BACKGROUND In the search for plant-based mosquito repellents, volatile emanations were investigated from five plant species, Corymbia citriodora, Ocimum suave, Ocimum lamiifolium, Olea europaea and Ostostegia integrifolia, traditionally used in Ethiopia as protection against mosquitoes. METHODS The behaviour of two mosquitoes, the malaria vector Anopheles arabiensis and the arbovirus vector Aedes aegypti, was assessed towards volatiles collected from the headspace of fresh and dried leaves, and the smoke from burning the dried leaves in a two-choice landing bioassay and in the background of human odour. RESULTS Volatile extracts from the smoke of burning dried leaves were found to be more repellent than those from fresh leaves, which in turn were more repellent to mosquitoes than volatiles from dried leaves. Of all smoke and fresh volatile extracts, those from Co. citriodora (52-76%) and Oc. suave (58-68%) were found to be the most repellent, Os. integrifolia (29-56%) to be intermediate while Ol. europaea (23-40%) and Os. integrifolia (19-37%) were the least repellent. One volatile present in each of the fresh leaf extracts of Co. citriodora, Oc. suave and Os. integrifolia was ß-ocimene. The levels of ß-ocimene reflected the mosquito repellent activity of these three fresh leaf extracts. Female host-seeking mosquitoes responded dose-dependently to ß-ocimene, both physiologically and behaviourally, with a maximal behavioural repulsion at 14% ß-ocimene. ß-ocimene (14%) repels mosquitoes in our 6-minute landing assays comparable to the synthetic insect repellent N,N-diethyl-m-toluamide (10% DEET). CONCLUSIONS Volatiles in the smoke of burning as well as fresh leaves of Co. citriodora and Oc. suave have significant repellent properties against host seeking An. arabiensis and Ae. aegypti mosquitoes. ß-ocimene, present in the fresh leaf headspace of Co. citriodora, Oc. suave and Os. integrifolia, is a significantly effective volatile mosquito repellent in the laboratory. In addition to its repellent properties, ß-ocimene has long approved safe for use in food and cosmetics, making this volatile an intriguing compound to pursue in further tests in the laboratory and field to validate its mosquito repellent activity and potential for use in a commercial product. Also, the landing bioassay with humanised membranes is a potentially useful repellent screening technique that does not require the exposure of humans to the vectors, however further tests in parallel with conventional techniques are advised.

The leaves of Angelica anomala Lallemant, Angelica cartilagino-marginata var. distans (Nakai) Kitag, Angelica czernevia (Fisch. et Meyer) Kitagawa, Angelica dahurica Benth. et Hooker, Angelica decursiva (Miq.) Franch.& Sav, Angelica fallax Boissieu, Angelica gigas Nakai, Angelica japonica A. gray were essential oil extracted and immunotoxicity effects were studied. The Angelica anomala, A. cartilagino-marginata var. distans, A. czernevia, A. dahurica, A. decursiva, A. fallax, A. gigas, A. japonica essential oil yield were 4.13, 4.83, 4.45, 3.25, 4.11, 4.73, 4.34 and 4.21%. The A. dahurica essential oil had a significant toxic effect against early fourth-stage larvae of Aedes aegypti L with a lethal concentration 50 (LC(50)) value of 43.12 ppm and an LC(90) value of 65.23 ppm. The above indicates that essential oil contents may play a more important role in the toxicity of essential oil.

The stems of Allium monanthum were extracted, and the major essential oil composition and larvicidal effects were studied. The analyses were conducted by gas chromatography and mass spectroscopy revealed that the essential oils of A. monanthum stems. The A. monanthum essential oil yield was 4.25%, and gas chromatography and mass spectroscopy analysis revealed that its major constituents were dimethyl trisulfide (23.21%), dimethyl tetrasulfide (11.24%) and methlyl propyl trisulfide (8.21%). The essential oil had a significant toxic effect against early fourth-stage larvae of Aedes aegypti L with an LC(50) value of 23.14 ppm and an LC(90) value of 36.31 ppm. Also, dimethyl trisulfide (≥95.0%), dimethyl tetrasulfide (≥95.0%) and methlyl propyl trisulfide (≥95.0%) were tested against the F(21) laboratory strain of A. aegypti. Methlyl propyl trisulfide (≥95.0%) has good activity with an LC(50) value of 19.38 ppm. Also, the above indicates that other major compounds may play a more important role in the toxicity of essential oil.

CONTEXT Vector control is facing a threat due to the emergence of resistance to synthetic insecticides. In this context, essential oils have received much attention as potentially useful bioactive compounds against insects. Therefore, our present study aimed to evaluate the efficacy of essential oils from the aerial parts of Salvia elegans Vahl, Salvia dorisiana Standl., Salvia splendens Sello ex J.A. Schult Blue Ribbon, and S. splendens Sello ex J.A. Schult Scarlet Sage Red (Lamiaceae) against the fourth instar larvae of Aedes albopictus Skuse (Diptera: Culicidae). OBJECTIVE The mosquito larvicidal activities of the essential oils and chemical composition of four taxa of Salvia are investigated in this article for the first time. MATERIALS AND METHODS Chemical compositions of essential oils obtained from four taxa of Salvia were analyzed by gas chromatography-mass spectrometry (GC-MS), GC-FID, and the effects of essential oils on fourth instar larvae of A. albopictus were investigated. RESULTS The main components identified from each Salvia essential oils were as follows: spathulenol (38.73%) and caryophyllene (10.32%) from S. elegans; ledol (45.8%) and 4,4'-[(p-phenylene)diisopropylidene]diphenol (17.38%) from S. dorisiana; β-cubebene (22.9%), and caryophyllene (12.99%) from S. splendens Blue Ribbon; phytol (41.46%) and cyclooctasulfur (24.88%) from S. splendens Scarlet Sage Red. The essential oils of S. elegans and S. splendens Blue Ribbon had excellent inhibitory larvicidal effect against A. albopictus larvae, and their LC(50) values in 24 h were 46.4 ppm (LC(90) = 121.8 ppm) and 59.2 ppm (LC(90) = 133.0 ppm), respectively. DISCUSSION AND CONCLUSION These findings demonstrate that the essential oils of these Salvia species could be considered as the powerful candidates to bring about useful botanicals so as to prevent the resurgence of mosquito vectors.

Laboratory bioassays on insecticidal activity of essential oils (EOs) extracted from six Mediterranean plants (Achillea millefolium, Lavandula angustifolia, Helichrysum italicum, Foeniculum vulgare, Myrtus communis, and Rosmarinus officinalis) were carried out against the larvae of the Culicidae mosquito Aedes albopictus. The chemical composition of the six EOs was also investigated. Results from applications showed that all tested oils had insecticidal activity, with differences in mortality rates as a function of both oil and dosage. At the highest dosage (300 ppm), EOs from H. italicum, A. millefolium, and F. vulgare caused higher mortality than the other three oils, with mortality rates ranging from 98.3% to 100%. M. communis EO induced only 36.7% larval mortality at the highest dosage (300 ppm), a similar value to those recorded at the same dosage by using R. officinalis and L. angustifolia (51.7% and 55%, respectively). Identified compounds ranged from 91% to 99%. The analyzed EOs had higher content of monoterpenoids (80-99%) than sesquiterpenes (1-15%), and they can be categorized into three groups on the basis of their composition. Few EOs showed the hydrocarbon sesquiterpenes, and these volatile compounds were generally predominant in comparison with the oxygenated forms, which were detected in lower quantities only in H. italicum (1.80%) and in M. communis (1%).

The leaves of Zingiber officinale Roscoe were extracted and the major essential oil composition and immunotoxicity effects were studied. The analyses were conducted by gas chromatography and mass spectroscopy (GC-MS) revealed that the essential oils of Z. officinale leaves. The Z. officinale essential oil yield was 0.26%, and GC/MS analysis revealed that its major constituents were Camphene (5.26%), Phellandrene (6.58%), Zingiberene (36.48%), Geranial (4.32%), β-gurjunene (2.74%), and Citronellol β-sesguiphellandrene (12.31%). The essential oil had a significant toxic effect against early fourth-stage larvae of Aedes aegypti L with an LC(50) value of 46.38 ppm and an LC(90) value of 84.32 ppm. Also, Camphene (≥95.0%), Phellandrene (≥95.0%), Zingiberene (≥95.0%), Geranial (≥95.0%), β-gurjunene (≥97.0%), and Citronellol (≥95.0%) were tested against the F21 laboratory strain of A. aegypti. Zingiberene (≥95.0%) and Citronellol (≥95.0%) have medium activity with an LC(50) value of 99.55 ppm and 141.45 ppm. This indicates that other major compounds may play a more important role in the toxicity of essential oil.

The leaves of Lindera obtusiloba Blume var. obtusiloba were extracted and the major essential oil composition and immunotoxicity effects were studied. The analyses were conducted by gas chromatography and mass spectroscopy (GC-MS) revealed that the essential oils of L. obtusiloba. The L. obtusiloba essential oil yield was 4.23%, and GC/MS analysis revealed that its major constituents were α-copaene (31.42%), β-caryophyllene (32.11%), α-humulene (4.12%), β-farnesene (4.15%), α- cadinene (3.21%) and Nerolidol (6.84%). The essential oil had a significant toxic effect against early fourth-stage larvae of Aedes aegypti L with an LC(50) value of 24.32 ppm and an LC(90) value of 36.42 ppm.

The flower parts of Paulownia coreana were extracted and the major essential oils composition and immunotoxicity effects were studied. The analyses were conducted by gas chromatography-mass spectroscopy (GC-MS) revealed that the essential oils of P. coreana. The P. coreana essential oil (PCEO) yield was 0.175%, and GC/MS analysis revealed that its major constituents were benzyl alcohol (13.72%), phenol, 3,4-dimethoxy-methyl ester (3.64%), phenol, 2-methoxy-3-(2-popenyl)-methyl ester (6.24%), 1,2,4-Trimethoxybenzene (8.32%), tricosane (3.28%), and pentacosane (3.26%). The essential oil had a significant toxic effect against early fourth-stage larvae of Aedes aegypti L with an LC(50) value of 31.64 ppm and an LC(90) value of 56.43 ppm. 1,2,4-Trimethoxybenzene was the most toxic among the major components with an LC(50) value near 23.1 ppm. The results could be useful in search for newer, safer, and more effective natural immunotoxicity agents against A. aegypti.

The rhizomes and roots of Valeriana fauriei were extracted and the major essential oil composition and immunotoxicity effects were studied. The analyses were conducted by gas chromatography-mass spectroscopy (GC-MS) revealed that the essential oils of V. fauriei. The V. fauriei essential oil (VFEO) yield was 1.93%, and GC/MS analysis revealed that its major constituents were bornyl acetate (32.83%), terpinyl acetate (3.82%), bornyl isovalerate (2.11%), β-sesquiphellandrene (2.21%), sesquiterpene alcohol (7.32%), and cedrol (2.45%). The essential oil had a significant toxic effect against early fourth-stage larvae of Aedes aegypti L with an LC(50) value of 30.44 ppm and an LC(90) value of 82.64 ppm. The results could be useful in search for newer, safer, and more effective natural immunotoxicity agents against Aedes aegypti L.

The leaf parts of Clerodendron trichotomum were extracted and the major essential oils composition and immunotoxicity effects were studied. The analyses were conducted by gas chromatography-mass spectroscopy (GC-MS) revealed that the essential oils of C. trichotomum (CTEO). The CTEO yield was 0.071%, and GC/MS analysis revealed that its major constituents were Hexanal (3.31%), 5-Me-3-heptanone (1.71%), 2,6,6-trime-cyclohexanone (2.23%), 2,6,10,15-tetrame-heptadecane (24.21%) and Linalool (31.2%). The essential oil had a significant toxic effect against early fourth-stage larvae of Aedes aegypti L with an LC(50) value of 32.78 ppm and an LC(90) value of 93.72 ppm. 2,6,10,15-tetrame-heptadecane was the most toxic among the two major components (2,6,10,15-tetrame-heptadecane and Linalool), with an LC(50) value near 43.9 ppm. The results could be useful in search for newer, safer, and more effective natural immunotoxicity agents against A. aegypti.

OBJECTIVE To study the antibacterial activity of the leaf methanol extracts of five different species of Vitex namely, Vitex altissima (V. altissima), Vitex diversifolia (V. diversifolia), Vitex negundo (V. negundo), Vitex peduncularis (V. peduncularis) and Vitex trifolia (V. trifolia). METHODS Antibacterial assay was carried out by using disc diffusion method, determination of minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) against five strains of Gram-positive and seven strains of Gram-negative human pathogenic bacterial strains. RESULTS The results of antibacterial activity of Vitex species showed that the extracts possessed a broad spectrum of antibacterial activity. The V. peduncularis possessed the highest activity against all the microorganisms screened. It produced a zone of inhibition ranged between (11.000 ± 0.577) and (22.670 ± 0.667) mm and the MIC values were from 62.5 to 1 000.0 μg/mL and the MBC values were from 125.0 to 2 000.0 μg/mL. CONCLUSIONS Based on the present study, V. peduncularis is recommended for the isolation of antibacterial molecule responsible for the activity against the tested human pathogenic bacterial strains.

The larvicidal activity of fatty acid methyl ester (FAME) extracts of Vitex altissima, Vitex negundo and Vitex trifolia was studied against early fourth-instar larvae of Culex quinquefasciatus. The fatty composition was analysed by gas chromatography. The highest percentage of lauric acid, palmitic acid, stearic acid, oleic acid and linolenic acid were recorded in V. negundo. The highest percentage of linolenic acid was recorded in V. trifolia. The FAME extract of V. trifolia showed the highest larvicidal activity with an LC50 value of 9.25 ppm followed by V. altissima (14.82 ppm) and V. negundo (18.64 ppm).

The early fourth instar larvae of Culex quinquefasciatus, reared in the laboratory were used for larvicidal assay with leaf extracts of Vitex negundo, Vitex trifolia, Vitex peduncularis and Vitex altissima. The methanol extracts of the four species possessed varying levels of larvicidal nature. The highest larvicidal activity was found with the extract of V. trifolia (LC(50)= 41.41 ppm) followed by V. peduncularis (LC(50)= 76.28 ppm), V. altissima (LC(50)= 128.04 ppm) and V. negundo (LC(50)= 212.57 ppm).

ABSTRACT: BACKGROUND: Essential oils are currently studied for the control of different disease vectors, because of their efficacy on targeted organisms. In the present investigation, the larvicidal potential of essential oil extracted from Indian borage (Plectranthus amboinicus) was studied against the African anthropophagic malaria vector mosquito, Anopheles gambiae. The larvae of An. gambiae s.s laboratory colony and An. gambiae s.l of wild populations were assayed and the larval mortality was observed at 12, 24 and 48 h after exposure period with the concentrations of 3.125, 6.25, 12.5, 25, 50 and 100 ppm. FINDINGS: Larval mortality rates of the essential oil was entirely time and dose dependent. The LC50 values of the laboratory colony were 98.56 (after 12h) 55.20 (after 24 h) and 32.41 ppm (after 48 h) and the LC90 values were 147.40 (after 12h), 99.09 (after 24 h) and 98.84 ppm (after 48 h). The LC50 and LC90 values of the wild population were 119.52, 179.85 (after 12h) 67.53, 107.60 (after 24 h) and 25.51, 111.17 ppm (after 48 h) respectively. The oil showed good larvicidal potential after 48 h of exposure period against An. gambiae. The essential oil of Indian borage is a renowned natural source of larvicides for the control of the African malaria vector mosquito, An. gambiae. CONCLUSION: The larvicidal efficacy shown by plant extracts against An. gambiae should be tested in semi field and small scale trials for effective compounds to supplement the existing larval control tools.

Essential oil of Plectranthus amboinicus was studied for its chemical composition and larvicidal potential against the malarial vector mosquito Anopheles stephensi. Totally 26 compounds were identified by GC and GC-MS. The major chemical compounds were carvacrol (28.65%) followed by thymol (21.66%), α-humulene (9.67%), undecanal (8.29%), γ-terpinene (7.76%), ρ-cymene (6.46%), caryophyllene oxide (5.85%), α-terpineol (3.28%) and β-selinene (2.01%). The larvicidal assay was conducted to record the LC(50) and LC(90) values and the larval mortality was observed after 12 and 24 h of exposure period. The LC(50) values of the oil were 33.54 (after 12 h) and 28.37 ppm (after 24 h). The LC(90) values of the oil were 70.27 (after 12 h) and 59.38 ppm (after 24 h). The results of the present study showed that the essential oil of P. amboinicus is one of the inexpensive and eco-friendly sources of natural mosquito larvicidal agent to control/reduce the population of malarial vector mosquito.

Fatty acid methyl ester (FAME) extracts of four halophytic plants, viz. Arthrocnemum indicum, Salicornia brachiata, Suaeda maritima and Suaeda monoica belonging to the family Chenopodiaceae, were prepared and their composition was analyzed by GC-MS. The FAME extracts were also screened for antibacterial and antifungal activities. The GC-MS analysis revealed the presence of more saturated fatty acids than unsaturated fatty acids. Among the fatty acids analyzed, the relative percentage of lauric acid was high in S. brachiata (61.85%). The FAME extract of S. brachiata showed the highest antibacterial and antifungal activities among the extracts tested. The other three extracts showed potent antibacterial and moderate anticandidal activities.

The rhizomes and roots of Valeriana fauriei were extracted and the major essential oil composition and immunotoxicity effects were studied. The analyses were conducted by gas chromatography-mass spectroscopy (GC-MS) revealed that the essential oils of V. fauriei. The V. fauriei essential oil (VFEO) yield was 1.93%, and GC/MS analysis revealed that its major constituents were bornyl acetate (32.83%), terpinyl acetate (3.82%), bornyl isovalerate (2.11%), β-sesquiphellandrene (2.21%), sesquiterpene alcohol (7.32%), and cedrol (2.45%). The essential oil had a significant toxic effect against early fourth-stage larvae of Aedes aegypti L with an LC(50) value of 30.44 ppm and an LC(90) value of 82.64 ppm. The results could be useful in search for newer, safer, and more effective natural immunotoxicity agents against Aedes aegypti L.

Essential oils (EOs) are extremely complex mixtures containing compounds of several different functional-group classes. A specific aromatic profile should be determined by gas-chromatography-mass detection methods, to define standards for their safety and efficacy. The chemical constituents of the essential oils, their flavour and their taste act both alone and in synergy, always determining a global psychosomatic action. The main therapeutic activities of the EOs are reported as spasmolythic, revulsive, anti-inflammatory and decongestant, immunomodulant, antimicrobial, antimycotic, expectorant, mucolythic, antioxidant, psychotrope, analgesic and acaricide. The use, posology, route of administration as well as toxicity and adverse effects are reviewed.

Essential oils extracted by steam distillation from Zingiber officinalis was evaluated for larvicidal and repellent activity against the filarial mosquito Culex quinquefasciatus. The larval mortality was observed after 24 h treated for late third instar. The LC50 value was 50.78 ppm. Skin repellent test at 1.0, 2.0, 3.0, and 4.0 mg/cm2 concentration of Z. officinalis gave 100% protection up to 15, 30, 60, and 120 min. These results clearly reveal that the essential oil of Z. officinalis served as a potential larvicidal and repellent agent against filarial vector C. quinquefasciatus.

BACKGROUND & OBJECTIVES In view of the recently increased interest in developing plant origin insecticides as an alternative to chemical insecticide, this study was undertaken to assess the larvicidal potential of the essential oil from the seeds of Zanthoxylum armatum DC [syn. Z. alatum Roxb](Rutaceae) against three medically important species of mosquito vectors, Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus. METHODS Essential oil was hydro distilled in the laboratory from the seeds obtained from the market and the chemical constituents of the oil were determined using GC/GC-MS. Bioefficacy of the essential oil was evaluated under laboratory conditions using III instar mosquito larvae. RESULTS Among the three mosquito species tested, Cx. quinquefasciatus was the most sensitive (LC50 = 49 ppm) followed by Ae. aegypti (LC50 = 54 ppm) and An. stephensi (LC50 = 58 ppm). GC-MS analysis of the oil revealed at least 28 compounds, consisting mainly of oxygenated monoterpenes (75%) and monoterpenes (22%). Linalool though constituted a major part (57%), failed to produce any appreciable mortality when tested alone. INTERPRETATION & CONCLUSION From the results it can be concluded that the larvae of the three mosquito species were susceptible to the essential oil composition. Such findings would be useful in promoting research aiming at the development of new agent for mosquito control based on bioactive chemical compounds from indigenous plant sources as an alternative to chemical larvicides.

The chemical composition of the essential oils from aerial parts of Pectis apodocephala and Pectis oligocephala were analyzed by GC-MS. The essential oils of these species were predominantly constituted by monoterpenes. Geranial (42.9-44.5%), neral (32.2-34.2%) and alpha-pinene (10.7-11.4%) were the main constituents in the oil of P. apodocephala, while p-cymene (50.3-70.9%) and thymol (24.4-44.7%), were the prevalent compounds in the oil of P. oligocephala. The essential oils were tested against the root knot nematode Meloidogyne incognita and Aedes aegypti larvae survival. The results obtained show that both essential oils exhibited significant activity and could be considered as potent natural namaticidal and larvicidal agents.

In this work the essential oil composition of some less known Dracocephalum species was studied and compared the effectiveness, selectivity and influence of different extraction methods (hydrodistillation, Soxhlet extraction with organic solvents and supercritical fluid extraction) on essential oils. For investigations in Hungary and Transylvania cultivated plant material was used. The analysis of essential oils was carried out by GC and GC-MS methods. The components were identified by standard addition, retention factors and mass spectra. The percentile evaluation of each volatile constituents was made on basis of GC-FID chromatograms. The accuracy of measurements was characterized by relative standard deviation. In the essential oil of D. renati Emb.(studied firstly by us) 18.3% of limonene was measured and carvone, citrals and linalyl acetate monoterpenes, methyl chavicol and some sesquiterpene (e.g. bicyclovetivenol) determined in lower quantities. We established that more than 50% of essential oil of D. grandiflorum L. was formed by sesquiterpenes (beta-caryophyllene and- oxide, beta-bourbonene, beta-cubebene, aromadendrene) and the essential oil of D. ruyschiana L. contained pinocamphone isomers in more than 60%. The oxygenated acyclic monoterpenes, the characteristic constituents of Moldavian dragonhead were present in some tenth percent only in D. renati oil. We found significant differences in the composition of the SFE extract and traditional essential oil of D. moldavica L. The supercritical fractions collected at the beginning of the extraction process were richer in valuable ester component (geranyl acetate) than the essential oil obtained by hydrodistillation. The fractions collected at the end of supercritical were poor in oxygenated monoterpenes but rich in minor compounds of traditional oil, e.g. palmitic acid.

The seasonal variation of the essential oil, in terms of both yield and composition, of a population of Santolina etrusca (Asteraceae) is reported in detail for different aerial parts, including sterile branches, fertile branches, and capitula. The yields generally increased from November to June, and then decreased in August and September. The main constituents of the sterile branches were 1,8-cineole and viridiflorol. The oil from fertile branches was characterized by myrcene as principal compound, whereas the essential oil obtained from the capitula contained germacrene D as the main constituent. Several compounds, as identified by GC and GC/MS, were found to prevail during the cold season.

From the essential oil of myrrh, COMMIPHORA ABYSSIMICA (B ERG) E NGLER (Burseraceae) have been isolated: nine sesquiterpenoid hydrocarbons, the sesquiterpene alcohol elemol and the furanosesquiterpenoids furanodiene, furanodienone, isofuranogermacrene, curzerenone and lindestrene.

The essential oil of PLECTRANTHUS FRUTICOSUS L'Hérit.(Labiatae) is shown to contain at least fifty components, among which the major one, i.e. sabinyl acetate, accounts for more than 60% of the total. To our knowledge, this compound is described in Labiatae at such a high concentration for the first time. A preliminary study on rats reveals that this essential oil is teratogenic and/or highly foetotoxic.