Showing papers on "Benzoic acid published in 2010"
TL;DR: It is proposed that at least a part of the biological activities ascribed to berry polyphenols and other PPT are due to their colonic catabolites.
Abstract: The absorption of dietary phenols, polyphenols and tannins (PPT) is an essential step for biological activity and effects on health. Although a proportion of these dietary bioactive compounds are absorbed intact, depending on their chemical structure and the nature of any attached moiety (e.g. sugar, organic acid), substantial amounts of lower molecular weight catabolites are absorbed after biotransformation by the colon microflora. The main products in the colon are (a) benzoic acids (C6-C1), especially benzoic acid and protocatechuic acid; (b) phenylacetic acids (C6-C2), especially phenylacetic acid per se; (c) phenylpropionic acids (C6-C3), where the latter are almost entirely in the dihydro form, notably dihydrocaffeic acid, dihydroferulic acid, phenylpropionic acid and 3-(3'-hydroxyphenyl)-propionic acid. As a result of this biotransformation, some of these compounds can each reach mm concentrations in faecal water. Many of these catabolites are efficiently absorbed in the colon, appear in the blood and are ultimately excreted in the urine. In the case of certain polyphenols, such as anthocyanins, these catabolites are major products in vivo; protocatechuic acid is reported to represent a substantial amount of the ingested dose of cyanidin-3-O-glucoside. The major catabolites of berries, and especially blackcurrants, are predicted based on compositional data for polyphenols from berries and other sources. Since microbial catabolites may be present at many sites of the body in higher concentration than the parent compound, it is proposed that at least a part of the biological activities ascribed to berry polyphenols and other PPT are due to their colonic catabolites.
403 citations
TL;DR: The selective syntheses of 1,3- and 1,4-distyrylbenzenes have also been realized through the reactions of simple benzoic acid and phthalic acid, respectively, with styrene under similar conditions.
183 citations
TL;DR: In this paper, a new Schiff base, 3-ethoxy salicylidene amino benzoic acid (ETSAN), has been synthesized from 3-ethylsalicylaldehyde and 2-amino benzosic acid.
Abstract: A new Schiff base, 3-ethoxy salicylidene amino benzoic acid (ETSAN), has been synthesized from 3-ethoxy salicylaldehyde and 2-amino benzoic acid. Metal complexes of the Schiff base were prepared from nitrate/chloride salts of Ni(II), Co(II) Cu(II) and Zn(II) in an alcoholic medium. The complexes were non-electrolytes in dimethyl sulfoxide solvent (DMSO). The chemical structures of the Schiff-base ligand and its metal complexes were confirmed by various spectroscopic studies like IR, UV-VIS, 1 H NMR, 13 C NMR, ESI-mass spectra, elemental analysis, molar conductance, thermogravimetric studies and magnetic susceptibility measurements. On the basis of elemental and spectral studies, six-coordinated geometry was assigned to these complexes. In the light of these results, it is suggested that this ligand acts as neutral and tridentate and coordinates to each metal atom by azomethine nitrogen and oxygen atoms of hydroxyl group of the 3-ethoxy salicylaldehyde, besides the hydroxyl group of the carboxyl group of 2-amino benzoic acid. The mass spectral data confirm s the monomeric structure of the metal complexes while the TGA studies confirm the presence of water molecules in the complex. The free Schiff base and its complexes have been tested for their antibacterial as well as antifungal activity by using disc diffusion method and the results discussed. Keywords: Schiff base; 3-ethoxy salicylaldehyde; 2-amino benzoic acid; Metal complexes; Antibacterial activity; Antifungal activity. © 2010 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. DOI: 10.3329/jsr.v2i3.4899 J. Sci. Res. 2 (3), 513-524 (2010)
170 citations
TL;DR: The products of oxidation of 1,2-diphenyl-2-methoxyethanol depend on the solvent; in DMSO benzaldehyde and methanol are the major products, while benzoic acid and methyl benzoate are theMajor products obtained in pyridine solvent.
Abstract: Dipicolinate vanadium(V) complexes oxidize lignin model complexes pinacol monomethyl ether (A), 2-phenoxyethanol (B), 1-phenyl-2-phenoxyethanol (C), and 1,2-diphenyl-2-methoxyethanol (D). With substrates having C−H bonds adjacent to the alcohol moiety (B−D), the C−H bond is broken in pyridine-d5 solvent, yielding 2-phenoxyacetaldehyde from B, 2-phenoxyacetophenone from C, and benzoin methyl ether from D. In DMSO-d6 solvent the reaction is slower, and both C−H and C−C bond cleavage products are observed for D. The vanadium(IV) products of these reactions have been identified and characterized. Catalytic oxidation of C and D has been demonstrated using air and (dipic)V(O)OiPr. For both substrates, the C−C bond between the alcohol and ether groups is broken in the catalytic oxidation. 1-Phenyl-2-phenoxyethanol is oxidized to a mixture of phenol, formic acid, benzoic acid, and 2-methoxyacetophenone. The products of oxidation of 1,2-diphenyl-2-methoxyethanol depend on the solvent; in DMSO benzaldehyde and meth...
167 citations
TL;DR: In this article, Alcell and soda lignin were dissolved in the ionic liquid 1-ethyl-3-methylimidazolium diethylphosphate (EMIM DEP) and subsequently oxidized using several transition metal catalysts and molecular oxygen under mild conditions.
152 citations
TL;DR: In this article, a correlation between CNT content and the changes in the UV-vis absorption properties is observed especially in the visible spectral range, which may be explained in terms of a strong interphase interaction between carbon nanotubes and TiO 2 in the composite catalysts.
Abstract: Nanostructured composite catalysts produced using multi-walled carbon nanotubes (CNT) and titanium dioxide were prepared by means of a modified acid catalyzed sol–gel method. Materials were extensively characterized by XRD, TG, N 2 adsorption–desorption isotherms, TEM, UV–vis spectroscopy and TPD. Composite catalysts with different CNT contents were tested in the photo-oxidation of phenol under different irradiation wavelengths. A correlation between CNT content and the changes in the UV–vis absorption properties is observed especially in the visible spectral range. The introduction of CNT into the titanium matrix induced a synergic effect when irradiating in the near-UV to visible spectral range. This effect may be explained in terms of a strong interphase interaction between CNT and TiO 2 in the composite catalysts. CNT with different surface chemical groups were used to produce CNT–TiO 2 composites. The presence of mild concentrations of oxygen containing surface groups, mainly carboxylic acids and phenols, appears to produce a beneficial effect in the photocatalytic activity of CNT–TiO 2 composite catalysts. The photocatalytic oxidation of other monosubstituted benzene derivatives such as, aniline, nitrobenzene and benzoic acid, has been investigated under visible irradiation. The primary intermediates of photocatalytic reaction are single substituted hydroxy derivatives. The photoefficiency of the composite catalyst showed to be affected by the aromatic ring reactivity properties of the substrate.
140 citations
TL;DR: It is proved that all three key steps in the catalytic cycle of CuAAC can proceed in the presence of carboxylic acids and the latter two steps can be promoted significantly by carboxYlic acids.
Abstract: In this article, we proved that all three key steps in the catalytic cycle of CuAAC can proceed in the presence of carboxylic acids and the latter two steps can be promoted significantly by carboxylic acids. Benzoic acid showed the best promotion activity, and the acids with strong chelating ability to Cu(I) ion could not serve for this purpose. Thus, the first carboxylic acid-promoted highly efficient CuAAC was established.
136 citations
TL;DR: In this paper, superhydrophobic silver films on copper (Cu) substrates can be created in just a one-step process via galvanic reactions by immersing the Cu substrates in silver nitrate solution containing benzoic acid, simplifying the complexity of two different steps involved in the former method.
Abstract: In general, creation of superhydrophobic surfaces is composed of two steps: (i) creation of a rough surface and (ii) passivation of the surface with the low surface energy molecules or coatings. Superhydrophobic properties cannot be achieved on a surface without these two essential factors fulfilled. In the present work we have demonstrated that superhydrophobic silver films on copper (Cu) substrates can be created in just a one-step process via galvanic reactions by immersing the Cu substrates in silver nitrate solution containing benzoic acid, simplifying the complexity of two different steps involved in the former method. Silver films were also fabricated using similar process without benzoic acid for comparative studies. The X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) confirmed the formation of benzoic acid incorporated silver films. Scanning electron microscopy (SEM) images showed micro-nano structured leaf-like and flower-like morphological features in the films prepared without and with benzoic acid, respectively. Benzoic acid incorporated flower-like silver films demonstrated water repellency as the water drops rolled off those surfaces whereas complete absorption of water drops were encountered on the leaf-like silver surfaces prepared without benzoic acid.
115 citations
TL;DR: The participation of the monocarboxylic acid transporter MCT1 in the intestinal absorption of weak organic acids has been clarified by functional characterization, by use of stably transfected cells, and by immunohistochemical location of the transporter in intestinal tissues.
Abstract: The participation of the monocarboxylic acid transporter MCT1 in the intestinal absorption of weak organic acids has been clarified by functional characterization, by use of stably transfected cells, and by immunohistochemical location of the transporter in intestinal tissues. Immunohistochemical analysis by use of the anti-MCT1 antibody showed that MCT1 is distributed throughout the upper and lower intestines, especially in the basolateral membrane and, to a lesser extent, in the brush-border membrane. When the transporter gene rat MCT1 was transfected into MDA-MB231 cells, transport of benzoic acid, a model weak organic acid that has been generally believed to be transported across the cell membranes by passive diffusion, and lactic acid in rat MCT1-transfected cells was significantly increased compared with transport in cells transfected with the expression vector pRc-CMV alone (mock cells). The observed transport was pH-dependent and activity increased between pH 7.5 and pH 5.5, whereas pH-dependence in mock cells was moderate. Rat MCT1-mediated benzoic acid uptake was saturable, with an apparent Km value of 3.05 mM. In addition, MCT1 increased the efflux of [14C]benzoic acid from the cells. Several weak organic acids were also transported by rat MCT1. These results show that pH-dependent intestinal absorption of weak organic acids, previously explained in terms of passive diffusion according to the pH-partition hypothesis, is at least partially accounted for by MCT1-mediated transport energized at acidic pH by utilization of the proton gradient as a driving force.
109 citations
TL;DR: Three new 4-benzyloxy benzoic acid derivatives have been employed as ligands for the support of six lanthanide coordination compounds with the aim of testing the influence of electron releasing (-OMe) or electron withdrawing (-NO(2)) substituents on the photophysical properties.
Abstract: Three new 4-benzyloxy benzoic acid derivatives [4-benzyloxy benzoic acid = HL1; 3-methoxy-4-benzyloxy benzoic acid = HL2; 3-nitro-4-benzyloxy benzoic acid = HL3] have been employed as ligands for the support of six lanthanide coordination compounds [Tb3+ = 1–3; Eu3+ = 4–6] with the aim of testing the influence of electron releasing (-OMe) or electron withdrawing (-NO2) substituents on the photophysical properties. The new complexes have been characterized by a variety of spectroscopic techniques and two of the Tb3+ complexes [1 and 2] have been structurally authenticated by single-crystal X-ray diffraction. Compounds 1 and 2 crystallize in the monoclinic space group P21/n and their molecular structures consist of homodinuclear species that are bridged by two oxygen atoms from two benzoate ligands. In the case of 1, the carboxylate ligands coordinate to the central Tb3+ ion in bidentate chelating and bidentate bridging modes. By contrast, three different coordination modes (bidentate chelating, bidentate bridging and monodentate) are observed in the case of compound 2. Examination of the packing diagrams for 1 and 2 revealed the presence of a one-dimensional molecular array that is held together by intermolecular hydrogen-bonding interactions. The incorporation of an electron-releasing substituent on position 3 of 4-benzyloxy benzoic acid increases the electron density of the ligand and consequently improves the photoluminescence of the Tb3+ complexes. On the other hand, the presence of an electron-withdrawing group at this position dramatically decreases the overall sensitization efficiency of the Tb3+-centered luminescence due to dissipation of the excitation energy by means of a π*-n transition of the NO2 substituent along with the participation of the ILCT bands. The weaker photoluminescence of the Eu3+ complexes is attributable to the poor match of the triplet energy levels of the 4-benzyloxy benzoic acid derivatives with that of the emitting level of the central metal ion.
101 citations
TL;DR: Two new polyphenols containing both phenolic bisabolane sesquiterpenoid and diphenyl ether units and two known compounds, (S)-(+)-sydonic acid (5) and diorcinol (6), were isolated from the metabolites of the marine-derived fungus Penicillium expansum 091006 endogenous with the mangrove plant Excoecaria agallocha.
Abstract: Two new polyphenols containing both phenolic bisabolane sesquiterpenoid and diphenyl ether units, expansols A (1) and B (2), and two new phenolic bisabolane sesquiterpenoids, (S)-(+)-11-dehydrosydonic acid (3) and (7S,11S)-(+)-12-acetoxysydonic acid (4), along with two known compounds, (S)-(+)-sydonic acid (5) and diorcinol (6), were isolated from the metabolites of the marine-derived fungus Penicillium expansum 091006 endogenous with the mangrove plant Excoecaria agallocha. On the basis of spectroscopic analysis, chemical transformation, and theoretical calculation, the structures of 1-4 were elucidated as (S)-(+)-2-[3-hydroxy-4-(2- methoxy-6-methylheptan-2-yl)benzyl]-5-(3-hydroxy-5-methylphenoxy)-3-methylphenol, S-(+)-2-[3-hydroxy-4-(2-hydroxy-6-methylheptan-2-yl)benzyl]-5-(3-hydroxy-5-methylphenoxy)-3-methylphenol, (S)-(+)-3-hydroxy-4-(2-hydroxy-6-methylhept-6-en-2-yl)benzoic acid, and 4-[(2S,6S)-7-acetoxy-2-hydroxy-6-methylheptan-2-yl]-3-hydroxybenzoic acid, respectively. Expansol A (1) exhibited moderate cytotoxicity against the HL-60 cell line with an IC(50) value of 15.7 microM, and expansol B (2) inhibited the proliferation of A549 and HL-60 cells with IC(50) values of 1.9 and 5.4 microM, respectively.
TL;DR: Meltdown temperatures and heats of fusion for 2-acetoxy benzoic acid, N-acetyl-p-aminophenol and 2-(p-isobutylphenyl)propionic acid required for the calculations have been determined by differential scanning calorimetry.
TL;DR: The solubility of benzoic acid has been determined in ethanol, toluene, heptane, cyclohexane, pentane, and chloroform in the temperature range of (278.15 to 323.15) K as mentioned in this paper.
Abstract: The solubility of benzoic acid has been determined in ethanol, toluene, heptane, cyclohexane, pentane, and chloroform and in binary mixtures of ethanol + heptane and ethanol + toluene, in the temperature range of (278.15 to 323.15) K. The solubility is high in ethanol, reasonably high in chloroform, lower in toluene, and quite low in the remaining three pure solvents. In the binary mixtures the solubility of benzoic acid increases with increasing concentration of ethanol. The solubility of benzoic acid increases with increasing temperature.
TL;DR: The phonon modes of crystalline benzoic acid have been investigated using terahertz time-domain spectroscopy, rigid molecule atom-atom model potential and plane-wave density functional theory lattice dynamics calculations and the influence of the observed disorder in the hydrogen atom positions on the lattice Dynamics is systematically explored.
Abstract: The phonon modes of crystalline benzoic acid have been investigated using terahertz time-domain spectroscopy, rigid molecule atom–atom model potential and plane-wave density functional theory lattice dynamics calculations. The simulation results show good agreement with the measured terahertz spectra and an assignment of the terahertz absorption features of benzoic acid is made with the help of both computational methods. Focussing on the strongest interactions in the crystal, we describe each vibration in terms of distortions of the benzoic acid hydrogen bonded dimers that are present in the crystal structure. The terahertz spectrum is also shown to be highly sensitive to the location of the carboxylic acid hydrogen atoms in the cyclic hydrogen-bonded dimers and we have systematically explored the influence of the observed disorder in the hydrogen atom positions on the lattice dynamics.
TL;DR: In this paper, the solubility of benzoic acid in acetone, 2-propanol, acetic acid and cyclohexane was experimentally determined over the temperature range of (277-346) K at around 5 k intervals by employing a gravimetric method.
TL;DR: In this article, the electrochemical oxidation of benzoic acid over boron-doped diamond electrodes was studied and the effects of operating parameters such as applied current intensity, electrolysis time and initial benzo acid concentration on the degradation and mineralization efficiency were investigated with the application of factorial design methodology and simple linear models describing and predicting adequately the removal of the substrate and dissolved organic carbon.
TL;DR: Gallic acid was shown to be an effective charging additive, which provided stabilization of TiO (2) and MnO(2) particles in the suspensions and enabled their deposition, and it was shown that composite TiO( 2)-MnO(1) films can be obtained using gallic acid as a common dispersing agent for TiO
TL;DR: In this study, different concentrations of four benzyl derivatives used as flavour ingredients were investigated for genotoxicity in in vitro and the highest concentration of benzoic acid increased both tail moment and % tail DNA.
TL;DR: It is shown that C-H activation of benzoic acids with Pd(II) generates an oxapalladacycle that can decarboxylate to produce a palladium-associated aryne that undergoes trimerisation to afford triphenylenes.
TL;DR: Chromium was incorporated into the silica matrix extracted from rice husk in basic, neutral and acidic medium, and the prepared catalysts were labeled as RHCr-10,RHCr-7 and RHCr3 according to their pH as mentioned in this paper.
TL;DR: The reaction of benzoic acid with the uranyl(V) complex with the pyridine complex leads to immediate disproportionation with formation of a hexanuclear U(IV) benzoate cluster, a bis-benzoate complex of Uranyl(VI) and water.
TL;DR: The first generation and spectroscopic identification of the higher-lying E conformer of the simplest aromatic carboxylic acid, benzoic acid (1a), as its O-deuterated isotopologue (E)-d(1)-1a using matrix-isolation techniques and the first Hammett relationships for atom tunneling are derived.
Abstract: We present the first generation and spectroscopic identification of the higher-lying E conformer of the simplest aromatic carboxylic acid, benzoic acid (1a), as its O-deuterated isotopologue (E)-d1...
TL;DR: In conclusion, addition of 2% benzoic acid to pig diets effectively reduced ammonia volatilization, but interactions with dietary S may increase odor problems.
Abstract: Supplementation of benzoic acid to pig diets reduces the pH of urine and may thereby affect emissions of ammonia and other gases from slurry, including sulfur-containing compounds that are expected to play a role in odor emission. Over a period of 112 d, we investigated hydrogen sulfide (H(2)S), methanethiol (MT), dimethyl sulfide (DMS), dimethyl disulfide (DMDS), and dimethyl trisulfide (DMTS), as well as ammonia and methane emissions from stored pig slurry. The slurry was derived from a feeding experiment with four pig diets in a factorial design with 2% (w/w) benzoic acid and 1% (w/w) methionine supplementation as treatments. Benzoic acid reduced slurry pH by 1 to 1.5 units and ammonia emissions by 60 to 70% for up to 2 mo of storage, and a considerable, but transitory reduction of methane emissions was also observed after 4 to 5 wk. All five volatile sulfur (S) compounds were identified in gas emitted from the slurry of the control treatment, which came from pigs fed according to Danish recommendations for amino acids and minerals. The emission patterns of volatile S compounds suggested an intense cycling between pools of organic S in the slurries, with urinary sulfate as the main source. Diet supplementation with methionine significantly increased all S emissions. Diet supplementation with benzoic acid reduced emissions of H(2)S and DMTS compared with the control slurry and moderately increased the concentrations of MT. Sulfur gas emissions were influenced by a strong interaction between methionine and benzoic acid treatments, which caused a significant increase in emissions of especially MT, but also of DMDS. In conclusion, addition of 2% benzoic acid to pig diets effectively reduced ammonia volatilization, but interactions with dietary S may increase odor problems.
TL;DR: In this article, a highly hydroxylated barium titanate (BaTiO3) nanopowder has been prepared by oxidizing the Ba TiO3 with an aqueous solution of hydrogen peroxide (H2O2).
TL;DR: In this article, it was observed that the energy of the antisymmetric stretching mode of the carbonyl group of the free benzenecarboxylic acid invariably shifted to higher energies when that acid formed a cocrystal with a sodium salt of another benzenic acid.
Abstract: X-ray powder diffraction, differential scanning calorimetry, infrared absorption spectroscopy, and Raman spectroscopy have been used to study the phenomenon of salt formation in four benzenecarboxylic acids (benzoic acid, phenylacetic acid, hydrocinnamic acid, and 4-phenylbutanoic acid), and in the 1:1 stoichiometric products formed by the cocrystallization of a free acid and a sodium salt. Assignments were derived for the observed peaks in both infrared absorption and Raman spectra of the reactants and their products. In all instances, it was observed that the energy of the antisymmetric stretching mode of the carbonyl group of the free benzenecarboxylic acid invariably shifted to higher energies when that acid formed a cocrystal with a sodium salt of another benzenecarboxylic acid. In addition, the symmetric stretching mode of the benzenecarboxylic acid carbonyl group disappeared in the Raman spectrum of its sodium salt and was also absent in the Raman spectrum of the cocrystal product. It was also foun...
TL;DR: In this article, the reduction of alkyl-substituted benzoic acids with lithium in liquid ammonia has been investigated without added proton donor the aromatic acid yields a dianion which can either be protonated with ammonium chloride or alkylated to give the corresponding 1,4-dihydrobenzoic acid and 1-alkyl 2,5-cyclohexadiene-1-carboxylic acid, respectively.
Abstract: The reduction of alkyl-substituted benzoic acids with lithium in liquid ammonia has been investigated Without added proton donor the aromatic acid yields a dianion which can either be protonated with ammonium chloride or alkylated to give the corresponding 1,4-dihydrobenzoic acid and 1-alkyl 2,5-cyclohexadiene-1-carboxylic acid, respectively
In the presence of ethanol, 3- and 4-alkylbenzoic acids yield either 1,4-dihydro or 4,5-dihydro products depending on the working up procedure Benzoic acid behaves similarly Water is shown to be a useful proton donor in the reduction of 3- and 4-alkylbenzoic acids to 1,4-dihydro products 2-Alkylbenzoic acids yield 1,4-dihydro products, irrespective of the experimental procedure
Experiments with 4-deuterobenzoic acid show the first proton addition to be irreversible in ammonia as well as in ammonia-ethanol
Some thirty new alkyl- and dialkyl-cyclohexadienecarboxylic acids are described
TL;DR: The Oscail software package as mentioned in this paper provides attachment energy calculations, crystal surface analysis, and crystal visualization for flat π-stacking systems, which can be used to identify the density of available hydrogen bond donors and acceptors on crystal faces.
Abstract: Crystals of benzoic acid grown from dichloromethane and acetonitrile are greatly extended along the b-axis. The enhanced growth is not related to hydrogen bonding as benzoic acid is respectively dimeric and monomeric in these solvents. A mechanism is suggested for enhanced growth in the π-stacking direction for flat π-stacking systems. Facilities have been added to the Oscail software package which provide attachment energy calculations, crystal surface analysis and crystal visualization. Crystal surface analysis can be used to find the π-stacking direction and to identify the density of available hydrogen bond donors and acceptors on crystal faces. Observed and calculated morphologies for crystals of sulfathiazole form 2 grown from ethanol are in good agreement. Differences in the observed and calculated shapes of sulfathiazole forms 1, 3, 4 and 5 are attributed to solvent effects which correlate with the density of available hydrogen bond acceptors on crystal faces.
TL;DR: It is suggested that, irrespective of pH, the acid adaptation response will lead to a similar alteration in fatty acid composition [decreasing the ratio of branched chain/saturated straight fatty acids of total lipids], mainly originating from the neutral lipid class of adapted cultures.
Abstract: This study provides a first approach to observe the effects on Listeria monocytogenes of cellular exposure to acid stress at low or neutral pH, notably how phospho- or neutral lipids are involved in this mechanism, besides the fatty acid profile alteration. A thorough investigation of the composition of polar and neutral lipids from L. monocytogenes grown at pH 5.5 in presence of hydrochloric, acetic and lactic acids, or at neutral pH 7.3 in presence of benzoic acid, is described relative to cells grown in acid-free medium. The results showed that only low pH values enhance the antimicrobial activity of an acid. We suggest that, irrespective of pH, the acid adaptation response will lead to a similar alteration in fatty acid composition [decreasing the ratio of branched chain/saturated straight fatty acids of total lipids], mainly originating from the neutral lipid class of adapted cultures. Acid adaptation in L. monocytogenes was correlated with a decrease in total lipid phosphorus and, with the exception of cells adapted to benzoic acid, this change in the amount of phosphorus reflected a higher content of the neutral lipid class. Upon acetic or benzoic acid stress the lipid phosphorus proportion was analysed in the main phospholipids present: cardiolipin, phosphatidylglycerol, phosphoaminolipid and phosphatidylinositol. Interestingly only benzoic acid had a dramatic effect on the relative quantities of these four phospholipids.
TL;DR: In this article, a simple method based on three-phase hollow-fibre liquid-phase microextraction (HF-LPME) was proposed for the determination of phenolic acids in fruit juices.
TL;DR: In this paper, the authors compared the oxidative degradation of a series of hydroxy and hydroxynitro derivatives of benzoic acid by Fenton-like and photo-Fenton processes under identical conditions (initial concentrations, pH and temperature).
Abstract: The oxidative degradation of a series of hydroxy and hydroxynitro derivatives of benzoic acid by Fenton-like and photo-Fenton processes was compared under identical conditions (initial concentrations, pH and temperature). In spite of closely related chemical structures, (2-hydroxybenzoic (2H-BA), 2,4-dihydroxybenzoic (24DH-BA), 2-hydroxy-5-nitrobenzoic (2H5N-BA), 4-hydroxy-3-nitrobenzoic (4H3N-BA) and 2-hydroxy-4-nitrobenzoic (2H4N-BA) acids), the degradation timescales were remarkably different. A common feature was, however, that autocatalytic decay profiles were displayed by the substrates and H 2 O 2 . A simple equation, which may be used as a valuable tool for a semiquantitative analysis of the main kinetic features of the inverted “S” profiles, is presented. In addition, a method for the estimation of the relative contribution of photoinduced pathways in photo-Fenton systems (photoenhancement factors) is proposed. In order to assess the key processes governing the kinetic profiles observed, complementary studies were performed to evaluate the formation of ferric complexes, the reactivity towards HO and Fe(II) production efficiencies. Except for 4H3N-BA, the model substrates form highly stable complexes with Fe(III). Competition experiments showed that the reactivities of both the substrates and the ferric complexes with hydroxyl radicals cannot explain the large timescale differences observed in Fenton-like and photo-Fenton systems. The comparison of Fe(II) production under irradiation in the absence of H 2 O 2 with the decay profiles observed in both Fenton-like and photo-Fenton systems confirms that the main factor controlling the autocatalytic behavior is the formation of organic intermediates that are capable of reducing Fe(III) species. An additional factor in the photo-Fenton process may be the efficiency of photoinduced Fe(II) production, which is affected by complex formation since the studied complexes exhibit a lower efficiency of Fe(III) photoreduction than the Fe(III)–aquo complex.