Greek Pinus essential oils: larvicidal activity and repellency against Aedes albopictus (Diptera: Culicidae).

The needle volatiles metabolites of seven Pinus spp.: Pinus nigra (3 samples), Pinus stankewiczii, Pinus brutia, Pinus halepensis, Pinus canariensis, Pinus pinaster and Pinus strobus from Greece were determined by gas chromatography and gas chromatography-mass spectrometry. P. nigra and P. canariensis essential oils were dominated by α-pinene (24.9-28.9 % and 15 %, respectively) and germacrene D (20.3-31.9 % and 55.8 %, respectively), whereas P. brutia and P. strobus by α-pinene (20.6 % and 31.4 %, respectively) and ß-pinene (31.7 % and 33.6 %, respectively). P. halepensis and P. pinaster oils were characterized by ß-caryophyllene (28.5 % and 22.5 %, respectively). Finally, ß-pinene (31.4 %), germacrene D (23.3 %) and α-pinene (17.5 %) were the most abundant compounds in the needle oil of P. stankewiczii. Additionally the larvicidal and repellent properties of their essential oils were evaluated against Aedes albopictus, a mosquito of great ecological and medical importance. The results of bioassays revealed that repellent abilities of the tested essential oils were more potent than their larvicidal activities. The essential oils of P. brutia, P. halepensis and P. stankewiczii presented considerable larvicidal activity (LC50 values 67.04 mgL(-1) and 70.21 mgL(-1), respectively), while the others were weak to inactive against larvae. The essential oils of P. halepensis, P. brutia, and P. stankewiczii presented a high repellent activity, even at the dose of 0.2 µL cm(-2), while in the dose of 0.4 µL cm(-2), almost all the tested EOs displayed protection against the mosquito.

Volatile compounds in Thymus sect. Teucrioides (Lamiaceae): intraspecific and interspecific diversity, chemotaxonomic significance and exploitation potential.

Thymus sect. Teucrioides comprises three species, namely, T. hartvigii, T. leucospermus, and T. teucrioides, distributed in Greece and Albania. The volatile constituents of all species of the section were obtained by hydrodistillation and investigated by GC-FID and GC/MS analyses. Twenty populations were sampled and a total of 103 compounds were identified, representing 98.0-99.9% of the oil compositions. The oils were mainly characterized by high contents of monoterpene hydrocarbons (42.7-92.4%), with the exception of three oils for which oxygenated monoterpenes were the dominating constituents, viz., that of T. hartvigii ssp. macrocalyx, with linalool as main compound (89.2±0.5%), and those of T. hartvigii ssp. hartvigii and of one population of T. teucrioides ssp. candilicus, containing thymol as major component (46.4±3.1 and 38.2±3.9%, resp.). The most common compound in the oils of the 20 populations of the section was p-cymene. Considerable variation was detected within and among populations, and seven chemotypes were distinguished, i.e., p-cymene, linalool, p-cymene/thymol, p-cymene/γ-terpinene, p-cymene/borneol, p-cymene/γ-terpinene/borneol, and p-cymene/linalool chemotypes. Different chemotypes may exist in the same population. Multivariate statistical analyses enabled the segregation of the oils within Thymus sect. Teucrioides into two groups, one consisting of the three subspecies of T. teucrioides and the second comprising the species T. hartvigii and T. leucospermus. A linalool-rich chemotype, unique within the section, distinguished the oil of T. hartvigii ssp. macrocalyx from all other oils. The high oil content of p-cymene and the preference for serpentine substrates render T. teucrioides species promising for future exploitation.

Essential oil composition, adult repellency and larvicidal activity of eight Cupressaceae species from Greece against Aedes albopictus (Diptera: Culicidae).

The present study evaluated leaf essential oils from eight Cupresaceae species; Cupressus arizonica, Cupressus benthamii, Cupressus macrocarpa, Cupressus sempervirens, Cupressus torulosa, Chamaecyparis lawsoniana, Juniperus phoenicea, and Tetraclinis articulata for their larvicidal and repellent properties against Aedes albopictus, a mosquito of great ecological and medical importance. Based on the LC(50) values, C. benthamii essential oil was the most active (LC(50) = 37.5 mg/L) while the other tested Cupressaceae essential oils provided rather moderate toxicity against larvae (LC(50) = 47.9 to 70.6 mg/L). Under the used laboratory conditions, three of the essential oils (C. benthamii, C. lawsoniana, and C. macrocarpa) provided sufficient protection against mosquito adults, equivalent to the standard repellent "Deet" in the 0.2 mg/cm(2) dose, while C. macrocarpa assigned as the superior repellent oil in the 0.08 mg/cm(2) dose. Chemical analysis of the essential oils using gas chromatography and gas chromatography-mass spectrometry revealed the presence of 125 components.

Chemical composition, larvicidal evaluation, and adult repellency of endemic Greek Thymus essential oils against the mosquito vector of West Nile virus.

The volatile metabolites of Greek wild growing Thymus leucospermus and Thymus teucrioides subsp. candilicus were determined by gas chromatography and gas chromatography-mass spectrometry. The monoterpene hydrocarbon p-cymene (64.2%) dominated T. leucospermus oil, followed by γ-terpinene (7.9%), thymol (4.8%), and borneol (4.7%), whereas the most abundant constituents in T. teucrioides subsp. candilicus oil were p-cymene (25.5%), γ-terpinene (19.0%), thymol (18.8%), borneol (5.7%), and α-pinene (5.7%). The larvicidal and repellent activities of the analyzed essential oils were tested on Culex pipiens larvae and adults, respectively. Additionally, the main metabolite of the essential oils, p-cymene was tested against C. pipiens adults in order to define the affiliation between p-cymene and the repellent properties of the oil. The essential oils of T. leucospermus and T. teucrioides subsp. candilicus provided repellency 78.1% and 72.9%, respectively, statistically equal to the reference product icaridin. The compound p-cymene showed almost no repellent activity. The essential oil of T. leucospermus presented lower larvicidal activity (LC(50) = 34.26 mgl(-1)) against C. pipiens third-fourth instar larvae while T. teucrioides subsp. candilicus was the most active with an estimated LC(50) value of 23.17 mgl(-1).

Chemical composition and larvicidal evaluation of Mentha, Salvia, and Melissa essential oils against the West Nile virus mosquito Culex pipiens.

The volatile metabolites of wild-growing Mentha spicata, M. longifolia, M. suaveolens, Melissa officinalis, Salvia fruticosa, S. pomifera subsp. calycina, and S. pomifera subsp. pomifera from Greece were determined by gas chromatography and gas chromatography-mass spectrometry. The insecticidal properties of the analyzed essential oils were screened on Culex pipiens larvae. Additionally two of the main components of the essential oils, piperitenone oxide and 1,8-cineole were assayed against C. pipiens in order to define the affiliation between them and the larvicidal properties of the oils. The most effective oils were M. suaveolens (major constituent piperitenone oxide, 62.4%), M. spicata (piperitenone oxide, 35.7% and 1,8-cineole, 14.5%) and M. longifolia--Central Greece (piperitenone oxide, 33.4%; 1,8-cineole, 24.5% and trans-piperitone epoxide, 17.4%), which exhibited LC(50) values ranging from 47.88 to 59.33 mg l(-1). Medium activity revealed the oils of M. officinalis (terpin-4-ol, 15.8%; caryophyllene oxide, 13.2%; sabinene, 12.9%; beta-pinene, 12.1%; and trans-caryophyllene, 10.2%), M. longifolia--Southern Greece (carvone, 54.7% and limonene 20.0%), S. pomifera subsp. pomifera (trans-caryophyllene, 22.5% and trans-thujone, 21.0%), S. pomifera subsp. calycina--West Southern Greece (trans-thujone, 56.1% and 1,8-cineole, 10.4%), and S. fruticosa--population 2 (camphor, 23.1%; alpha-pinene, 12.7%; and borneol, 12.6%), with LC(50) values ranging from 78.28 to 91.45 mg l(-1). S. pomifera subsp. calycina (Central Greece) essential oil (trans-thujone, 26.5% and cis-thujone, 12.0%) presented rather low activity (LC(50) values 140.42 mg l(-1)), while S. fruticosa--population 1 (1,8-cineole, 31.4% and camphor, 22.6%) was the only inactive oil. Additionally, the constituent piperitenone oxide was found to be highly active (LC(50) values 9.95 mg l(-1)), whereas 1,8-cineole revealed no toxicity.

Volatile metabolites from Salvia fruticosa as antifungal agents in soilborne pathogens.

The volatile metabolites of Salvia fruticosa plants, growing wild in 15 localities scattered across Greece, were analyzed by means of GC and GC-MS. The essential oil content ranged from 0.69 to 4.68%, and the results of the analyses showed a noticeable variation in the amounts of the five main components [1,8-cineole, alpha-thujone, beta-thujone, camphor, and (E)-caryophyllene]. The antifungal activities of the essential oils from two localities, belonging in two different groups of cluster and principal component analysis, and their main components (1,8-cineole and camphor) were evaluated in vitro against five phytopathogenic fungi. Both oils were slightly effective against Fusarium oxysporum f. sp. dianthi and Fusarium proliferatum, whereas against Rhizoctonia solani, Sclerotinia sclerotiorum, and Fusarium solani f. sp. cucurbitae the oils exhibited high antifungal activities.

Composition and antifungal activity on soil-borne pathogens of the essential oil of Salvia sclarea from Greece.

The hydrodistilled essential oils of the aerial parts of wild-growing Salvia sclarea originated from two localities in Greece were analyzed by GC-MS. Sixty-six compounds, representing 93.26-98.19% of the oils, were identified. Linalyl acetate (19.75-31.05%), linalool (18.46-30.43%), geranyl acetate (4.45-12.1%), and alpha-terpineol (5.08-7.56%) were the main components. The antifungal activity of the oil of one locality and of the main components, linalyl acetate and linalool, was evaluated in vitro against three soil-borne pathogens.