothers and suggested that AeDNV treatment of larvae could cause up to a 76% reduction of infectious mosquito days.     

Iron loaded ferritin secretion and inhibition by CI-976 in Aedes aegypti larval cells

Ferritin is a multimer of 24 subunits of heavy and light chains. In mammals, iron taken into cells is stored in ferritin or incorporated into iron-containing proteins. Very little ferritin is found circulating in mammalian serum; most is retained in the cytoplasm. Female mosquitoes, such as Aedes aegypti (yellow fever mosquito, Diptera), require a blood meal for oogenesis. Mosquitoes receive a potentially toxic level of iron in the blood meal which must be processed and stored. We demonstrate by ⁵⁹Fe pulse-chase experiments that cultured A. aegypti larval CCL-125 cells take up iron from culture media and store it in ferritin found mainly in the membrane fraction and secrete iron-loaded ferritin. We observe that in these larval cells ferritin co-localizes with ceramide-containing membranes in the absence of iron. With iron treatment, ferritin is found associated with ceramide-containing membranes as well as in cytoplasmic non-ceramide vesicles. Treatment of CCL-125 cells with iron and CI-976, an inhibitor of lysophospholipid acyl transferases, disrupts ferritin secretion with a concomitant decrease in cell viability. Interfering with ferritin secretion may limit the ability of mosquitoes to adjust to the high iron load of the blood meal and decrease iron delivery to the ovaries reducing egg numbers.     

Transient expression of the Drosophila melanogaster cinnabar gene rescues eye color in the white eye (WE) strain of Aedes aegypti

The lack of eye pigment in the Aedes aegypti WE (white eye) colony was confirmed to be due to a mutation in the kynurenine hydroxylase gene, which catalyzes one of the steps in the metabolic synthesis of ommochrome eye pigments. Partial restoration of eye color (orange to red phenotype) in pupae and adults occurred in both sexes when first or second instar larvae were reared in water containing 3-hydroxykynurenine, the metabolic product of the enzyme kynurenine hydroxylase. No eye color restoration was observed when larvae were reared in water containing kynurenine sulfate, the precursor of 3-hydroxykynurenine in the ommochrome synthesis pathway. In addition, a plasmid clone containing the wild type Drosophila melanogaster gene encoding kynurenine hydroxylase, cinnabar (cn), was also able to complement the kynurenine hydroxylase mutation when it was injected into embryos of the A. aegypti WE strain. The ability to complement this A. aegypti mutant with the transiently expressed D. melanogaster cinnabar gene supports the value of this gene as a transformation reporter for use with A. aegypti WE and possibly other Diptera with null mutations in the kynurenine hydroxylase gene.     

Identification of novel LTR retrotransposons in the genome of Aedes aegypti

We have detected seventy-six novel LTR retrotransposons in the genome of the mosquito Aedes aegypti by a genome wide analysis using the LTR_STRUC program. We have performed a phylogenetic classification of these novel elements and a distribution analysis in the genome of A. aegypti. These mobile elements belong either to the Ty3/gypsy or to the Bel family of retrotransposons and were not annotated in the mosquito LTR retrotransposon database (TEfam). We have found that  1.8% of the genome is occupied by these newly detected retrotransposons that are distributed predominantly in intergenic genomic sequences and introns. The potential role of retrotransposon insertions linked to host genes is described and discussed. We show that a retrotransposon family belonging to the Osvaldo lineage has peculiar structural features, and its presence is likely to be restricted to the A. aegypti and to the Culex pipiens quinquefasciatus genomes. Furthermore we show that the ninja-like group of elements lacks the Primer Binding Site (PBS) sequence necessary for the replication of retrotransposons. These results integrate the knowledge on the complicate genomic structure of an important disease vector.     

Comparative larvicidal activity of essential oils from three medicinal plants against Aedes aegypti L

This work aimed at comparing larvicidal activity of essential oils extracted from the dried leaves of Alpinia speciosa, Cymbopogon citratus, and Rosmarinus officinalis against Ae. aegypti larvae. The larvae were observed for 4 h and at 24 h according to a completely randomized design with three replications and the following concentrations [μl/ml]: 0.25, 0.5, 1.0, 1.5, 2.0, 2.5, and controls were distilled water, and commercial standard citral, camphor, eucalyptol, α‐pinene, and β‐myrcene. The essential oil of C. citratus had the lowest LC₅₀ (0.28) and LC₉₀ (0.56) values, followed by that of A. speciosa (0.94 and 1.2, resp.) and of R. officinalis (1.18 and 1.67, resp.), and only the commercial standards citral and α‐pinene were larvicidal.     

Chemical composition and anticancer activity of leaf essential oil of Myrica gale L.

Myrica gale L. (Myricaceae), a native plant from Canada used in traditional medicine, was extracted by hydrodistillation and the oil was collected after 30 and 60 min. The chemical composition of these two extracts was determined using GC-MS analysis. We identified 53 components and myrcene (23.18-12.14%), limonene (11.20-6.75%), alpha-phellandrene (9.90-6.49%) and beta-caryophyllene (9.31-10.97%) were the major components in the 30- and 60-min fractions, respectively, whereas higher caryophyllene oxide content was detected in the 60-min fraction (9.94%) than in the 30-min fraction (3.47%). The anticancer activities of these extracts were assessed against human lung carcinoma cell line A-549 and human colon adenocarcinoma cell line, DLD-1. The 60-min fraction showed higher anticancer activity against both tumor cell lines with an IC50 value of 88 +/- 1 microg/ml. The 30-min fraction had an IC50 value of 184 +/- 4 microg/ml for A-549 and 160 +/- 3 microg/ml for DLD-1. The higher cell growth inhibition induced by the 60-min fraction, as compared to the 30-min fraction, could be due to sesquiterpene enrichment.     

伊蚊C型凝集素mosGCTL-2是登革病毒感染相关的重要蛋白质

C型凝集素是一类含有糖结合结构域的蛋白质,从节肢动物到哺乳动物的C型凝集素都具有共同的基序,它在进化上相当保守,在免疫反应中发挥重要作用. 埃及伊蚊表达30多种C型凝集素蛋白,它是登革病毒的关键传播媒介,这些蛋白质对病毒和细菌感染均有至关重要的作用. 最近研究表明,C型凝集素mosGCTL-3与二型登革热病毒包膜蛋白具有相互作用,能够增强登革病毒对埃及伊蚊的感染. 在本文中,我们发现了C型凝集素蛋白mosGCTL-2具有与mosGCTL-3类似的功能. 两种C型凝集素mosGCTL-2和mosGCTL-3的氨基酸残基序列一致性高达43.56％. 为研究mosGCTL-2在登革病毒蚊媒传播中的作用,我们通过果蝇S2细胞表达系统表达纯化了mosGCTL-2蛋白. 结果表明,mosGCTL-2与二型登革热病毒包膜蛋白的结合具有钙离子依赖性. 进一步的研究表明,埃及伊蚊感染登革病毒能够诱导mosGCTL2表达上调,是二型登革热病毒感染埃及伊蚊所必需的蛋白质. 以上研究说明,mosGCTL-2蛋白可能是在登革热病毒感染埃及伊蚊中起重要作用的一种模式识别受体.     

Larvicidal activity against Aedes aegypti of some plants native to the West-Central region of Brazil

A total of 42 ethanolic extracts from 30 different plant species, native to the Pantanal and Cerrado of the West-Central region of Brazil, have been evaluated for their larvicidal activity against Aedes aegypti larvae, the vector of dengue and dengue hemorrhagic fevers. Among the extracts tested, that obtained from the trunk bark of Ocotea velloziana was the most active. Using a bioassay-directed fractionation of this extract, the active constituent was isolated and characterized as the aporphine alkaloid (+)-dicentrine. Its structure was established on the basis of ¹H and ¹³C NMR spectra, optical rotation and by comparison with an authentic sample. This is the first report on the larvicidal activity against A. aegypti of this alkaloid. Our results suggest that (+)-dicentrine may be considered as a promising natural mosquito larvicidal agent.     

Dopachrome conversion activity in Aedes aegypti: Significance during melanotic encapsulation of parasites and cuticular tanning

Phenol oxidase (PO) and dopachrome conversion enzyme (DCE) were partially purified from Aedes aegypti larvae by ammonium sulfate fractionation. PO from A. aegypti functions in the hydroxylation of monophenols (e.g., tyrosine and tyramine) to their related o-diphenols, and the oxidation of o-diphenols (e.g., l-dopa, dopamine, N-acetyldopamine) to their respective o-quinones. Partially purified DCE showed high specificity toward dopachrome generated from dopa with the l-configuration. The combined effects of PO and DCE significantly accelerated melanization pathways when l-dopa was used as substrate. Significant DCE activity also was detected in hemolymph samples from adult, female A. aegypti, and undoubtedly plays a role in melanotic encapsulation reactions.     

Synergy effects of the antibiotics gentamicin and the essential oil of Croton zehntneri

The leaves of Croton zehntneri Pax et Hoffm (Euphorbiaceae) were subjected to hydrodistillation, and the essential oil extracted was examined with respect to antibacterial and antibiotic modifying activity by gaseous contact. The gaseous component of the oil inhibited the bacterial growth of Staphylococcus aureus and Pseudomonas aeruginosa with a MID of 0.5 and<1 mg/l air, respectively. The activity of the antibiotic gentamicin was increased by 42,8% against P. aeruginosa after contact with the gaseous component, showing that this oil influences the activity of the antibiotic and may be used as an adjuvant in the antibiotic therapy of respiratory tract bacterial pathogens.     

Assessment of the essential oil composition of Tornabenea annua, Tornabenea insularis and Tornabenea tenuissima fruits from Cape Verde Islands

The essential oils of Tornabenea annua, Tornabenea insularis and Tornabenea tenuissima herbarium or in vivo fruits, collected in Fogo, Santiago, Santo Antão, São Nicolau and São Vicente Islands, from Cape Verde archipelago, or from plants grown in Lisbon, Portugal, were isolated by hydrodistillation and analysed by GC and GC–MS. The yellowish oils were obtained in variable average yields, lower in herbarium samples [0.05% (v/w)] and higher from in vivo samples [1.3% (v/w)]. Whereas T. annua fruits' oils were all dominated by myristicin (92–100%), most of the T. insularis fruit samples' oils were elemicin rich (82–90%). No clear information could be obtained for T. tenuissima fruits' oils as each of the samples gave different chemical composition. Cluster analysis of the essential oil composition from the fruits' samples studied, confirmed these chemical differences.     

Chemical composition and antibacterial activity of the essential oil of Drimys granadensis L.f. leaves from Colombia

Drimys granadensis L.f., a native plant from Colombia, has been included in the Vademecum de Plantas Medicinales de Colombia by the Instituto de Investigación de Recursos Biológicos Alexander von Humboldt, due to its widespread use in the folk medicine for the treatment of gastrointestinal ailments. The chemical composition of the essential oil of Drimys granadensis obtained by hydrodistillation of the leaves was analyzed by GC and GC/MS analyses. A total of 85 components were identified, with the major compounds germacrene D (1, 14.7%), sclarene (9.5%), a-cadinol (7.3%), longiborneol acetate (2, 6.3%), drimenol (4.2%), (Z)-β-ocimene (3, 4.2%), a-pinene (4, 3.2%), and β-elemene (5, 2.7%). The essential oil was also tested against eight bacteria using the Kirby-Bauer disk-diffusion method. Most of the Gram-positive bacteria tested were susceptible to the D. granadensis essential oil, while the Gram-negative bacteria tested were not.     

有机栽培龙脑百里香精油对白色念珠菌体外抑菌活性的研究

【背景】白色念珠菌(Candidaalbicans)属于条件致病性真菌,可引起严重的黏膜真菌感染及全身系统性真菌感染,是导致患者高发病率和高死亡率的主要菌群之一。【目的】探究百里香精油对白色念珠菌的抑菌活性及抑制机理。【方法】测定5种百里香精油对白色念珠菌的抑菌圈直径,分析具有高抑菌活性的精油成分。在此基础上,通过扫描电子显微镜(scanning electron microscope, SEM)观察精油对白色念珠菌菌体细胞形态的影响。测定碱性磷酸酶(alkaline phosphatase, AKP)含量、胞外溶液电导率并进行碘化丙啶(propidium iodide, PI)染色分析,探究精油对白色念珠菌生物膜的形成与黏附及磷脂酶活性的影响,并通过实时荧光定量PCR法分析与白色念珠菌生物膜形成相关基因(凝集素样序列基因ALS4,从酵母型向菌丝型细胞的形态转变基因HWP1、磷脂酶基因PLB1)的表达水平,探究该精油对白色念珠菌的抑菌机制。【结果】筛选出了对白色念珠菌高度敏感的有机栽培龙脑百里香精油(Thymus vulgaris CT borneol essential oil, T...     

Efficacy of an essentifal oil of Cinnamomum zeylanicum against Psoroptes cuniculi

The aim of the present study was to investigate the in vitro and in vivo acaricidal effects of an essential oil of Cinnamomum zeylanicun leaves on Psoroptes cuniculi, a mange mite. In vitro, 2.5 ml of the essential oil diluted at different concentrations, from 10% to 0.03%, in paraffin oil were added to Petri dishes containing all motile stages of P. cuniculi. Mites mortality observed in these dishes was compared with that observed in untreated and treated (AcaCerulen R) control plates. In vivo, one group of six P. cuniculi infected rabbits was topically treated two times at seven days interval with two ml of the essential oil at the concentration of 2.5% in paraffin oil and compared with untreated and treated (AcaCerulen R) control groups of six rabbits each. After 24 h of contact, all concentrations of essential oil between 0.10 and 10% showed a good in vitro acaricidal efficacy if compared with the untreated controls (p<0.01), but only the concentrations between 0.16 and 10% turned out as active as the drug. In vivo, the treatment with the essential oil cured all infested rabbits and no statistical differences were observed with the treated control group.     

Stochastic eco-epidemiological model of dengue disease transmission by Aedes aegypti mosquito

We present a stochastic dynamical model for the transmission of dengue that takes into account seasonal and spatial dynamics of the vector Aedes aegypti. It describes disease dynamics triggered by the arrival of infected people in a city. We show that the probability of an epidemic outbreak depends on seasonal variation in temperature and on the availability of breeding sites. We also show that the arrival date of an infected human in a susceptible population dramatically affects the distribution of the final size of epidemics and that early outbreaks have a low probability. However, early outbreaks are likely to produce large epidemics because they have a longer time to evolve before the winter extinction of vectors. Our model could be used to estimate the risk and final size of epidemic outbreaks in regions with seasonal climatic variations.     

Chemical compositions of Casuarina equisetifolia L., Eucalyptus toreliana L. and Ficus elastica Roxb. ex Hornem cultivated in Nigeria

Essential oils were obtained by separate hydrodistillation of three different plants cultivated in Nigeria and analysed comprehensively for their constituents by means of gas chromatography (GC) and gas chromatography-mass spectrometry (GC–MS). The leaf essential oil of Casuarina equisetifolia L. (Casuarinaceae) comprised mainly of pentadecanal (32.0%) and 1,8-cineole (13.1%), with significant amounts of apiole (7.2%), α-phellandrene (7.0%) and α-terpinene (6.9%), while the fruit oil was dominated by caryophyllene-oxide (11.7%), trans-linalool oxide (11.5%), 1,8-cineole (9.7%), α-terpineol (8.8%) and α-pinene (8.5%). On the other hand, 1,8-cineole (39.4%) and α-terpinyl acetate (10.7%) occurred in large quantities in the essential oils of the leaf of Eucalyptus toreliana L. (Myrtaceae). The oil also features high levels of sabinene (5.9%), caryophyllene-oxide (4.7%) and α-pinene (4.2%). The main compounds identified in the leaf oil of Ficus elastica Roxb. ex Hornem. (Moraceae) were 6,10,14-trimethyl-2-pentadecanone (25.9%), geranyl acetone (9.9%), heneicosene (8.4%) and 1,8-cineole (8.2%).