Chiral 2-alkylbranched acids, esters and alcohols. Preparation and stereospecific flavour evaluation

Detection of Fungi and Oomycetes by Volatiles Using E-Nose and SPME-GC/MS Platforms

Fungi and oomycetes release volatiles into their environment which could be used for olfactory detection and identification of these organisms by electronic-nose (e-nose). The aim of this study was to survey volatile compound emission using an e-nose device and to identify released molecules through solid phase microextraction-gas chromatography/mass spectrometry (SPME-GC/MS) analysis to ultimately develop a detection system for fungi and fungi-like organisms. To this end, cultures of eight fungi (Armillaria gallica, Armillaria ostoyae, Fusarium avenaceum, Fusarium culmorum, Fusarium oxysporum, Fusarium poae, Rhizoctonia solani, Trichoderma asperellum) and four oomycetes (Phytophthora cactorum, P. cinnamomi, P. plurivora, P. ramorum) were tested with the e-nose system and investigated by means of SPME-GC/MS. Strains of F. poae, R. solani and T. asperellum appeared to be the most odoriferous. All investigated fungal species (except R. solani) produced sesquiterpenes in variable amounts, in contrast to the tested oomycetes strains. Other molecules such as aliphatic hydrocarbons, alcohols, aldehydes, esters and benzene derivatives were found in all samples. The results suggested that the major differences between respective VOC emission ranges of the tested species lie in sesquiterpene production, with fungi emitting some while oomycetes released none or smaller amounts of such molecules. Our e-nose system could discriminate between the odors emitted by P. ramorum, F. poae, T. asperellum and R. solani, which accounted for over 88% of the PCA variance. These preliminary results of fungal and oomycete detection make the e-nose device suitable for further sensor design as a potential tool for forest managers, other plant managers, as well as regulatory agencies such as quarantine services.

Immunosuppressive Activities of Novel PLA2 Inhibitors from Xenorhabdus hominickii, an Entomopathogenic Bacterium

Eicosanoids mediate both cellular and humoral immune responses in insects. Phospholipase A2 (PLA2) catalyzes the first committed step in eicosanoid biosynthesis. It is a common pathogenic target of two entomopathogenic bacteria, Xenorhabdus and Photorhabdus. The objective of this study was to identify novel PLA2 inhibitors from X. hominickii and determine their immunosuppressive activities. To identify novel PLA2 inhibitors, stepwise fractionation of X. hominickii culture broth and subsequent enzyme assays were performed. Eight purified fractions of bacterial metabolites were obtained. Gas chromatography and mass spectrometry (GC-MS) analysis predicted that the main components in these eight fractions were 2-cyanobenzoic acid, dibutylamine, 2-ethyl 1-hexanol, phthalimide (PM), dioctyl terephthalate, docosane, bis (2-ethylhexyl) phthalate, and 3-ethoxy-4-methoxyphenol (EMP). Their synthetic compounds inhibited the activity of PLA2 in hemocytes of a lepidopteran insect, Spodoptera exigua, in a dose-dependent manner. They also showed significant inhibitory activities against immune responses such as prophenoloxidase activation and hemocytic nodulation of S. exigua larvae, with PM and EMP exhibiting the most potent inhibitory activities. These immunosuppressive activities were specific through PLA2 inhibition because an addition of arachidonic acid, a catalytic product of PLA2, significantly rescued such suppressed immune responses. The two most potent compounds (PM and EMP) showed significant insecticidal activities after oral administration. When the compounds were mixed with Bacillus thuringiensis (Bt), they markedly increased Bt pathogenicity. This study identified eight PLA2 inhibitors from bacterial metabolites of X. hominickii and demonstrated their potential as novel insecticides.

Review of catalytic systems and thermodynamics for the Guerbet condensation reaction and challenges for biomass valorization

This review deals with homogeneous and heterogeneous catalytic processes for the Guerbet condensation, as well as discusses biomass sources, thermodynamics and technological considerations.

Antimicrobial activities of naphthazarins from Arnebia euchroma

Bioassay-directed fractionation of extract of Arnebia euchroma led to the isolation of alkannin (1), shikonin (2), and their derivatives (3-8) as the active principles against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). The stereochemistry of alpha-methylbutyryl alkannin (8) is revealed for the first time, and the antimicrobial activity of 8 was compared with its corresponding diastereomer (9). The derivatives 3-9 showed stronger anti-MRSA activity [minimum inhibitory concentrations (MICs) ranged from 1.56 to 3.13 microg/mL] than alkannin or shikonin (MIC = 6.25 microg/mL). Anti-MRSA activity of derivatives was bactericidal with minimum bactericidal concentration (MBC)/MIC < or = 2. In a time-kill assay, the bactericidal activity against MRSA was achieved as rapidly as 2 h. The derivatives 3-9 were also active against vancomycin-resistant Enterococcus faecium (F935) and vancomycin-resistant Enterococcus faecalis (CKU-17) with MICs similar to those with MRSA. Aromatic ester derivatives were also synthesized for antimicrobial activity comparison. None of these compounds were active against Gram-negative bacteria tested. Their cytotoxicity was also evaluated on selected cancer cell lines, and they expressed their activity in the range 0.6-5.4 microg/mL (CD(50)). Our results indicate that the ester derivatives of alkannin are potential candidates of anti-MRSA and anti-VRE agents with antitumor activity.

Theoretical and experimental studies of biotin analogues that bind almost as tightly to streptavidin as biotin

We have used a newly developed qualitative computational approach, PROFEC (Pictorial Representation of Free Energy Changes), to visualize the areas of the ligand biotin where modifications of its structure might lead to tighter binding to the protein streptavidin. The PROFEC analysis, which includes protein flexibility and ligand solvation/desolvation, led to the suggestion that the pro-9R hydrogen atom of biotin, which is in alpha-position to the CO(2)(-) group, might be changed to a larger group and lead to better binding with streptavidin and avidin. Free energy calculations supported this suggestion and predicted that the methyl analogue should bind approximately 3 kcal/mol more tightly to streptavidin, with this difference coming exclusively from the relative desolvation free energy of the ligand. The PROFEC analysis further suggested little or no improvement for changing the pro-9S hydrogen atom to a methyl group, and great reduction in changing the ureido N-H groups to N-CH(3). Stimulated by these results, we synthesized 9R-methylbiotin and 9S-methylbiotin, and their binding free energies and enthalpies were measured for interaction with streptavidin and avidin, respectively. In contrast to the calculated results, experiments found both 9-methylbiotin isomers to bind more weakly to streptavidin than biotin. The calculated preference for the binding of the 9R- over the 9S-stereoisomer was observed. In addition, 9-methylbiotin is considerably less soluble in water than biotin, as predicted by the calculation, and the 9R isomer is, to our knowledge, thus far the tightest binding analogue of biotin to streptavidin. Subsequently, X-ray structures of the complexes between streptavidin and both 9R- and 9S-methylbiotin were determined, and the structures were consistent with those used in the free energy calculations. Thus, the reason for the discrepancy between the calculated and experimental binding free energy does not lie in unusual binding modes for the 9-methylbiotins.

Identification of the catalytic residue of human short/branched chain acyl-CoA dehydrogenase by in vitro mutagenesis

The acyl-CoA dehydrogenases (ACDs) are a family of related enzymes which catalyze the alpha,beta-dehydrogenation of acyl-CoA esters, transferring electrons to electron transferring flavoprotein. We have recently cloned and characterized the cDNA for human short/branched chain acyl-CoA dehydrogenase (SBCAD). Based on homology with the other ACDs we hypothesized that E381 is the catalytic residue for this enzyme. Alteration of this amino acid to glutamine, glycine or arginine resulted in an inactive enzyme. Substitution of aspartate at this position led to an enzyme with reduced activity compared to the wild type. An E381G/G260E double mutation (which places a glutamate in a position homologous to the catalytic residue identified in other members of this gene family) restored enzyme activity. These data confirm the crucial nature of E381 to the activity of this enzyme and strongly support its role as the alpha-proton abstracting base.