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PubMed2004

Preparation and promotion of fruit growth in kiwifruit of fluorinated N-phenyl-N'-1,2,3-thiadiazol-5-yl ureas.

Seventeen phenyl-fluorinated analogues of thidiazuron [N-phenyl-N'-(1,2,3-thiadiazol-5-yl)urea, TDZ] have been prepared and characterized. The effects of each fluorinated urea on growth and quality of kiwifruits (Actinidia deliciosa) were evaluated by comparison with untreated (control) and TDZ-treated fruits. The results obtained showed a clear dependence of the growth-promoting activity of these fluorinated ureas on the pattern and degree of fluorine substitution in the phenyl ring. The most effective for promoting fruit growth was N-(2,3,5,6-tetrafluorophenyl)-N'-(1',2',3'-thiadiazol-5'-yl)urea at 25 ppm (at harvest, treated fruits were 58% heavier than untreated ones) followed by N-(3,5-difluorophenyl)-N'-(1',2',3'-thiadiazol-5'-yl)urea at 10 ppm (50%). Comparatively, TDZ-treated fruits were 31% (10 ppm) and 38% (25 ppm) heavier than untreated ones. The results also indicate that the effects of the more active phenyl-fluorinated ureas on some standard quality parameters of fruits, for example, percent of fruit dry matter content, soluble solids contents, total titratable acids, shape, and internal structure, are similar to those of TDZ. Quantitative structure-activity relationships have been derived for the fruit growth promoting activity of the phenyl-fluorinated analogues of TDZ.

Actinidia↗
PubMed1986

Synthesis and adrenergic activity of ring-fluorinated phenylephrines.

2-Fluoro-, 4-fluoro-, and 6-fluorophenylephrine (6-FPE) were synthesized from the corresponding fluorinated 3-hydroxybenzaldehydes. New routes to 2-fluoro- and 6-fluoro-3-hydroxybenzaldehydes were developed based on regioselective lithiation of 2- and 4-[(dimethyl-tert-butylsilyl)oxy]fluorobenzene ortho to fluorine. As with norepinephrine and isoproterenol analogues, the adrenergic properties of phenylephrine were markedly altered by ring fluorination. The order of potency of the fluoro analogues as alpha 1-adrenergic agonists in the stimulation of contraction of aortic strips and of phosphatidylinositol turnover and potentiation of cyclic AMP accumulation in guinea pig synaptoneurosomes was 6-FPE greater than PE greater than 4-FPE greater than 2-FPE. The same pattern was observed for the displacement of radioligands specific for alpha 1- and alpha 2-adrenergic receptors on brain membranes. The order of potency for the displacement of [3H]dihydroalprenolol, a beta-specific adrenergic ligand from brain membranes, was 2-FPE greater than 4-FPE = PE much greater than 6-FPE. 6-FPE was much more selective for alpha-adrenergic receptors compared to beta-receptors than was phenylephrine. A rationale for the observed fluorine-induced alterations in potency and selectivity of the FPEs for alpha- and beta-adrenergic systems is presented based on fluorine-induced conformations due to electrostatic repulsion of fluorine and the benzyl hydroxyl group.

Animals↗
PubMed2004

Hydrogen bonding interactions of covalently bonded fluorine atoms: from crystallographic data to a new angular function in the GRID force field.

Through the years the GRID force field has been tuned to fit experimental observations in crystal structures. This paper describes the determination of the hydrogen bonding pattern for organic fluorines based on an exhaustive inspection of the Protein Data Bank. All the PDB complexes, whose protein structures have cocrystallized fluorine-containing ligands, were examined and geometrically inspected. By applying statistics, the hydrogen bonding geometry was described as a distribution function of the angle at the fluorine: a new specific angular function was consequently defined and inserted in the program GRID to estimate the effect of fluorine hydrogen bonds on the ligand-protein binding. All the fluorine-containing ligands collected from the PDB were docked within their corresponding protein binding sites: introducing the fluorine hydrogen bonding contribution improves the results of the docking experiments in terms of accuracy and ranking.

Binding Sites↗
PubMed1990

Reaction pathways for biodehalogenation of fluorinated anilines.

Pathways for biodehalogenation of fluorinated aniline derivatives were investigated. Microsomal NADPH-dependent dehalogenation of fluoroanilines was shown to proceed by three different reaction pathways. The first route appeared to result in monooxygenation at a fluorinated position and release of the fluorine atom as a fluoride anion. The primary additional reaction product formed is the reactive quinoneimine, not the 4-hydroxyaniline. In NADPH-containing microsomal systems with 4-fluoro-substituted anilines, formation of the 4-hydroxyaniline derivative is observed because NADPH chemically reduces this quinoneimine metabolite. A second pathway for dehalogenation proceeds by protein binding of a fluoro-containing (semi)quinoneimine metabolite, the formation of which may result from the mono-oxygenase reaction (pathway 1) and/or from (re)oxidation of a hydroxyaniline metabolite by superoxide anion radicals produced by the microsomal system. This latter reaction pathway becomes more important with increasing number of fluoro-substituents in the fluoroaniline derivative. The higher ratio of fluoride anion formed to 4-hydroxyaniline derivative detected in incubations with liver microsomes from dexamethasone-treated rats, as compared to incubations with liver microsomes from control rats, can in part be explained by the higher production of superoxide anion radicals observed in the dexamethasone systems. The third mechanism was shown to proceed by formation of a hydroxylated metabolite that loses fluoride anion upon exposure to oxygen. The reactive intermediate formed upon oxygen exposure might be the semiquinoneimine which loses its fluorine atom as a fluoride anion upon dimerization or polymerization and/or protein binding. The fluorohydroxyanilines, in which the hydroxyl group is ortho or para with respect to the fluoro substituent, appear especially to be highly unstable and lose fluoride anion in the presence of oxygen. Finally, it is concluded that all three pathways for dehalogenation of fluorinated aniline derivatives are bioactivation pathways. The reactivity of the (semi)quinoneimines formed in these reactions is dependent on their substitution pattern and increases with increasing number of fluoro-substituents. Therefore, bioactivation for a series of fluorinated aniline derivatives, can be expected to vary with the substitution pattern and to increase with increasing number of halogen substituents.

Aniline Compounds↗
PubMed1993

The effect of fluorine substitution on the physicochemical properties and the analgesic activity of paracetamol.

The physicochemical properties and analgesic action of six fluorinated analogues of 4-hydroxyacetanilide (paracetamol) have been investigated. Fluorine substitution adjacent to the hydroxyl group increased lipophilicity and oxidation potential whilst substitution adjacent to the amide had little effect on lipophilicity but led to a greater increase in oxidation potential. Lack of coplanarity and conjugation of the amide group and aromatic ring was also apparent with the analogues that had fluorine in the 2 and 6 positions. Introduction of fluorine into the amide group of paracetamol increased the lipophilicity 4-fold and also increased the oxidation potential of paracetamol. ED50 values for analgesic activity in the phenylquinone-induced abdominal constriction test on male Swiss White mice showed that ring substitution by fluorine reduced activity, especially at the 2,6-positions. Introduction of fluorine into the amide group enhanced activity significantly. Correlation of the analgesic activity with the physicochemical properties indicated that conjugation (and planarity) of the amide group with the aromatic ring is essential for activity and that ease of oxidation may also be an important factor.

Acetaminophen↗
PubMed1998

A new microwave acid digestion bomb method for the determination of total fluorine.

A new microwave acid digestion method for total fluorine analysis was compared to the reliable reverse-extraction technique. The commercially available Parr bombs which are compatible with microwave heating were modified for this purpose. The Mann-Whitney statistical test did not show any significant differences (p > 0.05) in the determinations of total fluorine in various samples between the two above-mentioned methods. The microwave method also gave high fluorine recoveries (> 97%) when fluoride was added to different samples. The great advantage of the microwave acid digestion bomb method is that the digestion under pressure is so aggressive that only a few minutes is needed for complete digestion (also of covalently bonded fluorine), which reduces the time for fluorine analysis dramatically, while no loss of fluorine or contamination from extraneous sources could take place during the ashing procedure. The digestion solution was made up of 300 microliter of concentrated nitric acid plus 537 microliter of water. After digestion 675 microliter of approximately 8.5 M sodium hydroxide plus 643 microliter of citrate/TISAB buffer was added resulting in an alkaline solution (pH approximately 12) which was finally adjusted to a pH of approximately 5.3 for fluoride determination.

Acids↗
PubMed2005

Fluorine-18-labelled fluoropyridines: advances in radiopharmaceutical design.

Positron Emission Tomography is a high-resolution, sensitive, functional imaging technique, which can efficiently give access to the distribution, pharmacokinetics and -dynamics of a drug in vivo and which can therefore advantageously play a key-role in both drug discovery and development. This molecular imaging technique requires the preparation of a positron-emitting radiolabelled probe or radiotracer and for this purpose, fluorine-18 is becoming, more and more often, the radionuclide of choice (adequate physical and nuclear characteristics and potential wide use and -distribution of fluorine-18-labelled radiopharmaceuticals). Considering chemical structures showing a fluoropyridinyl moiety, nucleophilic heteroaromatic substitution at the ortho-position with no-carrier-added [18F]fluoride appears today as the most efficient method for the radiosynthesis of radiotracers and radiopharmaceuticals of high specific radioactivity when compared to homoaromatic-, but also aliphatic, nucleophilic radiofluorination. Like for the aliphatic nucleophilic radiofluorinations, only a good leaving group is required (a halogen, or better a nitro- or a trimethylammonium group). There is no need for an additional strong electron-withdrawing substituent for activation of the aromatic ring such as in the homoaromatic nucleophilic radiofluorinations, except if one considers meta-fluorination. Nucleophilic heteroaromatic substitution and consequent fluorine-18 incorporation are generally performed in DMSO with the no-carrier-added, activated K[18F]F-K222 complex using conventional heating at a moderately high temperature (120-150 degrees C) or microwave irradiation (100 Watt) for a short period of time (1-2 minutes) and often lead to high radiochemical yields. This review summarizes some of the recent applications of these nucleophilic heteroaromatic substitutions in the pyridine series and highlights its potential in the design (not seldom by hydrogen, hydroxyl or halogen replacement by fluorine) and preparation, of often drug-based, fluorine-18-labelled radiotracers and radiopharmaceuticals of high specific radioactivity for PET imaging.

Drug Design↗
PubMed1991

[Fluorine excretion in urine and feces of rats dependent on the source of this element and content of protein in the diet].

Wistar rats of both sexes were fed semisynthetic diets containing 12 or 24% of protein derived from casein or from krill meal, as well as comprising fluorine (357 mg/kg diet) either from krill meal or from sodium fluoride. After 7, 14 and 32 weeks urine and feces were collected for constructing the fluorine balance. It was found that rate fed krill meal excrete fluorine mainly in feces, and those administrated sodium fluoride--mainly in urine. A higher dietary protein level leads to enhanced fluorine excretion. Fluorine from krill meal is definitely less able to be assimilated than that from sodium fluoride. When fluorine administration is discontinued, this element is released from the organism and is excreted mainly in feces.

Animals↗
PubMed1987

Fluorine uptake in bovine enamel from various treatment agents.

Bovine tooth enamel with a low and uniform fluorine content was used for the study of fluorine uptake by the Micro-Acid-Drop enamel biopsy technique from different treatment agents commonly used in Sweden. The fluorine concentration in the enamel was also measured after an exposure of the treated test surfaces in artificial saliva for 90 minutes. Sodium fluoride 0.2% and 2%, ferric aluminum fluoride solution and Duraphat varnish showed a high uptake of fluorine in the enamel with the highest concentration in the surface layer. Fluor Protector and the toothpastes showed a considerably lower fluorine uptake. After immersion in artificial saliva of the specimens, the concentration of fluorine in the enamel decreased.

Acid Etching, Dental↗
PubMed1984

Fluorine concentration in primary tooth enamel in 6-year-olds after 3 years of daily intake of fluoride-containing tablets (Fludent).

The purpose of this study was to determine the posteruptive uptake of fluorine in primary tooth enamel after daily consumption of a fluoride-containing sucking tablet for three years. The material consisted of 17 children, who had been advised to suck on 1 NaF tablet (Fludent, 0.25 mg F) daily at bedtime from 3 to 6 years of age (test group), and 17 children without tablet supply (control group). No other fluoride preparation was used during the period. A chemical biopsy method, described by Koch et al. (1982), was used to determine the fluorine concentration in enamel at the age of 6. Two consecutive layers on the upper central primary incisors of each child were etched off by perchloric acid. Chemical analysis of the test solutions was used to determine the thickness of the enamel layers and the fluorine content. Statistical evaluations were performed by analysis-of-variance. The results showed that fluorine was incorporated in primary tooth enamel as a topical effect of the fluoride tablet intake. There was a statistically significant difference (p less than 0.05) between the groups regarding fluorine measured on the layers combined and in the out layer (approximately equal to 5 micron thick), but not in the inner layer (approximately equal to 8 micron). It was concluded that the posteruptively increased enamel fluorine concentration probably contributes to the caries-preventive effect of NaF tablets.

Biopsy↗
PubMed1981

Theoretical motivations of fluorine incorporation into the complex therapy of parodontosis.

The results of experiments on dogs with periodontal disease have proved the following: 1. Mobility of calcium in the jaws and skeleton occurs in periodontal disease. 2. The body of the mandible plays a particular role in the compensatory mineralization of the alveolar process. 3. There is a discernible increase in fluorine content in pathologically affected zones of jaw bones. 4. Small doses of fluorine are able to increase calcium deposition in jaw bones. Clinical proof has been obtained of the beneficial influence of fluorine in the complex treatment of periodontal disease, which is manifest in the retention of calcium and fluorine in the organism. The ability of fluorine to substitute for calcium in resorption of the alveolar margin and to stimulate calcium deposition in jaw bones provides theoretical support for the recommendation to incorporate small doses of fluorine into the complex therapy of periodontal disease.

Animals↗
PubMed1998

[Fluorine in vegetables and potatoes from the market in Warsaw].

In 65 samples of vegetables: cabbages, carrots, beetroots, onions and potatoes, of whose consumption is the highest in Poland, fluorine content was determined. The samples were prepared according to AOAC method, and fluorine concentration was determined in the filtrate by the potentiometric method using a Fluoride--selective electrode--model 920A of Orion Research Inc. The recovery rate of fluorine was 95 +/- 5%. The average level of soluble fluorine ranged from 3.36 mg/kg of dry weight of cabbage to 5.37 mg/kg of dry weight of onion and from 0.38 mg/kg of fresh weight of cabbage to 1.02 mg/kg of fresh weight of potatoes. In over 50% of the investigated samples fluorine content exceeded 0.56 mg/kg of fresh weight, which is the upper limit value of fluorine content found in the vegetables from the areas ecologically clean.

Fluorine↗
PubMed2006

Consumption and metabolism of 1,2-dimethoxy-4-(3-fluoro-2-propenyl)benzene, a fluorine analog of methyl eugenol, in the oriental fruit fly Bactrocera dorsalis (Hendel).

Methyl eugenol (ME) is a natural phenylpropanoid highly attractive to oriental fruit fly Bactrocera dorsalis (Hendel) males. The flies eagerly feed on ME and produce hydroxylated metabolites with both pheromonal and allomonal functions. Side-chain metabolic activation of ME has long been recognized as a primary reason for hepatocarcinogenicity of this compound on rodents. In an attempt to develop a safer alternative to ME for fruit fly management, we developed a fluorine analog 1,2-dimethoxy-4-(3-fluoro-2-propenyl)benzene (I), which, in earlier field tests, was as active to the oriental fruit fly as ME. Now we report that B. dorsalis males are not only attracted to, but also eagerly consume (up to approximately 1 mg/insect) compound I, thus recognizing this fluorinated benzene as a close kin of the natural ME. The flies metabolized the fluorine analog I in a similar fashion producing mostly two hydroxylated products, 2-(3-fluoro-2-propenyl)-4,5-dimethoxyphenol (II) and (E)-coniferyl alcohol (III), which they stored in rectal glands. However, the introduction of the fluorine atom at the terminal carbon atom of the double bond favors the ring hydroxylation over a side-chain metabolic oxidation pathway, by which coniferyl alcohol is produced. It also appears that fluorination overall impedes the metabolism: at high feed rate (10 mul per 10 males), the flies consumed in total more fluorine analog I than ME but were unable to metabolize it as efficiently as ME.

Animals↗
PubMed1991

Bioactivation of 4-fluorinated anilines to benzoquinoneimines as primary reaction products.

Metabolism and bioactivation of fluoroanilines was studied both in vitro in microsomal systems and in vivo. 4-Fluoroaniline and pentafluoroaniline and their non-para fluorinated analogues were used as the model compounds. Special attention was focussed on bioactivation to reactive benzoquinoneimines. Cytochrome P-450 dependent monooxygenation at a non-fluorinated para position in (fluoro)aniline derivatives proceeds by formation of the para hydroxylated derivative as the primary metabolite. Monooxygenation at a fluorinated para position in an aniline derivative, however, proceeds by formation of fluoride anion and the reactive benzoquinoneimine as primary reaction products. Thus, for fluoroanilines with a fluorine substituent at the para position bioactivation to the reactive benzoquinoneimine can be a direct result of the cytochrome P-450 dependent conversion. In systems containing NAD(P)H and/or other reducing equivalents part of the benzoquinoneimine can be chemically reduced to give the corresponding 4-hydroxyaniline. In vivo this reduced form of the metabolite can be sulphated or glucuronidated and excreted into urine. The results obtained point to increased chances of bioactivation for aniline derivatives with a fluorinated para position as compared to their non-para fluorinated analogues, both in vitro but also in vivo.

Aniline Compounds↗
PubMed1992

Fluorine modification of nitroazole radiosensitizers for the enhancement of sensitizing activity with lowering toxicity: a pharmacokinetic characterization.

Pharmacokinetic characterization of various nitroazole radiosensitizers was carried out to clarify the effect of fluorine modification of the side-chain groups on the sensitizing activity and the acute toxicity. The in vivo tumor/plasma partition coefficient (PTP) of sensitizers increased with increase in the octanol/water partition coefficient (Pow) up to approximately 0.3 and was almost unity (maximum) for sensitizers with their Pow values larger than approximately 0.3. This relationship was observed commonly for all types of sensitizers independent of the fluorine modification. The in vivo brain/plasma partition coefficient (PBP) of sensitizers increased with increase in the Pow, attaining a constant value of almost unity at Pow greater than 0.5 for non-fluorine sensitizers or at Pow greater than 1.5 for fluorine-modified sensitizers. The maximum brain-affinity factor ((FB,t)max = (CB,t)max/Ds, where (CB,t)max and Ds are the maximum intrabrain concentration and the administered dose of sensitizer, respectively) was proportional to the maximum tumor-affinity factor ((FT,t)max = (CT,t)max/Ds, where (CT,t)max is the maximum intratumor concentration of sensitizer), depending on the side-chain structure of the sensitizer. A series of non-fluorine and fluorine-modified nitroazole derivatives, including N-(2'-hydroxyethyl)-2,2-difluoro-3-(3''-nitro-1'-triazolyl)propionamide (KU-2285), gave a smaller brain to tumor ratio of approximately 1/7. The toxicity index defined by 1/LD50/7 was parallel to the sensitizing activity measured by 1/DS,1.5 (DS,1.5 is the sensitizer dose to obtain the SER of 1.5 in vivo). The therapeutic risk index defined by Ds,1.5/LD50/7 depended on the side-chain structures of sensitizers. The DB,1-5LD50-/7 values of KU-2285 and ethanidazole (SR-2508) were 1/3 that of misonidazole (MISO). The sensitizers were smaller Ds,1.5/LD50/7 values showed higher sensitizing activities as their tumor affinities increased, without an increase in serious toxicity.

Animals↗
PubMed2005

Influence of fluorination on surface and dielectric characteristics of polyimide thin film.

In this study, the effects of fluorine treatment on surface properties, surface free energies, and dielectric constants of polyimide thin films were studied using X-ray photoelectron spectroscopy, contact angles, and dielectric characteristics, respectively. The glass transition temperature of fluorinated polyimide film gradually decreases with increasing fluorine pressure. The surface free energies and dielectric constants of the film decreased with increasing amount of the treatment fluorine gas. It was explained that the replacement of fluorine led to a decrease of the local electron polarization of polyimide and an increase of the free volume, which could be attributed to the relatively large volume of fluorine.

Journal Article↗
PubMed2003

Evaluation of cytotoxicity of new semi-fluorinated amphiphiles derived from dimorpholinophosphate.

Water-in-fluorocarbon reverse emulsions and microemulsions stabilized by semi-fluorinated amphiphiles derived from the dimorpholinophosphate polar head group, C(n)F(2n+1)(CH(2))(m)OP(O)[N(CH(2)CH(2))(2)O](2) (FnHmDMP), are being investigated as new delivery systems for drugs or genetic materials into the lung. Since information related to the toxicity of fluorinated surfactants is still very limited, we evaluated herein the cytotoxicity of a series of FnHmDMP (n=4, 6, 8 and 10 and m=2, 5, and 11). Both solutions of FnHmDMP in fluorocarbons, and reverse water-in-fluorocarbon emulsions stabilized by FnHmDMP were assessed in order to determine the relation between surfactant structure and cell toxicity, and select the most innocuous emulsifier. A first short-term evaluation on mouse fibroblasts using a viability/cytotoxicity assay indicated that amphiphiles (in solution) with a chain length longer than C12 exhibit less toxicity than amphiphiles with shorter chain. Moreover cytotoxicity decreased also with length of the fluorinated segment. The protective effect of the fluorinated chain was strongly supported by the fact that the hydrogenated analog, C(15)H(31)OP(O)[N(CH(2)CH(2))(2)O](2) (H15DMP), was highly toxic. Qualitative evaluation on human lung epithelial cells (HLEC) using a colorimetric method (Mayer's hematoxylin) confirmed that amphiphiles (in solution) with longer chain were the least cytotoxic. The protective effect of the fluorinated chain appeared, however, to be significant only at low amphiphile concentrations (0.1% w/v). In contrast, at higher concentrations (1% and 5% w/v), the total chain length was the determining factor. Quantitative evaluation of the least cytotoxic amphiphiles using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) method then showed that F10H11DMP (in solution) was harmless until its solubility limit (1% w/v); cell growth was even enhanced due to improved oxygenation provided by the fluorocarbon phase. F8H11DMP exhibited some cytotoxicity at both 1% and 5% w/v, but the toxicity appeared to level off with concentration. Reverse water-in-perfluorooctyl bromide (PFOB) emulsions stabilized by either F10H11DMP or F8H11DMP were found to be non-cytotoxic. In conclusion, the present evaluation indicates that the cytotoxicity of FnHmDMP depends on both total and fluorinated amphiphile chain length, and leads us to select F8H11DMP and F10H11DMP as the less cytotoxic amphiphiles among a series of FnHmDMP compounds. Furthermore, water-in-fluorocarbon emulsions stabilized with F8H11DMP and F10H11DMP appeared to be non-cytotoxic towards HLEC in culture.

Animals↗
PubMedDate not supplied

Highly fluorinated lipospermines for gene transfer: synthesis and evaluation of their in vitro transfection efficiency.

Fluorinated double-chain lipospermines (one or both of these chains being ended by a highly fluorinated tail of various length) which are close analogues of DOGS (Transfectam) were designed as synthetic vectors for gene delivery. For N/P ratios (N = number of amine functions of the lipid; P = number of DNA phosphates) from 0.8 to 10, these lipospermines condensed DNA, with or without the use of DOPE, to form fluorinated lipoplexes. The efficiency of the fluorinated lipoplexes to transfect lung epithelial A549 cells was significantly higher than that of the DOGS lipoplexes. No specific cell toxicity was evidenced for the fluorinated lipoplexes as compared to that of the DOGS ones. The palette of structural elements explored allowed to determine those required for efficient transfection, highlighting the importance of highly fluorinated chains, the unique properties of unsaturated double-chain lipids and of the use of DOPE as helper lipid on transfection.

Cell Survival↗