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PubMed2001

Microfabrication of individual 200 microm diameter transdermal microconduits using high voltage pulsing in salicylic acid and benzoic acid.

We describe an extension of semiconductor fabrication methods that creates individual approximately 200 microm diameter aqueous pathways through human stratum corneum at predetermined sites. Our hypothesis is that spatially localized electroporation of the multilamellar lipid bilayer membranes provides rapid delivery of salicylic acid to the keratin within corneocytes, leading to localized keratin disruption and then to a microconduit. A microconduit penetrating the isolated stratum corneum supports a volumetric flow of order 0.01 ml per s with a pressure difference of only 0.01 atm (about 10(2) Pa). This study provides a method for rapidly microengineering a pathway in the skin to interface future devices for transdermal drug delivery and sampling of biologically relevant fluids.

Administration, Cutaneous↗
PubMed1989

Liver function in protein-energy malnutrition measured by cinnamic acid tolerance and benzoic acid tolerance: effect of carnitine supplementation.

1. Rats fed on a protein-depleted diet for 8 weeks were repleted for 5 weeks on high-protein (HP), high-protein + 20 g DL-carnitine/kg (HP + C), or low-protein + 20 g DL-carnitine/kg (LP + C) diets. At 4 and 8 weeks of depletion, and 1 and 5 weeks of repletion, rats from each treatment group were given a benzoic acid tolerance test (BATT) or a cinnamic acid tolerance test (CATT) as a measure of liver function. 2. BATT and CATT measured the molar percentage of a test dose (1 mmol/kg body-weight) of benzoic acid or cinnamic acid excreted in the urine as hippuric acid within 24 h. Liver weight, liver lipid levels, and carnitine concentration in plasma and liver were also measured following liver-function testing. 3. BATT and CATT were severely impaired in protein-depleted rats, but returned rapidly to control levels following protein refeeding. Correlations of BATT and CATT with liver lipid concentration were high (r -0.49 and -0.62 respectively), and both tests show promise as clinical tests for liver function in protein-energy malnutrition. 4. Carnitine supplementation was required to return liver carnitine concentration of protein-depleted rats to control levels during repletion, but was not associated with accelerated reduction in liver fat concentration in protein-repleted rats.

Animals↗
PubMed1985

Effect of diffusion layer pH and solubility on the dissolution rate of pharmaceutical acids and their sodium salts. II: Salicylic acid, theophylline, and benzoic acid.

The pH-solubility profiles of salicylic acid and theophylline, as determined by the addition of HCl or NaOH to their aqueous suspensions, were identical with those of their sodium salts except during phase transitions from acid to salt or vice versa. Supersaturated solutions were formed during phase transitions. Unlike the solubility profiles, the pH-intrinsic dissolution rate profiles of an acid and its salt differed greatly. Good conformity with the Noyes-Whitney equation was demonstrated when the solubility values under pH conditions as the diffusion layer thickness, h, approaches zero (Cs,h = 0) were used rather than solubilities under pH conditions of the bulk media (Cs). The pH when h approaches zero (pHh = 0) was estimated by equilibration of a dissolution medium with an excess of material. Good correlation was shown between the pHh = 0 values of benzoic acid estimated according to this method and the pHh = 0 values reported in the literature. The intrinsic dissolution rate constant, the ratio of the diffusion coefficient to the diffusion layer thickness (D/h), may be assumed constant when comparing the dissolution rates of salicylic acid, theophylline and sodium theophylline. On the other hand, D/h decreased significantly during dissolution of sodium salicylate due to a large increase in Cs,h = 0 and the consequent increase in viscosity in the diffusion layer. A simple method of predicting the dissolution rate of an acid or a salt at different pH values has been developed.

Acids↗
PubMed1988

Determination of benzoic acid and hippuric acid in human plasma and urine by high-performance liquid chromatography.

For patients with inborn errors of urea synthesis, oral administration of sodium benzoate is the usual treatment to increase the nitrogen excretion. Thus, monitoring hippuric acid and benzoic acid simultaneously in human biological fluids is considered to be clinically important. We developed a simple and accurate high-performance liquid chromatographic method for the simultaneous determination of hippuric acid and benzoic acid in human plasma and urine. This method requires no extraction step. Aliquots of urine and plasma are added to a solution of internal standard (o-chlorobenzoic acid) in acetonitrile and directly injected onto a reversed-phase column using an acidic (pH 2.7) eluent and ultraviolet detection at 235 nm. The preliminary plasma concentration-time and urinary excretion rate-time profiles of hippuric acid and benzoic acid from a healthy subject receiving small, medium and large doses of sodium benzoate are reported.

Administration, Oral↗
PubMed1982

3-Hydroxy- and 3-keto-3-phenylpropionic acids: novel metabolites of benzoic acid in horse urine.

The metabolism of benzoic acid has been examined in the horse, using 14C- and deuterium-labelled compounds. Chromatographic analysis of the urine showed the presence of hippuric acid, benzoyl glucuronide and benzoic acid and a discrete band which accounted for 2% of the dose administered. This material was isolated by solvent extraction and HPLC and, following treatment with diazomethane, examined by GC/MS. The major component of this fraction was 3-hydroxy-3-phenylpropionic acid methyl ester, which was accompanied by very much smaller amounts of cinnamic acid methyl ester and acetophenone. The two latter minor components have been shown to be artefacts produced during workup and analysis. Cinnamic acid methyl ester arises by the thermal decomposition of 3-hydroxy-3-phenylpropionic acid methyl ester on the GC column. It is proposed that acetophenone has formed, during workup, by decarboxylation of 3-keto-3-phenylpropionic acid. It is suggested that 3-hydroxy and 3-keto-3-phenylpropionic acids, which are also endogenous in horse urine, have arisen by an addition of a 2 carbon fragment to benzoyl CoA, in a sequence analogous to the reactions of fatty acid biosynthesis. Some implications of the metabolic interrelationships between xenobiotic acids and fatty acids are discussed.

Animals↗
PubMed1986

Effects of solvent polarity on the acid dissociation constants of benzoic acids.

The pKa values of benzoic acid, p-methylbenzoic, and p-aminobenzoic acid (PABA) were determined by potentiometric titration in mixtures of 0-0.5 volume fractions of various cosolvents and water. The differences between the aqueous and semiaqueous pKa values were similar for the three solutes at a particular cosolvent-water mixture for most of the cosolvents studied. The largest differences occurred in the dimethyl sulfoxide (Me2SO)-water system, where the pKa changes were larger for PABA than the other two solutes. The data are analyzed by a consideration of both electrostatic and nonelectrostatic medium effects. The electrostatic medium effect was calculated from the Born Equation while any residual pKa change was attributed to nonelectrostatic medium effects. The residual effects were found to correlate well with indexes of solvent hydrogen bond acceptor ability such as HBA and beta-values. These results provide a rationale for the use of two solvent polarity indexes for more accurate estimates of pKa values of weak electrolytes in semiaqueous solvent systems. Analysis of solubility data of the salt and acid forms of PABA and benzoic acid in ethanol-water and Me2SO-water mixtures suggests that the higher activity of the anionic form of PABA in Me2SO-water mixtures is primarily responsible for the large pKa changes observed for that solute.

Benzoates↗
PubMed1996

Lipoic acid impairs glycine conjugation of benzoic acid and renal excretion of benzoylglycine.

Glycine conjugation of benzoic acid is catalyzed by the mitochondrial enzymes benzoyl-coenzyme A(CoA) synthetase and benzoyl-CoA: glycine N-acyltransferase and requires ATP, CoA, and glycine as cosubstrates. Lipoic acid (LA), an important endogenous and also therapeutic compound, depletes hepatic CoA; therefore, it may interfere with glycine conjugation. To test this hypothesis, LA (0.5-1.5 mmol/kg ip) was given to anesthetized, glycine-loaded rats 1 hr before administration of benzoic acid (1 mmol/kg iv). LA inhibited glycine conjugation of benzoic acid in a dose-dependent manner as indicated by: 1) reduced clearance of benzoic acid from blood; 2) delayed appearance of benzoylglycine in blood; and 3) decreased excretion of benzoylglycine in urine. LA also decreased urinary excretion of injected benzoylglycine, indicating that reduced excretion of this metabolite after benzoic acid injection is caused by diminished formation and impaired renal transport of benzoylglycine. Urine formation was decreased by LA in a dose-dependent fashion, and acute renal failure was evident in rats receiving the highest dose. LA depleted hepatic CoA, carnitine, and glutathione, but not ATP, whereas it increased the hepatic concentration of glycine. In isolated and solubilized rat liver mitochondria, LA inhibited both benzoyl-CoA synthetase (IC50 approximately 1.5 mM) and benzoyl-CoA:glycine N-acyltransferase (IC50 approximately 0.3 mM). Thus, depletion of CoA and inhibition of the pertinent enzymes seem responsible for impairment of glycine conjugation of benzoic acid by LA. LA may also impair renal tubular cell function, compromising the tubular secretion of benzoylglycine and causing acute renal failure.

Acyltransferases↗
PubMed2001

Genetic manipulation of 6-phosphofructo-1-kinase and fructose 2,6-bisphosphate levels affects the extent to which benzoic acid inhibits the growth of Saccharomyces cerevisiae.

The mechanisms by which the weak acid preservative benzoic acid inhibits the growth of Saccharomyces cerevisiae have been investigated. A reduction in the pyruvate kinase level, which decreases glycolytic flux, did not increase the sensitivity of yeast to benzoic acid. However, a decrease in 6-phosphofructo-1-kinase (PF1K), which does not affect glycolytic flux, did increase sensitivity to benzoic acid. Also, resistance was increased by elevating PF1K levels. Hence, resistance to benzoic acid was not dependent upon optimum glycolytic flux, but upon an adequate PF1K activity. Benzoic acid was shown to depress fructose 2,6-bisphosphate levels in YKC14, a mutant with low PF1K levels. This effect was partially suppressed by overexpressing constitutively active 6-phosphofructo-2-kinase (Pfk26(Asp644)) or by inactivating fructose-2,6-bisphosphatase (in a Deltafbp26 mutant). The inactivation of PF2K (in a Deltapfk26 Deltapfk27 mutant) increased benzoic acid sensitivity. Therefore, the antimicrobial effects of benzoic acid can be relieved, at least in part, by the genetic manipulation of PF1K or fructose 2,6-bisphosphate levels.

Antifungal Agents↗
PubMed2002

2-[1-(Phenylsulfonyl)ethyl]benzoic acid and 2-[1-(phenylsulfonyl)propyl]benzoic acid.

In the title acids, C(15)H(14)O(4)S, (I), and C(16)H(16)O(4)S, (II), respectively, the angle between the planes of the benzene ring and the carboxyl group is 13.7 (1) degrees for (I) and 21.3 (1) degrees for (II). The molecular structures are stabilized by intramolecular C-H.O hydrogen bonds. The crystal packing is stabilized by a single O-H.O hydrogen bond in both compounds, in which the O and H atoms are ordered; H.O 1.87 A for (I) and 1.83 A for (II), O.O 2.680 (2) A for (I) and 2.652 (3) A for (II), and O-H.O 172 degrees for (I) and 175 degrees for (II). The hydrogen bond forms a cyclic dimer, with graph-set descriptor R(2)(2)(8), about a centre of symmetry.

Benzoates↗
PubMed2004

Pi-stacked hydrogen-bonded dimers in 2-(2-nitrophenylaminocarbonyl)benzoic acid, and hydrogen-bonded sheets in orthorhombic and monoclinic polymorphs of 2-(4-nitrophenylaminocarbonyl)benzoic acid.

Molecules of 2-(2-nitrophenylaminocarbonyl)benzoic acid, C(14)H(10)N(2)O(5), are linked into centrosymmetric R(2)(2)(8) dimers by a single O-H.O hydrogen bond [H.O = 1.78 A, O.O = 2.623 (2) A and O-H.O = 178 degrees ] and these dimers are linked into sheets by a single aromatic pi-pi stacking interaction. The isomeric compound 2-(4-nitrophenylaminocarbonyl)benzoic acid crystallizes in two polymorphic forms. In the orthorhombic form (space group P2(1)2(1)2(1) with Z' = 1, crystallized from ethanol), the molecules are linked into sheets of R(4)(4)(22) rings by a combination of one N-H.O hydrogen bond [H.O = 1.96 A, N.O = 2.833 (3) A and N-H.O = 171 degrees ] and one O-H.O hydrogen bond [H.O = 1.78 A, O.O = 2.614 (3) A and O-H.O = 173 degrees ]. In the monoclinic form (space group P2(1)/n with Z' = 2, crystallized from acetone), the molecules are linked by a combination of two N-H.O hydrogen bonds [H.O = 2.09 and 2.16 A, N.O = 2.873 (4) and 2.902 (3) A, and N-H.O = 147 and 141 degrees ] and two O-H.O hydrogen bonds [H.O = 1.84 and 1.83 A, O.O = 2.664 (3) and 2.666 (3) A, and O-H.O = 166 and 174 degrees ] into sheets of some complexity. These sheets are linked into a three-dimensional framework by a single C-H.O hydrogen bond [H.O = 2.45 A, C.O = 3.355 (4) A and C-H.O = 160 degrees ].

Journal Article↗
PubMed2003

Differential changes in taste perception induced by benzoic acid prickling.

Benzoic acid (Bz) is a prickling compound used to preserve foods. However, its effects on taste are unknown. This work examines Bz-taste interaction using psychophysical methods [magnitude estimation (ME) and paired comparison (PC)] to measure taste intensity in aqueous solutions of pure tastants (T) and their respective mixtures with 10 mM Bz (Mix). Prototypical tastants induced basic taste qualities (mM): sucrose [90-1440, sweetness (Sw)], citric acid [1-64, sourness (So)], NaCl [15-960, saltiness (Sa)], quinine [0.01-0.64, bitterness (Bitt)], KCl (12.5-400, Sa and Bitt). MEs were analysed using Steven's and Beidler's equations. Bz increased Sw (all concentrations) and ionic tastes (low concentrations) and Bz effects were reduced by concentration increase according with quality and tastant Bz reduced Bitt(Quinine) (high concentrations). Bz reduced taste slopes (percentage decrease): Sw 45% (P<.02), So 34% (P<.01), Sa 35% or 41% (NaCl or KCl, P<.03), Bitt 33% or 60% (quinine P<.01 or KCl P<.04). Bz reduced K(diss) (affinity(-1)) (percentage reduction): Sw 79% (P<.0002), So 40% (P<.03), Sa(NaCl) 63% (P<.005), Sa(KCl) 48% (P<.04), Bitt(KCl) 64% (P<.04). Bz reduced ME(max) (percentage reduction): Sw 31% (P<.004), Bitt(Quinine) 29% (P<.03). PCs confirmed taste increases by Bz (percentage of 'Mix(intensity)>T(intensity)' answers/total answers): Sw 79-69% (90-1440 mM sucrose), So 75% (1 mM citric acid) and 71% (2 mM citric acid), Sa 75-71% (15-120 mM NaCl). Negative concentration dependence of taste increases by Bz suggests different levels of interaction. Biophysical and neurophysiological changes are discussed in relation with Bz properties and mechanism of interaction with taste.

Adult↗