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PubMed2001

Sorption of weak organic acids in soils: clofencet, 2,4-D and salicylic acid.

The sorption behaviour of a new wheat hybridising agent (clofencet, 2-4-(chlorophenyl)-3-ethyl-2,5-dihydro-5-oxopyridazine-4-carboxylic acid) was investigated in batch equilibrium experiments and compared to that of two other organic acids (2,4-D and salicylic acid). Sorption coefficients Kd for the three compounds were determined in 18 Cambisols and Ferralsols. Kd values for clofencet were 0.3-9.4 l/kg for Cambisols and 2.1-68 l/kg for Ferralsols. Sorption of clofencet was strongly related statistically to that of salicylic acid. Sorption of clofencet and salicylic acid decreased exponentially with increasing solution pH in Cambisols whereas a bell-shaped curve was obtained for the sorption of salicylic acid in Ferralsols. Sorption of 2,4-D (2,4-dichlorophenoxyacetic acid) was not statistically related to the pH of the different soils. Positively charged oxide surfaces were shown to play a significant role in the sorption of clofencet and salicylic acid. The use of simple correlation and multiple linear regressions suggested that the main sorption mechanisms of clofencet in soils were likely to be ligand exchange on oxide surfaces and, to a lesser extent, cation bridging. Differences in the sorption behaviour of clofencet/salicylic acid and 2,4-D might be attributed to the possibility of the two former compounds forming bidentate complexes with metals.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1996

Influence of Salicylic Acid on the Induction of Competence for H2O2 Elicitation (Comparison of Ergosterol with Other Elicitors).

Hypocotyls from etiolated cucumber (Cucumis sativus L.) seedlings were gently abraded at their epidermal surface, and cut segments were used to study the rapid and transient elicitation of H2O2 by ergosterol, chitosan, mastoparan, and a polymeric fungal elicitor. Freshly abraded segments were only barely competent for any H2O2 production, but they developed this competence subsequent to abrasion. This process was enhanced by 2,6-dichloroisonicotinic acid and salicylic acid, which induced acquired resistance to fungal penetration in the epidermal cells. Enhancement of competence induction by salicylic acid was also evident for spontaneous H2O2 production and differed in degree for the various elicitors, indicating that mainly the enzyme complex producing H2O2, but also other components of the elicitation system, improved. Ergosterol, chitosan, and fungal elicitor also rendered the segments refractory to a second stimulation by the same compound, whereas mastoparan was inactive in this respect. The four elicitors also differed markedly in their ability to diminish or enhance H2O2 production by a second treatment with a different elicitor, indicating that several sites of the H2O2 elicitation system are subject to short-term regulation.

Journal Article↗
PubMed1995

[Comparative randomized open study of the efficacy and tolerance of enemas with 2 gr of 4-amino-salicylic acid (4-ASA) and 1 gr of 5-amino-salicylic acid (5-ASA) in distal forms of hemorrhagic rectocolitis].

OBJECTIVES AND METHODS: The aim of this multicentre, randomized open trial was to compare the efficacy and tolerance of 4-ASA vs 5-ASA enemas in the treatment of distal moderately active ulcerative colitis. Fifty patients were randomized to receive enemas in 100 mL suspension of 4-ASA (2 g, n = 26), or 5-ASA (1 g, n = 24). The subjects filled a daily questionnaire on enema retention duration, and tolerance. Clinical and endoscopic evaluations were performed at baseline and after 2 and 4 weeks. RESULTS: Significant clinical and endoscopic improvements occurred in both groups. Efficacy and enema retention time did not differ between groups. Tolerance was significantly better for 4-ASA: score 0.46 +/- 0.77 vs 1.00 +/- 0.73, P = 0.03. CONCLUSIONS: Efficacy of both treatments was equivalent, but 4-ASA enemas were better tolerated than 5-ASA in this open trial.

Adult↗
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↗
PubMed1978

The inhibition of cyclo-oxygenase of rabbit platelets by aspirin is prevented by salicylic acid and by phenanthrolines.

Salicylic acid, 1,10- and 1,7-phenanthroline prevented inhibition by aspirin of platelet aggregation and of generation of thromboxane A2 due to arachidonic acid, to the ionophore A21387, to thrombin and to collagen. Dithiothreitol, another drug which prevents aggregation and formation of thromboxane A2, but only reversibly, failed to interfere with the inhibition by aspirin. Irreversible inhibition by indomethacin and by the substrate analogue 5,8,11,14-tetraynoic acid was also unaffected by salicylic acid or by 1,10-phenanthroline, which thus probably exert a specific interaction with the aspirin-binding site. Inactivation of platelet cyclo-oxygenase with arachidonic acid led to inhibition of the formation of thromboxane A2 and of aggregation due to arachidonic acid itself and to collagen, but barely affected aggregation by thrombin, even though generation of thromboxane A2 was blocked. Use of salicylic acid and of reversible inhibitors of cyclo-oxygenase may help to unravel the mechanism of inhibition due to other agents.

Animals↗
PubMed1990

Electrokinetic energy conversion by aqueous oxalic acid, citric acid, ascorbic acid, hippuric acid, and acetyl salicylic acid across urinary bladder membranes.

Efficiency of energy conversion for electro-osmosis and streaming potential and the degree of coupling of acids across urinary bladder membranes of goat have been computed using non-equilibrium thermodynamic theory. The energy conversion maxima and degree of coupling for acids responsible for the formation of urinary calculi are found to be much low as compared to urea and urine.

Animals↗
PubMed1994

pH-dependent and carrier-mediated transport of salicylic acid across Caco-2 cells.

The transport of monocarboxylic acid drugs such as salicylic acid was examined in the human colon adenocarcinoma cell line, Caco-2 cells that possess intestinal epithelia-like properties. [14C]Salicylic acid transport was pH-dependent and appeared to follow the pH-partition hypothesis. However, 10 mM unlabelled salicylic acid significantly reduced the permeability coefficient of [14C]salicylic acid. Kinetic analysis of the concentration dependence of the permeation rate of salicylic acid across Caco-2 cells showed both saturable (Kt = 5.28 +/- 0.72 mM Jmax = 36.6 +/- 3.54 nmol min-1 (mg protein)-1) and nonsaturable (kd = 0.37 +/- 0.08 microL min-1 (mg protein)-1) processes. The permeation rate of [14C]salicylic acid was competitively inhibited by both acetic acid and benzoic acid, which were demonstrated in our previous studies to be transported in the carrier-mediated-transport mechanism which is responsible for monocarboxylic acids. Furthermore, certain monocarboxylic acids significantly inhibited [14C]salicylic acid transport, whereas salicylamide and dicarboxylic acids such as succinic acid did not. From these results, it was concluded that the transcellular transport of [14C]salicylic acid across Caco-2 cells is by the pH-dependent and carrier-mediated transport mechanism specific for monocarboxylic acids.

Acetates↗
PubMed1988

Inhibition of fatty acid beta oxidation by influenza B virus and salicylic acid in mice: implications for Reye's syndrome.

Injection of concentrated influenza B/Lee/40 virus into 4-week-old Balb C mice resulted in 60% inhibition of 14C-palmitate oxidation in isolated hepatic mitochondria. Oral feeding of carnitine to infected mice prevented the inhibition of fatty acid oxidation. High concentrations of salicylic acid given orally also inhibited 14C-palmitate oxidation. Serum free fatty acid concentrations of infected mice and of those fed salicylic acid were significantly higher than in control mice. A combination of low-dose virus and low-dose salicylic acid inhibited palmitate oxidation, suggesting an additive effect on the metabolic derangement when the two agents were present simultaneously.

Animals↗
PubMed2003

The salicylic acid loop in plant defense.

Salicylic acid is an important signal molecule in plant defense. In the past two years, significant progress has been made in understanding the mechanism of salicylic-acid biosynthesis and signaling in plants. A pathway similar to that found in some bacteria synthesizes salicylic acid from chorismate via isochorismate. Salicylic-acid signaling is mediated by at least two mechanisms, one requiring the NON-EXPRESSOR OF PR1 (NPR1) gene and a second that is independent of NPR1. Feedback loops involving salicylic acid modulate upstream signals. These feedback loops may provide a point for integrating developmental, environmental and other defense-associated signals, and thus fine-tune the defense responses of plants.

Arabidopsis Proteins↗
PubMed1995

Topical acetylsalicylic, salicylic acid and indomethacin suppress pain from experimental tissue acidosis in human skin.

Topically applied acetylsalicylic acid (ASA), salicylic acid (SA) and indomethacin were tested in an experimental pain model that provides direct nociceptor excitation through cutaneous tissue acidosis. In 30 volunteers, sustained burning pain was produced in the palmar forearm through a continuous intradermal pressure infusion of a phosphate-buffered isotonic solution (pH 5.2). In 5 different, double-blind, randomized cross-over studies with 6 volunteers each, the flow rate of the syringe pump was individually adjusted to result in constant pain ratings of around 20% (50% in study 4) on a visual analog scale (VAS). The painful skin area was then covered with either placebo or the drugs which had been dissolved in diethylether. In the first study on 6 volunteers, ASA (60 mg/ml) or lactose (placebo) in diethylether (10 ml) was applied, using both arms at 3-day intervals. Both treatments resulted in sudden and profound pain relief due to the cooling effect of the evaporating ether. With lactose, however, the mean pain rating was restored close to the baseline within 6-8 min while, with ASA, it remained significantly depressed for the rest of the observation period (another 20 min). This deep analgesia was not accompanied by a loss of tactile sensation. The further studies served to show that indomethacin (4.5 mg/ml) and SA (60 mg/ml) were equally effective as ASA (each 92-96% pain reduction) and that the antinociceptive effects were due to local but not systemic actions, since ASA and SA dis not reach measurable plasma levels up to 3 h after topical applications. With a higher flow rate of acid buffer producing more intense pain (VAS 50%). ASA and SA were still able to significantly reduce the ratings by 90% or 84%, respectively. On the other hand, by increasing the flow rate by a factor of 2 on average, during the period of fully developed drug effect it was possible to overcome the pain suppression, which suggests a competitive mechanism of (acetyl-) salicylic antinociception.

Acidosis↗
PubMed1998

Accumulation of salicylic acid and 4-hydroxybenzoic acid in phloem fluids of cucumber during systemic acquired resistance is preceded by a transient increase in phenylalanine ammonia-lyase activity in petioles and stems.

Cucumber (Cucumis sativa) leaves infiltrated with Pseudomonas syringae pv. syringae cells produced a mobile signal for systemic acquired resistance between 3 and 6 h after inoculation. The production of a mobile signal by inoculated leaves was followed by a transient increase in phenylalanine ammonia-lyase (PAL) activity in the petioles of inoculated leaves and in stems above inoculated leaves; with peaks in activity at 9 and 12 h, respectively, after inoculation. In contrast, PAL activity in inoculated leaves continued to rise slowly for at least 18 h. No increases in PAL activity were detected in healthy leaves of inoculated plants. Two benzoic acid derivatives, salicylic acid (SA) and 4-hydroxybenzoic acid (4HBA), began to accumulate in phloem fluids at about the time PAL activity began to increase, reaching maximum concentrations 15 h after inoculation. The accumulation of SA and 4HBA in phloem fluids was unaffected by the removal of all leaves 6 h after inoculation, and seedlings excised from roots prior to inoculation still accumulated high levels of SA and 4HBA. These results suggest that SA and 4HBA are synthesized de novo in stems and petioles in response to a mobile signal from the inoculated leaf.

Cucumis sativus↗