Search

The aim of this study was to compare the effect of different heat treatments (pan-frying, oven-baking, and grilling) on the contents of polyunsaturated fatty acids (PUFAs) in fish tissue. Four fish species were examined: pike, carp, cod, and herring. High performance liquid chromatography, coupled with electrospray ionization and mass spectrometric detection (HPLC/ESI/MS), was employed for determination of intact lipid molecules containing n-3 and n-6 PUFAs. Although mostly non-polar lipids (triacylglycerols, TGs) were present in the fish tissue, the PUFAs were present preferentially in the phospholipid fraction. Omnivorous fish species (carp, herring) contained more TGs than did predatory ones (pike, cod). Higher amounts of PUFAs were detected in the marine species than in the freshwater ones. The impact of heat treatments on the lipid composition in the fish tissue seems to be species-specific, as indicated by multivariate data analysis. Herring tissue is most heat-stable, and the mildest heat treatment for PUFA preservation was oven-baking.

Thirteen samples of an efflorescence collected from the surface of beeswax seals or from beeswax used for their restoration were analysed in detail. The samples were of different origin, age and storage history. The composition and the incidence of the efflorescence was correlated with a chemical composition of historical and recent beeswax samples. The composition of the crystalline layer was found to be very similar in all the samples. Linear monounsaturated alkenes containing 31 and 33 carbon atoms, more precisely ( Z )-hentriacont-10-ene and ( Z )-tritriacont-10-ene, were identified as main components. The analyses of beeswax have revealed that all compounds identified in “wax bloom” naturally occur in recent beeswax. However, the historical beeswaxes contained only traces of unsaturated hydrocarbons, if anything. The efflorescence was observed primarily on the surfaces of those samples which contained larger proportion of alkenes. The presented results could be of particular importance not only for better understanding of the described phenomenon, but also for the development of new beeswax-based materials, which would be “bloom resistant” and useful for conservation purposes.

Among promising alternative methods to control food spoilage much attention is being paid to the use of essential oils (EOs), and lately also to their activity in vapor phase. Until now, no standard assay exists, and there are many methods used by different authors, but any of them is suitably adapted for fast screening of large quantities of samples. We have modified most commonly used disc volatilization method by using four-section Petri dish (PD, 90 mm diameter), large filter paper disc (85 mm diameter) evenly impregnated with EO and medium containing lid. In comparison to normal disc volatilization method, labor and material needed are several times reduced, while the composition of headspace is more uniform than in case of 6 mm disc, where different volatility of particular compounds could influence the results. Sixty nine EOs were tested for its antimicrobial activity against three bacteria (Staphylococcus aureus, Salmonella enteritidis, Pseudomonas aeruginosa) and three fungi (Alternaria alternata, Aspergillus niger, Penicillium digitatum). Thirty nine EOs inhibited at least one microorganism, Armoracia rusticana and Cinnamomum zeylanicum being the most active, followed by EOs of Eugenia caryophyllata, Origanum compactum, Origanum vulgare, Pimenta racemosa, Thymus serpyllum and Thymus vulgaris inhibiting all six or five microorganisms, respectively. According to our opinion, this method is suitable for screening of large quantities of samples for antimicrobial activity in vapor phase.

The interpretation of the electron ionization mass spectra of straight-chain and methyl-branched saturated and unsaturated wax esters (WEs) is discussed in this study based on the spectra of 154 standards. The most important fragments indicative of the structure of the acid and alcohol chains are identified and summarized for WEs with various number of double bonds in the chains. Briefly, most WEs provide acylium ions allowing structural characterization of the acid part, whereas the alcohol part gives corresponding alkyl radical cations. The elemental composition of selected important fragments is established from a high-resolution accurate mass analysis. The ion abundances are discussed with respect to the length and unsaturation of the aliphatic chains. The interpretation of the spectra of branched or unsaturated WEs requires the recognition of small but important peaks that are difficult to discern among the other fragments. We demonstrate that such fragments are easily detected in differential mass spectra. This approach requires spectra of WE standards (e.g., straight-chain analogs in the case of branched WEs) recorded under the same experimental conditions. The WEs mass spectral database provided in the supplemental data can be used as a reference for the analysis of the GC/EI-MS data.

Two mass spectrometric methods for analysing triacylglycerols (HPLC/APCI-MS and MALDI-MS) were used and compared in terms of the relevance of the data for further biostatistical evaluation. While MALDI-MS is simpler and significantly faster, the time-consuming and labour-intensive HPLC/APCI-MS provides more complete information about the lipid components. However, both methods provide well-comparable results concerning the grouping of specimens belonging to different species when evaluated with multivariate exploratory approaches. The compositions of triacylglycerols in the fat bodies of males in 11 bumblebee species (Bombus terrestris, B. lucorum, B. lapidarius, B. pratorum, B. sylvarum, B. ruderatus, B. pomorum, B. subterraneus, B. campestris, B. bohemicus, and B. rupestris) were found to be species-specific.

A detailed analysis of Rhaponticum carthamoides (Willd.) Iljin root essential oil was carried out by GC, GC–MS and GC–FTIR techniques. In total, 30 components were identified, accounting for 98.0% of total volatiles. A norsesquiterpene 13-norcypera-1(5),11(12)-diene (22.6%), followed by aplotaxene (21.2%) and cyperene (17.9%), were isolated and their structures confirmed by 1D and 2D-NMR spectra (COSY, ROESY, HSQC, HMBC and INADEQUATE). Selinene type sesquiterpenes and aliphatic hydrocarbons were among minor constituents of the essential oil. The oil exhibited antimicrobial activity against 5 of 9 strains of bacteria and yeast, when tested using broth micro-dilution method. Minimum inhibitory concentrations ranged between 32 and 256 μg/ml.

Nigella sativa L. seed essential oils obtained by hydrodistillation (HD), dry steam distillation (SD), steam distillation of crude oils obtained by solvent extraction (SE-SD), and supercritical fluid extraction (SFE-SD) were tested for their antibacterial activities, using the broth microdilution method and subsequently analyzed by gas chromatography and gas chromatography-mass spectrometry. The results showed that the essential oils tested differed markedly in their chemical compositions and antimicrobial activities. The oils obtained by HD and SD were dominated by p-cymene, whereas the major constituent identified in both volatile fractions obtained by SD of extracted oils was thymoquinone (ranging between 0.36 and 0.38 g/ml, whereas in oils obtained by HD and SD, it constituted only 0.03 and 0.05 g/ml, respectively). Both oils distilled directly from seeds showed lower antimicrobial activity (MICs > or = 256 and 32 microg/ml for HD and SD, respectively) than those obtained by SE-SD and SFE-SD (MICs > or = 4 microg/ml). All oil samples were significantly more active against gram-positive than against gram-negative bacteria. Thymoquinone exhibited potent growth-inhibiting activity against gram-positive bacteria, with MICs ranging from 8 to 64 microg/ml.

Axially chiral bipyridine N , N ′-dioxides (Lewis basic organocatalysts) are easily accessible in three steps from commercially available material. The key step of this reaction sequence is cobalt-catalyzed heterocyclotrimerization of 1-pyridyl-1,7-octadiynes with nitriles. Our effort was focused on the synthesis of unsymmetrically substituted bipyridines. The scope of the cyclotrimerization reaction was tested under thermal and microwave conditions. Two of the synthesized bipyridine N , N ′-dioxides were successfully resolved into enantiomers and tested in enantioselective allylation of aldehydes.

Labial gland secretions of males of six cuckoo bumblebee species (Bombus vestalis, Bombus rupestris, Bombus campestris, Bombus sylvestris, Bombus bohemicus, and Bombus maxillosus) were analysed and components of their extracts were identified. The specimens of two species collected in the Czech Republic had a significantly different composition of the labial gland secretions than those described earlier in Scandinavia (B. rupestris, B. campestris). Czech populations of three other species studied (B. vestalis, B. sylvestris, and B. bohemicus) produced similar components as those known from the literature. Marking pheromone of B. maxillosus is here reported for the first time. This paper describes detailed analyses of the labial gland secretions including minor and trace components and a determination of the double bond positions in unsaturated compounds.

When subjected to a Picea abies suspension cell culture, beta-pinene, either one of the pure enantiomers or the racemate, was transformed mainly to trans-pinocarveol along with the minor products myrtenol, alpha-terpineol, pinocarvone, myrtenal and cis-pinocarveol. The absolute configuration of the major products corresponded to that of the starting beta-pinene enantiomer. Some of the primary transformation products, i.e. (1S)-cis- and (1S)-trans-pinocarveol, (1R)-myrtenol and (4S)-alpha-terpineol, were also tested as substrates of the P. abies suspension culture. They reacted more slowly than beta-pinene but, except for (4S)-alpha-terpineol, they were all transformed. Thus, (1R)-myrtenol was converted into both (1R)-myrtenal and (1R)-myrtanol, whereas (1S)-trans-pinocarveol was converted into (1S)-pinocarvone. (4R)-Limonene was slowly transformed by the suspension culture into limonene-(1,2)-epoxide as the major product, with carveol, perillyl alcohol and 1,8-cineole as minor products. Autoxidation of terpenes in cell-free nutrient medium was investigated in detail. Alpha-pinene and beta-pinene were both autoxidized to a certain extent, while limonene remained unaffected. The rate of the autoxidation was more than one order of magnitude slower than that of the biotransformation. Moreover, different products were formed by autoxidation than by biotransformation.

Two bioactive compounds, viz. 4-methylheptan-3-ol (I) and 4-methylheptan-3-one (II) have been identified in European oak bark beetle (Scolytus intricatus) extracts by gas chromatography coupled with mass spectrometric and electroantennographic detector systems. Further examination of these compounds using gas chromatography on chiral stationary phases, as well as a comparison with optically active standards proved the absolute configuration of the identified compounds to be (3R,4S)-I and (S)-II. The discovery of (3R,4S)-I and (S)-II as insect-produced compounds in both sexes of S. intricatus constitutes the first reported occurrence in this species.

The release of volatile compounds from a flower of Hydrosme rivieri was recorded during the whole flowering period (7 days). The quantities of six odour components (dimethyl disulphide, dimethyl trisulphide, n -alkanes C 10 , C 11 , C 12 and C 13 ) forming the main part of emanating volatiles were plotted versus time. n -Alkanes started to emanate 3 days before the release of dimethyl disulphide and dimethyl trisulphide (the components with a rotting meat odour).

(S)-(−)- and (R)-(+)-limonene was transformed to carvone via corresponding cis- and trans-carveol using Solanum aviculare and Dioscorea deltoidea plant cells. Both carveols and carvone formed were racemic in all biotransformations.

Sixtee n belonging to the family Apiaceae were examined for their acceptance as host plants by Trioza apicalis in non-choice tests. The number of eggs laid per day varied from 18 on Daucus carota subsp, sativus to zero on Aegopodium podagraria. In a comparative test, the psyllids landed significantly faster and started egg-laying earlier on carrots (D. carota subsp, sativus) than on dill (Anethum graveolens). In a study of shelter plants for T. apicalis, the psyllids survived on spruce, Picea abies, for more than 30weeks, but they died on grass, Phleum pratense and Brachypodium sylvaticum, within 2 weeks. The length of the day is one of the factors regulating hibernation. At 20°C, light regimes shorter than 17 h induced hibernation, while longer light periods led to reproduction. Both the shelter plants and the summer hosts, including the Apiaceae species, released large amounts of monoterpene hydrocarbons, with great differences among the species. The most preferred host plants (carrots) were found to contain (+)- and (-)-c~-pinene and (+)-sabinene, while large amounts ( > 20%) of either (+) - or ( - ) -limonene were released by the species of low preference. ( - ).-c~- Pinene, ( - ) -J3-pinene, and (-) -limonene were the main components of the spruce odour. A multivariate data analysis of the chemical results showed clearly the significant similarities of the summer host and shelter plants (Daucus carota, Picea abies, and Juniperus communis). © 1997 Elsevier Science Ltd

The stereoselectivity of the reduction of rac-3-methyl-1-(phenylsulfonyl)hexan-2-one (1) to 3-methyl-1-(phenylsulfonyl)hexan-2-ol (2) diastereomers by more than 20 yeasts was studied. Reduction of carbonyl group in 1 proceeds with a high Re-face enantioselectivity: Candida guillermondii (989% e.e.), C. zeylanoides (>99.9%) and Kloeckera apiculata (99.6%), respectively and the (R)- 1 enantiomer usually reacted faster. The enantioselectivity was determined by GC on chiral cyclodextrine phases and absolute configurations of products were assigned by NMR spectroscopy and a chemical correlation.

The floral fragrance of the shrub Daphne mezereum in central Sweden was collected by means of the head-space technique and investigated by GC-MS and multi-dimensional GC. ( S )-(+)-Linalool was the main constituent (95%) of the flower fragrance and its enantiomeric purity exceeded 99% in the samples. The (2 S , 5 S )- and (2 R , 5 S )-furanoid and the (3 R , 6 S )- and (3 S , 6 S )-pyranoid linalool oxide isomers constituted 2–5% of the fragrance. The elution order of these compounds on a permethylated β-cyclodextrin column is reported. A fragrance sample of D. mezereum as well as ( S )-(+)-linalool attracted males of the vernal solitary bee species Colletes cunicularius and Andrena cinerea . A racemic mixture of the two enantiomeric pairs of known furanoid linalool oxides was only weakly attractive to the bees. The role of the fragrance in the pollination specialization of the plant is discussed.

Monoterpene hydrocarbons from the xylem oleoresins of Pinus tropicalis, P. caribaea var. caribaea, P. cubensis and P. maestrensis growing in Cuba were investigated. A large number of oleoresin samples from trees, attacked and unattacked by the moth Dioryctria horneana , as well as from trees growing in different localities, were analyzed. In each sample, the relative amounts of the volatiles and the enantiomeric compositions of six chiral monoterpene hydrocarbons were determined using a two-dimensional gas chromatographic (2D-GC) system. The GC-data were evaluated using two methods for multivariate data analysis, PCA (principal components analysis) and PLS-DA (projections to latent structures-discriminant analysis). PC-plots based on the relative amounts of the monoterpenes present in the volatile oleoresin fractions analyzed, showed that P. tropicalis and P. cubensis formed one group, separated from P. caribaea , while pines belonging to the species P. maestrensis were found in both groups. The species P. tropicalis and P. maestrensis , both of which are resistant to D. horneana , and the subgroups within the species P. caribaea and P. cubensis , that had not been attacked by D. horneana , showed no signs of constituting a chemical subgroup. No significant difference was found between the attacked and the unattacked P. cubensis trees. In P. caribaea , on the other hand, the composition of volatiles in attacked trees was significantly different from that in unattacked trees. However, an influence of monoterpenes on the oviposition of D. horneana was not proved.

Volatile compounds from flowers, buds and leaves of Aegopodium podagraria, Anthriscus sylvestris, Carum carvi, Heracleum sibiricum, Laserpitium latifolium and Pastinaca sativa were collected on PorapakQ and TenaxGC and identified by GC-MS. The enantiomeric compositions of the main chiral monoterpenes were determined by multidimensional gas chromatography. The characteristics of the floral fragrances were found to originate in differences in the proportions of the monoterpene hydrocarbons, among which α-pinene, β-pinene, cis-β-ocimene, trans-β-ocimene, limonene, sabinene and myrcene dominated. Heracleum sibiricum and P. sativa had very similar fragrances. Pure (+)-3-carene was found in H. sibiricum and C. carvi, and (-)-sabinene was the main compound in L. latifolium and A. sylvestris. Nitrogenous compounds, some aliphatic short-chain esters and linalool were found exclusively in the flower scents. The possible biological functions of the volatile compounds are discussed.

Volatiles from the essential oil of the liverwort Conocephalum conicum were analysed. The chirality of the monoterpene hydrocarbons was studied by two-dimensional ps chromatography. All compounds e ...

Key Word Index--lsoptera; Nasudtermes; termite soldiers; monoterpenes; diterpenes; bioassay; biological activity; Peru. Abstract--The soldiers of the termite species, NasuEtermes ephratae (Isoptera, Termitidae, Nasutitermitinae), contain a mixture of monoterpene hydrocarbons and oxygenated diterpenes in the defence secretion produced in the frontal gland. In the secretions of termites of two allopatric populations of N. ephratae from a lowland tropical jungle in Peruvian Amazonia, 12 monoterpenes have been identified: ¢-pinene, camphene, sabinene, ~-pinene, myrcene, 4-carene, 3-carene, ¢-terpinene, limonene, ~'-terpinene, ~-phellandrene and terpinolene. In the diterpene fractions, 6 trinervitane derivatives were identified (I-Vl). Significant differences in the composition of the monoterpene fraction of the defence secretion of termites from various localities were observed. Determinable LDs0 of the defence substances, tested on Prorhinotermes simplex, Coptotermes formosanus and Monomorium pharaonis as model species, range from 4 to 800 p,g/individual.