Salicylic acid generation

The ability of an esterase or a -glucosidase to hydrolyze the in vitro generated metabolite was tested. An assay mixture that had been incubated for 22 h (ca. 50% conversion of salicylic acid) was incubated with either 10 units of hog-liver esterase (E.C. 3.1.1.1, Sigma Chemical Co.) at pH 8.0 or 20 units of -glucosidase (E.C. 3.2.1.21, Sigma) at pH 5.0 for 1 h at 37 °C. Salicylic acid and the metabolite were separated by thin layer chromatography with BAW and quantified by liquid scintillation chromatography. 

Thus, antioxidant effects of nitrite in cured meats appear to be due to the formation of NO. Kanner et al. (1991) also demonstrated antioxidant effects of NO in systems where reactive hydroxyl radicals ( OH) are produced by the iron-catalyzed decomposition of hydrogen peroxide (Fenton reaction). Hydroxyl radical formation was measured as the rate of benzoate hydtoxylation to salicylic acid. Benzoate hydtoxylation catalyzed by cysteine-Fe +, ascorbate - EDTA-Fe, or Fe was significantly decreased by flushing of the reaction mixture with NO. They proposed that NO liganded to ferrous complexes reacted with H2O2 to form nitrous acid, hydroxyl ion, and ferric iron complexes, preventing generation of hydroxyl radicals. 

Oturan MA, Pinson J, Deprez D, Terlain B. Polyhydroxylation of salicylic acid by electrochemically generated OH radicals. New J Chem 1992 16 705-710. 

From a synthetic standpoint, a historical landmark, after the discovery of electrophilic substitution in the 1860 s, was the synthesis of aspirin, acetylsalicylic acid. The earliest known use of the drug can be traced back to the Greek physician Hippocrates in the 5 century BC. He used powder extracted from the bark of willow trees to treat pain and reduce fever. Sali-cin, the parent of the salicylate drug family that generates salicylic acid in vivo, was isolated... 

The electro-Fenton method (or EFR) was initially used for synthetic purposes considering the hydroxylation of aromatics in the cathodic compartment of a divided cell. Thus, the production of phenol from benzene (Tomat and Vecchi 1971 Tzedakis et al. 1989), (methyl)benzaldehydes and (methyl)benzyl alcohols from toluene or polymethylbenzenes (Tomat and Rigo 1976,1979,1984,1985) by adding Fe3+ to generate Fe2+ via reaction (19.13), as well as benzaldehyde and cresol isomers from toluene or acetophenone and ethylphenol isomers from ethylbenzene (Matsue et al. 1981) with direct addition of Fe2+, have been described. Further studies have reported the polyhydroxylation of salicylic acid (Oturan et al. 1992)... 

Many currently used drugs like acetyl salicylic acid, digitalis, nitrates, and quinine have existed for a long time, and so have many poisons like cyanide and neurotoxins. However, their mechanism of action was not known until the middle of 20th century or even later. CO is unique. The details of its mechanism of toxicity were published by Haldane as early as 1895 and subsequent work has only elaborated these details while affirming its correctness. The generation of COHb is the principal cause of CO toxicity however, it is not the only one. Much research has been done to elaborate these additional mechanisms of CO... 

Development of ethylene [64] starts about 40-60 min after mechanical perturbation, much earlier than generation of salicylic acid [53]. This perturbation is induced, for instance, just by wind [30], explaining the observation that the rice blast disease (induced by pathogens) is suppressed in seasons of strong wind (apparently the perturbation induces expression of ethylene, this stimulates generation of phytoalexins which prevent attack by fungi). 

Degradation products of LOOHs are able to initiate the production of the ethylene, kinases and G-proteins required to induce an oxidative burst. These events are apparently followed by activation of the genes which encode the generation of jasmonic acid and of salicylic acid. These are in turn able to induce the production of enzymes of the phenylpropanoid pathway [149,150], and enzymes which initiate the biosynthesis of terpenes (e.g. 3-hydroxy-3-methylglutaryl coenzyme A reductase [145,151-153]) and lignins. 

Figure 4.16 shows the increased generation of free salicylic acid at 37°C in the tablets containing paracetamol, it is interesting to note from this figure the effect on stability of tablet excipients. Addition of 1% talc caused only a minimal increase in the decomposition,... 

The most widely used method to prepare salicylanilides (35) involves condensation of an appropriate salicylic acid (33) with an aniline (34) in the presence of phosphorus trichloride [7,50-54] or phosphorus oxychloride [55] in boiling chlorobenzene, toluene or xylene. In these reactions salicyloyl chloride (36) is generated in situ, which then reacts with aniline to form 35. Alternatively salicyloyl chloride... 

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