Xavier Tomas

Chemical polymorphism of the essential oil of Thymus carnosus from portugal

Abstract The composition of the essential oils of 11 populations of Thymus carnosus from Portugal and their infraspecific variability were investigated by GC, GC-MS and 13CNMR. The results obtained were submitted to Principal Component and Chemometric Cluster Analyses. Borneol was the main constituent in all the populations except in one, which had a high content of linalool. This compound showed high percentages in samples originating from the region of Estremadura. Multivariate analysis allowed the distinction between three different groups of essential oils, (i) borneol/cis-sabinene hydrate/terpinen-4-ol, (ii) linalool/borneol/trans-sabinene hydrate and (iii) borneol/camphene.

Intraneural Injection during Anterior Approach for Sciatic Nerve Block

To the Editor:—We read with interest the case report by Sala-Blanch et al. The authors describe an unorthodox but interesting treatment for patients undergoing continuous sciatic nerve block that raises several concerns. In short, using computed tomographic imaging without clear clinical indication, the authors documented that nerve stimulator–guided needle placement during sciatic nerve block through the anterior approach resulted in an intraneural needle placement. The authors then inserted the catheter and administered local anesthetics. Conventional wisdom suggests that intraneural needle placement and catheter insertion should be avoided because intraneural application of local anesthetics has been shown to result in neurologic injury in animal models. However, despite the documented intraneural needle and catheter placement—although it is not clear whether the stimulating needle lies between fascia and epineurium or between epineurium and perineurium—the patients did not have neurologic injury. Therefore, this case report suggests that not all intraneural injections lead to neurologic injury. It also suggests that nerve stimulators may not be reliable in avoiding intraneural needle or catheter placement. Finally, a better definition of what constitutes an intraneural versus an intraepineural sheath injection during blockade of peripheral nerves and plexuses is needed for more meaningful discussion of this matter. Some experts may view the patient treatment in report by Sala-Blanch et al. unusual or even potentially hazardous. However, their findings should be welcomed because they clearly pose some important questions. At the least, they suggest that future research should continue to focus on developing more reliable and objective tools of nerve localization and injection monitoring techniques to help avoid intraneural injection and reduce the risk of consequent neurologic injury. In any case, it is recommended to withdraw the needle or the catheter if one has any doubt that its position is too close to the nerve, for the safety of regional anesthesia.

Composition and variability of the essential oils of Thymus species from section Mastichina from Portugal

The composition and chemical polymorphism of the essential oils of several populations of Thymus mastichina subsp. mastichina, T. mastichina subsp. donyanae and T. albicans, which belong to the Section Mastichina of the genus Thymus, were investigated by GC and GC-MS. All representative population samples of these three taxa were characterized by their high 1,8-cineole content, which is a discriminatory and common feature of the essential oils of the Section Mastichina. Linalool is another major constituent of the essential oils of some populations of T. mastichina subsp. mastichina and T. albicans. The essential oil of T. mastichina subsp. donyanae is also characterized by large amounts of borneol. This feature distinguishes its essential oil from the type subspecies. To study the infraspecific variability of each taxon, the results obtained in the GC analyses of the volatile oil of several idtividual plants from each population were submitted to a Principal Component Analysis and a Cluster Analysis, which showed that the essential oils of the only population investigated of T. mastichina subsp. donyanae have no chemical polymorphism, whereas the oils of T. mastichina subsp. mastichina and T. albicans have infraspecific variability. Some correlation between the amount of linalool in the essential oil of T. mastichina subsp. mastichina and the Atlantic humidity was established.

Composition and infraspecific variability of essential oil from Thymus camphoratus

Abstract The composition of the essential oils of seven populations of Thymus camphoratus from Portugal and their infraspecific variability were investigated by GC, GC-mass spectrometry and 13C NMR. The results obtained from GC analyses of the volatile oils from individual plants were submitted to Principal Component and Chemometric Cluster analyses. 1,8-Cineole, linalool, borneol, α-pinene, camphene, trans-sabinene hydrate, and terpinen-4-ol were the main constituents. 13 C NMR spectra of the essential oil, previously fractioned by column chromatography, let to the identification of two new oxygenated sesquiterpenes for the genus Thymus: intermedeol, which is reported for the first time in the Lamiaceae, and homalomenol-D. Multivariate analysis enabled four different groups of essential oils to be distinguished: (i) linalool, (ii) borneol, (iii) 1,8-cineole and (iv) 1,8-cineole/borneol.

Water quality and diatom communities in two catalan rivers (N.E. Spain)

Benthic diatom assemblages have been used to evaluate the water quality of two rivers subjected to marked human influences. These rivers, the Llobregat and the Ter, are located in N.E. Spain, and supply water for industrial, agricultural and urban requirements of roughly three million people. The diatom communities in the headwaters are similar in both rivers (Achnanthes minutissima, Cymbella ventricosa, Gomphonema anguslatum). Species of Navicula, Nitzschia and Gomphonema develop in the middle reaches of both rivers when not disrupted by extraneous factors. In the river Ter significant pollution modifies this community and Nitzschia palea, Nitzschia gandersheimiensis and Gomphonema parvulum appear as the most tolerant species. In the Llobregat, the pollution from the salt mine operations also modifies the diatom assemblage and Nitzschia frustulum, Surirella ovata, Navicula atomus are the most abundant species. Reservoirs in the river Ter improve the quality of water and a community of Fragilaria sp. pl. becomes dominant downstream.

Composition and chemical polymorphism of the essential oils from Piper lanceaefolium.

Essential oils obtained by hydrodistillation from leaves and spikes of Piper lanceaefolium H.B.K. of Costa Rica were analysed by GC-FID, GC-MS and 13C-NMR methods. Main constituents found in the oil from leaves were sesquiterpene hydrocarbons - especially beta-caryophyllene and germacrene D - and phenylpropanoids, of which elemicin and parsley apiol were the major ones. The volatile oil from spikes showed monoterpene hydrocarbons, namely alpha- and beta-pinene, and the same phenylpropanoids as in the oil from leaves as the major constituents. Results obtained in the analysis by GC-FID and GC-MS of the essential oils from individual plants of different geographic origin were submitted to chemometric cluster analysis and principal component analysis, showing the presence of three different types of oils (i) parsley apiol/elemicin, (ii) elemicin/parsley apiol/dill apiol, and (iii) parsley apiol/dill apiol.

Composition and variability of the essential oil of Thymus willkomii

Abstract Qualitative and quantitative analysis of the essential oil of Thymus willkomii showed linalool, α-terpinyl acetate and 1,8-cineole as major constituents. Chemometric investigation of the infraspecific variability of the essential oil of a population of this species led to the differentiation of two main chemotypes; type A: linalool (49% of the plants) and type B: α-terpinyl acetate (36% of the plants). The remaining plants (15%) could not be included in either of these two types; some of them showed significant amounts of other constituents such as trans -sabinene hydrate, myrcen-8-ol, and terpinen-4-ol.

Chemotaxonomic study on Thymus villosus from Portugal

The composition of the essential oils of four populations of Thymus villosus subsp. lusitanicus (Boiss.) Coutinho from Portugal was investigated by GC and GC-MS. To study the chemical polymorphism the results obtained from GC analyses of the volatile oils from individual plants from four populations were submited to Principal Component and Cluster analyses. A comparision with the essential oil of T. villosus subsp. villosus, previously studied by us was done. Important differences with regard to the major constituents in these two taxa were found. Linalool, geranyl acetate, geraniol and terpinen-4-ol were the main components of the essential oils of T. villosus subsp. lusitanicus, whereas in the oil of T. villosus subsp. villosus p-cymene, myrcene and alpha-terpineol were the major ones. Although, both taxa showed chemical polymorphism, different types of essential oils were characterized in each one: linalool; linalool/ terpinen-4-ol/trans-sabinene hydrate; linalool/1,8-cineole; geranyl acetate/geraniol; geranyl acetate/geraniol/1,8-cineole in T. villosus subsp. lusitanicus and p-cymene/camphor/linalool; p-cymene/borneol; linalool/geraniol/geranyl acetate; alpha-terpineol/camphor/myrcene in T. villosus subsp. villosus. Thus, the two subspecies of T. villosus can be easely differenciated by the composition of their essential oils.

The Essential Oil of Thymus villosus L. ssp. villosus and its Chemical Polymorphism

The composition of the essential oils of six populations of Thymus villosus L. ssp. villosus, an endemic species of Portugal belonging to the section Pseudothymbra Bentham of the genus Thymus (Lamiaceae), was investigated mainly by GC and GC-MS. In order to study the infraspecific variability, the results obtained by the analysis of individual plants were submitted to a principal component analysis and a cluster analysis. Four types of essential oils were found: p-cymene/camphor/linalol, p-cymene/borneol, linalol/geraniol/geranyl acetate, and α-terpineol/ camphor/myrcene.

Chemometrics and essential oil analysis: chemical polymorphism in two Thymus species

The utility of multivariate analysis techniques in the study of infraspecific variability of essential oils is shown through its application to Thymus moroderi and T. antoninae. The composition and chemical polymorphism of their essential oils is investigated. Both taxa showed the same major constituents: 1,8-cineole, camphor, camphene and borneol, but several differences in their sesquiterpene fraction. Chemometric analysis of the oil of individual plants from different populations of the two species showed the existence of two types of essential oils in T. moroderi with different sesquiterpene composition and low degree of chemical polymorphism in the case of T. antoninae