Solid-liquid phase behavior of binary fatty acid mixtures. 2. Mixtures of oleic acid with lauric acid, myristic acid, and palmitic acid

Solid-liquid phase behavior was investigated for binary fatty acid mixtures composed of oleic acid (OA; cis-9-octadecenoic acid) and saturated fatty acids, lauric acid (LA; dodecanoic acid), myristic acid (MA; tetradecanoic acid), and palmitic acid (PA; hexadecanoic acid), by means of differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR). When the mixture was heated immediately after the solidification from the melt, the heat effect due to the gamma-to-alpha transformation of OA varied depending on the composition of the mixture. However, the mixture subjected to an annealing at the temperature slightly below the melting temperature provided the transformation at constant temperature which corresponds to the gamma-to-alpha transformation temperature of pure OA. This suggests that a solid phase formed by cooling of the melt of the mixture is not in an equilibrium state, but it relaxes to a stable solid during the annealing process. The T-X phase diagrams of these mixtures constructed from the DSC measurements demonstrate that the two fatty acid species are completely immiscible in a solid phase regardless of the type of polymorphs of OA, alpha- or gamma-form. According to a thermodynamic analysis of liquidus line basing on the regular solution model for the melt, the non-ideality of mixing tends to increase with the decrease in the acyl chain length of the saturated fatty acid, although the mixing is rather close to ideal.     

Solid-liquid phase behavior of binary fatty acid mixtures. 1. Oleic acid/stearic acid and oleic acid/behenic acid mixtures

Solid-liquid phase behavior of binary fatty acid mixtures was investigated by means of differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR) for the mixture composed of oleic acid (OA) and stearic acid (SA) and that composed of OA and behenic acid (BA). The DSC results provided a monotectic type T-X phase diagram for these mixtures, from which it was suggested that the two fatty acid species are completely immiscible in a solid phase regardless of the two polymorphs of OA, i.e., alpha-form or gamma-form. The solid phase immiscibility was confirmed by the FT-IR observation that the spectra obtained for the mixtures correspond to the superposition of the two spectra for respective components. Thermodynamic analysis of liquidus line demonstrated that OA and SA form an ideal mixture in a liquid phase, whereas the mixing of OA and BA in a liquid phase is slightly non-ideal.     

Crystallization and phase behavior of 1,3-propanediol esters II. 1,3-propanediol distearate/1,3-propanediol dipalmitate (SS/PP) and 1,3-propanediol distearate/1,3-propanediol dimyristate (SS/MM) binary systems

Polymorphic influences on the phase behavior of two types of binary mixtures of saturated monoacid 1,3-propanediol esters (PADEs), dipalmitate/distearate (PP/SS) and dimyristate/distearate (MM/SS) were examined by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and by solid fat content (SFC), hardness and microscopy measurements. Three stacking modes have been found in the PP/SS binary system. Mixed SS-PP bilayers were detected in all mixtures, SS-SS bilayers in x(PP)=0.0-0.4 mixtures and PP-PP bilayers in x(PP)=0.6-0.1 mixtures. Two different but close beta polymorphs and one beta' polymorph were detected for this system. beta' was only detected in x(PP)=0.5-0.9 mixtures for the mixed bilayers. For the MM/SS binary system, only MM-MM and SS-SS bilayers were detected and both solid phases crystallized in two different beta forms. XRD data evidenced clearly that the MM and SS components were completely immiscible in the solid state. The phase diagrams constructed using DSC data, exhibited a typical eutectic-type phase boundary. The presence of eutectics, the shape of the solidus lines as well as the analysis of the individual enthalpies of melting indicated typical phase separation for both systems. A thermodynamic study based on the Hildebrand equation and using the Bragg-Williams approximation for non-ideality of mixing confirmed the phase separation in the solid phase and suggested that the PP and SS were miscible in the liquid phase and that SS formed an ideal mixing with MM. Avrami analysis of SFC vs. time curves indicated heterogeneous nucleation and spherulitic crystal development from sporadic nuclei, and suggested that the nucleation rate was higher for the mixture at the eutectic composition. The relative hardness was correlated with the enthalpies, the final SFC and the microscopy measurements.     

The solid-liquid phase diagrams of binary mixtures of consecutive, even saturated fatty acids: differing by four carbon atoms

The complete solid-liquid phase diagrams for four binary mixtures of saturated fatty acids are presented, for the first time, in this work. These mixtures are formed by caprylic acid (C_8:0) + lauric acid (C_12:0), capric acid (C_10:0) + myristic acid (C_14:0), lauric acid (C_12:0) + palmitic acid (C_16:0) and myristic acid (C_14:0) + stearic acid (C_18:0). The phase diagrams were obtained by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). FT-Raman spectrometry and polarized light microscopy were used to complement the characterization for a complete understanding of the phase diagram. All of the phase diagrams here reported show the same global behavior that is far more complex than previously accepted. They present not only peritectic and eutectic reactions, but also metatectic reactions, due to solid-solid phase transitions common in fatty acids, and regions of solid solution not previously reported. This work contributes to the elucidation of the phase behavior of these important biochemical molecules with implications in various industrial applications.     

Phase behaviour of oleanolic acid/stearyl stearate binary mixtures in bulk and at the air-water interface

The solid-liquid phase behaviour of oleanolic acid (OLA)/stearyl stearate (SS) was investigated by differential scanning calorimetry and polarizing optical microscopy. A eutectic type diagram, with the eutectic composition close to pure SS was obtained. Complementary studies by NMR, X-ray diffraction (XRD) and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy were performed. A mutual influence was detected in mixtures: the low melting form of SS is favoured at low OLA molar fractions (X_OLA) and spherulitic structures appear at high X_OLA and high temperature. Additionally, H-bonding between OLA carbonyl groups increases in the presence of SS. The study of OLA/SS by the Langmuir method and Brewster angle microscopy revealed the organization at the air-water interface: OLA interacts with water in the first layer, while SS is completely segregated to the upper layer for X_OLA > 0.3, and it distributes in the first and upper layers for X_OLA < 0.3.     

The solid–liquid phase diagrams of binary mixtures of consecutive, even saturated fatty acids

For the first time, the solid–liquid phase diagrams of five binary mixtures of saturated fatty acids are here presented. These mixtures are formed of caprylic acid (C_8:0) + capric acid (C_10:0), capric acid (C_10:0) + lauric acid (C_12:0), lauric acid (C_12:0) + myristic acid (C_14:0), myristic acid (C_14:0) + palmitic acid (C_16:0) and palmitic acid (C_16:0) + stearic acid (C_18:0). The information used in these phase diagrams was obtained by differential scanning calorimetry (DSC), X-ray diffraction (XRD), FT–Raman spectrometry and polarized light microscopy, aiming at a complete understanding of the phase diagrams of the fatty acid mixtures. All of the phase diagrams reported here presented the same global behavior and it was shown that this was far more complex than previously imagined. They presented not only peritectic and eutectic reactions, but also metatectic reactions, due to solid–solid phase transitions common in fatty acids and regions of solid solution not previously reported. This work contributes to the elucidation of the phase behavior of these important biochemical molecules, with implications in various industrial applications.     

Production of a new compound, 7,10-dihydroxy-8-(E)-octadecenoic acid from oleic acid byPseudomonas sp. PR3

Summary Sixty-two cultures from the ARS Culture Collection and 10 cultures isolated from soil and water samples collected in Illinois were screened for their ability to convert agricultural oils to value-added industrial chemicals. A new compound, 7,10-dihydroxy-8-(E)-octadecenoic acid (DOD) was produced from oleic acid by a new strain,Pseudomonas sp. PR3 isolated from a water sample in Morton, IL. Strain PR3 is a motile, small rod-shaped, Gram-negative bacterium. It has multiple polar flagellae and is oxidase-positive. Strain PR3 grows aerobically and cannot grow anaerobically. The strain produces white, smooth colonies on agar plate and no water-soluble pigment. The yield of the product was greater than 60%. The optimum time, pH and temperature for the production of DOD were: 2 days, 7.0, and 30°C, respectively. Glycerol and dextrose support the growth of strain PR3, but the cells grown from the former failed to catalyse the conversion of oleic acid to DOD. The production of DOD is unique in that it involves a hydroxylation at two positions and a rearrangement of the double bond of the substrate molecule.The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.     

The discovery and development of inhibitors of fatty acid amide hydrolase (FAAH)

A summary of the discovery and advancement of inhibitors of fatty acid amide hydrolase (FAAH) is presented.     

Effects of growth phase and nitrogen starvation on expression of fatty acid desaturases and fatty acid composition of Isochrysis aff. galbana (TISO)

Very long-chain polyunsaturated fatty acids (VLC-PUFAs) are important dietary requirements for maintaining human health. Many marine microalgae are naturally high in ω − 3 VLC-PUFAs, however, the molecular mechanisms underpinning fatty acid (FA) desaturation and elongation in algae are poorly understood. An advanced molecular understanding would facilitate improvements of this nascent industry. We aimed to investigate expression responses of four front-end fatty acid desaturase genes and downstream effects on FA profiles to nitrogen limitation and cultivation growth stage in Isochrysis aff. galbana (TISO). Cultures were grown in nitrogen-replete and -deplete medium; samples were harvested during logarithmic, late logarithmic and stationary growth phases to analyse FA content/composition and gene expression of ?⁶-, ?⁸-, ?⁵- and ?⁴-desaturases (d6FAD (putative), d8FAD, d5FAD and d4FAD, respectively). d6FAD (putative) exhibited no differential expression, while d8FAD, d5FAD and d4FAD were significantly upregulated during logarithmic growth of nutrient-replete cultures, coinciding with rapid cell division. In conclusion, it is demonstrated that expression of some FADs in I. aff. galbana varies with culture age and nitrogen status which has downstream consequences on FA desaturation levels. This has implications for the commercial production of VLC-PUFAs where a trade-off between total lipid yield and VLC-PUFAs has to be made.     

Discovery and optimization of novel piperazines as potent inhibitors of fatty acid synthase (FASN)

The discovery, structure-activity relationships, and optimization of a novel class of fatty acid synthase (FASN) inhibitors is reported. High throughput screening identified a series of substituted piperazines with structural features that enable interactions with many of the potency-driving regions of the FASN KR domain binding site. Derived from this series was FT113, a compound with potent biochemical and cellular activity, which translated into excellent activity in in vivo models.     

The role of fatty acid biosynthesis and degradation in the supply of substrates for poly(3-hydroxyalkanoate) formation in Pseudomonas putida

Abstract The relationship between fatty acid metabolism and PHA biosynthesis in P. putida is described. Detailed ¹H and ¹³C NMR studies were performed to investigate the structures of poly(3-hydroxyalkanoates) (PHAs) formed from carbohydrates and fatty acids. On the basis of these results, it is proposed that during growth on glucose the 3-hydroxyacyl-acyl carrier protein intermediates of the de novo fatty acid biosynthetic pathway are diverted to PHA biosynthesis. Similarly, further evidence is presented that during cultivation on fatty acids, intermediates of the β-oxidation cycle serve as precursors of PHA biosynthesis.     

Effect of fatty acid chain length,fatty acid hydroxylation,and various cations on phase behavior of synthetic cerebroside sulfate

Synthetic species of CBS containing palmitic, stearic, lignoceric, D-2-hydroxy palmitic, or D-2-hydroxy stearic acid were prepared and their phase behavior in the presence of a number of mono- and divalent cations was studied by differential scanning calorimetry and the use of fatty acid spin labels. The results showed that both the non-hydroxy fatty acid (NFA) and hydroxy fatty acid (HFA) forms of cerebroside sulfate (CBS) can occur in two different gel states, a metastable state and a lower entropy stable state. The phase behavior is more sensitive to the type and concentration of cation present than in the case with acidic phospholipids. The sensitivity of the transition temperature (T_m) to cation concentration reflects, in part, increased participation of the lipid in intermolecular hydrogen bonding interactions as the negative charge of the sulfate is shielded. The extra hydroxyl group on the HFA also contributes to the intermolecular hydrogen bonding network causing a significant increase in the T_m.The HFA has an even more significant effect in causing inhibition of formation of the stable state. Formation of the stable state is also inhibited by Li⁺ and divalent cations. A similar mechanism may be involved, i.e.; cross-linking of adjacent lipids or increased intermolecular interactions inhibit the molecular rearrangement necessary to form the stable state. This inhibition is counteracted by an increase in fatty acid chain length. The results suggest that the stable state may be interdigitated as a result of the unequal chain length between the sphingosine base and the fatty acid.     

Crystallization behavior and environmental biodegradability of the blend films of poly(3-hydroxybutyric acid) with chitin and chitosan

Crystallization behavior and environmental biodegradability were investigated for the films of bacterial poly(3-hydroxybutyric acid) (PHB) blends with chitin and chitosan. The blend films showed X-ray diffractive peaks that arose from the PHB crystalline component. It was suggested that the lamellar thickness of the PHB crystalline component in the blends was large enough to show detectable X-ray diffractive peaks, but this was too small to show observable melting endotherm in the DSC thermogram and the crystalline band absorption in the FT-IR spectrum. In the PHB/chitin and PHB/chitosan blends, thermal transition temperatures of PHB amorphous region observed by dynamic mechanical thermal analysis were almost the same as that of neat PHB. Both the PHB/chitin and the PHB/chitosan blend films biodegraded in an environmental medium. Several blend films showed faster biodegradation than the pure-state component polymers.     

Effect of cholesterol on miscibility and phase behavior in binary mixtures with synthetic ceramide 2 and octadecanoic acid. Infrared studies

The three main lipid components of the stratum corneum, namely ceramides, free fatty acids and cholesterol, play a fundamental role in the maintenance of the skin barrier. The current investigation is aimed toward understanding the miscibility and intermolecular interactions of these lipids. Toward this end, Fourier transform infrared spectroscopic studies of the three possible equimolar binary mixtures of cholesterol, a synthetic non-hydroxylated fatty acid N-acyl sphingosine with a C18 chain length (N-stearoylsphingosine, approximating human ceramide 2), and stearic acid were undertaken. The thermotropic responses of the methylene stretching and scissoring vibrations were used to evaluate chain conformation and packing respectively. Selective perdeuteration, of either the stearic acid or the ceramide acid chains, permitted separate and simultaneous evaluation of the conformational order and packing properties of the sphingosine chain, the amide linked fatty acid chains and/or the stearic acid chain. Whereas cholesterol mixed well with ceramide at physiological temperatures, the stearic acid was miscible with the cholesterol only at relatively high temperatures where the fatty acid is disordered. A complex interaction between stearic acid and ceramide was detected. A separate fatty acid-rich phase persisted until at least 50 degrees C, whereas at higher temperatures the components appear to be quite miscible. However, a preferential association of the fatty acid with the ceramide base chain is indicated. None of the binary systems studied exhibit miscibility and interactions resembling those in the ternary mixtures of these substances, which is widely used to model stratum corneum. The role of cholesterol in controlling the miscibility characteristics in the ternary system is evident.     

Arylpiperazines as fatty acid transport protein 1 (FATP1) inhibitors with improved potency and pharmacokinetic properties

The discovery and optimization of a novel series of FATP1 inhibitors are described. Through the derivatization process, arylpiperazine derivatives 5k and 12a were identified as possessing potent in vitro activity against human and mouse FATP1s as well as excellent pharmacokinetic properties. In vivo evaluation of triglyceride accumulation in the liver, white gastrocnemius muscle and soleus is also described.     

New unsaturated fatty acid and other chemical constituents from the roots of Cola rostrata K. Schum. (Malvaceae)

Phytochemical investigation of the roots of Cola rostrata K. Schum. led to the isolation of a new unsaturated fatty acid, named rostratanic acid (1), together with fourteen known compounds, lignoceric acid, friedelan (7), friedelanone (8), bauerenol (3), lupeol (4), herranone (9), acotatarone A (11), betulinic acid (6), betulin (5), nonanedioc acid (2), arjunolic acid (10) stigmasterol, β−sitosterol, and β−sitosterol-3-O-β-D-glucopyranoside. The structure of the new compound as well as those of the known compounds were established by means of spectroscopic methods: NMR analysis (¹H and ¹³C NMR, ¹H–¹H–COSY, HSQC and HMBC) and high-resolution mass spectrometry (HR-ESI-MS), and by comparison with previously reported data. Two of those known compounds were modified chemically to afford three new derivatives. All those compounds were tested for their cytotoxic activity against the human cervix carcinoma KB-3-1 cells and their antibacterial activity against Escherichia coli, Salmonella enterica, Pseudomonas aeruginosa and Staphylococcus aureus. Although the crude extract gave weak antibacterial activity, none of the isolated compounds showed antibacterial activity, and, only the prenylated derivative showed weak cytotoxicity. In addition, the chemotaxonomic significance of the species Cola rostrata is discussed.     

Enhanced antitumor activities of (-)-epigallocatechin-3-O-gallate fatty acid monoester derivatives in vitro and in vivo

(−)-Epigallocatechin-3-O-gallate (EGCG) monoesters modified with butanoyl (EGCG-C4), octanoyl (EGCG-C8), palmitoyl groups (EGCG-C16) were synthesized by a lipase-catalyzed transesterification method and their antitumor activities were investigated in vitro and in vivo. The in vitro antitumor activities of EGCG-monoester derivatives increased in an alkyl chain length-dependent manner. The cytotoxicity of EGCG, EGCG-C4, EGCG-C8 was mainly caused by H₂O₂ which was generated with their oxidation. On the other hand, EGCG-C16 was more stable than EGCG and it did not generate H₂O₂ in the cell culture medium. Furthermore, EGCG-C16 inhibited cell proliferation and induced apoptosis in the presence of catalase. EGCG-C16 was found to inhibit the phosphorylation of the epidermal growth factor receptor (EGFR), which is related to various types of tumor growth. EGCG-C16 suppressed tumor growth in vivo in colorectal tumor bearing mice in comparison to an untreated control, vector control (DMSO) and EGCG.     

Formation of binary complexes of Pb(II), Cd(II) and Hg(II) with maleic acid in CTAB-water mixtures

Abstract

Complexation of toxic metal ions with maleic acid in (0.0–2.5% w/v) cetyltrimethylammonium bromide (CTAB)–water mixtures has been studied pH-metrically at ambient conditions and an ionic strength of 0.16 mol L^-1. The existence of different binary species was established from modelling studies using the computer program MINIQUAD75. The best-fit chemical models were selected based on statistical parameters such as the crystallographic R factor and sum of the squares of residuals in mass-balance equations. The models for binary complex systems contain the chemical species ML₂, ML₂H and ML₃ for Pb(II), Cd(II) and Hg(II) in CTAB–water mixtures. The trend in the variation of stability constants with change in the mole fraction of the medium was explained based on electrostatic and non-electrostatic forces. Distribution of the species with pH at different compositions of CTAB–water mixtures was also presented.