Characterization of military fog oil by comprehensive two-dimensional gas chromatography.

The most commonly used military fog oil is characterized by comprehensive two-dimensional gas chromatography (GC x GC) coupled to either Flame Ionization Detection (FID) or Time-of-Flight Mass Spectrometric Detection (TOFMS) to advance the knowledge regarding the complete chemical makeup of this complex matrix. Two different GC x GC column sets were investigated, one employing a non-polar column combined with a shape selective column and the other an inverse column set (medium-polar/non-polar). The inverse set maximizes the use of the two-dimensional separation space and segregates aliphatic from aromatic fractions. The shape selective column best separates individual polycyclic aromatic hydrocarbons (PAHs) from the bulk oil. The results reveal that fog oil (FO) is composed mainly of aliphatic compounds ranging from C(10) to C(30), where naphthenes comprise the major fraction. Although many different species of aromatics are present, they constitute only a minor fraction in this oil, and no conjugated PAHs are found. The composition of chemically similar aliphatic constituents limits the analytical power of silica gel fractionation and GC-MS analysis to characterize FO. Among the aliphatic compounds identified are alkanes, cyclohexanes, hexahydroindanes, decalins, adamantanes, and bicyclohexane. The aromatic fraction is composed of alkylbenzene compounds, indanes, tetrahydronaphthalenes, partially hydrogenated PAHs, biphenyls, dibenzofurans and dibenzothiophenes. This work represents the best characterization of military fog oil to date. As the characterization process shows, information on such complex samples can only be parsed using a combination of sample preprocessing steps, multiple detection schemes, and an intelligent selection of column chemistries.

Sesquiterpene and acyclic diterpenes from Hyptis verticillata Jacq.

From the methanolic extract of the plant Hyptis verticillata Jacq, was isolated five compounds: the novel compounds cadina-10(15)-en-3-one and 3,7,11,15-tetramethylhexadec-1-en-3-ol and the known compounds 3,7,11,15-tetramethylhexadec-2-en-1-ol, 7,11,15-trimethyl-3-methylenehexadecane-1,2-diol and myo-inositol. All structures were established by spectroscopic means.

A new acyclic diterpene acid and bioactive compounds from Knema glauca.

Investigation of the chemical constituents of the fruits of Knema glauca (Myristicaceae) yielded a new acyclic diterpene acid, named glaucaic acid 4, together with four acylphenols, including 1-(2,6-dihydroxyphenyl) tetradecan-1-one 1, malabaricone A 6, dodecanoylphloroglucinol 7 and 1-(2,4,6-trihydroxyphenyl)-9-phenylnonan-1-one 8, two lignans sesamin 2 and asarinin 3, and a flavan, myristinin D 5. In addition, myristinin A 9 and (+/-)-7,4'-dihydroxy-3'-methoxyflavan 10 were isolated from its leaves and stems, respectively. When tested against small-cell lung cancer (NCI-H187), epidermoid carcinoma (KB) and breast cancer (BC) cell lines, compounds 1, 6-8 and 10 displayed weak to moderate cytotoxicity. The acylphenols 6-8 displayed antituberculosis activity against the microbe Mycobacterium tuberculosis with MIC values of 25, 50 and 100 microg/mL, respectively, and antiviral activity against herpes simplex virus type 1, with 7 as the most active compound (IC(50) = 3.05 microg/mL). Malabaricone A 6 was also active against the malarial parasite Plasmodium falciparum with an IC(50) value of 2.78 microg/mL.

Efficient preparation of an acyclic permutant of kalata B1 from a recombinant fusion protein with thioredoxin.

A new approach to prepare an acyclic permutant of kalata B1, a cysteine-rich plant cyclopeptide with uterotonic activity, is described. The synthetic codon-optimized cDNA sequence encoding this 29-residue peptide was cloned and fused in-frame to the His(6)-tagged thioredoxin gene in the bacterial expression vector pET-32a. The fusion protein was overexpressed in the bacterial host, Escherichia coli strain BL21 (DE3), and isolated by affinity chromatography on a metal-chelating Sepharose column. An enterokinase recognition sequence incorporated immediately upstream of the target peptide allowed the 29-residue peptide to be released without any unwanted residues upon treatment with enterokinase. This peptide was subsequently separated from the larger thioredoxin moiety by ultracentrifugation through a semipermeable membrane. Further purification was achieved using reversed-phase HPLC. Hydrogen peroxide was found to enhance the rate of enterokinase cleavage in a concentration-dependent manner. Thermal stability studies demonstrated that the recombinant acyclic kalata B1 (ac kalata) was exceptionally stable against thermal denaturation. Mass spectrometric analysis revealed that the recombinant ac kalata was obtained in a fully oxidized form, indicating a high reducing potential and a strong tendency of the 29-residue peptide to form a tightly folded structure.

Gas chromatography method for the characterization of ethanol steam reforming products.

Ethanol steam reforming is a promising reaction for producing fuel cell hydrogen. Depending on catalyst and reaction conditions, mixtures of condensable hydrocarbons and organic and inorganic gases are produced. This paper proposes an economic and effective solution for separating and detecting these compounds employing a gas chromatograph equipped with two columns, two 6-way valves, and two detectors.

Polar acyclic diterpenoids from Bifurcaria bifurcata (Fucales, Phaeophyta).

From the lipophilic extract of the brown alga Bifurcaria bifurcata collected off the Atlantic coast of Southern Brittany (Quiberon, France), five polar linear diterpenoids have been isolated. These metabolites have been identified as hydroxylated derivatives of 13-oxo- and 13-hydroxygeranylgeraniol. Their structures were characterized on the basis of chemical and spectral evidence including two-dimensional NMR experiments and mass spectrometric techniques. The absolute configuration of the 13-position has been determined, for the 13-hydroxygeranylgeraniol derivatives, to be R by means of a modified Mosher's method and therefore that of 13-hydroxygeranylgeraniol (eleganediol) has been revised. Along with these compounds, three related known geranylgeraniol derivatives were also identified, and these data were used for chemotaxonomical purposes.