Apolar Compound Research Articles

On the solubility of azodicarbonamide in water/DMSO mixtures: an experimental and computational study.

This work aims at studying why azodicarbonamide (ADCA), a formally apolar compound with good hydrogen bond (HB) acceptors, is soluble only in polar aprotic solvents like dimethyl sulfoxide (DMSO) but not in water. Solubility measurements, as well as quantum mechanical and classical molecular dynamics simulations, were employed to tackle the problem. We found that in the liquid phase a polar conformer of ADCA (µ = 8.7 D), unreported to date, is favoured under the enthalpic drive provided by a highly polar solvent. At the same time, the very high hydrogen bond propensity of water with itself prevents this solvent from providing an effective hydrogen bond-mediated solvation. Solvents bearing good HB acceptors, while lacking strong HB donors, contribute to further stabilizing solute-solvent adducts through weak and fluxional HBs that involve the amide groups of ADCA. Implications for the solubility of ADCA down to µM concentrations were evaluated, also with the aid of classical simulations of solution nanodroplets.

African Under-Utilized Medicinal Leafy Vegetables Studied by Microtiter Plate Assays and High-Performance Thin-Layer Chromatography-Planar Assays.

Biological activities of six under-utilized medicinal leafy vegetable plants indigenous to Africa, i.e., Basella alba, Crassocephalum rubens, Gnetum africanum, Launaea taraxacifolia, Solanecio biafrae, and Solanum macrocarpon, were investigated via two independent techniques. The total phenolic content (TPC) was determined, and six microtiter plate assays were applied after extraction and fractionation. Three were antioxidant in vitro assays, i.e., ferric reducing antioxidant power (FRAP), cupric reduction antioxidant capacity (CUPRAC), and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging, and the others were enzyme (acetylcholinesterase, butyrylcholinesterase, and tyrosinase) inhibition assays. The highest TPC and antioxidant activity from all the methods were obtained from polar and medium polar fractions of C. rubens, S. biafrae, and S. macrocarpon. The highest acetyl- and butyrylcholinesterase inhibition was exhibited by polar fractions of S. biafrae, C. rubens, and L. taraxacifolia, the latter comparable to galantamine. The highest tyrosinase inhibition was observed in the n-butanol fraction of C. rubens and ethyl acetate fraction of S. biafrae. In vitro assay results of the different extracts and fractions were mostly in agreement with the bioactivity profiling via high-performance thin-layer chromatography-multi-imaging-effect-directed analysis, exploiting nine different planar assays. Several separated compounds of the plant extracts showed antioxidant, α-glucosidase, α-amylase, acetyl- and butyrylcholinesterase-inhibiting, Gram-positive/-negative antimicrobial, cytotoxic, and genotoxic activities. A prominent apolar bioactive compound zone was tentatively assigned to fatty acids, in particular linolenic acid, via electrospray ionization high-resolution mass spectrometry. The detected antioxidant, antimicrobial, antidiabetic, anticholinesterase, cytotoxic, and genotoxic potentials of these vegetable plants, in particular C. rubens, S. biafrae, and S. macrocarpon, may validate some of their ethnomedicinal uses.

Physics informed neural networks reveal valid models for reactive diffusion of volatiles through paper

Predictive models for the transport of volatile organic compounds in paper need to consider the complex interplay of diffusion, adsorption, desorption, or chemical reactions. The relative importance of each of these processes is determined by the polarity of the volatile. Hence, it is challenging to pick a valid theoretical model that correctly predicts transport regardless of the polarity. Here, physics-informed neural networks (PINNs) assess which of five different models correctly describe transport of DMSO as polar and n-tetradecane as apolar model compound: (i) a pseudo first-order adsorption model for an irreversible sorption process, (ii) a first-order kinetics model allowing reversible sorption, (iii) a second-order model with a reversible process, and an effective diffusion model accounting for a constant (iv) and for a variable effective diffusivity (v). Each tested model is given as set of partial differential equations (PDE). Considering the model under testing and experimentally obtained spatially and temporally resolved concentration profiles through stacks of paper sheets, PINNs predict concentration of the volatiles and associated material constants such as sorption constants and effective diffusion coefficients by solving the inverse problem. Our PINNs revealed two models, pseudo first-order sorption and second-order reversible sorption, that correctly predict concentration profiles and polarity-driven differences in sorption times. While a PINN-based picking of valid transport models has important implications for the development of effective methods for controlling emission of volatiles from paper materials, PINNs represent a versatile mathematical tool to validate or refute the capability of PDE-based theoretical models to describe experimental data.

Understanding the role of sorption and biodegradation in the removal of organic micropollutants by membrane aerated biofilm reactor (MABR) with different biofilm thickness

The role of sorption and biodegradation in a membrane aerated biofilm reactor (MABR) were investigated for the removal of 10 organic micropollutants (OMPs) including endocrine disruptors and pharmaceutical active compounds. The influence of the biofilm thickness on the mechanisms of removal was analyzed via kinetic test at three different stages. At all biofilm stages, biodegradation was demonstrated to dominate the removal of selected OMPs. Higher OMPs rates of removal via biodegradation (Kbiol) were achieved when biofilm increased its thickness from (stage T1) 0.26 mm, to (stage T2) 0.58 mm and (stage T3) 1.03 mm. At stage T1 of biofilm, heterotrophs contribute predominantly to OMPs degradation. Hydrophilic compounds removal (i.e., acetaminophen) continue to be driven by heterotrophic bacteria at the next stages of biofilm thickness. However, for medium hydrophobic neutral and charged OMPs, the combined action of heterotrophic and enriched nitrifying activity at stages T2 and T3 enhanced the overall removal. A degradation pathway based on heterotrophic activity for acetaminophen and combined action of nitrifiers-heterotrophs for estrone was proposed based on identified metabolites. Although biodegradation dominated the removal of most OMPs, sorption was also observed to be essential in the removal of biologically recalcitrant and lipophilic compounds like triclosan. Furthermore, sorption capacity of apolar compound was enhanced as the biofilm thickness grew and increased in EPS protein fraction. Microbial analysis confirmed the higher abundance of nitrifying and denitrifying activity at stage T3 of biofilm, which not only facilitated near complete ammonium removal but also enhanced degradation of OMPs.

Prediction of Apolar Compound Sorption to Aquatic Natural Organic Matter Accounting for Natural Organic Matter Hydrophobicity Using Aqueous Two-Phase Systems.

The equilibrium partitioning of organic compounds to natural organic matter (NOM) plays a key role in their environmental fate as well as bioavailability. In this study, a prediction model for organic compound sorption to NOM was theoretically derived based on two-phase systems. In this model, the hydrophobicity of NOM was scaled by their partition coefficients in an aqueous two-phase system (KATPS) and that of organics was scaled by their octanol-water partition coefficients (KOW). The model uses only KATPS and KOW as variables. Coefficients in the model were determined using a data set including the organic carbon-water partition coefficient (KOC) of four polycyclic aromatic hydrocarbons (PAHs) sorption to 10 NOM samples collected from surface waters. The resulting model was validated using additional NOM samples and reference NOM, which suggested good prediction power for PAH sorption to aquatic NOM. The model performance was compared with commonly used linear free energy relationship models, and its applicability was discussed. Sorption behavior unexpected by this model is attributed to additional sorption mechanisms other than partitioning. Overall, this approach allows prediction of KOC for apolar organic compound sorption to aquatic NOM simply using their respective partition coefficients in two-phase systems based on a specific model.

Required Withholding Period for Vine Leaves Following Spraying with Pesticide

Vine leaves are consumed in many countries but little attention is paid to the residues left on them after the application of pesticides that help prevent pests and protect the grapes, the economically important target. Therefore, it is of outmost importance to study the dissipation of the pesticides applied to this crop to protect the consumers that also eat vine leaves. Dissipation kinetics of chlorpyrifos, chlorpyrifos-methyl, diazinon and dimethoate residues were studied in vine leaves grown under sunny conditions in Syria, using an ethyl acetate based sample preparation followed by GC-MS/MS determination. The dissipation rate for all doses applied followed first-order kinetics, with half-lives in grape leaves in the range of 2.9 – 3.9 days. At the recommended application dose, a withholding period of 8.9-37.1 days before consumption should be applied to meet current MRLs and minimise risks to consumers. The effectiveness in the reduction of pesticide loads in vine leaves through washing with either cold or hot water was dependant on the physicochemical properties of the studied pesticides. Hot water washing was very effective for dimethoate, a polar and water-soluble pesticide, with an effective reduction of 92% of the residue level; but no significant effect was observed for chlorpyrifos, the most apolar compound in this study.

A New Prenylated, A‐polar Compound (AGSO7) Mediates Vasoconstriction through Alpha‐1 Receptors, and Inhibited Norepinephrine Induced Contractions on Thoracic Aortic Rings

A new prenylated, a-polar compound isolated from a fungal extract showed significant bioactivity. The objective was to investigate its pharmacological activities on Sprague-Dawley rat blood pressure and isolated aortic rings. Rats weighing 250g – 300g were anaesthetized with 15 % urethane (0.8 mL / 100g body weight). The femoral vein and carotid artery were cannulated for intravenous drug administration and blood pressure measurements respectively. A pressure transducer attached to a polyview recorded the responses. Isolated thoracic aortic rings were placed separately in a multi-channel 20 mL organ bath system in Krebs physiological solution kept at 37 ºC and aerated with CO2: O2 (5 %: 95 %). FT3 force transducers connected to a polyview were used to measure isometric tensions. AGSO7 ( 65.6 µg/mL) produced a dose-dependent increase in blood pressure which was attenuated by prazosin (1.8 x 10-5 mmol/mL). AGSO7 ( 14.4 µg/mL), however, dose dependently inhibited norepinephrine (10 ng/mL) induced contractions on the aortic rings. Results showed that AGSO7 has vasoconstrictor activity which may be mediated through alpha-1 receptors. Further studies are being done on AGSO7 analyzing its dose-dependent vasodilatory effects on the thoracic aortic rings and its pharmacological activities on other tissues, in order to elucidate a more detailed mechanism of action.

Association between lipoxygenase and peroxidase activity and systemic protection of cucumber plants against Podosphaera xanthii induced by Oudemansiella canarii extracts

This study was done to determine the relationship between the changes in lipoxygenase (LOX) and peroxidase (POX) activity and the protection of cucumber (Cucumis sativus) against powdery mildew (Podosphaera xanthii) induced by hexane or ethyl acetate extracts of basidiocarps of Oudeman-siella canarii. At the two-leaf stage, only the primary leaves of the greenhouse grown cucumber plants were sprayed with either extract. The secondary leaves were inoculated at 1, 4, 7 or 10 days after the spray and the number of powdery mildew colonies were counted after 6 days. The LOX and POX activity in secondary leaves was determined 24 h after inoculation. In vitro antimicrobial effect of the extracts was tested against Bacillus and Cladosporium. Maximum disease reduction (85%) occurred when plants were inoculated one day after applying hexane extract. The disease reduction then decreased abruptly to 30% on the 4th day, but then increased again when plants were inoculated seven or ten days after treatment. LOX activity increased only by the hexane extract application, but not by the pathogen. POX activity was higher in inoculated plants previously treated with the hexane extract. On the other hand, ethyl acetate extract did not affect the enzyme activity and its protection efficacy decreased continuously with increasing time interval between treatment and inoculation. Although both extracts showed antimicrobial activity in vitro, the results suggest that apolar compound(s) from the basidiocarps of O. canarii also induce systemic resistance to powdery mildew.

Growth of nutrient‐replete Microcystis PCC 7806 cultures is inhibited by an extracellular signal produced by chlorotic cultures

The frequency of cyanobacterial blooms has been increasing all over the world. These blooms are often toxic and have become a serious health problem. The aim of this work was to search for population density control mechanisms that could inhibit the proliferation of the toxic bloom-forming genus Microcystis. Microcystis PCC 7806 cultured for long periods in liquid ASM-1 medium loses its characteristic green colour. When a medium of chlorotic cultures is added to a nutrient-replete culture, cell density increase is drastically reduced when compared with controls. Inhibition of cell proliferation occurs in Microcystis cultures from any growth stage and was not strain-specific, but other genera tested showed no response. Investigations on the mechanism of growth inhibition showed that cultures treated with the conditioned medium acquired a pale colour, with pigment concentration similar to that found in chlorotic cultures. Ultrastructural examination showed that the conditioned medium induced thylakoid membrane disorganization, typical of chlorotic cells, in nutrient-replete cultures. An active extract was obtained and investigations showed that activity was retained after heating and after addition of an apolar solvent. This indicates that activity of the conditioned medium from chlorotic cells results from non-protein, apolar compound(s).

Solid/gas biocatalysis: an appropriate tool to study the influence of organic components on kinetics of lipase-catalyzed alcoholysis

The influence of the addition of an extra component in a gaseous reaction medium, on the kinetics of alcoholysis of methyl propionate and n-propanol catalyzed by immobilized lipase B from Candida antarctica was studied in a continuous solid/gas reactor. In this reactor, the solid phase is composed of a packed enzymatic sample, which is percolated by gaseous nitrogen, simultaneously carrying gaseous substrates and additional components to the enzyme while removing reaction products. The system permits to set thermodynamic activity of all gaseous components (substrates or not) independently at the desired values. This allows in particular to study the influence of an extra added component at a constant thermodynamic activity value, contrary to classical solid/liquid system, which involves large variations of thermodynamic activity of added solvent, when performing full kinetic studies. Alcohol inhibition constant ( K I) and methyl propionate and propanol dissociation constants ( K MP and K P) have been determined in the solid/gas reactor in the presence of 2-methyl-2-butanol, and compared with values previously obtained in the absence of added component and in the presence of water. Complementary experiments were carried out in the presence of an apolar compound (hexane) and led to the conclusion that the effect of added organic component on lipase-catalyzed alcoholysis is related to their competitive inhibitory character towards first substrate methyl propionate. The comparison of data obtained in liquid or with gaseous 2-methyl-2-butanol shows that lower K MP and K I are found in gaseous medium, which would correspond on the one hand to a lower acylation rate k 2, and on the other hand to a higher binding rate k 1 between substrate and free enzyme in gaseous medium.

Phase Behavior of Tetradecyldimethylaminoxide in the Presence of Perfluorooctanol and HCl

The ternary phase diagrams of zwitterionic single-chain hydrocarbon surfactant (tetradecyldimethylaminoxide, C14DMAO)—a perfluoro cosurfactant (1,1-H-dihydroperfluorooctanol, C7F15CH2OH)-H2O, and C14DMAO-C7F15CH2OH-H2O-HCl have been studied at 25°C. The identification of the phases was done by means of electrical conductivity, optical polarizing microscopy, and 2H-NMR techniques. In this system the originally uncharged zwitterionic surfactant was increasingly charged by protonation through addition of HCl. The sequence of the phases observed is similar to that observed for hydrocarbon surfactant–cosurfactant mixtures, namely, L1, L1/Lα, Lα and L2, as relative volume fraction of apolar compound increases over that of polar compound. The absence of sponge phase (L3) is a result of the high bending constant of the mixed bilayers in this perfluoro system.

Agonistic behaviour of female Tegenaria atrica in the presence of different aged spiderlings

SummaryThe agonistic behaviour of adult female T. atrica increases with increasing age of spiderlings until 80 days post‐emergence, then decreases. In all cases, cannibalism of spiderlings increases markedly after completion of their pre‐dispersal period with a correlation between the switch of behaviour, from tolerance to cannibalism, and a modification of individual’s cuticular compounds. Experiments that compare spiderlings weight and mobility indicate that female agonistic behaviour are always low with spiderlings in pre‐dispersal period, and high with spiderlings in post‐dispersal period. Female reproductive state and the weight/mobility of spiderlings are not the only factors controlling the adult female’s agonistic behaviour towards spiderlings on her web, as tactochemical information plays an important role in modulating agonistic behaviour after close contact between female spiders and spiderlings. The agonistic behaviour of females appears to correspond with a change in the increase of polar compound levels (methylesters and fatty acids) and the decrease of apolar compound levels (hydrocarbons) in spiderlings of different ages.

An apolar GA-like compound responsible for the antheridiogen activity in Blechnum spicant

An apolar GA-like compound responsible for the antheridiogen activity in Blechnum spicant

Adsorption properties of polar/apolar inducers at a charged interface and their relevance to leukemia cell differentiation

The interfacial adsorption properties of polar/apolar inducers of cell differentiation (PAIs) were studied on a mercury electrode. This study, on a clean and reproducible charged surface, unraveled the purely physical interactions among these compounds and the surface, apart from the complexity of the biological membrane. The interfacial behavior of two classical inducers, hexamethylenebisacetamide (HMBA) and dimethylsulfoxide, was compared with that of a typical apolar aliphatic compound, 1-octanol, that has a similar hydrophobic moiety as HMBA but a much smaller dipolar moment. Both HMBA and Octanol adsorb flat in contact with the surface because of hydrophobic forces, with a very similar free energy of adsorption. However, the ratio of polar to apolar moieties in PAIs turned out to be crucial to drive the adsorption maximum toward physiological values of surface charge density, where octanol is desorbed. The electrostatic effects in the interfacial region reflected the adsorption properties: the changes in the potential drop across the interfacial region as a function of the surface charge density, in the physiological range, were opposite in PAIs as compared with apolar aliphatic compounds, as exemplified by octanol. This peculiar electrostatic effect of PAIs has far-reaching relevance for the design of inducers with an adequate therapeutic index to be used in clinical trials.

Subcutaneous administration of HMG-CoA reductase inhibitors in hyperlipidaemic and normal rats

Recent reports demonstrate a hypocholesterolaemic effect of daily subcutaneous injections of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors in different rat models of hyperlipidaemia. However, this effect is not seen after oral administration of HMG-CoA reductase inhibitors in rats. We found that oral administration of the HMG-CoA reductase inhibitor Simvastatin also had no effect on plasma cholesterol in severely hyperlipidaemic Nagase analbuminaemic rats (NAR). Simvastatin (an apolar compound dissolved in propylene glycol) was infused continuously for 28 days into the subcutis of control Sprague-Dawley rats (SDR) and NAR using an implanted osmotic pump. All doses which were effective in reducing cholesterol in the NAR (reductions up to approximately 60%), reduced apolipoprotein AI but not apolipoprotein B and caused a severe inflammatory reaction in the dermis. Similar toxicity was observed in the SDR. Subcutaneous administration of the vehicle (propylene glycol) did not cause this reaction and did not affect plasma lipids. Administration of Lovastatin in osmotic pumps resulted in a similar inflammatory reaction. Incorporation of Simvastatin into liposomes did not diminish the toxic effect. On the other hand, infusion of Pravastatin (a polar HMG-CoA reductase inhibitor dissolved in isotonic saline) caused no changes in the dermis and had no effect on plasma lipids in NAR or SDR. Liver microsomes prepared from the Pravastatin-treated rats demonstrated a 3- to 4-fold increase in HMG-CoA reductase activity as compared to untreated rats, confirming uptake of the drug. We conclude that continuous subcutaneous administration of the HMG-CoA reductase inhibitors Simvastatin, Lovastatin and Pravastatin for 28 days may not reduce plasma cholesterol in rats by a mechanism which is related to inhibition of HMG-CoA reductase activity in the liver. The decrease of plasma cholesterol effected by subcutaneous infusion of Simvastatin or Lovastatin in NAR coincides with, and may be related to inflammatory changes caused by administering these compounds into the dermis.

Sulfhydryl-selective fluorescence labeling of lipoprotein(a) reveals evidence for one single disulfide linkage between apoproteins(a) and B-100

Human lipoprotein(a) and low-density lipoprotein were labeled with two different sulfhydryl-selective fluorescence markers. The hydrophilic fluorophore lucifer yellow iodoacetamide and the apolar compound 6-acryloyl-2-(dimethylamino)naphthalene were used to derivatize free -SH groups in the lipoproteins. Three sulfhydryls could be detected in low-density lipoprotein, whereas only two cysteines were available in lipoprotein(a). One of the three -SH groups in low-density lipoprotein was shown to be located in close proximity to the particle surface. We suggest that this surface-exposed cysteine of apoprotein B-100 serves as a component for the disulfide linkage to apoprotein(a) in lipoprotein(a).

Ecdysone metabolism in adult crickets, Gryllus bimaculatus

The fate of injected [ 3H]ecdysone has been investigated in female and male adults of the Mediterranean field cricket, Gryllus binaculatus (de Geer). The metabolism is similar in both sexes and at various stages of adult life. Several classes of apolar metabolites (A1–A5) represent the major compounds. The amount of polar conjugates is low in all tissues, as are the concentrations of 20-hydroxyecdysone. Ovaries are the only organs capable of storing considerable amounts of ecdysteroids. The amount of radiolabelled ecdysteroid activity (mostly [ 3H]ecdysone) excreted during the first 24 hr after injection is high. The chemical identity of the apolar metabolites is not yet known. A2, which is the major apolar compound, has recently been identified as a complex of ecdysone conjugates with abundant long-chain fatty acids (Hoffman et al., 1985 Life Sci. 37, 185–192). Incubations with tissue homogenates in vitro have shown that several organs are capable of converting ecdysone into apolar compounds. Apolar ecdysteroid acyl esters represent a newly identified class of ecdysone conjugates from insects. Their role in regulation of free ecdysteroid titres during the reproductive period in female crickets is discussed.

Apolar ecdysteroid esters in adult female crickets, [formula omitted][formula omitted

Six hours after injection of 0.5 uCi 3H-ecdysone into the hemocoele of adult female crickets, several labelled compounds could be separated from hemolymph and tissues by silicic acid column chromatography, TLC, and HPLC. The amount of conjugated, polar ecdysteroids was low in all tissues. whereas apolar metabolites were predominant in all tissues. The apolar compound A2, which is the most abundant in quantity, could be hydrolyzed by porcine liver esterase, yielding ecdysone and various long chain fatty acids. This represents a new class of apolar ecdysteroid conjugates not yet found in other insects.

Rules for the regulation of enzyme activity in reserved micelles as illustrated by the conversion of apolar steroids by 20 beta-hydroxysteroid dehydrogenase.

20 beta-Hydroxysteroid dehydrogenase was enclosed in reversed micellar media consisting of cetyltrimethyl-ammonium bromide, hexanol, organic solvent and Hepes buffer. The influence of the composition of these media on the enzymatic reduction of the apolar steroids progesterone and prednisone was investigated by varying the water content, concentration of hexanol and type of organic solvent. By changing the water content and the type of organic solvent, the hexanol to cetyltrimethylammonium bromide ratio in the interphase can be varied. This ratio was determined by phase boundary titrations. It was found that the higher this ratio, the higher the rate of steroid conversion. From variations of the hexanol content it was concluded that the rate of steroid conversion is determined by the hydrophobicity of the steroid relative to the hydrophobicity of the continuous phase and the hydrophobicity of the interphase. The hydrophobicity of the phases was expressed in log P-values. Log P is defined as the logarithm of the partition coefficient in an octanol-water two-phase system. This enabled us to derive the following relations between the hydrophobicity values for the substrate (log Ps), for the interphase (log Pi) and for the continuous phase (log Peph): [log Pi-log Ps] must be minimal to ensure a high steroid concentration in the interphase and [log Pcph-log Ps] must be large to keep the steroid concentration in the continuous phase low. With these considerations, for any given apolar compound, a medium can be composed that gives optimal enzymatic conversion.

Metabolism of daunorubicin in sensitive and resistant Ehrlich ascites tumor cells. Determination by high pressure liquid chromatography.

The intracellular metabolism of daunorubicin (DNR) has been studied in sensitive and resistant Ehrlich ascites tumor (EAT) cells. The subcellular localization of metabolites has been followed by normal-phase and reverse-phase high-pressure liquid chromatography (HPLC). The metabolism of DNR by either sensitive or resistant EAT cells is not significant; unmetabolized DNR is always the main intracellular compound. Daunorubicinol (DOL) accounts for less than 5% after 24 h and an unidentified product is also observed. This highly apolar compound, having an intrinsic fluorescence one order of magnitude greater than that of DNR is formed in acellular conditions and could be a chemical artifact. DNR and DOL are mainly associated with DNA-containing fractions. No significant differences can be observed in the metabolism of DNR in sensitive and resistant EAT cells.