Formation Mechanism of 2,6-Dimethyl-2,6-Octadienes from Thermal Decomposition of Linalyl β-D-Glucopyranoside

Thermally decomposed products of (±)-linalyl β-D-glucoside were analyzed by GC and GC/MS. 2,6-Dimethyl-2,6-octadienes produced by mild pyrolysis of linalyl β-D-glucopyranoside under a vacuum were detected and characterized by MS and NMR spectroscopy. This suggests that 2,6-dimethyl-2,6-octadienes are produced during thermal decomposition of the glucoside via proton transfer from the anomeric position to C-6 in the aglycon moiety. A stable isotope labeling experiment directly indicated the new reaction mechanism.     

Bacterial Metabolism of 2,6-Xylenol

Strain DM1, a Mycobacterium sp. that utilizes 2,6-xylenol, 2,3,6-trimethylphenol, and o-cresol as sources of carbon and energy, was isolated. Intact cells of Mycobacterium strain DM1 grown with 2,6-xylenol cooxidized 2,4,6-trimethylphenol to 2,4,6-trimethylresorcinol. 4-Chloro-3,5-dimethylphenol prevents 2,6-xylenol from being totally degraded; it was quantitatively converted to 2,6-dimethylhydroquinone by resting cells. 2,6-Dimethylhydroquinone, citraconate, and an unidentified metabolite were detected as products of 2,6-xylenol oxidation in cells that were partially inactivated by EDTA. Under oxygen limitation, 2,6-dimethylhy-droquinone, citraconate, and an unidentified metabolite were released during 2,6-xylenol turnover by resting cells. Cell extracts of 2,6-xylenol-grown cells contained a 2,6-dimethylhydroquinone-converting enzyme. When supplemented with NADH, cell extracts catalyzed the reduction of 2,6-dimethyl-3-hydroxyquinone to 2,6-dimethyl-3-hydroxyhydroquinone. Since a citraconase was also demonstrated in cell extracts, a new metabolic pathway with 2,6-dimethyl-3-hydroxyhydroquinone as the ring fission substrate is proposed.     

Stereochemistry of Female-Specific Normonoterpenes,Sex Pheromone Candidates from the Acarid Mite,Tyreophagus sp. (Astigmata: Acaridae)

Two normonoterpenes were detected from an unidentified Tyreophagus sp. as new female-specific components. Both planar structures were identified to be 2,6-dimethyl-5-heptenal (1) and 2,6-dimethyl-5-hepten-1-ol (2) by GC/MS co-chromatography with synthetic 1 and 2. The stereochemistry of 2 was determined to be R by a GC analysis with a chiral column, while that of 1 was presumed to be similar to 2 based on the biosynthetic aspects.     

Mutagenicities of 2,4- and 2,6-dinitrotoluenes and their reduced products in Salmonella typhimurium nitroreductase- and O-acetyltransferase-overproducing Ames test strains

Mutagenicities of 2,4- and 2,6-dinitrotoluene (2,4-and 2,6-DNT), and reduced metabolites formed by the incubation of 2,4- and 2,6-DNT with Salmonella typhimurium TA98, were tested using S. typhimurium YG strains possessing high level of nitroreductase (NR) and/or O-acetyltransferase (OAT) activities. All compounds tested showed greatest mutagenic activities toward strains YG1041 and YG1042, which possess high levels of NR and OAT activities. The relative mutagenic activities of 2,4-DNT and its related compounds toward YG1041 and YG1042 were aminonitrotoluenes (2A4NT, 4A2NT)<2,4-DNT<2,2′-dimethyl-5,5′-dinitroazoxybenzene (2,2′-DM-5,5′-DNAOB)4-hydroxylamino-2-nitrotoluene (4HA2NT)4,4′-dimethyl-3,3′-dinitroazoxybenzene (4,4′-DM-3,3′-DNAOB), and aminonitrotoluenes (2A4NT, 4A2NT)<2,4-DNT<4HA2NT4,4′-dimethyl-3,3′-dinitroazoxybenzene (4,4′-DM-3,3′-DNAOB)<2HA4NT, respectively. In addition, the relative mutagenic activities of 2,6-DNT and its related compounds toward YG1041 and YG1042 were 2,6-DNT<2-hydroxylamino-6-nitrotoluene (2HA6NT)<2,2′-dimethyl-3,3′-dinitroazoxybenzene (2,2′-DM-3,3′-DNAOB), and 2-amino-6-nitrotoluene (2A6NT)<2,6-DNT<2HA6NT, respectively. These results, together with previous findings, suggested that aminohydroxylamino dimethylazoxybenzenes or aminohydroxylamino dimethylazobenzenes produced either by the reduction of hydroxylaminonitrotoluenes or by the reduction of dimethyl dinitroazoxybenzenes are active metabolites responsible for the mutagenic activities of 2,4- and 2,6-DNT.     

More about the role of 2,6-dichlorophenol in tick courtship: identification and olfactometer bioassay in Amblyomma cajennense and Rhipicephalus sanguineus

This study aimed to identify 2,6-dichlorophenol (2,6-DCP) in Amblyomma cajennense and to evaluate its role in A. cajennense and Rhipicephalus sanguineus courtship. Hexanic extract from attractive females was purified by solid phase extraction and the phenol was identified by the single ion monitoring method using GC/MS. In an olfactometer, the responses of A. cajennense and R. sanguineus males to females, control rubber septa or rubber septa impregnated with 2,6-DCP at 50, 500, and 5000 ng, respectively, were studied. 2,6-DCP was identified in A. cajennense extract and the males oriented themselves toward the concentration of 500 ng. These septa and the females were recognized as copula partners. The septa treated with 2,6-DCP did not attract and were not even recognized by the R. sanguineus males, whereas the females were recognized. Due to the presence of 2,6-DCP in A. cajennense and the results of biological bioassays, it was concluded that this compound acts as an attractant and mounting sex pheromone in this tick, but it does not play any role in R. sanguineus courtship.     

Dioxygenative cleavage of C-methylated hydroquinones and 2,6-dichlorohydroquinone by Pseudomonas sp. HH35

The dioxygenolytic catabolism of five C-methylated hydroquinones and 2,6-dichlorohydroquinone in Pseudomonas sp. strain HH35 was elucidated. This organism, which is known to catabolise 2,6-dimethylhydroquinone by 1,2-cleavage, accumulated metabolites from 2-methyl-, 2,3-dimethyl-, 2,5-dimethyl-, 2,3,5-trimethyl- and 2,3,5,6-tetramethylhydroquinone which we isolated and characterised by mass spectrometry and ¹H NMR and UV spectroscopy. The identification of these metabolites defined the impact of methyl groups present in the hydroquinone and showed how each substitution pattern determined the site of the initial enzymic attack. With the exception of the 2,3,5,6-tetramethylhydroquinone, all C-methylated hydroquinones were catabolised by an initial dioxygenolytic cleavage occurring adjacent (1,2- or 3,4-cleavage) to a hydroxy group. In addition, our results indicated that the 2,6-dichlorohydroquinone is catabolised in a similar way by this strain.     

Synthesis and characterization of cis-4-decenoyl-CoA, 3-phenylpropionyl-CoA, and 2,6-dimethylheptanoyl-CoA

The measurement of acyl-CoA dehydrogenase activities is an essential part of the investigation of patients with suspected defects in fatty acid oxidation. Multiple methods are available for the synthesis of the substrates used for measuring acyl-CoA dehydrogenase activities; however, the yields are low and the products are used without purification. In addition, the reported characterization of acyl-CoAs focuses on the CoA moiety, not on the acyl group. Here we describe the synthesis of three medium-chain acyl-CoAs from mixed anhydrides of the fatty acids using an aqueous-organic solvent mixture optimized to obtain the highest yield. First, cis-4-decenoic acid and 2,6-dimethylheptanoic acid were prepared (3-phenylpropionic acid is commercially available). These were characterized by gas chromatography/mass spectrometry (GC/MS), ¹H nuclear magnetic resonance (NMR), and ¹³C NMR. Then cis-4-decenoyl-CoA, 3-phenylpropionyl-CoA, and 2,6-dimethylheptanoyl-CoA were synthesized. These were then purified by ion exchange solid-phase extraction using 2-(2-pyridyl)ethyl-functionalized silica gel, followed by reversed-phase semipreparative high-performance liquid chromatography with ultraviolet detection (HPLC-UV). The purified acyl-CoAs were characterized by analytical HPLC-UV followed by data-dependent tandem mass spectrometry (MS/MS) analysis on the largest responding MS mass (HPLC-UV-MS-MS/MS) and ¹³C NMR. The yields of the purified acyl-CoAs were between 75% and 78% based on coenzyme A trilithium salt (CoASH). Acyl-CoA dehydrogenase activities were measured in rat skeletal muscle mitochondria using, as substrates, the synthesized cis-4-decenoyl-CoA, 3-phenylpropionyl-CoA, and 2,6-dimethylheptanoyl-CoA. These results were compared with the results using our standard substrates butyryl-CoA, octanoyl-CoA, and palmitoyl-CoA.     

Dioxygenative cleavage of C-methylated hydroquinones and 2,6-dichlorohydroquinone by Pseudomonas sp. HH35.

The dioxygenolytic catabolism of five C-methylated hydroquinones and 2,6-dichlorohydroquinone in Pseudomonas sp. strain HH35 was elucidated. This organism, which is known to catabolise 2,6-dimethylhydroquinone by 1,2-cleavage, accumulated metabolites from 2-methyl-, 2,3-dimethyl-, 2,5-dimethyl-, 2,3,5-trimethyl- and 2,3,5,6-tetramethylhydroquinone which we isolated and characterised by mass spectrometry and (1)H NMR and UV spectroscopy. The identification of these metabolites defined the impact of methyl groups present in the hydroquinone and showed how each substitution pattern determined the site of the initial enzymic attack. With the exception of the 2,3,5,6-tetramethylhydroquinone, all C-methylated hydroquinones were catabolised by an initial dioxygenolytic cleavage occurring adjacent (1,2- or 3,4-cleavage) to a hydroxy group. In addition, our results indicated that the 2,6-dichlorohydroquinone is catabolised in a similar way by this strain.     

(1R,2S,6R)-Papayanal: a new male-specific volatile compound released by the guava weevil Conotrachelus psidii (Coleoptera: Curculionidae)

The guava weevil, Conotrachelus psidii is an aggressive pest of guava (Psidium guajava L.) that causes irreparable damages inside the fruit. The volatile compounds of male and female insects were separately collected by headspace solid-phase microextraction or with dynamic headspace collection on a polymer sorbent, and comparatively analyzed by GC–MS. (1R,2S,6R)-2-Hydroxymethyl-2,6-dimethyl-3-oxabicyclo[4.2.0]octane (papayanol), and (1R,2S,6R)-2,6-dimethyl-3-oxabicyclo[4.2.0]octane-2-carbaldehyde (papayanal) were identified (ratio of 9:1, respectively) as male-specific guava weevil volatiles. Papayanal structure was confirmed by comparison of spectroscopic (EIMS) and chromatographic (retention time) data with those of the synthetic pure compound. The behavioral response of the above-mentioned compounds was studied in a Y-tube olfactometer bioassay, and their role as aggregation pheromone candidate components was suggested in this species.     

Alkylpyrazines: alarm pheromone components of the little fire ant, Wasmannia auropunctata (Roger) (Hymenoptera, Formicidae)

The previous identification of 2,5-dimethyl-3-(3-methylbutyl)pyrazine as the mandibular alarm pheromone of the little fire ant Wasmannia auropunctata (Roger), has been found to be incorrect. Gas chromatography–mass spectrometry (GC/MS) of ant extracts suggested the correct structure to be the regioisomer 2,5-dimethyl-3-(2-methylbutyl)pyrazine, which was confirmed by comparison with the synthetic pyrazine. GC/MS analysis also revealed the presence of an additional disubstituted alkylpyrazine which was identified as 3-methyl-2-(2-methylbutyl)pyrazine. Headspace sampling of confined ants with SPME and Porapak Q followed by GC/MS analysis showed 2,5-dimethyl-3-(2-methylbutyl)pyrazine as the major volatile released by W. auropunctata workers while 3-methyl-2-(2-methylbutyl)pyrazine was only detected in trace amounts. In laboratory bioassays, W. auropunctata workers were attracted and arrested by both pyrazines, although the results were not always consistent. Synthetic pyrazines generally attracted as many W. auropunctata workers as were attracted to a single crushed ant. However, higher numbers of W. auropunctata were arrested by crushed ant treatments than by synthetic pyrazines in all bioassays but one.     

Comparison of DNA binding between the carcinogen 2,6-dinitrotoluene and its noncarcinogenic analog 2,6-diaminotoluene

We used ³²P-postlabelling to compare DNA binding between the potent hepatocarcinogen 2,6-dinitrotoluene and its noncarcinogenic analog 2,6-diaminotoluene. The two compounds were compared to determine whether differences in DNA binding could partly explain the differences in their carcinogenicity. Fischer-344 rats were administered 1.2 mmol/kg of a compound by single i.p. injection and examined for DNA adduct formation in the liver. Four adducts were detected following administration of 2,6-dinitrotoluene, with a total adduct yield of 13.5 adducted nucleotides per 10⁷ nucleotides. Qualitatively identical adducts were also detected after treatment with the derivative 2-amino-6-nitrotoluene. Adduct yields from 2,6-dinitrotoluene were 30 times greater than from 2-amino-6-nitrotoluene. No adducts were observed following treatment with 2,6-diaminotoluene. 2,6-Dinitrotoluene and 2,6-diaminotoluene were also compared for qualitative differences in hepatotoxicity. 2,6-Dinitrotoluene produced extensive hemorrhagic necrosis in the liver, whereas no evidence of hepatocellular necrosis was detected following administration of the latter. The differences between the two compounds in both DNA binding and cytotoxicity were consistent with the differences in their carcinogenicity.     

1,3,6-Trihydroxy-7-methoxy-8-(3,7-dimethyl-2,6-octadienyl)xanthone from Garcinia cowa

1,3,6-Trihydroxy-7-methoxy-8-(3,7-dimethyl-2,6-octadienylxanthone has been isolated from the stems of Garcinia cowa.     

2,6-Dichlorobenzonitrile and Boron Deficiency

Symptoms of 2,6-dichlorobenzonitrile poisoning in plants aredescribed and compared with the symptoms produced by phenylboronicacid and boron deficiency. The effects on the macroscopic andmicroscopic appearance of plants and on their ability to translocategrowth regulators are so alike that it is thought that both2,6-dichlorobenzonitrile and boron deficiency affect the samebasic process.     

Reactivity of 2,6-diethyl-4,8-dimethyl-1,5-dioxo-s-hydrindacene towards radical, anionic and cationic germylation

The synthesis and diastereoisomeric resolution of 2,6-diethyl-4,8-dimethyl-1,5-dioxo-s-hydrindacene allowed the determination of the structure of the meso compound by X-ray diffractometry. The diastereoisomers were inactive towards radical germylation but reacted with acidic hydrogermanes or germylithium yielding α-germylated alcohols. By contrast, they were poorly reactive towards germylamines or SET reactions. This diketone acts as an efficient spin trap in radical hydrogermylation of alkenes.     

Role of Alicyclobacillus acidoterrestris in the development of a disinfectant taint in shelf-stable fruit juice

AIMS: This study was undertaken to identify the bacterium and metabolic products contributing to a disinfectant taint in shelf-stable fruit juice and to determine some of the growth conditions for the organism. METHODS AND RESULTS: Microbiological examination of tainted and untainted fruit juice drinks detected low numbers of acid-dependent, thermotolerant, spore-forming bacteria in the tainted juices only. The presence of omega-cyclohexyl fatty acids was confirmed in two of the isolates by cell membrane fatty acid analysis. The isolates were subsequently identified as Alicyclobacillus acidoterrestris by partial 16S rDNA sequencing. Studies on the isolates showed growth at pH 2.5-6.0 and 19.5-58 degrees C. Gas chromatography/mass spectrometry (GC/MS) was used to identify and quantify 2,6-dibromophenol (2,6-DBP) and 2,6-dichlorophenol (2,6-DCP) in the tainted juice. Challenge studies in a mixed fruit drink inoculated with the two isolates and the type strain of A. acidoterrestris, incubated at 44-46 degrees C for 4 d, showed the production of both metabolites, which were confirmed and quantified by GC/MS. CONCLUSIONS: The results show that A. acidoterrestris can produce 2,6-DBP and 2,6-DCP in shelf-stable juices. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report detailing experimental methodology showing that A. acidoterrestris can produce 2,6-DCP in foods. Control of storage temperatures (to < 20 degrees C) immediately after processing may provide an effective control measure for the fruit juice industry to prevent spoilage by A. acidoterrestris.     

Metabolization of beta-(2,6)-linked fructose-oligosaccharides by different bifidobacteria

Low-molecular-mass beta-(2,6)-linked fructose-oligosaccharides (beta-(2,6)-FOS) were examined as a new carbohydrate source for growth of bifidobacteria. beta-(2,6)-FOS were prepared from microbial high-molecular-mass levan by acid hydrolysis and refined by cation-exchange chromatography. (13)C-NMR spectroscopy confirmed the presence of predominantly beta-(2,6)-fructosyl linkages in the oligosaccharides. More than 80% beta-(2,6)-FOS was recovered after in vitro incubation with amylolytic and proteolytic enzymes, implying resistance to degradation in the upper intestinal tract. Bifidobacterium adolescentis, B. longum, B. breve, and B. pseudocatenulatum were studied in vitro for their ability to metabolize beta-(2,6)-FOS. Growth, decrease in pH, formation of short- chain fatty acids (lactate, acetate, formate) and degradation of beta-(2,6)-FOS were markedly different among species. B. adolescentis showed the best growth, produced the highest amounts of organic acids and metabolized both short- and long-chain beta-(2, 6)-FOS.     

Monitoring of BHT-quinone and BHT-CHO in the gas of capsules of Asclepias physocarpa

Three volatile components, namely benzoic acid ethyl ester (1), 2,6-di-tert-butyl-p-benzoquinone (BHT-quinone) (2), and 3,5-di-tert-butyl-4-hydroxybenzaldehyde (BHT-CHO) (3), were detected from the gas in the capsules of Asclepias physocarpa by means of GC/MS analysis. BHT-quinone and BHT-CHO as organic pollutants are the degradation products of the antioxidant 2,6-di-tert-butyl-4-methylphenol (BHT). Ground water, lake water and/or rain water are a source of BHT metabolites in the plant Asclepias physocarpa.     

Regulation of fructose 2,6-bisphosphate levels in Neurospora crassa

Both wild type and cr-1 mutant (adenylate cyclase and cyclic AMP-deficient) strains of Neurospora crassa contain fructose 2,6-bisphosphate at levels of 27 nmol/g dry tissue weight. This level decreases by about 50% in both strains upon depriving the cells of carbon or nitrogen sources for 3 h. An increase in cyclic AMP levels produced by addition of lysine to nitrogen-starved cells produced no increase in fructose 2,6-bisphosphate levels. Both strains respond to short-term addition of salicylate, acetate, or 2,4-dinitrophenol with an increase in fructose 2,6-bisphosphate. Thus, the above-described regulation of fructose 2,6-bisphosphate levels is cyclic AMP-independent. A suspension of the wild type produces a transient increase of fructose 2,6-bisphosphate in response to administration of glucose, whereas the mutant strain does not respond unless it is fed exogenous cyclic AMP. Substitution of acetate for sucrose as a sole carbon source for growth leads to a differential decrease in fructose 2,6-bisphosphate levels between the two strains: the wild type strain has 63% and the cr-1 mutant strain has 37% of the levels of fructose 2,6-bisphosphate on acetate as compared to sucrose-grown controls. This may be the basis for an advantage of cr-1 over wild type in growth on acetate. Thus, although most regulation of fructose 2,6-bisphosphate is cyclic AMP-independent, the levels can be regulated by a combination of carbon source and cyclic AMP levels.     

Effects of fructose 2,6-bisphosphate and glucose 1,6-bisphosphate on phosphofructokinase from chicken erythrocytes

1. Phosphofructokinase (EC 2.7.1.11) from chicken erythrocytes is activated by fructose 2,6-bisphosphate, glucose 1,6-bisphosphate and AMP, and it is inhibited by 2,3-bisphosphoglycerate and inositol hexaphosphate. 2. The stimulatory effects produced by the two bisphosphorylated hexoses are additive and the effects produced by fructose 2,6-bisphosphate and by AMP are synergistic. 3. The activatory effect produced by fructose 2,6-bisphosphate is counteracted by fructose 1,6-bisphosphate. 4. The inhibition produced by both 2,3-bisphosphoglycerate and inositol hexaphosphate is released by fructose 2,6-bisphosphate. 5. It is concluded that, like phosphofructokinase from mammalian tissues, the enzyme from chicken erythrocytes can be modulated by the relative concentrations of those metabolites.     

Thiophene-containing dinucleating ligands for the copper-catalyzed oxidative coupling of 2,6-dimethylphenol

The copper-catalysed polymerisation of 2,6-dimethylphenol leads to poly(2,6-dimethyl-1,4-phenylene) ether, which is a widely used high-performance thermoplastic. The oxidative coupling reactions have been performed in acetonitrile with structurally related dinucleating phenol-based “end-off” compartmental N,O,S- ligands. The bio-inspired copper catalysts appeared to be of great interest for a better understanding of the parameters governing the catalytic activities. Steric effects (difference between three side-arm and four side-arm ligands), as well as electronic effects (thiophene versus pyridine substituents) have been evidenced on the initial dioxygen-uptake rates.