Comparison of methods employing gas chromatography retention data to determine vapour pressures at 298 K.

Validity of five models suggested for expressing the relationship between vapour pressures and GC retention times measured on a non-polar capillary column were tested on a common set of compounds [five homologous series of the type H-(CH2)n-Y, where Y denotes Cl, Br, CHO, OCOCH3 and COOCH3, and n varies from 6 to 14]. Standard methods of statistical analysis, as well as vapour pressure values obtained independently from direct vapour pressure measurements were used as validity criteria. For the 40-compound data set examined, the methods provided vapour pressures agreeing within 9.2-24.7% (average absolute percent error) with direct experimental data.

Lipase-mediated hydrolysis of blackcurrant oil.

Four commercially available lipases, both free and immobilized, were tested for their ability to catalyze hydrolysis of blackcurrant (Ribes nigrum) oil using two different approaches. The lipase from Mucor miehei was studied free and immobilized in two different ways. The former series of enzymic reactions were performed in tap water at 40 degrees C, but the latter series of enzymic processes were carried out in mixtures of isooctane and phosphate buffer (in a typical 2/1 ratio of the components) at 30 degrees C. These conditions were optimized to increase and/or to maximize the yields of the products, which were priority targets in this study. A rate of hydrolysis and a selective preference of the hydrolytic enzymes towards fatty acids, with a special focus on enrichment of alpha-linolenic acid and/or gamma-linolenic acid, were studied. Higher rates of hydrolysis of the blackcurrant oil in the former series of reactions were observed with the immobilized lipase from Pseudomonas cepacia used as biocatalyst. In the latter approach, the most favorable results of the rate of hydrolysis of the target blackcurrant oil were achieved with the immobilized lipase from Mucor miehei employed as biocatalyst. Only three lipases, selected from a series of lipases tested during this investigation, displayed specificity towards alpha-linolenic acid and gamma-linolenic acid, i.e. the immobilized lipase from P. cepacia, lipase from M. miehei and lipase from P. fluorescens.

Volatiles released from oak, a host tree for the bark beetle Scolytus intricatus.

Volatile compounds emitted in different phases of oak (Quercus robur) development (bark, unopened buds, young developing leaves, and blossoms) were analyzed with the aim of finding possible host-plant attractants for the European oak bark beetle, Scolytus intricatus. Complex mixtures of aliphatic, aromatic, and terpenoid compounds were identified in the samples. (E)-2-Hexenal and hexanal dominated in samples of bark. In buds, (Z)-3-hexenyl acetate formed a substantial part of the mixture. In both leaves and blossoms (E,E)-alpha-farnesene was the main component.Volatiles released from oak twigs and branches during both the maturation feeding and construction of maternal galleries by Scolytus intricatus were also analyzed. Most compounds found in the samples from females' and males' maturation feeding were identical. High contents of anisole, (E)-beta-ocimene, alpha-copaene, one unidentified sesquiterpenic hydrocarbon C(15)H(24) and beta-caryophyllene were found in both samples of twigs attacked by beetles. During the construction of maternal galleries by bark beetles in oak logs, monoterpene hydrocarbons such as p-cymene, (E)-beta-ocimene, and gamma-terpinene, and sesquiterpenes alpha-copaene and beta-caryophyllene were released in large quantities. No new compound appeared when males were added to the log with feeding females.

New mimics of the acetate function in pheromone-based attraction.

Several analogues of (Z)-8-dodecenyl acetate (1a), the major pheromone component of the Oriental fruit moth, Cydia molesta, with chloroformate and lactone functional groups in place of the acetate moiety, were synthesized and investigated for their biological activity at four evaluation levels, i.e. by electroantennography (EAG), electrosensillography (ESG), short-range sexual stimulation and activation in the flight-tunnel. We found very strict requirements on the shape as well as on the electron distribution of the acetate group for a productive interaction with the receptor. The behavioral results showed that, among the analogues investigated, the chloroformate 1b, alken-4-olide 2a and also dodecyl acetate (1c) possess significant (60-85%) inhibitory activities. Based on electrophysiological evidence demonstrating that (i) only 1b is competing with the major pheromone component 1a for the same receptor sites on the male antennal sensilla, (ii) 1c elicits moderate EAG but no ESG responses and (iii) 2a does not produce any electrophysiological response at all, three possible inhibitory mechanisms by which these analogues are acting could be distinguished.

Inhibitors of arachidonoyl ethanolamide hydrolysis.

Arachidonoyl ethanolamide (anandamide) is a naturally occurring brain constituent that binds to a specific brain cannabinoid receptor (CBR1). An amidase activity (anandamide amidase) in membrane fractions of brain and in cultured neuroblastoma cells rapidly degrades anandamide to arachidonic acid (Deutsch, D. G., and Chin, S. (1993) Biochem. Pharmacol. 46, 791-796). In the current study, analogs of anandamide representing three classes of putative transition-state inhibitor (trifluoromethyl ketones, alpha-keto esters, and alpha-keto amides) were synthesized and tested as inhibitors of anandamide hydrolysis in vitro and as ligands for CBR1. The trifluoromethyl ketones and alpha-keto esters showed nearly 100% inhibition of anandamide hydrolysis in vitro at 7.5 microM inhibitor and 27.7 microM anandamide. Arachidonyl trifluoromethyl ketone was the only synthetic compound in the series of fatty acid derivatives able to displace [3H]CP-55940 binding to CBR1 with a Ki of 0.65 microM. It was also the most effective inhibitor in intact neuroblastoma cells, leading to a 12-fold increase of cellular anandamide levels at 12 microM. From the action of these inhibitors on this hydrolytic enzyme, it seems likely that anandamide is cleaved by a mechanism that involves an active-site serine hydroxyl group. These inhibitors may serve as useful tools to elucidate the role anandamide plays in vivo.

Structure-activity correlations among analogs of the currant clearwing moth pheromone.

Eleven analogs of (E,Z)-2,13-octadecadien-1-yl acetate1, a main pheromone component of the currant clearwing moth,Synanthedon tipuliformis Clerk (Lepidoptera: Sesiidae) were synthesized and tested for their biological activities by electroantennography (EAG). To correct the EAG data for differences in volatility of the analogs, their vapor pressures were estimated by a gas chromatographic method. All structural changes in the parent molecule were found to reduce the biological activity to various degrees. The most active analog tested was the carbamate12, whose activity was almost comparable to that of the pheromone component1. Structure-activity correlations showed that hydrophobic, steric, and electronic effects of chain terminal groups might be responsible for variations in biological activity of the conformationally unchanged (E,Z)-2,13-analogs.