Jean-Marie Bessière

Geographic variation of Greek oregano (Origanum vulgare ssp. hirtum) essential oils

Essential oils of Origanum vulgare ssp. hirtum from twenty-three localities, scattered all over Greece, were analysed in order to determine their quantitative and qualitative features. The total oil content of plants and the percentage contribution of the major oil constituents, carvacrol, thymol, γ-terpinene and p-cymene, varied remarkably between localities. The contents of carvacrol and thymol were significantly correlated, varying inversely. The same holds for their sum and the sum of the two major monoterpene hydrocarbons. Altitude seems to be the most important environmental factor influencing the oil content; high values were recorded at low altitudes, coinciding with Mediterranean-type ecosystems. The sum of the four major oil constituents, representing the phenol pathway, seems influenced by the climates thermal efficiency. The hotter the climate, the higher their total concentration.

Specific attraction of fig-pollinating wasps: role of volatile compounds released by tropical figs.

Floral scents often act as pollinator attractants. In the case of obligate and specific plant–pollinator relationships, the role of floral signals may be crucial in allowing the encounter of the partners. About 750 Ficus species (Moraceae) are involved in such interactions, each with a distinct species of pollinating wasp (Chalcidoidea, Agaonidae). Several species have been shown to release volatile compounds, but their role in pollinator attraction has rarely been simultaneously tested. We investigated the floral scents of four tropical fig species and combined chemical analysis with biological tests of stimulation of insects. Pollinators of three species were stimulated by the odor of their associated fig species and generally not by the odor of another species. The fourth actually comprised two distinct varieties. The main compound was often a different one in each species. Floral blends of different species always shared compounds, but ratios of these compounds varied among species.

Fig volatile compounds—a first comparative study

We analysed the compounds of volatile blends released by receptive figs of twenty Ficus species to attract their specific pollinating wasps. In all, 99 different compounds were identified. The compounds are mainly terpenoids, aliphatic compounds and products from the shikimic acid pathway. In each species blend, there are few major compounds, which are generally common among floral fragrances. Most species blends also include rare compounds, but generally their proportion in the blend is low. A possible basis for species-specificity of Ficus-wasp interactions is discussed in relation to the patterns of volatiles found in this interspecies comparison.

The Antifungal Activity of Essential Oils as Determined by Different Screening Methods

Abstract The existing methods for studying the antimicrobial activity of essential oils (e.g. the dilution of the test substances in broth or agar medium) are not adequate to evaluate the effects of the volatile components. Growth inhibition of fungi by various essential oils was determined by direct contact in broth and agar media and compared with the fungistatic action of their vapors using the micro-atmosphere method. Tests were performed on eight cellulolytic mold strains that often contaminate archive and museum reserves. Thirty-seven essential oils were screened to find the most antifungal ones with potential to be employed as atmospheric preservatives. Chenopodium ambrosioides L. var. anthelminticum, Cymbopogon martinii (Roxb.) W. Watson var. martinii, Cymbopogon nardus (L.) W. Watson var. nardus, Syzygium aromaticum (L.) Merr. et L. M. Perry and Pimenta racemosa (Mill.) J.W. Moore were the most active essential oils on the eight strains tested according to direct contact methods. C. martinii was inhibitory even after 12 days of incubation. Using the micro-atmosphere method, C. nardus and C. martinii volatiles were the most fungistatic, but the vapors of Ch. ambrosioides, S. aromaticum and P. racemosa gave moderate results with a specific short effect of P. racemosa.

Composition and antimalarial activity in vitro of volatile components of lippia multiflora

The essential oil of Lippia multiflora was prepared by hydrodistillation of leaves and stalks and characterized by GC and mass spectroscopy. The oil was tested for antimalarial activity on in vitro cultures of Plasmodium falciparum (FcB1-Columbia chloroquine-resistant strain and F32-Tanzania chloroquine-sensitive strain). The dilutions inhibiting the in vitro growth of the parasite by 50% 24 and 72 hr after administration of the essential oil to the parasite culture were 1/12,000 and 1/21,000, respectively. When tested on a highly synchronized culture, the essential oil inhibited growth mostly at the trophozoite-schizont step, indicating a potential effect on the first nuclear division of the parasite.

In vitro antimalarial activity of eight essential oils

Abstract Essential oils of eight plants were prepared by hydrodistillation of leaves and twigs (stems) of Artemisia vulgaris, Eucalyptus globulus, Myrtus communis, Juniperus communis, Lavandula angusti/olia, Origanum vulgare, Rosmarinus officinalis and Salvia officinalis. Their oil components were characterized by GC and MS. These oils were then tested for in vitro antimalarial activity on Plasmodium falciparum. Two strains of P. falciparum were tested: FcBl-Columbia (chloroquine-resistant) and a Nigerian chloroquine-sensitive strain. Concentrations inhibiting 50% of the parasite in vitro growth, obtained after 24 and 72 h contact between the oil and the parasite culture, ranged from 150 μg/mL to 1 mg/mL. The best results were obtained with Myrtus communis and Rosmarinus officinalis oils which inhibited P. falciparum at concentrations ranging from 150 to 270 μg/mL.

Individual Odor Recognition in Birds: An Endogenous Olfactory Signature on Petrels' Feathers?

A growing body of evidence indicates that odors are used in individual, sexual, and species recognition in vertebrates, and may be reliable signals of quality and compatibility. Petrels are seabirds that exhibit an acute sense of smell. During the breeding period, many species of petrel live in dense colonies on small oceanic islands and form pairs that use individual underground burrows. Mates alternate between parental duties and foraging trips at sea. Returning from the ocean at night (to avoid bird predators), petrels must find their nest burrow. Antarctic prions, Pachyptila desolata, are thought to identify their nest by recognizing their partner’s odor, suggesting the existence of an individual odor signature. We used gas chromatography and mass spectrometry to analyze extracts obtained from the feathers of 13 birds. The chemical profile of a single bird was more similar to itself, from year to year, than to that of any other bird. The profile contained up to a hundred volatile lipids, but the odor signature may be based on the presence or absence of a few specific compounds. Our results show that the odor signature in Antarctic prions is probably endogenous, suggesting that in some species of petrels it may broadcast compatibility and quality of potential mates.

Human skin volatiles : a review

Odors emitted by human skin are of great interest to biologists in many fields; applications range from forensic studies to diagnostic tools, the design of perfumes and deodorants, and the ecology of blood-sucking insect vectors of human disease. Numerous studies have investigated the chemical composition of skin odors, and various sampling methods have been used for this purpose. The literature shows that the chemical profile of skin volatiles varies greatly among studies, and the use of different sampling procedures is probably responsible for some of these variations. To our knowledge, this is the first review focused on human skin volatile compounds. We detail the different sampling techniques, each with its own set of advantages and disadvantages, which have been used for the collection of skin odors from different parts of the human body. We present the main skin volatile compounds found in these studies, with particular emphasis on the most frequently studied body regions, axillae, hands, and feet. We propose future directions for promising experimental studies on odors from human skin, particularly in relation to the chemical ecology of blood-sucking insects.

Leaf volatile compounds and the distribution of ant patrollingin an ant-plant protection mutualism: Preliminary results onLeonardoxa (Fabaceae: Caesalpinioideae) andPetalomyrmex(Formicidae: Formicinae)

While observations suggest that plant chemicals could be important in maintaining the specificity and permitting the functioning of ant-plant symbioses, they have been little studied. We report here the strongest evidence yet for chemical signalling between ants and plants in a specific ant-plant protection symbiosis. In the mutualism between Leonardoxa africana subsp. africana and Petalomyrmex phylax, ants continuously patrol young leaves, which are vulnerable to attacks by phytophagous insects. We provide experimental evidence for chemical mediation of ant attraction to young leaves in this system. By a comparative analysis of the related non-myrmecophytic tree L. africana subsp. gracilicaulis, we identify likely candidates for attractant molecules, and suggest they may function not only as signals but also as resources. We also propose hypotheses on the evolutionary origin of these plant volatiles, and of the responses to them by mutualistic ants.

Catnip (Nepeta cataria L.) Essential Oil: Analysis of Chemical Constituents, Bacteriostatic and Fungistatic Properties

ABSTRACT The composition of the essential oil of flowering catnip (Nepeta cataria L., Lamiaceae) was analyzed by means of GC/MS. Besides the already known nepetalactones 4aα, 7α, 7aα-nepetalactone; 3,4β-dihydro-4aα, 7α, 7aα-nepetalactone; 4aα, 7α, 7aβ-nepetalactone and β-caryophyllene, five new constituents were identified: dimethyl-3,7 oxa-1 bicyclo [3,3,0] oct-2-ene, piperitone, thymol methyl ether, hexenyl benzoate and humulene oxide. The essential oil of two samples of the plant, collected at two different stages of development, was compared as to their nepetalactone content. The oil samples and a hexane extract were subjected to microbiological tests (five bacteria and seven fungi) and compared to natural compounds known for their antimicrobiological activities.