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PubMed2003

Isolation of volatile oil from thyme (Thymbra spicata) by steam distillation.

The effects of steam flow rate (1.03 and 0.64 L/h), distillation time, and particle size (0.50, 1.00, 2.05 mm) of Thymbra spicata on essential oil yield and sequence of extraction of compounds were studied. A logarithmic model fitted well to experimental data. The composition of the essential oil obtained by steam distillation was investigated for whole leaves only since the grinding had an adverse effect on yield. The oil obtained was very rich with respect to its carvacrol content. For both steam flow rates, oxygenated monoterpenes were recovered the most rapidly. Using whole leaves (2.05 mm) and a higher steam flow rate (1.03 L/h) for 75 min of distillation was chosen as the optimum which gives the lowest amount of monoterpene hydrocarbons, the complete recovery of oxygenated compounds, and the highest yield in a shorter time. Yield was 1.57% at this optimum condition. The oil was composed of 53.1% oxygenated compounds, 25.7% monoterpene hydrocarbons, 4.4% sesquiterpenes, and 14.1% p-cymene.

Chromatography, Gas↗
PubMed1995

[Reactive oxygen species and arachidonic acid metabolites of polymorphonuclear leukocytes].

The activation of polymorphonuclear leukocytes by stimulants from host or parasites leads to various metabolic processes and to enhanced oxygen uptake. Oxygen is enzymatically processed to from reactive oxygen compounds and metabolites of arachidonic acid which are involved in killing of microbial pathogens and influence many processes in inflammation. Their activities are regulated intracellularly by antioxidants. A lack or exhaustion of these systems may lead to cell and organ damage in which DNA, proteins, lipids and sugars may be involved. Antioxidants and inhibitors of the arachidonic acid metabolism are applied to reduce these pathological changes. An essential aspect of microbial pathogenicity is the multifold modification of the formation of reactive oxygen compounds and arachidonic acid metabolites.

Animals↗
PubMedDate not supplied

Lipid formation by aqueous Fischer-Tropsch-type synthesis over a temperature range of 100 to 400 degrees C.

The formation of lipid compounds during an aqueous Fischer-Tropsch-type reaction was studied with solutions of oxalic acid as the carbon and hydrogen source. The reactions were conducted in stainless steel vessels by heating the oxalic acid solution at discrete temperatures from 100 to 400 degrees C, at intervals of 50 degrees C for two days each. The maximum lipid yield, especially for oxygenated compounds, is in the window of 150-250 degrees C. At a temperature of 100 degrees C only a trace amount of lipids was detected. At temperatures above 150 degrees C the lipid components ranged from C12 to > C33 and included n-alkanols, n-alkanoic acids, n-alkyl formates, n-alkanals, n-alkanones, n-alkanes, and n-alkenes, all with essentially no carbon number preference. The n-alkanes increased in concentration over the oxygenated compounds at temperatures of 200 degrees C and above, with a slight reduction in their carbon number ranges due to cracking. It was also noted that the n-alkanoic acids increased while n-alkanols decreased with increasing temperature above 200 degrees C. At temperatures above 300 degrees C synthesis competes with cracking and reforming reactions. At 400 degrees C significant cracking was observed and polynuclear aromatic hydrocarbons and their alkylated homologs were detected. The results of this work suggest that the formation of lipid compounds by aqueous FTT reactions proceeds by insertion of a CO group at the terminal end of a carboxylic acid functionality to form n-oxoalkanoic acids, followed by reduction to n-alkanoic acids, to n-alkanals, then to n-alkanols. The n-alkenes are intermediate homologs for n-alkan-2-ones and n-alkanes. This proposed mechanism for aqueous FTT synthesis differs from the surface-catalyzed stepwise FT process (i.e., gaseous) of polymerization of methylene reported in the literature.

Alkanes↗
PubMed2003

Spectroscopic behavior of oxygenated combustion by-products.

The oxygenated species, massively produced in the energy production plants based on combustion processes, constitute one of the most numerous categories of hazardous air pollutants. Therefore, development of real time diagnostic tools are needed in order to study their formation during combustion processes and to reveal their presence both in the exhaust and in the atmosphere. In this work, oxygenated compounds were identified inside fuel-rich premixed ethylene/air flames by means of ultraviolet fluorescence spectroscopy with the support of qualitative chemical analysis of the sampled combustion gases. Strong band progression, typical of aldehydic functionality, were recognized in fluorescence spectra (lambda(exc)=355 nm) measured in the early oxidation region of premixed flames varying the equivalence ratio from 3.0 up 21.6. Downstream of the oxidation region, spectroscopic signatures of pyrolytic species were found to prevail on those peculiar of oxygenated compound. The position and the extension of the two main flame zones were found to depend on the flame conditions (C/O ratio) due to the effect of the C/O ratio on the temperature history along the flame axis. This correlation was interpreted on the basis of the measured axial temperature profiles.

Air Pollutants↗
PubMedDate not supplied

[Effect of nitrogen and oxygen active compounds on exchange of Ca2+ and H+ through the myometrial cell membrane].

While using myometrium sarcolemma vesicles the action of sodium nitroprusside, NO2-, NO3- and H+ on delta pH-dependent Ca(2+)-transport and passive permeability for H+ vesicles sarcolemma was estimated in the wide concentration range (10(-10)-10(-3) M) of the substances tested. In order of studying calcium transport 45Ca2+ was used, while for H+ translocation registrating via sarcolemma delta pH-indicator 14C-methylamine was applied. Sodium nitroprusside was displayed as weakly effective, while nitrite-anions essentially increased delta pH-dependent Ca2+ transport in the physiologically significant nanomolar concentration region, however in the micromolar region these substances effect failed to differ from the control and restored its intensity starting at 10(-4) M and more. Under the experiment sodium nitroprusside produces considerable quantities of NO2-. Effectory action of NO3- was similar as of NO2-. In the micromolar region the compounds estimated increased considerably sarcolemma passive permeability for H+. Hydrogen peroxide decreased delta pH-dependent Ca(2+)-transport by 10(-8) M and 10(-3) M while at the concentration equal to 10(-3) M increased the sarcolemma passive permeability for proton. Sodium nitroprusside and NO2(-)-effect on the vesicles passive permeability for proton failed to be prevented by dithiotriitol, while H2O2 action was completely removed. The conclusion about the complex concentration-dependent character of the active oxygen metabolities to the sarcolemma transport processes was made, and it's noticeable that the important role in vivo, probably could be played by NO (NO2-) stable nitric metabolities.

Animals↗
PubMed2005

Link between spatial structure of microbial communities and degradation of a complex mixture of volatile organic compounds in peat biofilters.

AIMS: To investigate the relationships between the operation of the volatile organic compound (VOC) removal biofilter and the structure of microbial communities, and to study the impact on degradation activities and the structuring of microbial communities of biofilter malfunctions related to the qualitative composition of the polluted air. METHODS AND RESULTS: A microbiological study and a measurement of biodegradation activities were simultaneously carried out on two identical peat-packed columns, seeded with two different inocula, treating polluted air containing 11 VOCs. For both reactors, the spatial structure of the microbial communities was investigated by means of single-strand conformation polymorphism (SSCP) analysis. For both reactors, stratification of degradation activities in function of depth was observed. Oxygenated compounds were removed at the top of the column and aromatics at the bottom. Comparison of SSCP patterns clearly showed a shift in community structure in function of depth inside both biofilters. This distribution of biodegradation activities correlates with the spatialization of microbial density and diversity. Although the operating conditions of both reactors were identical and the biodegradation activities similar, the composition of microflora differed for biofilters A and B. Subdivision of biofilter B into two independent parts supplied with polluted air containing the complex VOC mixture showed that the microflora having colonized the bottom of biofilter B retained their potential for degrading oxygenated compounds. CONCLUSIONS: This work highlights the spatialization of biodegradation functions in a biofilter treating a complex mixture of VOCs. This distribution of biodegradation activities correlates with the spatialization of microbial density and diversity. SIGNIFICANCE AND IMPACT OF THE STUDY: This vertical structure of microbial communities must be taken into consideration when dealing with the malfunctioning of bioreactors. These results are also useful information about changes in microbial communities following natural or anthropogenic alterations in different ecosystems (soils and sediments) where structuring of microbial communities according to depth has been observed.

Air Microbiology↗
PubMed2003

The online 18O/16O analysis: development and application.

Oxygen is a globally important element, in inorganic compounds it is involved in key structural compounds of the earth, and it is providing functional groups for most organic compounds. Oxygen isotope ratio analyses on these compounds provide information on the oxygen sources and (formation) reactions in which the compound was involved. Therefore generally applicable analytical methods for the delta18O determination are highly desirable. After a description of online high temperature "carbon reduction" methods for the conversion of oxygen in the compounds mentioned into CO and discussion of problems involved, especially in analysis of inorganic substances like carbonates and silicates, selected examples for the application of these carbon reduction methods will be presented. The well-known correlation of delta18O values of cellulose (in tree rings) to that of (leaf) water is used since the 1970's as climate indicator. The observed enrichment in 18O in cellulose by about 27% in comparison to leaf water is attributed to an oxygen equilibrium isotope effect between carbonyl groups and water. But not all carbohydrates show this "general"18O enrichment relative to water. By means of a recently published model a non-statistical oxygen isotope distribution in carbohydrates is postulated. Oxygen isotope discrimination has been recognized long ago as an important principle of authenticity evaluation in food and beverages. Though many basic mechanisms of isotope discrimination in nature are known, the corresponding application of data is often based only on empirical observations in this field. The fact that oxygen in natural organic plant material is derived from three sources (CO2, H2O, O2) with distinct differences in and that their incorporation by different reactions implies oxygen isotope effects of different sizes, is therefore of special importance, and it is attempted by means of individual isotopic increments of functional groups to predict global delta18O values of natural and nature-identical compounds. Vice versa delta18O values can also give hints on the elucidation of biosynthetic pathways.

Cellulose↗
PubMed1986

The influence of oxygenated sterol compounds on dipalmitoylphosphatidylcholine bilayer structure and packing.

Fourier Transform Infra-red and Raman Spectroscopies indicate that 7 alpha-hydroxycholesterol and 7-ketocholesterol have a diminished capacity to condense (increase the packing order of) fluid-state dipalmitoylphosphatidylcholine (DPPC) acyl chains when compared with the effects of cholesterol and the other oxidized sterols studied. DPPC head groups were also more ordered by 7-ketocholesterol over the temperature range 10 degrees - 70 degrees C. Primary effects of these sterols appear to be associated with the hydrophillic regions of the DPPC bilayer, although packing arrangements with acyl chains are also involved. Phosphate and acyl chain ester groups were observed to possess a packing order which was invariant which indicates that these may be the target groups in the interaction with 7-ketocholesterol. A surprising observation was the synergistic amplification of the effects of 7-ketocholesterol by the presence of cholesterol in the DPPC bilayer.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2003

Compost as a soil supplement increases the level of antioxidant compounds and oxygen radical absorbance capacity in strawberries.

Compost as a soil supplement significantly enhanced levels of ascorbic acid (AsA) and glutathione (GSH) and ratios of AsA/dehydroascorbic acid (DHAsA) and GSH/oxidized glutathione (GSSG) in fruit of two strawberry (Fragaria x ananassa Duch.) cultivars, Allstar and Honeoye. The peroxyl radical (ROO(*)) as well as the superoxide radical (O(2)(*)(-)), hydrogen peroxide (H(2)O(2)), hydroxyl radical (OH(*)), and singlet oxygen ((1)O(2)) absorbance capacity in strawberries increased significantly with increasing fertilizer strength and compost use. The planting medium (compost) x fertilizer interaction for phenolics and flavonoids was significant. Fruit from plants grown in full-strength fertilizer with 50% soil plus 50% compost and 100% compost yielded fruit with the highest levels of phenolics, flavonol, and anthocyanin content. A positive relationship between antioxidant activities and contents of AsA and GSH and ratios of AsA/DHAsA and GSH/GSSG existed in fruit of both strawberry cultivars. Correlation coefficients for the content of antioxidant components versus antioxidant activity [against ROO(*), O(2)(*)(-), H(2)O(2), OH(*), or (1)O(2)] ranged from r( )()= 0.7706 for H(2)O(2) versus GSH/GSSH in cv. Allstar to r = 0.9832 for O(2)(*)(-) versus total flavonoids in cv. Allstar.

Anthocyanins↗
PubMed2001

Secretions of stingless bees: the Dufour gland of Nannotrigona testaceicornis.

The Dufour gland of Nannotrigona testaceicornis is a large, wide, pear-shaped sac. The gland secretion consists chiefly of the diterpene ester all-trans-geranylgeranyl acetate (64% of the total), together with a complex mixture of small amounts of cyclic ketals; mono-, sesqui-, and diterpene compounds; acetates; and other oxygenated compounds. Samples of N. testaceicornis collected at two sites in Brazil and one in México shared the same composition of their glands, suggesting that the species is uniform over this wide geographical area.

Animals↗
PubMed1991

Ultraviolet difference spectral studies in the gamma-radiolysis of DNA and model compounds. II. Oxygen and temperature dependence in adenine radiation chemistry.

Ultraviolet difference spectra between gamma-irradiated and unirradiated aqueous solutions of oxygenated adenine reveal spectral maxima at 224, 286 and 360 nm, and suggest the existence of multiple radiation products. The presence of long-wavelength absorbing products implies the extension of the conjugation of the adenine ring. The product absorbing at 360 nm appears only in the presence of oxygen, with its yield dependent on both oxygen concentration and temperature. The absorbance peak at 360 nm in the UV difference spectra appears to demonstrate simple first-order decay kinetics, with a half-life of 50 min at 3 degrees C. At temperatures below 23 degrees C relative yields of the radiation products are approximately constant, suggesting a common mechanism. Higher temperatures apparently induce a mechanistic alteration. Since the temperature during and subsequent to irradiation, as well as the oxygen concentration of the solution, affects the absolute yields and distribution of the radiation products, great care must be exercised in controlling these variables.

Adenine↗
PubMed1999

Analysis of the environment of beryllium, magnesium and alkaline earth atoms in oxygen-containing compounds.

About 2100 inorganic and organometallic compounds containing beryllium, magnesium and alkaline earth atoms (M) were investigated with Voronoi-Dirichlet polyhedra (VDPs). It is shown that the coordination numbers (CNs) of the M atoms in MO(n) coordination polyhedra can be determined by means of VDPs without crystal-chemical radii. The distributions of the M-O distances in the coordination spheres of the M atoms are bimodal for M = Be or Mg and monomodal for the other alkaline earth metals. Beryllium and magnesium coordination polyhedra containing weak M-O contacts were classified by variants of their distortions. It is found that the volume of the domains of the Mg, Ca, Sr and Ba atoms is independent of their CNs at CN >/= 6 (up to 16 for barium). The possibility of using the model of deformable spheres to describe the crystal structure of the compounds investigated is suggested.

Journal Article↗