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PubMed1988

Liquid-chromatographic measurement of p-aminobenzoic acid and its metabolites in serum.

This is a high-performance liquid-chromatographic method for measuring p-aminobenzoic acid (PABA) and its metabolites in plasma or serum. Samples are deproteinized, then extracted with organic solvents before chromatography. For quantification, the peak height of the individual compound is compared with that of the internal standard. Analytical recoveries ranged from 41% to 100%, depending on the compound studied. Comparison of patients' samples after oral administration of either N-benzoyl-L-tyrosyl-p-aminobenzoic acid or free PABA revealed that PABA is extensively metabolized and conjugated to either p-acetamidobenzoic acid, p-aminohippuric acid, or p-acetamidohippuric acid. PABA concentrations in serum as measured with the Bratton-Marshall ultraviolet spectrophotometric procedure would appear predominantly to reflect measurements of metabolites, with only a minor contribution from PABA itself.

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PubMed1982

Failure of p-aminobenzoic acid screening test to diagnose pancreatic insufficiency in Shwachman's syndrome.

The 6-h urine recovery of p-aminobenzoic acid (PABA) following the administration of a standard dose of N-benzoyl-L-tyrosyl-p-aminobenzoic acid (BTPABA) was performed in 13 control subjects and two siblings with Shwachman's syndrome. The control subjects showed a recovery of 67 +/- 12.1% (mean +/- 1 SD) of the administered dose, consistent with previously reported values. Unexpectedly, the recovery of PABA in two siblings with Shwachman's syndrome was found to be 67 and 63%, respectively. The values are well within the normal range. In these siblings, fecal chymotrypsin activities were very low when measured with N-acetyl-L-tyrosyl-ethyl ester (ATEE) as substrate, but were normal when BTPABA was the substrate. The duodenal juice of the younger affected child following pancreozymin-secretin stimulation showed very low chymotrypsin activity against ATEE, BTPABA, and N-benzoyl-L-tyrosyl-ethyl ester. These findings suggest that there may be BTPABA-splitting activity in the lower bowel of these siblings with Shwachman's syndrome. This activity might be that of enteric bacteria or of the intestinal mucosa.

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PubMedDate not supplied

High performance liquid chromatographic characterisation and quantitation of p-aminobenzoic acid N-acetylation in Chinese subjects.

p-Aminobenzoic acid (PABA), p-acetamidobenzoic acid (PADB) and p-aminohippuric acid (PAH) have been separated and determined by a reversed phase, isocratic high performance liquid chromatographic (HPLC) procedure simultaneously. The mobile phase, at 1.5 ml min-1, used was 10 mM sodium hydrogen phosphate buffer, pH 3.5, containing 40% methanol. The eluent was detected at 270 nm. Linear relationship was obtained from 0 to 2.0 micrograms ml-1 of each compound with the corresponding peak-height ratio using p-methylamino-benzoic acid (PMAB) as the internal standard. Urine samples were obtained from healthy Chinese volunteers after oral dosing of 200 mg PABA which was used as a model substance for metabolic investigation of N-acetylation and other conjugation reactions. The 24 hour urinary recovery, from 43 healthy subjects, of PABA, PABA-COOH conjugates, PADB and PADB-COOH conjugates were (mean +/- S.D.) 2.9 +/- 1.5%, 5.2 +/- 3.3%, 13.9 +/- 4.0% and 42.9 +/- 9.8% of the ingested dose respectively. These accounted for 64.9 +/- 12.0% of total dose ingested in 24 hour. In contrast to previously reported findings on one Caucasian subject, no PAH was identified in the urine, and N-acetylation was the major route of metabolism of PABA apart from conjugation at the -COOH group in this group of Chinese volunteers. It is proposed that PABA metabolism may be a useful probe to study ethnic and geographic variation in N-acetylation.

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PubMed1993

Capillary zone electrophoresis of p-aminobenzoic acid derivatives of aldoses, ketoses and uronic acids.

Aldoses, ketoses and uronic acids were derivatized with p-aminobenzoic acid and separated as their borate complexes by capillary zone electrophoresis, using a capillary tube of fused silica containing 150 mM borate buffer, pH 10.0, as carrier. The electrophoretic mobilities of 22 carbohydrates were determined and found to increase with increasing stability of the borate complexes formed. Besides the number of hydroxyl groups and the presence of substituents, complex stability depended most strongly on the configuration of the three vicinal hydroxyl groups at C2, C3 and C4. On-column UV monitoring at 285 nm allowed the detection of glucose with a lower mass detection limit of 15 fmol and a concentration sensitivity of 4 microM. Reproducible quantification of carbohydrates was achieved at least in the concentration range of 0.1-10 mM in reaction solutions by the relative peak area method, using cinnamic acid as internal standard. The method was applied successfully to the determination of the monosaccharide composition of polysaccharides extracted from Radix althaeae.

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PubMed1980

Follow-up studies of porphyrin excretion in porphyria cutanea tarda treated with p-aminobenzoic acid.

The treatment of porphyria cutanea tarda (PCT) with p-aminobenzoic acid (PABA) was suggested because PABA is capable of reversing the porphyrinogenic action of 3,5-dicarbethoxy-1,4-dihydrocollidine (DDC) in rats. Three patients with PCT were treated with 3 g of PABA daily during 6 and 12 months and the urinary and faecal porphyrin excretion were serially analyzed by solvent extraction techniques and by thin layer chromatography of their methyl esters. PABA treatment did not show any apparent effect on porphyrin excretion.

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PubMedDate not supplied

Distribution of 2-aminofluorene and p-aminobenzoic acid N-acetyltransferase activity in tissues of C57BL/6J rapid and B6.A-NatS slow acetylator congenic mice.

The distribution of N-acetyltransferase (NAT) activity in 35 tissues of inbred rapid acetylator C57BL/6J and slow acetylator congenic B6.A-NatS mice was determined by incubation of tissue cytosols with 2-aminofluorene or p-aminobenzoic acid followed by HPLC assay. Tissues examined included the gastrointestinal tract, lymphoid tissues, skin, blood components, and other major organs. NAT activity was found in all tissues examined except blood plasma and seminal vesicles. Peyer's patches had the highest activity with either substrate, and lymphoid tissue, in general, was high in NAT activity as was skin and much of the digestive system. The acetylator polymorphism was apparent in most tissues for both p-aminobenzoic acid and 2-aminofluorene. The difference between rapid and slow acetylator phenotypes was usually greater with p-aminobenzoic acid than with 2-aminofluorene. The presence of NAT in the 33 tissues of rapid and slow acetylator mice, as well as the absence of NAT in plasma and seminal vesicles, was confirmed by immunoblots using an anti-NAT antibody raised in rabbits. These results indicate the widespread distribution of NAT activity and the relative abundance of extrahepatic N-acetylation capacity in the mouse.

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PubMed1994

Human placental transfer and metabolism of p-aminobenzoic acid.

Studies in our laboratory have shown that the N-acetylation activity of the human term placenta is a predominantly attributable to the NAT1 form of arylamine N-acetyltransferase (NAT). To further assess the acetylation capacity of the placenta, the N-acetylation of the prototype NAT1-selective substrate, p-aminobenzoic acid (PABA), was studied using the in vitro human placental perfusion model. This study compared the net N-acetylation of PABA in intact placental tissue with the PABA acetylation activity observed in a subcellular fraction (cytosol). Such studies with intact tissue can permit assessment of the exposure of the fetus in vivo to drugs and their metabolites. Acetylated metabolite (N-acetyl-p-aminobenzoic acid) was detectable in fetal and maternal venous samples taken less than 5 min from the start of perfusion with PABA. In a closed recirculating system, the rate of placental PABA transfer decreased as PABA concentrations equilibrated across the placenta. In contrast, the rate of N-acetyl-p-aminobenzoic acid formation continued to increase throughout the entire time of perfusion. Kinetic parameters of PABA N-acetylation measured in cytosol prepared from perfused placental tissue show that the placenta retains its ability to N-acetylate PABA at fresh tissue levels even after 6 hr of in vitro perfusion (Vmax = 5.75 +/- 0.42 nmol/min/mg (fresh) vs. Vmax = 7.24 +/- 0.31 nmol/min/mg (perfused); mean +/- S.E.M., n = 6). These studies indicate that the human placenta has a significant capacity to N-acetylate NAT1-selective substrates of NAT and that it maintains its ability to metabolize xenobiotics during in vitro perfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1982

Urinary p-aminobenzoic acid determined in the pancreatic function test by liquid chromatography, with electrochemical detection.

We describe a liquid-chromatographic procedure for determining urinary p-aminobenzoic acid (PABA) in the exocrine pancreatic function test. The urine specimen, collected for 6 h after oral administration of N-benzoyl-L-tyrosyl-p-aminobenzoic acid, is hydrolyzed in 4 mol/L NaOH containing m-hydroxybenzoic acid as internal standard, to free PABA metabolites, then diluted and injected into the chromatograph. PABA and the internal standard are eluted from a reversed-phase C18 column with phosphate buffer (0.2 mol/L, pH 3.5)/acetonitrile, 87.5/12.5 (by vol), and detected with an electrochemical detector at +1100 mV. Urinary PABA concentration as measured by this method agreed well with that by colorimetry involving p-dimethylaminocinnamaldehyde. The present procedure is specific for PABA, precise, and fairly rapid. We hope that the present method will minimize instances of interference from drugs, which cannot be avoided in the colorimetric method.

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PubMed1988

Inhibitory effects of para-aminobenzoic acid on the formation and mutagenicity of N-nitroso compounds.

Naturally occurring para-aminobenzoic acid (PABA) inhibited the formation of N-methyl-N-nitrosourea (MNU) from a nitrosation mixture of N-methylurea and nitrite at pH 3. The suppressive effect of PABA on the formation of MNU is higher than that of ascorbic acid. The presence of the MNU was assayed by its mutagenicity in a higher plant, Arabidopsis thaliana. In addition, PABA markedly reduced the mutagenicity of N-methyl-N'-nitro-N-nitrosoguanidine in A.thaliana, but had no or only a low inhibitory effect on the mutagenicity of preformed MNU and on the promutagen N-nitrosodimethylamine.

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PubMed1983

Evaluation of exocrine pancreatic function by oral administration of N-benzoyl-L-tyrosyl-p-aminobenzoic acid (PFD test) in primary diabetes mellitus.

Exocrine pancreatic function was evaluated in patients with primary diabetes mellitus by oral administration of N-benzoyl-L-tyrosyl-p-aminobenzoic acid (pancreatic function diagnostic test, PFD test) and p-aminobenzoic acid (PABA absorption test). In both primary diabetes mellitus and chronic pancreatitis, the mean excretion of PABA in the urine in the PFD test was significantly less than in the controls, and in 19 of 31 (61.3%) patients with primary diabetes mellitus and 11 of 12 (91.7%) patients with chronic pancreatitis there was a low PABA excretion rate. In contrast, the mean excretion of PABA in the urine in the PABA absorption test was significantly less in those with primary diabetes mellitus than in the controls. Therefore, to detect disturbances of pancreatic exocrine function in patients with primary diabetes mellitus, differences in the excretion of PABA in the urine between PFD test and PABA absorption test should be calculated. According to this method, the rate of abnormality was 12.9% in primary diabetes mellitus and 100% in chronic pancreatitis. There was a significant correlation between the excretion of PABA in the urine in the PFD test and results of renal function tests in primary diabetic patients with a normal range of serum creatinine levels. The serum PABA levels in the PFD test remained high in patients with primary diabetes mellitus and decreased in cases of chronic pancreatitis, as compared with the controls.

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PubMed1994

Virulence studies of Aspergillus nidulans mutants requiring lysine or p-aminobenzoic acid in invasive pulmonary aspergillosis.

To identify steps in fungal intermediary metabolism required by Aspergillus spp. during invasive pulmonary aspergillosis, we have developed murine models involving Aspergillus nidulans as the inoculum. The advantages of using A. nidulans over Aspergillus fumigatus or Aspergillus flavus, which are the most common agents of clinical disease, are the well-understood genetics of A. nidulans and a large range of mutants of this species which are affected in a variety of metabolic pathways. Comparison of the virulence of A. nidulans strains carrying mutations which block the biosynthesis of lysine (lysA2) and p-aminobenzoic acid (pabaA1) shows that lysA2 strains have reduced virulence while pabaA1 strains are entirely nonpathogenic. The pathogenicity of pabaA1 strains can be restored by supplementing the drinking water of animals with p-aminobenzoic acid. The results indicate that the availability of lysine in the lung is limited, and p-aminobenzoic acid is probably not available at all. Thus, models of invasive pulmonary aspergillosis involving A. nidulans can be used to identify metabolic pathways that may be essential for the pathogenicity of A. fumigatus, the predominant pathogenic species, suggesting potential new targets for antifungal therapy.

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PubMed1977

The effect of para-aminobenzoic acid and taurocholic acid feeding on human bile composition.

Seven patients were investigated after cholecystectomy and exploration of the common bile duct to determine bile composition and excretion rates. An initial depression of the major components of bile stabilized by the sixth postoperative day. Feeding of para-aminobenzoic acid and taurocholic acid to these patients demonstrated an increase in excretion of total bile acids, taurine and glycine conjugates, cholates and deoxycholates. Para-aminobenzoic acid in the doses used failed to block glycine conjugation. Preferential conjugation of bile acid with glycine is due to a deficient taurine pool and not a preferential metabolic pathway.

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PubMed1978

Diagnosis of exocrine pancreatic insufficiency in cystic fibrosis by the synthetic peptide N-benzoyl-L-tyrosyl-p-aminobenzoic acid.

The synthetic peptide N-benzoyl-L-tyrosyl-p-aminobenzoic acid is specifically cleaved by chymotrypsin to Bz-Ty and PABA. The liberated PABA is absorbed and excreted in the urine. Accordingly, PABA recovery reflects intraluminal chymotrypsin activity and is an index of exocrine pancreatic function. This test was evaluated in 24 patients with cystic fibrosis to determine its role in the diagnosis of exocrine pancreatic insufficiency. Cumulative percent PABA recovery in six hours was significantly lower in CF patients compared with the control group. No overlap was noted between the two groups. There was good correlation between PABA recovery, fecal chymotrypsin activity, and coefficient of fat absorption. These findings indicate that PABA recovery is significantly reduced in patients with CF and steatorrhea and may prove a practical and reliable test of pancreatic insufficiency.

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PubMed2004

The reactions of oxicam and sulfoanilide non steroidal anti-inflammatory drugs with hypochlorous acid: determination of the rate constants with an assay based on the competition with para-aminobenzoic acid chlorination and identification of some oxidation products.

Hypochlorous acid (HOCl) is an oxygen-derived species involved in physiological processes related to the defence of the organism that may cause adverse effects when its production is insufficiently controlled. In order to examine its reactivity with potential scavenging molecules from the non steroidal anti-inflammatory drugs (NSAIDs) family, a competition assay based on para-aminobenzoic acid (PABA) chlorination was developed. The original optimised in vitro fluorimetric procedure offered the possibility to determine rate constants (ks) for the reaction with HOCl in physiologically relevant conditions. The specificity of the system was improved by a liquid chromatography (LC) which allows the separation of the drugs and their oxidation products. After determination of the rate constant for PABA chlorination by HOCl (mean +/- SD in M(-1) s(-1): 4.3 +/- 0.3 x 10(3)), the applied mathematical model for a chemical competition permits to obtain linear curves from competition studies between several NSAIDs and PABA. Their slopes provided the following rate constants for the different studied drugs: tenoxicam: 4.0 +/- 0.7 x 10(3), piroxicam: 3.6 +/- 0.7 x 10(3), lornoxicam: 4.3 +/- 0.7 x 10(3), meloxicam: 1.7 +/- 0.3 x 10(4), nimesulide: 2.3 +/- 0.6 x 10(2). Meloxicam therefore reacted significantly faster than the other oxicams and nimesulide, which is the weakest scavenger of the studied series. The identification of some of the oxidation products by NMR or MS permitted to explore the reaction mechanism and to examine some aspects of the structure/activity relationships for the molecules of the same chemical family.

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