Isoprenoid Structure Research Articles

Chemical Composition and Biological Activity of the Essential Oil from Artemisia glabella

Essential oils are complex mixtures of various organic compounds, most of which possess an isoprenoid structure. Data in the literature are indicative of the high biological activity of essential oils, which makes possible the use of these substances in medicine and pharmacology [1, 2]. The chemical and pharmacological properties of an essential oil isolated from wormwood species Artemisia glabella Kar. et Kir. have been thoroughly studied within the framework of investigations aimed at the complex use of these species, which are employed as a raw material for the drug arglabin [3] developed at the Institute of Phytochemistry (Karaganda). Recently [4], more than 70 compounds were identified in the essential oil from Artemisia glabella (EOAG) studied by a gas chromatography (GC) technique using a capillary column with nonpolar methyl silicon immobile phase and a flame-ionization detector. The main chemical components of the characteristic chemical composition of EOAG are 1,8-cineole (12%), linalool (8%), 4-terpineol (6.5%), -terpineol (5%), and sabinol derivatives (5%). These substances were also found in the essential oils isolated from medicinal plants of some other genuses. At the same time EOAG contains a series of genetically related compounds including para-cymene, cuminaldehyde, cuminyl alcohol and acetate, -thujene, sabinene, sabinene hydrate, sabinol and related esters with a homologous series of fatty acids, -pinene, myrtenal, and verbenone. The purpose of this study was to identify the essential oil isolated from Artemisia glabella Kar. et Kir. and characterize EOAG with respect to biological activity. EXPERIMENTAL CHEMICAL PART

New possibilities of isoprenoids chemistry when using a heterogeneous catalyst: Askanite—bentonite clay

Abstract We showed that new heterocyclization reactions resulting in the compounds of a unique structure and a potential biological activity proceed when hydroxyolefins of menthane and carane seriies are allowed to react with salicylaldehyde 1 on askanite—bentonite clay at room temperature. Slight changes in isoprenoid structure yield significantly different reaction products.

Replacement of the H-Ras farnesyl group by lipid analogues: implications for downstream processing and effector activation in Xenopus oocytes.

Ras proteins must undergo a series of posttranslational lipidation steps before they become biologically functional. While the fact that farnesylation is required for subsequent processing steps and indispensable for Ras function has been established, the significance of the isoprenoid structure per se in the context of fully processed Ras is unknown. Here, we describe a novel approach for studying the isoprenoid structure-function relationship in vivo by replacing the H-Ras farnesyl group with synthetic analogues and analyzing their biological functions following microinjection into Xenopus oocytes. We show that the H-Ras farnesyl group can be stripped of most of its isoprenoid features that distinguish it from a fatty acid without any apparent effect on its ability to induce oocyte maturation and activation of mitogen-activated protein kinase. In contrast, replacement by the less hydrophobic isoprenoid geranyl causes severely delayed oocyte activation. Analysis of posttranslational processing reveals a striking correlation between the kinetics of processing, membrane binding, and the onset of biological activity regardless of lipid structure and suggests that slow C-terminal proteolysis and/or methylation can become rate-limiting for H-Ras function. Thus, while our results suggest no stringent requirement for the H-Ras farnesyl structure for effector activation in Xenopus oocytes, they reveal an important role for the lipid present at the farnesylation site in promoting efficient proteolysis and/or methylation which allows rapid palmitoylation, membrane localization, and biological activity. Xenopus oocytes provide a useful in vivo system for the kinetic analysis of the function of the protein of interest present at the physiological dose, which is required for accurate determination of structure-function relationships.

Probing Substrate Binding Site of the Escherichia coli Quinol Oxidases Using Synthetic Ubiquinol Analogues

Substrate binding sites of the Escherichia coli bo- and bd-type quinol oxidases were probed with systematically synthesized ubiquinol analogues. The apparent Km values of ubiquinol-2 derivatives to the bo-type enzyme were much lower than that of the corresponding 6-n-decyl derivatives. The isoprenoid structure is less hydrophobic than the saturated n-alkyl group with the same carbon number; therefore, the native isoprenoid side chain appears to play a specific role in quinol binding besides simply increasing hydrophobicity of the molecule. The Vmax values of 2-methoxy-3-ethoxy analogues were greater than that of 2-ethoxy-3-methoxy analogues irrespective of the side chain structure. This result indicates not only that a methoxy group in the 2-position is recognized more strictly than the 3-position by the binding site but also that the side chain structure does not affect binding of the quinol ring moiety. Systematic analysis of the electron-donating activities of the analogues with different substituents in the 5-position revealed that the 5-methyl group is important for the activity. In the parallel studies with the bd-type enzyme, we obtained similar observations except that almost all quinol analogues, but not ubiquinol-1, elicited a remarkable substrate inhibition at higher concentrations. These results indicate that the two structurally unrelated terminal oxidases share common structural properties for the quinol-oxidation site.

Quantification of Isolated Methyl Groups in Aquatic Humic Substances by Means of1H and13C NMR Spectroscopy

To determine the proportion of isolated methyl groups (i.e. methyl groups attached to hydrogen-free carbon) in aground water humic substance (HS), four different techniques were applied: the standard proton spin–echo tech-nique, the 1H-INADEQUATE method, a short version of the latter with a π/4 pulse and the proton spin–echo DEPT technique. The standard spin–echo technique proved to be the most suitable. The proportion of isolated paraffinic methyl groups is as high as 60%. Polycyclic isoprenoid structures are considered to be responsible for the occurrence of isolated methyl groups in HS.

Mode of Action of Herbicides Affecting Carotenogenesis

Carotenoids (carotenes and xanthophylls) are obligate pigments in the photosynthetic apparatus. They transfer absorbed light to chlorophylls and quench singlet oxygen which otherwise may degrade chlorophyll. Absence of colored carotenoids will lead to bleaching of leaves and death of the plants. Carotenoids have a C40 isoprenoid structure with conjugated double bonds. These are formed by processing phytoene via lycopene into beta-carotene. Inhibition of H-abstraction along this pathway produces non-functional, non-colored precursors. Many of such inhibitors have been developed as herbicides, like norflurazon, diflufenican or sulcotrione. Research on the genetic and molecular level has been addressed to phytoene desaturase. The plant-type gene has been sequenced and mutagenized to produce a herbicide-resistant enzyme. A Japanese group has isolated a gene from the bacterium Erwinia uredovora whose enzyme exhibits a striking resistance to many bleaching herbicides. Transgenic resistant tobacco lines have been engineered.

Distribution of Acyclic Isoprenoids in Fractions from Stepwise Oxidation of Green River Kerogen

Abstract A study on the distribution of isoprenoid structures in the five fractions obtained by mild Na2Cr2O7/AcOH stepwise oxidation of Green River kerogen is presented. Gas chromatography-mass spectrometry analysis of the fractions resulted in the identification of a homologous series of isoprenoid acids ranging from C14-C21 with C16 as the largest and C18 entirely absent, as well as the two isoprenoidal ketones: 6,l0-dimethyl-2-undecanone and 6,10,l4-trimethyl-2-pentadecanone. A semiquantitative analysis of these components was performed using an INCOS 2300 data system. On the basis of the results obtained, it is suggested that isoprenoid structures do not constitute more than 4% of the kerogen matrix. The results also substantiate previous assumptions that the phytol side chain of chlorophyll is the most likely pre-genitor to the chain isoprenoids found in Green River kerogen.

Cyclanes of naphthalane crude oil

Summary o 1. Mass-spectrometry and 13C NMR spectroscopy were used to investigate the structure of cyclanes of particular crude oils. 2. The cyclanes of naphthalane crude oil contain 1–8 rings per molecule. Mono-, bi-, tri- and tetracycles account for 87·5% of the cyclanes. Bicyclanes (29·8%) and tricyclanes (24·4%) are the principal components. 3. The cyclanes on average contain 1–4 methyl groups and one alkyl substituent (C3–C14) of normal or branched structure. These are present in about the same quantities. Among branched substituents alkyls with isoprenoid and 2-methyl alkyl structures predominate.

The 3-Methyl-1,3-butadienyl Phenyl Sulfoxide I. Preparation and Some Properties

Abstract The title sulfoxide 5 is worthy of interest because of its isoprenoid structure and its synthetic potentialities1

Biodegradation of crude oil in the Aquitaine basin

Two crude oils from the Aquitaine basin (SW France) have been subjected to in vitro biodegradation with the bacterium Pseudomonas oleovorans for periods ranging from five days to three months. A rapid disappearance of the linear, branched and isoprenoid structures is observed in the alkane fraction. The degree of alteration is highly dependent upon the quality of the initial material but the residual oils, obtained after biodegradation of either immature or moderately mature crudes, display a virtually identical alkane distribution. Such a distribution is also observed in natural asphalts i.e. heavily biodegraded crudes from the Aquitaine tar belt or in crude oils biodegraded in soils from well sites. This alkane distribution displays a high concentration of tri-, tetra- and pentacyclic alkanes. These polycyclic alkanes, organized into several ubiquitous families in the Aquitaine crudes, remain unchanged by bacterial attack either in the laboratory or in nature (soils, boreholes). They therefore represent several classes of compounds that should be of potential interest to correlate unaltered to biodegraded crudes in other basins. Among the families of polycyclics which are ubiquitous in the Aquitaine crudes, we find a novel group of 4 low mol wt steranes (a C21 and a C2) sterane, a C22 and a C23 4 methylsterane), a series of tricyclic terpanes (C19C26) a series of tetracyclic terpanes (C24C26) and the α-β hopane series (C27C35).

Isoprenoids in a Costa Rican seep oil

The isoprenoid alkanes present in a seep oil from Costa Rica have been examined using gas chromatography and mass spectrometry. In addition to the predominance of the C 16 and C 18-C 20 regular isoprenoid alkanes, the C 21 and C 23-C 25 regular isoprenoid alkanes were identified. The C 26, C 28 and C 30 regular isoprenoid alkanes were tentatively identified. No evidence for the regular C 17, C 22 or C 27 isoprenoid alkanes was found. The compounds 3,7,11- trimethyltetradecane and 3,7,11-trimethylhexadecane were tentatively identified. It is suggested that a higher regular isoprenoid structure (or structures) is required in addition to phytol to account for the distribution of isoprenoid alkanes.

Recent Advances in the Chemistry and Biochemistry of Methyl Branched Fatty Acids

AbstractThe main aspects of recent research on the occurrence, isolation, structure, biogenesis and metabolism of the methyl branched fatty acids have been reviewed. For the purpose of this work the fatty acids were classified in the following 5 groups: 1. Iso‐ or anteiso‐acids; 2. Branched chain acids with one methyl branching in the middle of the chain; 3. Multiple branched acids with methyl branching on alternate carbon atoms; 4. Multiple branched acids with isoprenoid structure; 5. Mycolic acids. The literature has been covered up to 1969.

Organic compounds in meteorites—IV. Gas chromatographic-mass spectrometric studies on the isoprenoids and other isomeric alkanes in carbonaceous chondrites

Nine homologous series of isomeric alkanes, in addition to the normal alkane series, have been identified by gas Chromatographic and mass spectrometric techniques in the hydrocarbon fractions from the extracts of six carbonaceous chondrites (Essebi, Grosnaja, Mokoia, Murray, Orgueil and Vigarano). Two of these series show isoprenoid structures corresponding to 2,6,10-trimethyl and 2,6,10,14-tetramethyl alkanes ranging from C 14 to C 18 and C 19 to C 21, respectively. The rest is made up of five series of monomethyl alkanes (2-, 3-, 4-, 5-, 6-methyl alkanes) and two of monocycloalkanes (cyclohexyl and cyclopentyl). The presence of members of the n-paraffin series between C 11 and C 26 inclusive was also confirmed by mass spectral data. The hydrocarbon content ranged from 6.7 to 82.8 ppm. Isoprenoids are present in all samples analyzed. Usually they show a major maximum at C 19 (pristane) and a secondary maximum at C 16 (methyl farnesane) with a minimum at C 17.

The structure and stereochemistry of lyratol a new C 10 alcohol from Cyathocline lyrata

Chemical reactions of lyratol are shown to confirm the modified isoprenoid structure 1 derived earlier mostly on the basis of spectral data. The stereochemistry of lyratol and the structure of its reduction products are deduced from a study of their NMR spectra.

Isolation of isoprenoid acids from a California petroleum

By sequences involving fractional distillation, thiourea adduction, gas chromatography and crystallization of solid derivatives, there have been isolated from the naphthenic acids of a California petroleum four acyclic acids of isoprenoid structure: 2,6,10-trimethylhendecanoic acid, 3,7,11-trimethyldodecanoic acid, 2,6,10,14-tetramethylpentadecanoic acid, 3,7,11,15-tetramethylhexadecanoic acid. Structures were deduced by interpretation of spectra and confirmed by comparison with samples of the synthetic acids. Starting material for synthesis of the C 14 acid was farnesol, while phytol was starting material for synthesis of the C 19 and C 20 acids. No optical rotation could be observed for the acids isolated from petroleum. In mass spectrometry of amides of these acids, in addition to the set of fragments containing the amido grouping, there was also observed a complete set of irons containing the nitrile grouping.