Terpenoid Hydrocarbons Research Articles

CHEMICAL COMPOSITION OF THE ESSENTIAL OIL OF WORMWOOD (ARTEMISIA ABSINTHIUM L.), GROWING IN THE WESTERN REGION OF AZERBAIJAN

Wormwood (Artemisia absinthium L.) is a widespread plant species in the Western region of Azerbaijan. The dependence of the composition, quantity and growth of various biologically active substances contained in the above-ground parts of wormwood on the vegetation period and climatic conditions was studied. The results of the study of the essential oil obtained by the steam distillation method from wet and dry samples of the aerial parts of bitter wormwood are presented. The yield of essential oil is determined in % in terms of the weight of air-dried raw materials. The study of the yield of essential oil was different months of the year showed that its amount varies depending on the vegetation period (yield of 0.56-0.66% by mass of fresh raw materials; yield of 0.58-0.77% by mass of dry raw materials). The composition of volatile distillates was studied by the chromatography method. In all samples, the amount of camphor component, which belongs to oxygenated terpenoid hydrocarbons, prevailed with a percentage above 35%. 25.44-34.24% phase budding in June for fresh and dry plant material; 25.14-35.21% phase mass flowering in August; it was determined between 25.67-35.20% phase the seed ripening in September.

Allosteric inhibition via nonpolar terpenoid inhibitors.

Protein tyrosine phosphatases (PTPs) are promising drug targets for treating a wide range of diseases such as diabetes, cancer, and neurological disorders, but their conserved active sites have complicated the design of selective therapeutics. This study examines the allosteric inhibition of PTP1B by amorphadiene (AD) and α-bisabolene(AB), terpenoid hydrocarbons that are unusually selective inhibitors. Molecular dynamics (MD) simulations carried out in this study suggest that both AD and AB can stably sample multiple neighboring sites on the allosterically influential C-terminus of the catalytic domain. Intriguingly, the binding mode of AD and AB differs from that of the most well-studied allosteric inhibitor of PTP1B, BBR. Indeed, biophysical measurements and MD simulations indicate that AD and BBR can bind simultaneously. Upon binding, both inhibitors destabilize the α7 helix and disrupt hydrogen bonds that facilitate closure of the catalytically essential WPD loop. The α7 helix is destabilized through the significant disruption of localized interactions at the α3-α7 helix interface for AD, AB, and BBR. Additionally, our findings suggest that the selectivity of AD and AB to PTP1B over TCPTP is due to relatively small differences in the composition of the α7 which eliminate the hydrophobic pocket in which the ligands bind to PTP1B. These findings indicate that AD and AB may be promising scaffolds for building allosteric inhibitors of PTP1B and illustrate more broadly how unfunctionalized terpenoids can engage in specific interactions with protein surfaces.

Allosteric Inhibition of PTP1B by a Nonpolar Terpenoid.

Protein tyrosine phosphatases (PTPs) are promising drug targets for treating a wide range of diseases such as diabetes, cancer, and neurological disorders, but their conserved active sites have complicated the design of selective therapeutics. This study examines the allosteric inhibition of PTP1B by amorphadiene (AD), a terpenoid hydrocarbon that is an unusually selective inhibitor. Molecular dynamics (MD) simulations carried out in this study suggest that AD can stably sample multiple neighboring sites on the allosterically influential C-terminus of the catalytic domain. Binding to these sites requires a disordered α7 helix, which stabilizes the PTP1B-AD complex and may contribute to the selectivity of AD for PTP1B over TCPTP. Intriguingly, the binding mode of AD differs from that of the most well-studied allosteric inhibitor of PTP1B. Indeed, biophysical measurements and MD simulations indicate that the two molecules can bind simultaneously. Upon binding, both inhibitors destabilize the α7 helix by disrupting interactions at the α3-α7 interface and prevent the formation of hydrogen bonds that facilitate closure of the catalytically essential WPD loop. These findings indicate that AD is a promising scaffold for building allosteric inhibitors of PTP1B and illustrate, more broadly, how unfunctionalized terpenoids can engage in specific interactions with protein surfaces.

Miocene organic-rich layers of the Saouef Formation (Oriental Tunisia); insights into temporal and spatial variability of environmental conditions during deposition

Miocene organic-rich sediments (coal and carbonaceous clays) from the La Falaise section of the Saouef Formation have been investigated by organic petrographic, palynofacies and organic geochemical approaches. The results are compared with data obtained during a previous study of the nearby Saouef section. The sedimentary succession is built up by repetitive sedimentary sequences (i.e., parasequences) deposited during progradation and retrogradation, respectively. The coal, or carbonaceous layers, developed during the establishment of clay-dominated sedimentation.The organic-rich layers within the samples, containing high amounts of mineral matter, are dark brown, with a stratified texture and are classified as humic coal. Microscopically, the huminite group dominates the maceral composition of the carbonaceous clays and lignite (av. 75% mmf). The variable degrees of the tissue preservation index (TPI) and highly fluctuating vegetation index (VI) values provide evidence for different contributions of vascular plants vs. herbaceous vegetation and macrophytes, to peat formation. Higher contributions of macrophytes (e.g., reed grasses) to peat accumulation at La Falaise are concluded, based on n-alkane distributions. High mineral matter contents and changing gelification index (GI), and ground water index (GWI) values, found in both sections, provide evidence for rheotrophic hydrogeological conditions, and peat formation within wet forest swamp to inundated marsh environment. The low sulphur contents attest to peat formation within a freshwater environment and the relative proportions of ββ to (ββ + αβ)-C31 hopanes argue for slightly acidic conditions. In comparison to the results of the Saouef section (average pH of 5.6), a lower pH (4.2) is revealed from the average hopane isomerization ratio of the La Falaise samples.The palynofacies investigation of the La Falaise deposits indicates the dominance of phytoclasts over amorphous organic matter (AOM) in most of the samples and suggests good preservation of the higher plant remains. In contrast, increased degradation of plant tissues under oxygen-deficient conditions is concluded from the enhanced proportions of AOM found in several of the previously investigated Saouef samples. The molecular analysis of hydrocarbons from all the samples indicated the dominance of n-alkanes and hopanoids. The obtained pristane/phytane ratios argue for sub-oxic conditions during peatification at La Falaise, whereas data from our previous study of the Saouef section provided evidence for a reducing environment. Terpenoid hydrocarbon compositions reveal highly variable contributions of conifers and angiosperms to peat formation, consistent with previous findings at the Saouef sampling site. The presence of polycyclic aromatic hydrocarbons (PAHs), as well as fusinite, provides evidence for mire or forest fires.The comparison of the results from lignite of both sections of the Saouef Formation indicate comparable, highly variable conditions during peat accumulation, probably governed by eustatic sea level changes. The peatlands most likely developed due to the establishment of flood basins situated between alluvial ridges. The obtained regional differences are suggested to reflect slightly different hydrological conditions and associated vegetation cover in the peatlands.

Phytocontent and Biological Effects of Olea europaea L. : A Review

Olive tree (Olea europaea L., Oleaceae) leaves have been widely used in traditional herbal medicine to prevent and treat various diseases especially in Mediterranean countries. They contain several potentially bioactive com-pounds that may have hypoglycemic and hypolipidemic properties. Olea europaea is commonly known as Zaitoon. The ancient Egyptians, Greeks, Romans and other Mediterranean nations cultivated olives for its edible fruits and to obtain oil from them. Leaves of the tree became important when olive leaf extract was reported to be potent in reducing incidence of degenerative diseases, particularly coronary heart disease (CHD) and cancers of the breast, skin, and colon. Olive leaves have the highest antioxidant power among the different parts of the olive tree. While in olive fruit, phenols (e.g.,TYR) and terpenoid hydrocarbon (Squalene) are the major components found in the oil. Much research has been carried out on the medical applications of olive. The choice of the plant was based on the good previous biological study of Olea europaea. Interest to choose this plant, may have been due to the widespread use of olive species medicinally, food industry and cosmetics.

Application of two-dimensional gas chromatography/time-of-flight mass spectrometry (GC × GC-TOFMS) for the thorough study of hydrocarbons in lignite pyrolysates

Two-dimensional gas chromatography/time-of-flight mass spectrometry (GC × GC-TOFMS) was applied to analyze the complex molecular compositions of hydrocarbons in the four tars produced from the slow pyrolysis of a low-maturity lignite without and with the post cracking of volatile matter. The liquid (EL-tar) extracted from the lignite with the mixture solvent of acetone and dichloromethane was analyzed by way of contrast. Up to 866 hydrocarbons were identified in a lignite pyrolysis tar, in contrast to only 64 hydrocarbons found in EL-tar. It was revealed that the lignite was enriched with fatty acids and isoprene moieties, most of which were tightly incorporated in the macrostructures. The pyrolysis with the post cracking at 500 °C allowed the lignite to liberate a wide variety of biomarker hydrocarbons, which comprised a significant part of open-chain and cyclic aliphatic hydrocarbons. GC × GC-TOFMS was capable of distinguishing between various isomers of terpenoid hydrocarbons and a large array of homologues of cyclopentane/cyclopentene and cyclohexane/cyclohexene. The work has discussed the possible origins of typical biomarker hydrocarbons for the lignite studied, and also provided an insight on the variations of hydrocarbon compounds with the volatile matter cracking at different temperatures.

Chemical Constituents and Biological Activities of Genus Nepeta (Lamiaceae) from India and Western Himalaya: A Review

A literature-based survey of Nepeta species essential oil composition found in India and the Western Himalayan region was carried out. A concise review of the scientific literature pertaining to constituents of Nepeta essential oils and volatile fractions is presented in this mini review article. Labiatae (Mint) family (Genus Nepeta) remains quite important. Essential oils extracted from various parts of species of above mentioned genus have been a vital source of terpenoid and oxygenated terpenoid hydrocarbons especially sesquiterpene hydrocarbons and their oxygenated derivatives. These compounds have been known for their inherent biological activities viz. sedative, diaphoretic, febrifuge, expectorant, diuretic, stomach tonic, antispasmodic, antipyretics, antiviral, anti-inflammatory, antimicrobial, fungicidal, insecticidal, insect repellent and antidote against snakes and scorpion bites etc.

Biogenic and thermogenic terpenoid hydrocarbons as potential geochemical tools for the study of sedimentary organic matter in subtropical mangrove swamps

Terpenoid hydrocarbons are ubiquitous in the marine environment and may be linked to natural synthetic activities after the original carbon skeleton of the biological precursor is retained. The terpenoid profile in pristine environments should have a biogenic signature. However, the widespread use of petroleum-derived products contributes to the inventory of hydrocarbons found in recent sediments, including the introduction of cyclic hydrocarbons with a thermogenic signature. Terpenoid hydrocarbons were examined from the mangrove sediments of the Paranaguá Estuarine System (PES), which is a subtropical system in the South Atlantic. Intensive tourism has affected the PES, and it is at high risk of contamination due to extensive urban development and harbour activity. The biogenic compounds (BIO) in the PES were predominantly composed of unsaturated derivatives from higher plants (oleanoids, lupanoids, ursanoids and taraxeroids) with a des-A configuration and bacterial hopanoids. Thermogenic compounds (TRM) were distributed throughout the PES, and the sum of thermogenic and biogenic compounds exhibited a similar distribution, with significant correlations between these compounds. To better assess anthropogenic sources of hydrocarbons in mangrove, a ratio of TRM/BIO was proposed. Ratios higher than 1.0 were found near Paranaguá port and in the Paranaguá bay area. An important touristic destination, Mel Island, also exhibited ratios higher than 1.0 in two locations. The proposed terpenoids ratio accurately assessed the low-level chronic inputs of anthropogenic hydrocarbons in the study area. This innovative approach may be applied to areas with high biogenic inputs of organic matter, where chronic low-level hydrocarbon contributions are not evident using n-alkanes and polycyclic aromatic hydrocarbons.

B:Review article on chemical constituents and biological activity of Olea europaea.

The olive tree is a member of the Oleaceae family (Olea europaea). Olea europaea is commonly known as Zaitoon. The ancient Egyptians, Greeks, Romans and other Mediterranean nations cultivated olives for its edible fruits and to obtain oil from them. Leaves of the tree became important when olive leaf extract was reported to be potent in reducing incidence of degenerative diseases, particularly coronary heart disease (CHD) and cancers of the breast, skin, and colon. Olive leaves have the highest antioxidant power among the different parts of the olive tree. While in olive fruit, phenols (e.g. TYR) and terpenoid hydrocarbon (squalene) are the major components found in the oil. Much research has been carried out on the medical applications of olive. The choice of the plant was based on the good previous biological study of Olea europaea. Interest to choose this plant, may have been due to the widespread use of olive species medicinally, food industry and cosmetics.

Endophytic Pseudomonas induces metabolic flux changes that enhance medicinal sesquiterpenoid accumulation in Atractylodes lancea

The bacterial endophyte Pseudomonas fluorescens ALEB7B significantly enhances photosynthate accumulations in Atractylodes lancea. These carbohydrates are preferentially used by the host plant to synthesize secondary metabolites, rather than to increase plant biomass accumulation. Mechanisms underlying the allocation of endophyte–increased carbohydrate in different plant metabolic processes are largely unknown. We have studied how P. fluorescens ALEB7B enhances photosynthate accumulation and how bacterial elicitors regulate metabolic flux and increase medicinal sesquiterpenoid formation in A. lancea using the sterile tissue culture plantlets. P. fluorescens ALEB7B enhances plant photosynthate accumulation by synthesizing and secreting indole–3–acetic acid, which has been demonstrated using high–performance liquid chromatography analysis. The increased endogenous indole–3–acetic acid promotes plant root development and then assimilation. Increased carbohydrates provide the material basis for the formations of terpenoid hydrocarbon scaffolds, which has been proved using gas chromatography analysis. Further, protein and polysaccharide elicitors secreted by P. fluorescens ALEB7B have been separated and purified from the bacterial fermentation broth, which have been applied to A. lancea plantlets. Both elicitors can stimulate the conversions of terpenoid hydrocarbon scaffolds to oxygenous sesquiterpenoids, the active medicinal ingredients in A. lancea, by triggering the oxidative burst in planta. Moreover, this study separates an ABC transporter substrate–binding protein from protein elicitors secreted by P. fluorescens ALEB7B with an ÄKTA Prime Plus Purifier System and firstly shows that this protein is essential to induce oxygenous sesquiterpenoid accumulation in A. lancea. This study provides new perspectives for mechanisms of medicinal oxygenous terpenoid synthesis, which has important reference values to the cultivation of medicinal plants that have terpenoids as their active ingredients, such as Artemisia annua and Taxus chinensis.

Extraction of squalene from camellia oil by silver ion complexation

Abstract Separation of squalene, a type of terpenoid hydrocarbons with important biological properties, from camellia oil by silver ion complexation was studied. We showed that the UV–visible absorption wavelength of squalene in AgNO3-methanol solution was obviously red-shifted, and the infra-red vibration wavelength of C C bond slightly decreased, indicating that complexation between squalene and Ag+ took place. The distributions of squalene in AgNO3 methanol solution/petroleum ether under different conditions were further investigated. We found that the fraction of squalene in AgNO3-methanol phase was enhanced with increased percentage of methanol and AgNO3 concentration and decreased extraction temperature. The distribution coefficient of squalene was up to 7.87 under optimum extraction conditions with 70% methanol (v/v), 0.6 mol/L AgNO3, reaction time of 12 h, and at the temperature of 0 °C. Furthermore, under the optimum conditions, extraction of squalene from the unsaponifiable portion of camellia oil exhibited high selectivity with a raffinate rate and a back-extraction rate of 73.9% and 72.5%, respectively. The purity of extracted squalene was 37.8%, 108 times more concentrated than that in the starting material.

Coal characteristics and biomarker investigations of Dombayova coals of Late Miocene–Pliocene age (Afyonkarahisar-Turkey)

In Dombayova graben (Dinar-Afyonkarahisar, western Turkey) a 203-m-thick coal-bearing zone of Late Miocene to Pliocene age was recently drilled. The zone hosts several coal beds with a total thickness of 46m. Coal samples from the Dombayova field were studied by means of standard proximate, ultimate, petrological analyses, micro-FTIR spectroscopy and Rock-Eval pyrolysis, and organic geochemical analyses.Coal proximate analyses and the presence of carbonate minerals and fossil shell fragments point to alkaline surface waters of changing pH-values due to fluctuations of the water level in the paleomire and/or Ca-rich water influx. Low sulfur contents argue for sulfate-limitation of bacterial sulfate reduction. Petrographic observations reveal that the coal is dominantly composed of weakly altered wood fragments and roots. The mean random reflectance values of ulminite (0.33%Ro) indicate lignite rank of the coal.The micro-FTIR data of macerals of huminite group indicate higher contributions of aliphatic hydrogen in textinite, compared to more aromatic levigelinite. The semi-quantitative differences in the ratios of selected functional groups suggest that aromaticity and the extent of oxidation are higher in levigelinite. Aliphatic chains are longest in textinite and ulminite, and shortest in texto-ulminite and levigelinite. We interpret this difference to point to a different origin of levigelinite, probably from colloidal humic solutions that were gelified during diagenesis.The concentrations of n-alkanes and their distribution patterns provide evidence for higher terrestrial plants as the dominant source of organic matter. Decreasing pristane/phytane ratios with depth are interpreted to reflect more reducing conditions during peat formation due to higher (ground)water level. The absence of diasterenes is most probably caused by low clay mineral contents and is consistent with the presence of alkaline waters in the paleomire. The presence of terpenoid hydrocarbons in the lignite indicates a major contribution of angiosperms to peat formation. The positive relationship between the concentrations of perylene and lupane-type triterpenoids suggests an increasing abundances of wood-degrading fungi in the peat-forming vegetation characterized by a high density of Betulaceae.

Defensive effect of soldier-specific secretion by Reticulitermes speratus (Isoptera: Rhinotermitidae) on the facultative termitophagous ponerine ant Brachyponera chinensis (Hymenoptera: Ponerinae)

Soldiers of the Japanese subterranean termite Reticulitermes speratus Kolbe possess the caste-specific terpenoid hydrocarbon β-selinene in the frontal gland. They secrete the compound as an alarm pheromone when facing danger. Furthermore, while dispersing the nestmate workers it simultaneously recruits the nestmate soldiers and enhances their aggression level. This study aims to confirm that the alarm pheromone might have defensive effects against facultative termite-hunting (termitophagous) ants, such as the Asian needle ant Brachyponera chinensis Emery. According to our behavioral bioassay, which provided fresh termite bodies, the ponerine ants used in the study immediately fed on the termite workers but avoided feeding on the soldiers. However, they avoided feeding on the workers when presented with the soldiers. Furthermore, extracted chemicals from the termite soldiers showed similar effects on the foraging activity of the ponerine ants, while those from the workers had no such effect. Soldier chemicals also clearly repelled the ponerine ants when they were treated at the entrance of a glass tube in which the worker bodies had been placed. It is most likely, therefore, that the termite soldier secretions serve as a chemical defense against the termitophagous ponerine ants.

Spatial and temporal variability in vegetation and coal facies as reflected by organic petrological and geochemical data in the Middle Miocene Çayirhan coal field (Turkey)

Coal channel samples of Middle Miocene age are collected from the first (Tv) and second (Tb) seams from underground mines and from exploration boreholes within the Çayirhan coal field in the Beypazari Basin (Turkey). They are investigated in order to detect spatial and temporal changes in maceral and molecular composition of coal and to relate them to changes in vegetation and depositional environment.The mean random reflectance values of ulminite (0.40% Rr) indicate a lignite to subbituminous-C coal in rank. Maceral composition and biomarker ratios of the samples from both seams at the Çayirhan deposit argue for coal formation in a limno-telmatic environment under dysoxic to anoxic conditions. Alkaline surface waters of changing pH-values and a high and unstable water level at the palaeomire are evidenced by moderate to high gelification index (GI) and ground water influence (GWI) values, as well as high sulphur contents. Variations in tissue preservation index (TPI) and vegetation index (VI) values point to minor variations in the palaeovegetation during peat formation. Herbaceous plants dominated in both Tb and Tv palaeomires (low TPI and VI values), whereas in the surroundings arboreal vegetation were predominant.The decreasing trends in pristane/phytane ratios and carbon preference index (CPI) values towards the NE are suggested to reflect oxygen deficient conditions during peat formation due to a higher (ground)water level in this part of the basin. The occurrence of C29 diasterenes in low abundances provides evidence for periods of lower pH in the mire. The borehole samples from the NE show slightly enhanced contributions of n-alkanes from algal and microbial sources. The terpenoid hydrocarbons present in the lignite argue for a major contribution of angiosperms to peat formation and slightly enhanced proportions of gymnosperms in the Tv palaeomire in the NE. Based on the high concentrations of lupane-type triterpenoids in the coal seams from the underground mine, a higher density of Betulaceae in the arboreal vegetation in the SW is indicated.

New and less common sterane and terpane hydrocarbons in oils from the Nepa-Botuoba anteclise (Eastern Siberia)

A number of previously unknown or less common sterane and terpane hydrocarbons in crude oils of the Nepa-Botuoba anteclise (NBA) have been found by gas chromatography-mass spectrometry. The former include pregnane structures demethylated at C10 (principal fragment ion at m/z 203) and C26-C29 tricyclic secosteranes (m/z 219). By the m/z 123 mass chromatogram, a number of bicyclic sesquiterpanes with the drimane or tricyclic norisopimarane structure have been identified for the first time in NBA oils. The origin of these terpenoid hydrocarbons is usually associated with the involvement of higher plant debris in sedimentary source rocks. Their presence in Neoproterozoic oils suggests other precursors of these hydrocarbons. Like 10-desmethylpregnanes, 12- and 13-monomethylalkanes, which are unique biomarkers for Neoproterozoic oils of the Siberian platform, have been found in Vendian and Lower Cambrian oils of the Arabian platform and provide evidence for a close similarity between biotas that existed in these ancient basins.

Organofacies and paleoenvironment of the Oligocene Maikop series of Angeharan (eastern Azerbaijan)

The Maikop Formation, deposited in eastern Azerbaijan during Oligocene and Early Miocene times, contains prolific source rocks with primarily Type II organic matter. Paleontological analyses of dinoflagellate cysts revealed a Lower to Upper Oligocene age for the investigated succession near Angeharan. A major contribution of aquatic organisms (diatoms, green algae, dinoflagellates, chrysophyte algae) and minor inputs from macrophytes and land plants to organic matter accumulation is indicated by n-alkane distribution patterns, composition of steroids and δ13C of hydrocarbon biomarkers. Microbial communities included heterotrophic bacteria, cyanobacteria, chemoautotrophic bacteria, as well as green sulfur bacteria. Higher inputs of terrigenous organic matter occurred during deposition of the Upper Oligocene units of the Maikop Formation from Angeharan mountains. The terpenoid hydrocarbon composition argues for angiosperm dominated vegetation in the Shamakhy–Gobustan area.High primary bioproductivity resulted in a stratified water column and the accumulation of organic matter rich sediments in the Lower Oligocene units of the Maikop Formation. Organic carbon accumulation during this period occurred in a permanently (salinity-) stratified, mesohaline environment with free H2S in the water column. This is indicated by low pristane/phytane ratios of all sediments (varying from 0.37–0.69), lower methylated-(trimethyltridecyl)chromans ratio in the lower units and their higher contents of aryl isoprenoids and highly branched isoprenoid thiophenes. Subsequently, the depositional environment changed to normal marine conditions with oxygen deficient bottom water. The retreat of the chemocline towards the sediment–water interface and enhanced oxic respiration of OM during deposition of the Upper Oligocene Maikop sediments is proposed.Parallel depth trends in δ13C of total OM, n-alkanes, isoprenoids and steranes argue for changes in the regional carbon cycle, associated with the changing environmental conditions. Increased remineralisation of OM in a more oxygenated water column is suggested to result in low TOC and hydrocarbon contents, as well as 15N enriched total nitrogen of the Upper Oligocene units.

New geochemical data on fossil wood from the Albian of the Dolomites (Southern Alps, Italy)

Abstract Information is provided about organic-matter bearing sediments and fossil drift-wood from the Puez area (Col de Puez, Southern Alps) near Wolkenstein (S. Tyrol, Italy). The locality is located on the Trento Plateau which represents a submarine high during the Lower Cretaceous. Its terpenoid hydrocarbon composition indicates that the wood fragment derived from a conifer belonging to the family Podocarpaceae or Araucariaceae. Intense degradation of OM argues for lengthier drifting. Long-term drifting is also indicated by the infestation of the bivalve Teredo (“shipworm”). The finding of a fossil tree trunk sheds some light on the early Lower Cretaceous tectonic history of the Trento Plateau and the Dolomites.

Facies evolution and stratigraphic correlation in the early Oligocene Tard Clay of Hungary as revealed by maceral, biomarker and stable isotope composition

Hydrocarbon source rocks (i.e. Tard Clay Formation), containing type-II organic matter, were deposited in the Hungarian Paleogene Basin during Lower Oligocene. A major contribution of aquatic organisms (green algae, dinoflagellates, Chrysophyte algae) and minor inputs from macrophytes and land plants to organic matter accumulation is indicated by n-alkane distribution patterns, composition of steroids, and δ13C of hydrocarbon biomarkers. Microbial communities included heterotrophic bacteria, cyanobacteria, chemoautotrophic bacteria, as well as green sulphur bacteria. The presence of methanotrophic bacteria is indicated by 13C-depleted hop-17(21)-ene. Higher inputs of terrestrial organic matter occurred during deposition of the lower and uppermost units of the Tard Clay Formation. The terpenoid hydrocarbon composition argues for angiosperm-dominated vegetation in the area of the Hungarian Paleogene Basin. Diterpenoid hydrocarbons, derived from the resins of conifers, are about 2–3‰ enriched in 13C compared to the angiosperm biomarkers.Environmental conditions changed from marine to brackish, accompanied by oxygen-depletion in the lower parts of the water column. Organic carbon accumulation during this period was a consequence of stagnant bottom water conditions in the Hungarian Paleogene Basin due to salinity stratification. This is indicated by low pristane/phytane ratios (varying from 0.27 to 1.44), enhanced ratios of dimethylated versus trimethylated MTTCs (0.14–0.59), and the presence of aryl isoprenoids (from 0.4 to 14.1 μg/g TOC). A major marine incursion is evidenced by stable isotope ratios of organic matter and carbonates. In the uppermost member of the Tard Clay, a transition from brackish towards normal marine conditions is proposed.Up to 3 anoxic cycles are recognized in the drill core sections, separated by minima in pristane/phytane ratios and maxima in the depth trends of di-/tri-methylated MTTCs and aryl isoprenoid concentrations. In combination with the position of maxima of δ13C of carbonate and organic matter and an abrupt decrease in perylene concentrations, the cycles can be used for intra-formational correlation of the Tard Clay.

Terpenoid synthase structures: a so far incomplete view of complex catalysis.

The complexity of terpenoid natural products has drawn significant interest, particularly since their common (poly)isoprenyl origins were discovered. Notably, much of this complexity is derived from the highly variable cyclized and/or rearranged nature of the observed hydrocarbon skeletal structures. Indeed, at least in some cases it is difficult to immediately recognize their derivation from poly-isoprenyl precursors. Nevertheless, these diverse structures are formed by sequential elongation to acyclic precursors, most often with subsequent cyclization and/or rearrangement. Strikingly, the reactions used to assemble and diversify terpenoid backbones share a common carbocationic driven mechanism, although the means by which the initial carbocation is generated does vary. High-resolution crystal structures have been obtained for at least representative examples from each of the various types of enzymes involved in producing terpenoid hydrocarbon backbones. However, while this has certainly led to some insights into the enzymatic structure-function relationships underlying the elongation and simpler cyclization reactions, our understanding of the more complex cyclization and/or rearrangement reactions remains limited. Accordingly, selected examples are discussed here to demonstrate our current understanding, its limits, and potential ways forward.

Extracellular terpenoid hydrocarbon extraction and quantitation from the green microalgae Botryococcus braunii var. Showa

Mechanical fractionation and aqueous or aqueous/organic two-phase partition approaches were applied for extraction and separation of extracellular terpenoid hydrocarbons from Botryococcus braunii var. Showa. A direct spectrophotometric method was devised for the quantitation of botryococcene and associated carotenoid hydrocarbons extracted by this method. Separation of extracellular botryococcene hydrocarbons from the Botryococcus was achieved upon vortexing of the micro-colonies with glass beads, either in water followed by buoyant density equilibrium to separate hydrocarbons from biomass, or in the presence of heptane as a solvent, followed by aqueous/organic two-phase separation of the heptane-solubilized hydrocarbons (upper phase) from the biomass (lower aqueous phase). Spectral analysis of the upper heptane phase revealed the presence of two distinct compounds, one absorbing in the UV-C, attributed to botryococcene(s), the other in the blue region of the spectrum, attributed to a carotenoid. Specific extinction coefficients were developed for the absorbance of triterpenes at 190 nm (ε = 90 ± 5 mM −1 cm −1) and carotenoids at 450 nm (ε = 165 ± 5 mM −1 cm −1) in heptane. This enabled application of a direct spectrophotometric method for the quantitation of water- or heptane-extractable botryococcenes and carotenoids. B. braunii var. Showa constitutively accumulates ∼30% of the dry biomass as extractable (extracellular) botryococcenes, and ∼0.2% of the dry biomass in the form of a carotenoid. It was further demonstrated that heat-treatment of the Botryococcus biomass substantially accelerates the rate and yield of the extraction process. Advances in this work serve as foundation for a cyclic Botryococcus growth, non-toxic extraction of extracellular hydrocarbons, and return of the hydrocarbon-depleted biomass to growth conditions for further product generation.