Herminio Boira

Environmental factors affecting chemical variability of essential oils in Thymus piperella L.

Abstract Environmental factors affecting essential oils variability in Thymus piperella L. are studied. The relationship between the bioclimatics index and edaphic factors with three chemotypes is determined through the application of multivariate analysis (CANOCO) and other statistical processes to both ecological and the essential oil data set components. Chemotype p-cymene γ-terpinene carvacrol shows a positive relationship with the aridity index (Ia) and Altitude. The p-cymene thymol chemotype is related to factors affecting water balance in both the soils and plants. The influence of climatic factors over p-cymene carvacrol is less evident. The compound p-cymene, common to the three chemical groups and the most abundant of all, presents positive correlation with the organic matter in the soil.

Responses to salt stress in Juncus acutus and J. maritimus during seed germination and vegetative plant growth

Abstract Responses to increasing salinity, during seed germination and vegetative plant growth, were studied in two related species of Juncus, J. maritimus and J. acutus. In both species, germination was optimal in the absence of salt, reduced by about 50% in the presence of 200 mM NaCl, and completely inhibited by NaCl concentrations above 300 mM. Previous exposure of the seeds to salt, up to 500 mM NaCl, did not affect the germination capacity in J. acutus, and clearly enhanced it in J. maritimus. A concentration-dependent inhibition of plant growth was observed in the presence of NaCl for both species, together with the parallel accumulation of sodium ions in the leaves, as determined by cation exchange HPLC. Regarding the levels of divalent cations, in J. acutus Ca2+ and Mg2+ increased up to about two-fold in plants treated with 500 mM NaCl, as compared to control plants, whereas in J. maritimus they were three- to four-fold higher than in J. acutus in the absence of salt, and did not change significantly with increasing NaCl concentrations. These results suggest that Ca2+ and Mg2+ participate in defence mechanisms against salt stress, which would be constitutive in J. maritimus and salt-inducible in J.acutus.

Herbicidal Activity of Peumus boldus and Drimys winterii Essential Oils from Chile

The essential oil composition of Peumus boldus and Drimys winterii was analyzed by means of capillary GC-FID and GC-MS. More than 96% of the total oil components (43 and 54 compounds, respectively) were identified, with ascaridole (51.17 ± 9.51), p-cymene (16.31 ± 2.52) and 1,8-cineole (14.45 ± 2.99) as the main compounds in P. boldus and γ-eudesmol (21.65 ± 0.41), followed of elemol (12.03 ± 0.34) and terpinen-4-ol (11.56 ± 1.06) in D. winterii. The herbicidal activity was tested against Amaranthus hybridus and Portulaca oleracea. P. boldus essential oil was the most phytotoxic against both weeds, inhibiting seed germination and seedling growth at all concentrations assayed (0.125–1 µL/mL). D. winterii essential oil did not show any effect on A. hybridus germination and only affected P. oleracea germination at the highest concentration. The results suggest the possible use of the essential oil from P. boldus as a natural herbicide.

Evaluation of nonpolar metabolites in plant extracts by 13C NMR spectroscopy

(13)C nuclear magnetic resonance (NMR) spectroscopy was explored as a simple and efficient technique for the quantitative analysis of nonpolar metabolites in plants. The method was first optimized with a mixture of known metabolites and then applied to the nonpolar leaf extracts of plants harvested in the Valencian community (eastern Spain) belonging to three different genera: Euphorbia (Euphorbiaceae), Araujia (Apocynaceae), and Morus (Moraceae). Furthermore, an exhaustive analysis of Euphorbia characias leaf and stem extracts from different geographic locations allowed that quantitative (13)C NMR spectroscopy is a suitable tool for metabolic profiling purpose.

Chemotaxonomic value of the essential oil compounds in species of Teucrium pumilum aggregate

Volatile compounds from the aerial parts of Teucrium lepicephalum Pau and Teucrium carolipaui C. Vicioso ex Pau, both belonging to the Teucrium pumilum aggregate, were analysed by capillary GC and GC-MS. From the common and specific compounds (mono- and sesquiterpenes) of the two taxa, chemical characterization was carried out and taxonomic relationships were assessed. Application of the cluster and k-means discriminant analysis shows a differential chemical relationship between T. lepicephalum and Teucrium carolipaui.

Chemical composition and herbicidal activity of the essential oil from a Cistus ladanifer L. population from Spain

The essential oil composition of Cistus ladanifer grown in central Spain was analysed by gas chromatography and gas chromatography/mass spectrometry, revealing it to be rich in oxygenated compounds, with trans-pinocarveol (20.00%), bornyl acetate (7.03%) and terpinen-4-ol (6.37%) as the main monoterpene compounds. Viridiflorol (13.59%) and ledol (4.36%) were the main constituents of the oxygenated sesquiterpene fraction. Large amounts of α-pinene (4.70%) were found in the hydrocarbonated fractions. To study its possible use as a natural herbicide, the oil was tested in vitro against Amaranthus hybridus, Portulaca oleracea, Chenopodium album, Conyza canadensis and Parietaria judaica, completely inhibiting A. hybridus germination, and nearly blocking C. canadensis and P. judaica germination at all concentrations assayed. In P. oleracea, the oil showed less effect, inhibiting its germination at the higher doses studied. It did not control C. album germination. Regarding seedling length, the oil had strong phytotoxic activity, being effective at all concentrations tested.

Variability of the essential oil of Thymus piperella

Abstract Chemometric investigation of the infraspecific variability of the essential oil of 31 populations of Thymus piperella led to the differentiation of three main chemotypes; type A: p -cymene-carvacrol- γ -terpinene (11 populations); type B: p -cymene-thymol (5 populations); type C: p -cymene-carvacrol (15 populations). The compound p -cymene is the most abundant constituent in all samples.

Ecological germination requirements of the aggregate species Teucrium pumilum (Labiatae) endemic to Spain

Teucrium pumilum L., T. lepicephalum Pau, T. libanitis Schreber, T. turredanum Losa & Rivas Goday, and T. carolipaui Vicioso ex Pau (Labiatae) constitute an aggregate included in the Pumilum subsection (Polium section). These species are endemic and geographically restricted to central and south-eastern Spain. They grow under different climatic conditions and have different edaphic requirements, particularly the gypsum and lime affinities. The effects of some ecological factors (i.e. edaphic and climatic factors) on the germination parameters of these Teucrium species were investigated. The species under study differed in their germination behaviour. The majority of the germination parameters appeared more correlated to edaphic than to climatic factors and particularly to the water availability in the soil. The calcicolous T. carolipaui, which grows in the driest habitat, had a more rapid germination than the gypsophilous species. This could be due to the existence of a narrower optimal germination period for T. carolipaui. The different germination requirements of these species of Teucrium are important results to be considered in conservation programs of these endemic and endangered taxa.

Composition of the essential oil of Dictamnus hispanicus from Spain

Abstract The composition of the essential oil of Dictamnus hispanicus Webb ex. Willk. collected in eastern Spain was analyzed by GC and GC/MS. The main constituents identified were methyl chavicol (79%) and limonene (7%). The high oil yield (72.0% fresh plant material) and the proportion of the main compounds support the consideration of D. hispanicus as a separate species of the S. and CS. Europe as D. albus aggregate or as a new chemotype of the polymorphic D. albus.

Composition and Antibacterial Activity of Essential Oils of Cladanthus arabicus Cass. (Asteraceae)

Abstract The chemical composition of the essential oils of the aerial parts (stems and leaves: sample A) and flowers (sample B) of Cladanthus arabicus Cass., were analysed by GC-MS. Monoterpenes hydrocarbons constituted the main chemical group in both essential oils, with Sabinene, β-pinene, α-pinene, myrcene, α-phellandrene and p-cymene as the main compounds. Sample A was tested for its antimicrobial activity against six Gram positive and negative bacteria. Results showed that the oil exhibited a significant antibacterial activity.