Chemical composition and antifungal activity of the essential oils of Lippia rehmannii from South Africa

Lippia rehmannii H.Pearson (Verbenaceae) is an aromatic bush, indigenous to the northern parts of South Africa. As far as could be ascertained, the essential oil composition has not been previously reported and forms the subject of this investigation. Aerial parts of the shrub were collected from two localities in Gauteng, South Africa, and the isolated essential oils were analysed by gas chromatography. Citral, a mixture of the E- and Z-isomers, was found to be the main constituent of the oils, while borneol, camphor, neryl acetate, isocaryophyllene, p-cymene, β-caryophyllene and β-caryophyllene oxide were other major compounds present. Oil compositions, within and between the two localities, did not differ significantly. The in vitro antifungal activity of L. rehmannii essential oil was compared to that of Cympopogon citratus (lemongrass) and pure citral, against a number of pre- and postharvest fungal food pathogens. At a concentration of 3000 µL/L, lemongrass oil and pure citral caused complete growth inhibition of all the pathogens tested. Lippia rehmannii, containing less citral than lemongrass oil, was effective at this concentration against the majority of pathogens, but only partially restricted the growth of Lasiodiplodia theobromae and Botrytis cinerea. This finding suggests that citral may be largely responsible for the observed antifungal activities. Essential oil from L. rehmannii appears to be a good candidate for the in vitro control of Fusarium oxysporum and Rhizoctonia solani and application of these oils in the field should be investigated.     

Coexistence of Abies alba (Mill.) - Fagus sylvatica (L.) and climate change impact in the Iberian Peninsula: A climatic-niche perspective approach

Abies alba Mill. (European silver fir) and Fagus sylvatica L. (beech) are Eurosiberian species dispersed over the Iberian Peninsula. Climate change predictions indicate a rise in temperature and a decrease in precipitation in this region, threatening the future existence of these species. In the present study we analyzed the future topo-climatic suitability of Abies alba and Fagus sylvatica and the mixed forests of these two species, using the General Linear Models technique and data from the third National Forest Inventory (Ministerio de Agricultura PyA, 2007). We considered two modeling approaches based on niche theory: modeling community (Abieti-Fagetum) and overlapping individual species models. General trends showed an overall decrease in both species’ topo-climatic suitability and indicated that the Pyrenees will play a crucial role as a climatic refuge. The modeling approaches markedly differed, however, in their current and future spatial agreement. Despite good accuracy results, community modeling through co-occurrence does not encompass the environmental space of individual species prejudicing future assessments in new environmental situations, suggesting a need for future studies in community modeling.     

Chemical composition and antibacterial activities of the essential oils of Lippia chevalieri and Lippia multiflora from Burkina Faso

The chemical composition of the essential oils of Lippia chevalieri and Lippia multiflora obtained from the air-dried leaves by hydrodistillation were analysed using GC and GC-MS. L. chevalieri and L. multiflora belonged to thymol/p-cymene/2-phenyl ethyl propionate and thymol/p-cymene/thymyl acetate chemotypes, respectively. The essential oils were also tested against 09 strains using a broth microdilution method. The Gram-negative bacteria were the most sensitive. The essential oil of L. multiflora was the most active.     

Chemical composition and antigenotoxic properties of Lippia alba essential oils

The present work evaluated the chemical composition and the DNA protective effect of the essential oils (EOs) from Lippia alba against bleomycin-induced genotoxicity. EO constituents were determined by Gas Chromatography/Mass Spectrometric (GC-MS) analysis. The major compounds encountered being citral (33% geranial and 25% neral), geraniol (7%) and trans-β-caryophyllene (7%) for L. alba specimen COL512077, and carvone (38%), limonene (33%) and bicyclosesquiphellandrene (8%) for the other, COL512078. The genotoxicity and antigenotoxicity of EO and the compounds citral, carvone and limonene, were assayed using the SOS Chromotest in Escherichia coli. The EOs were not genotoxic in the SOS chromotest, but one of the major compound (limonene) showed genotoxicity at doses between 97 and 1549 mM. Both EOs protected bacterial cells against bleomycin-induced genotoxicity. Antigenotoxicity in the two L. alba chemotypes was related to the major compounds, citral and carvone, respectively. The results were discussed in relation to the chemopreventive potential of L. alba EOs and its major compounds.     

Chemical composition and larvicidal activity of essential oils from Piper species

The larvicidal activity of essential oils of four species of Piper from the Amazon Forest was tested using third-instar larvae of Aedes aegypti. The oils were extracted by steam distillation and analyzed by GC and GC–MS. The main components isolated from each Piper species were as follows: viridiflorol (27.50%), aromadendrene (15.55%) and β-selinene (10.50%) from Piper gaudichaudianum; β-selinene (15.77%) and caryophyllene oxide (16.63%) from Piper humaytanum; dillapiol (54.70%) and myristicin (25.61%) from Piper permucronatum; and asaricin (27.37%) and myristicin (20.26%) from Piper hostmanianum. Amongst all essential oils tested, the most active against larvae of A. aegypti was the oil extracted from P. permucronatum, with a LC₅₀ = 36 μg/ml (LC₉₀ = 47 μg/ml), followed by the essential oil of P. hostmanianum, with a LC₅₀ = 54 μg/ml (LC₉₀ = 72 μg/ml). The oils with higher content of arylpropanoids were more active against larvae of A. aegypti.     

Essential oil composition of Achyrocline flaccida (Weinm.) DC. (Asteraceae) from different locations of Argentina

The qualitative and quantitative composition of the essential oils obtained from the inflorescences of Achyrocline flaccida (Asteraceae) has been investigated for the first time. Plant material was collected from eleven locations in Argentina. The essential oils were obtained by hydrodistillation (0.1–0.8% v/w, dried material) and analyzed by GC–FID–MS. Eighty-three compounds were identified representing more than the 90% of the oils. The major components were α-pinene and β-caryophyllene. Statistical analysis was performed in order to evaluate the variability of the essential oils analyzed. Two groups were formed reflecting only quantitative differences in the content of major compounds. The chemical pattern of essential oils observed for A. flaccida is similar to other Achyrocline species studied, except Achyrocline hyperchlora.     

Variability in essential oil composition of Turkish basils (Ocimum basilicum L.)

Sweet basil (Ocimum basilicum L.), one of the most popular aromatic plants, shows great variation in both morphology and essential oil components. In this study, the composition of 18 Turkish basil essential oils was investigated by GC and GC–MS. Variation of essential oils in the landraces was subjected to cluster analysis, and seven different chemotypes were identified. They were (1) linalool, (2) methyl cinnamate, (3) methyl cinnamate/linalool, (4) methyl eugenol, (5) citral, (6) methyl chavicol (estragol), and (7) methyl chavicol/citral. Methyl chavicol with high citral contents (methyl chavicol/citral) can be considered as a “new chemotype” in the Turkish basils. Because methyl eugenol and methyl chavicol have structural resemblance to carcinogenic phenylpropanoids, chemotypes having high linalool, methyl cinnamate or citral contents and a mixture of these is suitable to cultivate for use in industry.     

Chemical composition and antimicrobial activity of Cymbopogon citratus and Cymbopogon giganteus essential oils alone and in combination

As part of ongoing research on the chemical composition and the antimicrobial properties of Burkinabe plants essential oils alone and in combination, essential oils (EOs) from leaves of Cymbopogon citratus and Cymbopogon giganteus from Burkina Faso were analyzed by GC-FID and GC-MS. Five constituents, which accounted for 96.3% of the oil, were identified in the EO of C. citratus. Geranial (48.1%), neral (34.6%) and myrcene (11.0%) were the major constituents. For C. giganteus a total of eight compounds were identified which represented 86.0% of the oils extracted. The dominant compounds were limonene (42%) and a set of monoterpene alcohols: trans-p-mentha-1(7),8-dien-2-ol (14.2%), cis-p-mentha-1(7),8-dien-2-ol (12%), trans-p-mentha-2,8-dien-1-ol (5.6%) and cis-p-mentha-2,8-dien-1-ol (5.2%). The EOs were tested against nine bacteria by using disc diffusion and microdilution methods. C. giganteus EO showed antimicrobial effects against all microorganisms tested whereas C. citratus EO failed to inhibit Pseudomonas aeruginosa. The antimicrobial activity of combinations of the two EOs was quantified by the checkerboard method. Combinations of the two EOs exerted synergistic, additive and indifferent antimicrobial effects. Results of the present investigation provide evidence that the combinations of plant EOs could be assessed for synergistic activity in order to reduce their minimum effective dose.     

Essential oil variability in Thymbra capitata (L.) Cav. growing wild in Southern Apulia (Italy)

Essential oils of Thymbra capitata (Thymus capitatus) collected from Southern Apulia (Italy) were analysed using gas chromatography and gas chromatography–mass spectrometry techniques, to check for chemical variability. The study showed that among the 75 components of the oils the most recurrent ones were thymol and carvacrol, which always constituted more than 50% of the oils, as well as γ-terpinene, borneol and p-cymene. Cluster analysis led to the identification of three chemotypes: thymol, carvacrol and thymol/carvacrol; this was presumably a crossbreed between the other two chemotypes. Principal component analysis showed the direct correlation among myrcene, α-terpinene and γ-terpinene; anti-correlation between thymol and carvacrol, and the inverse correlation between linalool and myrcene. Moreover, lower thymol concentrations were accompanied by an increase in myrcene, α-terpinene and γ-terpinene.     

Genetic diversity and inter-specific relations of western Mediterranean relic Abies taxa as compared to the Iberian A. alba

Several Abies species are currently present in the Mediterranean region and most of them are endemic taxa and tertiary relicts. Using six nuclear microsatellites, we studied the genetic structure and inter-specific relationships among West Mediterranean firs, A. pinsapo (Spain), A. maroccana and A. tazaotana (Morocco). Based on the hypothesis that A. pinsapo could historically exchange genes with A. alba growing in the Pyrenees via secondary contact, we investigated the level of genetic admixture between these species using a Bayesian approach. The studied populations showed moderate genetic diversity (mean H_E = 0.598) and a high level of genetic differentiation (F_ST = 0.225) that was especially pronounced between A. alba and the African firs. All populations experienced a strong bottleneck effect that was likely induced by climatic changes occurring in the West Mediterranean during the last glacial cycle and the Holocene. According to Bayesian clustering, both African taxa grouped together in a single cluster, the two A. pinsapo populations formed a second cluster, and two additional clusters were detected within A. alba. Our results indicate that A. tazaotana is genetically very close to A. maroccana, and hence these two taxa should probably not be considered as separate species. We found no genetic admixture between A. pinsapo and A. alba and only minor between A. pinsapo and the African fir populations suggesting an isolation effect of the Gibraltar Strait. Current limited distributions of firs in the Mediterranean region together with changing climate may lead to further deterioration of the genetic diversity levels. Hence, future efforts should focus on monitoring the demography and genetic threats to existing populations.     

Chemical composition,intraspecies variation and seasonal variation in essential oils of Calendula arvensis L.

The essential oil composition of Calendula arvensis was established for the first time using GC and GC/MS. Eighty-five essential oil components were identified, which accounted for 90.3 g/100 g of essential oil. The oil contained a high concentration of sesquiterpenes, of which δ-cadinene and α-cadinol were the main components. The chemical composition of 25 Corsican C. arvensis oils was analyzed to determine intraspecies variation in essential oil composition. A matrix linking essential oil composition to sample location was composed to identify relationships between concentrations of volatile samples and the geographical origins of samples. Two main groups of compounds were identified according to the amount of sesquiterpenic compounds (hydrocarbons and alcohols) and soil characteristics. Seasonal variation (winter vs. spring) in the concentrations of two major compounds during the flowering period was observed.     

The effects of laurel (Laurus nobilis L.) on development of two mycorrhizal fungi

Hundreds of aromatic plant species are growing naturally around Mediterranean. Plant essential oils are incorporated in aromatic plant material and follow the litter fall. During litter degradation, the presence of essential oils can affect soil microorganisms. Mycorrhizal fungi have never been investigated so far under the presence of volatile oils. The aim of this study was to explore the effect of aromatic Laurus nobilis L. on development of two mycorrhizal species Glomus deserticola and Glomus intraradices. The response of fungi colonization and host growth were monitored under different concentrations of L. nobilis leaves and essential oil. The major compounds of L. nobilis essential oil were 1,8-cineole (49.6%), sabinene (7.8%), ??-pinene (6.0%), eugenole (5.6%), ??-terpinyl acetate (5.2%) and ??-pinene (5.1%). Both mycorrhizal fungi colonized successfully the host plants whose growth was positively influenced by mycorrhizal fungi. G. deserticola presented higher infection level than G. intraradices. The addition of L. nobilis leaves in the soil resulted in mycorrhiza inhibition. The level of inhibition was positively correlated with the added amount of aromatic leaves in the soil. The essential oil presented a little higher inhibition than the leaves. The presence of this aromatic plant in many different ecosystems could contribute in mycorrhiza inhibition and it is suggested, when it’s possible, reduction of laurel litter before reforestation programs.     

Variation of the chemical composition of essential oils in Brazilian populations of Cunila menthoides Benth. (Lamiaceae)

Cunila menthoides Benth. is characterized as a xilopodiferous subshrub with strong and pleasant smell. This species is commonly used in South Brazilian folk medicine. Air-dried samples of four Brazilian populations of C. menthoides were extracted by steam distillation and analyzed using GS and GS–MS. A total of 15 volatile compounds were detected and identified. Two groups, which can be considered as chemotypes, were formed by the average linkage cluster analysis. The first group was characterized by high concentrations of pulegone, with some individuals showing variations to menthone; and the second group was characterized by high concentrations of linalool.     

Comparative analysis of volatiles from Drimys brasiliensis Miers and D. angustifolia Miers (Winteraceae) from Southern Brazil

The essential oils obtained from Southern Brazilian native Drimys brasiliensis Miers and Drimys angustifolia Miers were analyzed by GC and GC/MS. The oils from leaves of both species showed predominance of monoterpenoids, while the oils from stem barks were characterized by sesquiterpenoids. Bicyclogermacrene (20.0% in leaves and 25.4% in stem bark) and drimenol (1.4% in leaves and 26.2% in stem bark) were the most abundant in D. angustifolia, and cyclocolorenone (from 16.0% to 32.3% in fresh and dried leaves and almost 50% in stem bark) in D. brasiliensis. The oil from fruits of D. brasiliensis was also analyzed and presented 31.0% of cyclocolorenone. The predominance of this unusual aromadendrane-type sesquiterpene in D. brasiliensis essential oils could be used as a chemosystematic marker.     

Essential oil composition of Hypericum L. species from Southeastern Serbia and their chemotaxonomy

The essential oils of the aerial parts of nine species of Hypericum (Hypericum barbatum, Hypericum hirsutum, Hypericum linarioides, Hypericum maculatum, Hypericum olympicum, Hypericum perforatum, Hypericum richeri, Hypericum rumeliacum and Hypericum tetrapterum), collected from different locations in Southeast Serbia, were obtained by steam distillation and analyzed by GC and GC–MS. The essential oils investigated were characterized by a high content of non-terpene compounds and a low content of monoterpenes. The contents of non-terpenes, monoterpenes and sesquiterpenes in oils of the species H. barbatum, H. richeri and H. rumeliacum (section Drosocaprium) were similar and these oils were characterized by high contents of fatty acids. The oils of H. hirsutum and H. linarioides (section Taeniocarpium) contained a high percentage of n-nonane. There were similarities in contents of non-terpenes and sesquiterpenes in oils of species that belong to the section Hypericum (H. maculatum, H. perforatum and H. tetrapterum). The oil of H. olympicum differed from others by higher terpene content. A comparison was also carried out of the chemical composition of the essential oils from flower, leaf and stem of H. perforatum and it revealed that the highest concentration of non-terpene compounds was found in the flower and stem oil, while a high concentration of sesquiterpenes was characteristic for leaf oil. There were significant differences in the concentrations of the same compounds in the essential oils of H. maculatum, H. olympicum and H. perforatum, collected in different years from the same location which could be explained by seasonal differences. All data were statistically processed with principal component analysis and cluster analysis. The main conclusion from the above data is that genetic and environmental factors both play a role in determining the composition of essential oils of the Hypericum species studied.     

不同分枝数对桑树幼苗生长发育的影响

以我国常见经济林木桑树(Morus alba)为试验材料,从气体交换、形态变化和地上生物量方面研究5种分枝模式(1、2、3、4和5枝)对幼苗生长发育的影响。结果显示:(1)分枝数为1的植株的净光合速率(P n)最高,达到8.6μmol·m-2·s-1。随着分枝数增加,P n显著下降,直至分枝数达到3枝及其以上时,净光合速率保持相对稳定,为4.3μmol·m-2·s-1。而气孔导度(g s)、胞间CO2浓度(C i)和蒸腾速率(E)则不受分枝数的影响。(2)随着分枝数增加,总叶片数量、总叶面积和总枝长都显著增加,最终分别达到114.3,10481.1 cm2和457.1 cm,而平均单枝叶片数、平均单枝基径、平均单叶面积和比叶面积则显著减少。(3)随着分枝数的增加,植株的总叶生物量和总枝生物量无显著变化,但平均每枝叶干重、平均每枝枝干重和平均每枝总生物量随分枝数的增加而逐渐减少。研究结果表明了分枝数增加可能导致叶片间对光资源的竞争强度增大,引起净光合速率下降,叶片面积变小,单枝长度和生物量减小。另一方面,植株则通过生长出更多的叶片数量,以及更大的总叶片面积来尽可能地消除竞争带来的不利影响,提高对光环境资源的利用。