Family Of Compounds Research Articles

Comparative phytochemical profile and biological activity of three Terminalia species as alternative antimicrobial therapies

Ethnopharmacological relevanceMedicinal plants can help combat antibiotic resistance by providing novel, active molecules. Three plant species of the Terminalia genus are widely used in traditional medicine in the Mouhoun region for the treatment of cutaneous and respiratory diseases. Therefore, it is important to determine the ethnopharmacological potential of bark extracts from the trunks of these three Terminalia species. Aim of the studyThis study compared the phytochemical and biological activities of extracts from three Terminalia species to determine their ethnopharmacology. Materials and methodsThe medicinal properties of the extracts were assessed based on their ability to inhibit the growth of the following microorganisms: Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Candida albicans, Candida krusei, Candida glabrata, and Candida tropicalis. The significant interest in these medicinal plants among the local communities were elucidated by their antioxidant properties and phytochemical composition, along with the detection key bioactive compounds. Major phytochemical groups and phenolic compounds were determined using high-performance liquid chromatography with a diode array detector. These phytochemical findings were validated by evaluating the antioxidant capacity of the extracts using DPPH, FRAP, and ABTS assays. ResultsHydroethanolic, ethanolic, and hexane extracts from the bark of three Terminalia species inhibited the growth of both bacteria and fungi, as evidenced by their minimum inhibitory concentrations (MICs).The findings showed that Terminalia species were most effective against various tested bacteria and fungi, with MICs ranging from 0.1 to 6.25 mg/mL. Terminalia avicennioides, Terminalia macroptera, and Terminalia laxiflora extracts demonstrated 50 % inhibition of DPPH at concentrations ranging from 0.04 to 0.6 mg/mL. Phytochemical analysis revealed the presence of several families of chemical compounds, such as total phenolics and flavonoids. Phenolic compounds identified by HPLC in ethanolic extracts of T. avicennioides, such as isorhamnetin, quercetin, and ferulic acid, are recognised for their antimicrobial and antioxidant properties. ConclusionThese findings establish an ethnobotany for these three Terminalia species, with their chromatographic characteristics facilitating the identification of key molecules of interest. The ethanolic extract of T. avicennioides can be used in phytomedicinal formulations against bacterial (P. aeruginosa and S. aureus) and fungal (C. albicans and C. glabrata) infections, both of which are recurrently recorded in certain skin and respiratory tract diseases.

Phytochemical Screening and Evaluation of the Larvicidal Activities of Three Organic Extracts Derived from the Leaves of Cassia sieberiana to Control Anopheles gambiae, the Vector of Malaria

Senegal is one of the African countries where malaria remains a major public health problem. In the fight against mosquitoes, the vector of this disease, the significant accumulation of active ingredients in ecosystems treated with synthetic insecticides poses an increased environmental problem linked to the very high persistence time.
 The aim of this study is to propose an alternative method of vector control using natural products of plant origin.
 Three organic extracts (cyclohexanic, chloroformic and methanolic) from the leaves of Cassia sieberiana were tested by contact on mosquito larvae of the genus Anopheles gambiae. Four doses of each extract were prepared and monitored over 48 hours.
 The families of chemical compounds in the various organic extracts are identified using coloring and precipitation tests.
 The results obtained show a variable sensitivity of the larvae, reflected in low to very high mortality rates when moving from one extract to another. The chloroform extract was the most effective, with a mortality rate of just under 90% after 48 hours' exposure.
 Phytochemical screening reveals that this plant is rich in secondary metabolites such as polyphenols and alkaloids, which could explain its larvicidal activity.

Regarding the Montreal Protocol communication after the Kigali Amendment

Abstract The Kigali Amendment introduced a new family of chemical compounds, which do not contribute to stratospheric ozone depletion but present a high global warming potential, under the watch of the Montreal Protocol in 2016. Earlier this year, a press note from the World Meteorological Organization entitled “Ozone layer recovery is on track, helping avoid global warming by 0.5°C” caught our attention because of the wrong conclusions that can be potentially drawn by laypersons due to an apparent linkage of ozone depletion and global warming problems. Public communication of the Montreal Protocol since the Kigali Amendment should be more careful than ever to avoid lessening the social perception of the threat of climate change, particularly considering that society already has a distorted representation of these problems, assuming causal relations between ozone depletion and climate change, that could lead to unfounded optimism towards the climate crisis.

2-Quinolone-Based Derivatives as Antibacterial Agents: A Review

Abstract: The chemistry of 2-quinolones derivatives has received more attention in organic chemistry and medicinal chemistry. Moreover, several advancements in the application of this family of compounds are considered to be of great utility. In recent years, a variety of new, effective, and novel synthetic approaches (including green chemistry, catalyzed and microwave-assisted synthesis) have been discovered and developed for the designing of safe and non-toxic 2-quinolone-based scaffolds to investigate their antibacterial activities. This review summarizes the results of the literature on the synthesis strategies of 2-quinolones derivatives and their reactivity, as well as their antibacterial evaluations against different bacteria strains.

Oxysterols as Reliable Markers of Quality and Safety in Cholesterol Containing Food Ingredients and Products.

Cholesterol is a lipid of high nutritional value that easily undergoes oxidation through enzymatic and non-enzymatic pathways, leading to a wide variety of cholesterol oxidation products (COPs), more commonly named oxysterols. The major oxysterols found in animal products are 7α-hydroxycholesterol, 7β-hydroxycholesterol, 7-ketocholesterol, 5α,6α-epoxycholesterol, 5β,6β-epoxycholesterol, cholestan-3β,5α,6β-triol, and 25-hydroxycholesterol. They are all produced by cholesterol autoxidation, thus belonging to the non-enzymatic oxysterol subfamily, even if 7α-hydroxycholesterol and 25-hydroxycholesterol are, in part, generated enzymatically as well. A further oxysterol of the full enzymatic origin has recently been detected for the first time in milk of both human and bovine origin, namely 27-hydroxycholesterol. Nowadays, gas or liquid chromatography combined to mass spectrometry allows to measure all these oxysterols accurately in raw and in industrially processed food. While non-enzymatic oxysterols often exhibited in vitro relevant cytotoxicity, above all 7β-hydroxycholesterol and 7-ketocholesterol, 27-hydroxycholesterol, as well as 25-hydroxycholesterol, shows a broad spectrum in vitro antiviral activity, inhibition of SARS-CoV-2 included, and might contribute to innate immunity. Quantification of oxysterols was afforded over the years, almost always focused on a few family's compounds. More comprehensive COPs measurements, also including oxysterols of enzymatic origin, are, nowadays, available, which better display the many advantages of systematically adopting this family of compounds as markers of quality, safety, and nutritional value in the selection of ingredients in processing and storage. Regarding foodstuff shelf life, COPs monitoring already provided useful hints for more suitable packaging. The identification of a subset of non-enzymatic and enzymatic oxysterols to be routinely assessed in food production and storage is proposed.

A novel structural type of conformationally fixed, mixed phosphonium-iodonium ylides based on phenoxaphosphinine

A synthetic approach to a novel type of phosphonium and mixed phosphonium-iodonium ylides containing a conformationally fixed phosphonium fragment is developed. New representatives of these families of chemical compounds based on cyclic phenoxaphosphinine were synthesized. One compound was structurally characterized by single-crystal X-ray diffraction. Based on the 1H NMR data, one can state that phosphonium ylide exists in solution in the form of two geometric isomers even at room temperature. This is indicative of pronounced double-bond character of the bond between the ylide carbon atom and the stabilizing carbomethoxy group.

Biocatalytic Preparation of Chloroindanol Derivatives. Antifungal Activity and Detoxification by the Phytopathogenic Fungus Botrytis cinerea.

Indanols are a family of chemical compounds that have been widely studied due to their broad range of biological activity. They are also important intermediates used as synthetic precursors to other products with important applications in pharmacology. Enantiomerically pure chloroindanol derivatives exhibiting antifungal activity against the phytopathogenic fungus Botrytis cinerea were prepared using biocatalytic methods. As a result of the biotransformation of racemic 6-chloroindanol (1) and 5-chloroindanol (2) by the fungus B. cinerea, the compounds anti-(+)-6-chloroindan-1,2-diol (anti-(+)-7), anti-(+)-5-chloroindan-1,3-diol (anti-(+)-8), syn-(+)-5-chloroindan-1,3-diol (syn-(+)-8), syn-(-)-5-chloroindan-1,3-diol (syn-(-)-8), and anti-(+)-5-chloroindan-1,2-diol (anti-(+)-9) were isolated for the first time. These products were characterized by spectroscopic techniques and their enantiomeric excesses studied by chromatographic techniques. The results obtained in the biotransformation seem to suggest that the fungus B. cinerea uses oxidation reactions as a detoxification mechanism.

OH reactivity from the emissions of different tree species: investigating the missing reactivity in a boreal forest

Abstract. In forested area, a large fraction of total hydroxyl radical (OH) reactivity remains unaccounted for. Very few studies have looked at the variations in total OH reactivity from biogenic emissions. In the present study, we investigate the total OH reactivity from three common boreal tree species (Scots pine, Norway spruce, and downy birch) by comparing it with the calculated reactivity from the chemically identified emissions. Total OH reactivity was measured using the comparative reactivity method (CRM), and the chemical composition of the emissions was quantified with two gas chromatographs coupled with mass spectrometers (GC–MSs). Dynamic branch enclosures were used, and emissions from one branch of a tree at the time were measured by periodically rotating between them. Results show that birch had the highest values of total OH reactivity of the emissions (TOHRE), while pine had the lowest. The main drivers for the known reactivity of pine and spruce were monoterpenes and sesquiterpenes. Birch emissions were dominated by sesquiterpenes, but monoterpenes and green leaf volatiles (GLVs) were present as well. However, calculated reactivity values remained low, leading to the highest missing fraction of reactivity (>96 %), while pine and spruce had similar missing reactivity fractions between 56 % and 82 % (higher in the spring and decreasing as the summer proceeded). The high average values were driven by low-reactivity periods, and the fraction of missing reactivity got smaller for pine and spruce when the TOHRE values increased. Important exceptions were identified for periods when the emission profiles changed from terpenes to GLVs, a family of compounds containing a backbone of six carbon atoms with various functionalities (e.g. alcohols, aldehydes, esters) that indicate that the plant is suffering from stress. Then, very high TOHRE values were measured, and the missing fraction remained high. This study found a different trend in the missing OHRE fraction of the Norway spruce from spring to autumn compared to one previous study (Nölscher et al., 2013), which indicates that additional studies are required to fully understand the complexity of biogenic reactive emissions. Future studies of boreal trees in situ should be conducted to confirm the findings presented.

Phytochemical Characterization and Antimicrobial Potentialities of Two Medicinal plants, Chamaemelum nobile (L.) All and Matricaria chamomilla (L.)

Objective of the study was to evaluate the phytochemical characterization and antimicrobial effectiveness of two medicinal plants belonging to the Asteraceae family, growing spontaneously in the region of Boumerdes (Northeast Algeria) namely Chamaemelum nobile (L.) All and Matricaria chamomilla (L.). For this purpose, it was proposed to optimize the extraction parameters of the phenolic compounds of the aerial parts of two chosen species. The first step was intended to study the effect of different extraction solvents (water, chloroform and methanol) on the contents of different metabolites of these species. The qualitative screening of the aerial part of chamomile allowed to highlight different families of chemical compounds namely; flavonoids, total tannins, condensed tannins, gallic tannins, alkaloids, saponosides, glucosides, mucilages and total absence of anthocyanins and starch. This was confirmed by a quantitative analysis based on the determination of total phenolic compounds by spectrophotometry in the presence of the Folin-Ciocalteu reagent determined from the calibration curve of gallic acid. The results showed that the water was the best extraction solvent. At the second stage of our study, antimicrobial activity of the extracts was determined on six microbial strains such as Staphylococcus aureus, Bacillus thuringiensis, Escherichia coli and Fusarium sp., according to the disk diffusion method, and gave zones of inhibition ranging from 7 to 15 mm. Thus, the extracts had a moderately inhibitory activity and have reacted positively on at least one of the microbial strains tested with the exception of the fungal flora. However, the methanolic extract of M. chamomilla revealed a strong activity against to Pseudomonas sp. with an inhibition zone estimated at 22.5 mm.

Multiresponse and multiobjective latent variable optimization of modern analytical instrumentation for the quantification of chemically related families of compounds: Case study—Solid‐phase microextraction (SPME) applied to the quantification of analytes with impact on wine aroma

AbstractThe optimized operation of modern analytical instrumentation is a critical but complex task. It involves the simultaneous consideration of a large number of factors, both qualitative and quantitative, where multiple responses should be quantified and several goals need to be adequately pondered, such as global quantification performance, selectivity, and cost. Furthermore, the problem is highly case specific, depending on the type of instrument, target analytes, and media where they are dispersed. Therefore, an optimization procedure should be conducted frequently, which implies that it should be efficient (requiring a low number of experiments), as simple as possible (from experimental design to data analysis) and informative (interpretable and conclusive). The success of this task is fundamental for achieving the scientific goals and to justify, in the long run, the high economic investments made and significant costs of operation. In this article, we present a systematic optimization procedure for the prevalent class of situations where multiple responses are available regarding a family of chemical compounds (instead of a single analyte). This class of problems conducts to responses exhibiting mutual correlations, for which, furthermore, several goals need to be simultaneously considered. Our approach explores the latent variable structure of the responses created by the chemical affinities of the compounds under analysis and the orthogonality of the interpretable extracted components to conduct their simultaneous optimization with respect to different analysis goals. The proposed methodology was applied to a real case study involving the quantification of a family of analytes with impact on wine aroma.

Chemical and Sensory Characteristics of Extra Virgin Olive Oils Produced in Central Iberian Peninsula Under the Protected Designation of Origin Quality Scheme

The chemical and sensory characteristics of the extra virgin olive oils (EVOO) produced in the Spanish regions of Castilla‐La Mancha and Extremadura according to the protected designation of origin (PDO) quality scheme of the European Union are reviewed. This zone is the second in importance in Spain after the southern region of Andalusia. A total PDO olive trees cultivated surface of 694 800 ha, almost one‐third of the total, and some 380 related oil mills are currently registered in Spain. Cornicabra and Picual EVOOs − related to Montes de Toledo, Campo de Montiel, and Calatrava PDOs − are those with the highest intensity of bitterness and pungency, sensory attributes directly related to their higher content in phenolic compounds (556 ± 214 and 605 ± 180 mg kg−1, respectively). On the contrary, Manzanilla cacereña and Cornezuelo oils − associated with Gata‐Hurdes and Aceites Monterrubio PDOs − show a lower score in these two positive attributes. Differences in the fatty acid profile and in certain sterols and triterpenic alcohols (mainly total content, campesterol, Δ5‐Avenasterol, stigmasterol, and erythrodiol and uvaol) may be useful, not without difficulties and in combination with other families of chemical compounds (e.g., individual phenolics and volatiles) to discriminate between olive oils obtained from different varieties or geographical areas.Practical Applications: It is relevant to gather and compare the chemical and sensory characteristics of the PDO EVOOs produced in the central Iberian Peninsula, the second main zone of economic importance in Spain. Indeed, providing clear information on olive oils linked to geographical origin is of interest to farmers and producers and furthermore enable consumers to make more informed purchasing choices. A critical review on published data is also useful to focus the design of future studies needed for achieving the full characterization of these EVOOs.The chemical and sensory characteristics of the extra virgin olive oils (EVOO) produced according to the protected designation of origin (PDO) quality scheme in the central Iberian Peninsula, the Spanish regions of Castilla‐La Mancha (4 PDOs), and Extremadura (2 PDOs) are reviewed. This geographical zone is the second in Spain regarding cultivated surface and oil production after the southern region of Andalusia.

Convenient Electrocatalytic Synthesis of Azobenzenes from Nitroaromatic Derivatives Using SmI2

The synthesis of azobenzenes has been a long-standing challenge. Their current preparation at a preparative or industrial scale requires stoichiometric amounts of environmentally unfriendly reactants. Herein, we demonstrate that the catalytic use of electrogenerated samarium diiodide (SmI2) could promote, in one-step synthesis, the reduction of nitrobenzenes into azobenzenes in high yields under mild reaction conditions. This catalytic procedure contains many elements satisfying a sustainable chemical process for the preparation of one of the most widely wanted family of chemical compounds. The easy synthetic procedure, and the absence of precious metals, bases, and nonhazardous substances, already makes our catalytic procedure a serious alternative to currently available methods. This is a promising method for the efficient synthesis of both symmetrical and asymmetrical azo compounds with a high functional group tolerance.

Pleiotropic Role of Puupehenones in Biomedical Research.

Marine sponges represent a vast source of metabolites with very interesting potential biomedical applications. Puupehenones are sesquiterpene quinones isolated from sponges of the orders Verongida and Dictyoceratida. This family of chemical compounds is composed of a high number of metabolites, including puupehenone, the most characteristic compound of the family. Chemical synthesis of puupehenone has been reached by different routes, and the special chemical reactivity of this molecule has allowed the synthesis of many puupehenone-derived compounds. The biological activities of puupehenones are very diverse, including antiangiogenic, antitumoral, antioxidant, antimicrobial, immunomodulatory and antiatherosclerotic effects. Despite the very important roles described for puupehenones concerning different pathologies, the exact mechanism of action of these compounds and the putative therapeutic effects in vivo remain to be elucidated. This review offers an updated and global view about the biology of puupehenones and their therapeutic possibilities in human diseases such as cancer.

Human Exposure from Dioxins in Soil

Dioxins are a family of chemical compounds that has received considerable attention, both historically and currently. This article reviews scientific field studies that examine the relationship between living on soil contaminated with dioxins and the level of dioxins in people's serum, with an emphasis on the University of Michigan Dioxin Exposure Study (UMDES), the largest and most comprehensive study of its kind. These studies conclude that the levels of dioxins in serum are most strongly correlated with age, gender, body mass index, weight loss, breast feeding, and smoking. Levels of dioxins in soil are not significant predictors for dioxin concentrations in serum. The increase in serum dioxin levels that is seen with age results from historic exposure and does not represent ongoing exposure. Based on the scientific field studies conducted to date, it appears that, in the absence of the consumption of contaminated animal products, there is little evidence of ongoing exposure from contaminated soil.

Investigation on lattice constants of Mg-Al spinels

Mg-Al spinel is the most typical material in the family of chemical compounds with spinel crystalline structure that exhibits many applications [1, 2]. In general, it can be noted as MgO-n·Al2O3. MgAl2O4 spinel is an fcc structure of oxygen ions with a lattice parameter of 0.808 nm. There are eight molecules in its unit cell, in which there are 64 tetrahedral symmetry sites and 32 octahedral ones. In the perfect case, magnesium ions occupy 8 tetrahedral positions and aluminum ions occupy 16 octahedral sites [3]. In many cases, this MgO-n·Al2O3 compound is nonstoichiometric, n is not equal to 1. Form 1 up to 7.3, the excess Al3+ ions occupying tetrahedral sites, substitute for Mg2+ ions [4]. This causes a proportional decrease of lattice parameter with the amount of excess Al3+ due to a smaller diameter of Al3+ than that of Mg2+. In the present paper, we show the result of the unit cell parameters of Mg-Al spinels solid solutions with XRD and provide a formula for calculating the lattice parameter of such Mg-Al spinel compounds, which has a good physical meaning compared with that given by Sigalovsky et al. [5]. In our experiments ultra-fine powders of Mg-Al spinel were prepared with a method of high temperature solid reaction. Reagent grade AlNH4(SO4)2·12H2O and MgSO4·7H2O were mixed based on different n in de-ionized water. These solutions were calcimined at 1080 ◦C for 4–5 h to obtain a single spinel phase powder with being high pure, good disperse and homogeneous. The obtained powders were measured by XRD using Cu-Kα radiation on a D/max rA diffractometer. The XRD patterns of the obtained powder samples are given in Fig. 1. The stoichiometric spinel XRD pattern (a pattern labelled n= 1.0) is the same as the standard powder XRD pattern [6]. For the non-stoichiometric spinel samples, the peaks shift to the direction in higher values of 2θ as n increases. That means the distance of (hkl) plane dhkl became smaller according to the following expression:

Determination of the Stereochemistry of Substituted 4-(Sulfo- and Sulfonamidoalkyl) piperidine-2-carboxylic Acids with H NMR, COSY, and Homonuclear NOE Experiments

Abstract Basically the aim of this work is to define the accurate configuration of 4-substituted (sulfo- and sulfonamidoalkyl)piperidine-2-carboxylic acids which have been conceived as potential NMDA antagonists. H NMR and 2D NMR (COSY) followed by qualitative Homonuclear NOE have led to the assignement of the (±) cis and (±) trans configuration of the whole family's compounds.

Determination of the Stereochemistry of Substituted 5-Methylenehydantoins and Thiohydantoins by13C NMR and Homonuclear NOE Experiments

Abstract Basically the aim of this work is to define the accurate configuration of the exocyclic double bond of substituted 5-methylenehydantoins and thiohydantoins which have been conceived as potential Aldose Reductase inhibitors. A previsional survey based upon the chemical shifts analysis from 1H and decoupled 13C NMR spectra discloses, for a part of the family of compounds, the assignment of the Zconfiguration for unsubstituted (2,3) and N-3 substituted (6,7,9) derivatives, and the E-configuration for the N-1 substituted (8,11) ones. The qualitative study with Homonuclear NOE (8,11) and the coupling constant measuring 3 JC4-C=C-H6 from coupled 13C NMR (1–11), lead to the assignment of the accurate configuration of the whole family's compounds in agreement with the previsional study.

Air Toxics Emissions From Gas-Fired Engines

Summary In 1990, 14 natural-gas-fired internal combustion engines (ICE's) inoilfield service were tested in Santa Barbara County, CA, to satisfy Californiaair toxics legislation. The combustion exhaust was tested for formaldehyde, acetaidehyde, acrolein, benzene, toluene, xylenes, naphthalene, and polycyclicaromatic hydrocarbons. The fuel was test ed for aromatics to enable calculationof destruction efficiencies. Two-stroke and four-stroke engines were tested Four-stroke engines ranging from 39 to 208 hp were used in pumping unit andconstant load service. Emissions from four-stroke engines were unrelated tosize and service. The two stroke engines produced considerably higher emissionsthan the four stroke engines. Test results indicate natural-gas-fired ICE'sproduce toxic substances in small amounts. Formaldehyde and benzene dominatedthe toxic emission profile. Introduction Because the regulatory framework already exists for criteria pollutants such as NO, SO., and reactive organic compounds, pollutants such as NO, SO., andreactive organic compounds, legislative focus is being directed toward toxicair emissions. Title M of the 1990 U.S. Clean Air Act Amendment is a recentexample of federal legislation that will affect the oil industry. Variousstates, including California, New Jersey, and Illinois, have preceded the Clean Air Act Amendment by enacting stringent air toxics regulations. California's Air Toxics "Hot Spots" Information and Assessment Act has the mostrigorous testing requirements. This right-to- know law requires biennial testdata on chemical releases into the air. Test methods were developed andexecuted to comply with regulatory requirements. Testing was directed towardmeasurement of 22 potential compounds in ICE exhaust. Of these, only six werefound at levels exceeding 0.5 lbm/MMcf of fuel. Selection of Compounds Tested Application of thermodynamic principles indicates combustion products morecomplex than CO2, in measurable quantities, must result from interruption ofthe combustion process. Quenching of the combustion reaction through transferof heat and work was postulated to be the principal means for formation oftoxic substances. Thus, plausible principal means for formation of toxicsubstances. Thus, plausible reaction intermediates were considered within thecontext of fuel molecular structures to predict the relative abundance ofcombustion products. These tests support the proposition that a fuel composedof compounds with simple molecular structures favors products with equallysimple structures. products with equally simple structures. Natural gasconsists primarily of three simple molecules: methane (one carbon), ethane (twocarbons), and propane (three carbons). In the presence of heat and sufficientoxygen, combustion takes place, causing bonds to rearrange to lower energystates while releasing heat and work. Theoretically, if a sufficientoxygen/fuel mixture is allowed to reach thermodynamic equilibrium, only CO2 andwater will be measurable. Measurable amounts of products of incompletecombustion (PIC) indicate poor mixing, quenching, insufficient oxygen, orinsufficient reaction time. Tests were performed to determine the abundance oftoxic PIC. Aldehydes are a class of plausible stable-reaction intermediates(Fig. 1). A reaction between a single methane and oxygen molecule can directlyproduce formaldehyde as a stable intermediate combustion product. Quenching theformaldehyde molecule before it can be acted upon by oxygen can leaveformaldehyde in the exhaust. Similarly, acetaldehyde and acrolein are stablecompounds that can be produced from partial combustion of ethane. Becausenatural gas largely consists of methane and ethane, aldehyde testing waslimited to their direct analogs: formaldehyde, acetaldehyde, and acrolein. Froma thermodynamic perspective, creating more complicated molecules such asmonocyclic aromatic compounds (Fig. 1) from methane, ethane, and propane duringcombustion should not occur frequently. Benzene cannot be formed through asingle bimolecular collision between oxygen and small organic molecules, although formaldehyde can be formed this way. In contrast, benzene can beformed through partial destruction of a molecule, such as propane, to form anunstable intermediate, which then must combine with other carbon molecules tocreate a six-carbon benzene ring. Thermodynamic principles suggest that such achain of events is improbable. Nevertheless, benzene, toluene, and xylene (BTX)were included in the testing, because natural gas contains BTX in varyingamounts. Although it was anticipated that BTX in the exhaust would beattributed solely to failure of the engine to bum BTX in the fuel completely, the data proved otherwise. Based on the theory that combustion-productformation is inversely proportional to product complexity, a family ofcompounds known as polycyclic aromatic hydrocarbons (PAH's) are the leastprobable PIC's of natural gas fuel. Fig. 2 shows that naphthalene probable PIC's of natural gas fuel. Fig. 2 shows that naphthalene is the simplest of themultiring structures.

Bonding Patterns in Intermetallic Compounds

AbstractIntermetallic phases have long been among the black sheep in the family of chemical compounds. Their chemical bonding has eluded description by the valence rules, which otherwise are extremely effective. As a result, understanding of the structure–bonding relationships in these phases to date has remained nebulous, even though they form the largest group of inorganic compounds. Their broad industrial applicability and richly varied structural chemistry call for new approaches for explaining their structures, electronic structures, and physical properties. A combination of new experimental and theoretical investigations has revealed interesting local aspects of chemical bonding in metals and thereby pointed to a route from the valence compounds, through the cluster and electron‐deficient compounds, to the intermetallic phases.

The neuroendocrine paraventricular hypothalamus: receptors, signal transduction, mRNA and neurosecretion.

The hypothalamus is one of the most studied areas of the central nervous system. Many of its functions are understood and there is an extensive literature on its role in the control of pituitary hormone secretion, autonomic nervous system activity, regulation of salt, water and food ingestion, body temperature regulation and aspects of behaviour. Although the role of the hypothalamus in the control of pituitary secretion was postulated in the early 1900s, the chemical nature of these control mechanisms has only been documented in the last few years. The opioid peptides represent one particular family of chemical compounds which have been shown to have many effects on pituitary hormone secretion. Exogenous opioids inhibit the neurosecretion of both vasopressin and oxytocin from the posterior pituitary neurosecretory terminals of hypothalamic cell bodies. Opioids also have major actions on the secretory activity of the anterior pituitary which has no innervation from the hypothalamus, but which is regulated by blood-borne factors in the hypophyseal portal circulation which runs from the median eminence of the hypothalamus. It was therefore of considerable interest when it was discovered that endogenous opioid peptides could be detected both in the neurohypophyseal system and in cells which project into the median eminence. The simple presence of a peptide in a neurone does not necessarily imply a function. If, however, we can demonstrate that regulation of the synthesis of the peptide occurs in a manner which corresponds with the expected role of the agent, this provides powerful data in support of a genuine physiological function. The elucidation of the genomic structure of the precursors for the three endogenous opioid peptides has provided us with the ability to measure mRNA for these peptides in defined areas of the brain and to assess their response to appropriate stimuli. Not only does mRNA for the endogenous opioid dynorphin coexist in the same cells as vasopressin but we have now been able to demonstrate that stimuli to vasopressin secretion also result in a markedly increased accumulation of dynorphin mRNA. Similarly, previous studies have shown that opioid peptides derived from another precursor--pro-enkephalin A--coexist with corticotrophin releasing factor in a different group of hypothalamic cells. We have now been able to demonstrate that stresses which result in an accumulation of corticotrophin releasing factor mRNA also result in increased pro-enkephalin mRNA in the same area. This considerably strengthens the hypothesis that endogenous opioids do play a significant role in the control of hypophyseal secretion.(ABSTRACT TRUNCATED AT 400 WORDS)