Synthesis and evaluation of radioiodinated terminal-substituted 5-iodo-(2-thienyl) fatty acids as new myocardial imaging agents

In order to evaluate the stability of radioiodide attached to the 5 position of thiophenes substituted at the 2-position with tissue-specific groups as new radiopharmaceuticals, two [¹²⁵I]iodothienyl-substituted long-chain fatty acids have been prepared and evaluated in rats. Radioiodide was introduced into the 5 position of 17-(2-thienyi)heptadecanoic acid and 13-(2-thienyl)tridecanoic acid by K-¹²⁵I treatment of their corresponding 5-[bis-(trifluoroacetoxy)]thallium derivatives. Tissue distribution studies in rats with 17-[5-[¹²⁵I]iodo(2-thienyl)]heptadecanoic acid shows significant heart uptake and prolonged retention accompanied by in vivo deiod-ination and moderate blood levels. A comparison of the heart uptake of the 17 carbon fatty acid with a 13 carbon analogue, 13-[5-[¹³⁵I]iodo(2-thienyl)]tridecanoic acid, demonstrated a significantly greater myocardial uptake for the 17 carbon fatty acid than the 13 carbon analogue. These results suggest that the 5-iodothienyl moiety substituted at the terminal position of long chain fatty acids does not interfere with myocardial uptake and that such compounds may be of value as a new class of myocardial imaging agents.     

Development of 15-(p-123I-phenyl)-pentadecanoic acid for in-vivo diagnosis of the myocardium

Radioiodinated ω-phenylfatty acids were recently proposed as radiopharmaceuticals for determining myocardial metabolic alterations. Therefore uptake and elimination of different radiohalogenated phenylfatty acids were determined in blood and heart muscle of mice. The structure activity dependence i.e. the effect of length of the carbon chain, position of the substituent at the benzene ring and type of radiohalogen was studied. Highest myocardial accumulation was found in case of a phenylfatty acid with 15 carbon atoms in the alkylgroup and the radiohalogen attached to the benzene ring in the para position. No difference was observed between the radiobrominated and radioiodinated substrates. In contrast to aliphatic radioiodinated fatty acids, the radioactivity in the stomach remained almost constant (i.e. below 1% dose/organ). Thus 15-(¹²³I-phenyl)-pentadecanoic acid (IPPA) could be brought into clinical application with success. Blood clearance and urine excretion of the radioactivity were determined and the results found to agree with the expectations based on the principal metabolic path of phenylfatty acids.     

Synthesis and biological evaluation of fatty acid derivatives for myocardial imaging containing [<Superscript>99m</Superscript>Tc(CO)<Subscript>3</Subscript>]<Superscript>+</Superscript>

Radiolabeled fatty acids as myocardial metabolic agent are used for detecting ischemic heart disease, however, no ^99mTc-labeled fatty acids have potential use in clinical diagnosis. In this work, five fatty acid analogues labeled with ^99mTc were firstly synthesized and characterized, their biological behaviors were investigated. All Radiotracers had good stability when incubated in rat serum for 3 h at 37 °C. ^99mTc -CpT-12-ODPPA (8b) showed higher initial myocardial uptake (8.17% ID/g at 1 min postinjection) and good heart/blood ratio (2.58 at 30 min postinjection). ^99mTc-11-dpa-OUFA (2b) as positively charged lipophilic compounds had reasonable heart uptake (5.59% ID/g at 1 min postinjection) and good retention (1.89% ID/g at 60 min postinjection). Unfortunately, no great improvement was obtained by the five ^99mTc-labeled fatty acid analogues for the short myocardial retention and poor heart/liver ratios.     

Effects of L-Carnitine and its Derivatives – Studies on Isolated Hearts

Summary. The metabolism in the heart prefers long-chain fatty acids to other substrates. L-Carnitine, a co-factor of coenzyme A, plays an essential role in the transport of long-chain fatty acids through the inner mitochondrial membrane. Without carnitine, metabolisation of long-chain fatty acids in the mitochondria is not possible. In addition, acyl groups from acyl-CoA compounds can be transferred to L-carnitine, thus influencing the enzymatic activities of important mitochondrial enzymes.The isolated heart model developed by Langendorff was used to investigate the effects of L-carnitine on the heart. During aerobic perfusion, the hemodynamic parameters of isolated hearts reacted in a very sensitive way to alterations in the external conditions (temperature, preload, composition of the perfusion solution). During postischemic perfusion, recovery of the hearts was also influenced by the composition of the perfusion. The hemodynamic parameters of the reperfused hearts increased markedly if there was a sufficiently high supply of long-chain fatty acids and/or glucose. The insufficient recovery of hearts perfused without glucose and at low fatty acid concentrations could be improved by adding L-carnitine. Determination of carnitine levels in heart tissue found that the heart loses about 30% of its carnitine content during ischemia, and that exogenous carnitine is taken up by the heart during reperfusion. There it effects the restoration of sufficient concentrations of creatine phosphate and ATP, a fact that was confirmed by ³¹P NMR spectroscopy. NMR spectroscopy also established that L-carnitine lessens the harmful effects of ischemia-induced metabolic acidosis.The favourable influence of L-carnitine on the heart in the reperfusion period could be due to a reduction in oxygen radicals (lowering of MDA concentrations during reperfusion, raising of GP_x and SOD activities).The findings of these experiments on isolated hearts as well as the favourable results of two placebo-controlled and double-blind clinical studies (investigating the effects of carnitine in cardiomyopathy patients and the effects of L-carnitine in hemodialysis patients) demonstrate that L-carnitine produces positive therapeutic effects, particularly in heart and circulatory diseases.     

Synthesis,spectral characterization and antibacterial activity of O,O’-dialkyl and alkylene dithiophosphatogold (III)dichloride; crystal structure of [S2POCMe2CMe2O]AuCl2

Abstract

O, O’-Dialkyl and alkylene dithiophosphatogold (III)dichloride complexes of the type [(RO)₂PS₂]AuCl₂ and [S₂POGO]AuCl₂, where R?=?Et, nPr, iPr, iBu, Ph, cyclohexyl and cyclopentyl, where G?=?CMe₂CMe₂-, have been synthesized in 80-90% yields by reaction of the corresponding acid or sodium salts of the appropriate dithiophosphoric acids in 1:1 ratio with gold (III) chloride in dry dichloromethane at room temperature. The compounds have been characterized by elemental analyses, IR and (¹H, ^l3C, and ³¹P) NMR. The crystal structure of [S₂POCMe₂CMe₂O]AuCl₂, was determined. These new complexes have shown their growth inhibiting potential against various bacterial strains with moderate to good activity.     

Heterologous Co-expression of accA, fabD, and Thioesterase Genes for Improving Long-Chain Fatty Acid Production in Pseudomonas aeruginosa and Escherichia coli

The goal of the present study was to increase the content of intracellular long-chain fatty acids in two bacterial strains, Pseudomonas aeruginosa PA14 and Escherichia coli K-12 MG1655, by co-overexpressing essential enzymes that are involved in the fatty acid synthesis metabolic pathway. Recently, microbial fatty acids and their derivatives have been receiving increasing attention as an alternative source of fuel. By introducing two genes (accA and fabD) of P. aeruginosa into the two bacterial strains and by co-expressing with them the fatty acyl?Cacyl carrier protein thioesterase gene of Streptococcus pyogenes (strain MGAS10270), we have engineered recombinant strains that are efficient producers of long-chain fatty acids (C16 and C18). The recombinant strains exhibit a 1.3?C1.7-fold increase in the production of long-chain fatty acids over the wild-type strains. To enhance the production of total long-chain fatty acids, we researched the carbon sources for optimized culture conditions and results were used for post-culture incubation period. E. coli SGJS17 (containing the accA, fabD, and thioesterase genes) produced the highest content of intracellular total fatty acids; in particular, the unsaturated fatty acid content was about 20-fold higher than that in the wild-type E. coli.     

An improved derivatization method for sensitive determination of fatty acids by high-performance liquid chromatography using 9-(2-hydroxylethyl)-carbazole as derivatization reagent with fluorescence detection

Summary Tagging techniques with reagents used for fluorescent detection for short and long-chain fatty acids using high-performance liquid chromatography are evaluated in terms of the tagging reactions, handing, flexibility, stability of the reagents. Emphasis is given to the applications of the tagging techniques to relatively high molecular mass fatty acids. The fatty acids or carboxylic compounds were derivatized to their corresponding esters with 9-(2-hydroxy ethyl)-carbazole (HEC) in acetonitrile at 60°C with N, N′-carbonyldiimidazole (CDI) as a coupling agent in the presence of 4-dimethylaminopyridine (DMAP). A mixture of esters of C₁−C₂₀ fatty acids was completely separated with 45 min using gradient elution on a reversed-phase C₁₈ column. The maximum fluorescence emission for the derivatized fatty acids is at 365 nm (λ_ex 293 nm). Studies on derivatization conditions indicated that fatty acids react rapidly and smoothly with HEC in the presence of CDI and DMAP in acetonitrile to give the corresponding sensitively fluorescent derivatives. The application of this method to the analysis of long chain fatty acids in plasma is also investigated. The LC separation shows good selectivity and reproducibility for fatty acids derivatives. The relative standard deviations (n=6) for each fatty acid derivative are <5.0%. The detection limits are at 38–57 fmol levels for C₁₄−C₂₀ fatty acids and lower levels for <C₁₄ fatty acids.     

Correlations Between FAS Elongation Cycle Genes Expression and Fatty Acid Production for Improvement of Long-Chain Fatty Acids in Escherichia coli

Microorganisms have been used for biodiesel (fatty acid methyl ester) production due to their significant environmental and economic benefits. The aim of the present research was to develop new strains of Escherichia coli K-12 MG1655 and to increase the content of long-chain fatty acids by overexpressing essential enzymes that are involved in the fatty acid synthase elongation cycle. In addition, the relationship of β-ketoacyl-acyl carrier protein (ACP) synthase (fabH), β-ketoacyl-ACP reductase (fabG), β-hydroxyacyl-ACP dehydrase (fabZ), and β-enoyl-ACP reductase (fabI) with respect to fatty acid production was investigated. The four enzymes play a unique role in fatty acid biosynthesis and elongation processes. We report the generation of recombinant E. coli strains that produced long-chain fatty acids to amounts twofold over wild type. To verify the results, NAD⁺/NADH ratios and glucose analyses were performed. We also confirmed that FabZ plays an important role in producing unsaturated fatty acids (UFAs) as E. coli SGJS25 (overexpressing the fabZ gene) produced the highest percentage of UFAs (35 % of total long-chain fatty acids), over wild type and other recombinants. Indeed, cis-9-hexadecenoic acid, a major UFA in E. coli SGJS25, was produced at levels 20-fold higher than in wild type after 20 h in culture. The biochemically engineered E. coli presented in this study is expected to be more economical for producing long-chain fatty acids in quality biodiesel production processes.     

Preparation of radioactive bromamine-T by isotope exchange with radioactive bromine

In hearts of mice the accumulation of 15-/para-¹²³I-phenyl/-pentadecanoic acid /IPPA/ was determined 3 min after injection under different conditions. Using propionate as an agent competing with the albumin binding sites for fatty acids, the concentration of free fatty acids was increased in the circulating blood and the myocardial uptake of IPPA rose from 38.8±3.7% inj. dose/g under normal conditions to 46.2±5.1% inj. dose/g. On the other hand, the addition of 2-Br-palmitic acid reduced the myocardial uptake to a value of 31.0±2.5 inj. dose/g due to the known effect of blocking the transport of fatty acids into the cells. The results suggest the existence of a carrier-mediated transport process of fatty acids into the myocardial tissue.     

Synthesis and structural characterization of 3,4-diphenylcyclopenta-2,4-diene-1 thione and its reactivity with V(V)

In the first part of this work, we have studied the reactivity of an ethanolic solution of diphenylthiocarbazone (C₁₃H₁₂N₄S) with an aqueous solution of vanadium(V), leading to a new compound C₁₇H₁₂S (L). This compound was crystallographically characterized and identified by XRD. This technique reveals no metal in the structure. Then, we reacted L with the same metal, producing a dimeric complex V₂O₄(L)₂(H₂O)₂(OH)₂ (C1), characterized by elemental analysis, IR, UV–Visible, ¹H NMR, ¹³C NMR, and ⁵¹V NMR spectra. A probable structure has been proposed.     

The Determination of Trace Amounts of Tellurium and Selenium in Gallium Metal

Abstract

Analytical methods have been developed for the separation, concentration and determination of trace quantities of tellurium and selenium from primary and scrap gallium metal. A chloroform extraction is made of the tellurium diethyldithiocarbamate complex at a pH of 8.5. This extraction, in the presence of ammonium citrate, allows the satisfactory determination of tellurium by emission or atomic absorption spectrohcopy. The limit of sensitivity of the method is 0.5 pg of tellurium in 1.0 gram of gallium (0.5 ppm Te).     

Normal-phase high performance liquid chromatographic separation and characterization of short- and long-chain triacylglycerols

Summary Short- and long-chain triacylglycerols (SLCT) are a family of lipids prepared by chemical or enzymatic interesterification of triacetin, tripropionin and/or tributyrin, and long-chain (C_16!18) hydrogenated vegetable oils. In this study, a normal-phase cyanopropyl high-performance liquid chromatographic (HPLC) method was developed for the separation and quantification of SLCT. The method is capable of separating SLCT mixtures, free fatty acids and the neutral lipid classes of saturated long-chain triacylglycerols, diacylglycerols and monoacylglycerols. To characterize the specific SLCT classes, a normal-phase HPLC procedure using a non-modified silica column was developed to separate the SLCT into individual isomers based on total carbon number and position of fatty acids on the glycerol backbone. Online coupling with a mass detector (LC/MS) allowed the identification of the individual triacylglycerol structures.     

TELLURIUM(II)-THIOSEMICARBAZONE COMPLEXES‐A PARALLEL TO THE LIGATION OF THIOUREAS

Abstract

The tellurium(II)-complexes of the type Te(XTSC)₂Cl₂ (I) and Te(XTSC)₄Cl₂ (II), where XTSC=benzaldehyde, acetophenone, salicylaldehyde or 2-hydroxyacetophenone thiosemicarbazone have been isolated. The IR, PMR and CMR spectra of the complexes in conjunction with their elemental analyses and conductance measurements, indicate the formation of a three centre-four electron bond between tellurium and two sulphur atoms of the thiosemicarbazones, trans to each other. These results exhibit for the first time that thiosemicarbazones may ligate with tellurium(II) in a manner parallel to that of thioureas. The square planar and octahedral arrangement of the ligands around tellurium are proposed for I and II type complexes respectively.     

Synthesis and bio‐evaluation of Tc‐99 m‐labeled fatty acid derivatives for myocardial metabolism imaging

¹¹C, ¹⁸F and ¹²³I fatty acids are used for myocardial imaging, and ^99mTc‐labeled fatty acids are more desirable substitutes than other radiolabeled fatty acids. In the work reported, [^99mTc]‐CpTT‐10‐oxo‐FPA ( 1c ), [^99mTc]‐CpTT‐12‐oxo‐FPA ( 2c ), [^99mTc]‐CpTT‐14‐oxo‐FPA ( 3c ) and [^99mTc]‐CpTT‐16‐oxo‐FPA ( 4c ) were prepared with 60.76–70.92% of radiochemical yield and purity of more than 95%. These radiotracers ( 1c , 2c , 3c , 4c ) were chemically stable when incubated in Sprague Dawley rat serum for 3 h at 37 °C. Tissue distribution studies in female mice indicated that 2c had high initial heart uptake (8.84%ID g^?1 at 1 min post‐injection) and 4c had long retention in the heart (1.45%ID g^?1 at 30 min post‐injection). Metabolite analysis showed 4c could be metabolized to 5c via β‐oxidation with loss of two ? CH₂? in the myocardium, the radiometabolite being excreted via urine. However, low heart uptake suggested that 4c cannot be used as a diagnostic imaging agent. Copyright © 2016 John Wiley & Sons, Ltd.     

Determination of poly(ethylene glycol) 300 in long chain free fatty acid mixtures by reversed-phase high-performance liquid chromatography

A rapid sensitive method has been developed for the detection and quantitation of poly(ethylene glycol) 300 (PEG 300) in long-chain free fatty acid mixtures that requires minimal sample preparation. The PEG 300 was separated from the free fatty acids by RP-HPLC using a water–tetrahydrofuran gradient. PEG and the free fatty acids were detected using evaporative light scattering detection. The minimum detectable level of PEG in a free fatty acid mixture was 0.0125%.     

Radiopharmaceuticals

For studying the metabolism of fatty acids in the heart muscle in-vivo, ω-phenylpenta-decanoic acid (PPA) was labelled with radioiodine to the ortho and para position of the benzene ring with a radiochemical yield of 60%. The products were obtained in a relative isomer distribution of 29%ortho and 71%para radioiodinated PPA. The radiopharmaceutical quality control was performed by sequential radio high pressure liquid chromatography.     

Morphological silica-supported acid catalyst for esterification of aliphatic fatty acid

Abstract

Silica-supported acid catalysts were synthesized and characterized for composition, morphology, particle size distribution, and crystallinity. The catalysts are used for the esterification of long-chain aliphatic acids with alcohol to produce the corresponding ester. Process parameters such as time, temperature, and solvent ratio influence the conversion of fatty acid to ester. A supported catalyst was found to show higher catalytic activity as compared to the conventional sulfuric acid catalyst.     

DITHIOPHOSPHORIC ACIDS AND TETRAPHOSPHORUS DECASULFIDE IN THE SYNTHESIS OF BORON DITHIOPHOSPHATES

Abstract

The reactions of O,O-dialkyl dithiophosphoric acids with triisobutyl borate, ammonium O,O-diisobutyl dithiophosphate with fluorodiisobutyl borate, and tetraphosphorus decasulfide with triisobutyl borate were studied. On the basis of these studies, new boron derivatives of dithiophosphoric acids were obtained. Low frequency ultrasonic irradiation (22 kHz, power 130 W) leads to reduction in reaction temperature and time in the reactions studied.     

Unexpected Thioketene Derivative Formation During Thioacyl Dithiophosphate Synthesis

Abstract

The scope and limitations of the thioacylation method using thioacyl dithiophosphates were investigated. Thioacyl dithiophosphates are formed in the reaction of acyl dithiophosphates with dithiophosphoric acid. However when the acyl moiety contains two α-substituents then a thioketene derivative is formed thus lowering the yield of expected thioacyl dithiophosphate.