Salicylic acid radical

During the traditional qualitative inorganic analytical procedure, samples containing the lead and salicylate radicals can lead to the formation and possible detonation of lead picrate. This arises dining evaporation of the filtrate with nitric acid, after precipitation of the copper-tin group metals with hydrogen sulfide. Salicylic acid is converted under these conditions to picric acid, which in presence of lead gives explosive lead picrate. An alternative (MAQA) scheme is described which avoids this possibility. 

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. 

These reactions would produce a net e /h recombination and, conse-quendy, net null cycles, decreasing the rate of degradation [37]. As for salicylic acid cited earlier, the formation of surface-adsorbed cation radicals was invoked to increase the charge-carrier recombination rate and thus lower the quantum yields for degradation [27]. Added redox reagents can also act as recombination sites, so that the overall photocatalytic rate could increase, decrease, or remain unchanged [40]. 

Aminopyridine can be prepared by the reaction of 4-chloro-l,3-benzoxazines (47) with pyridine TV-oxides. Here it is proposed that an ion or radical pair is formed initially, which through displacement of hydrogen chloride and rearrangement leads to an TV-substituted benzoxazine (48). Finally, acid hydrolysis gives 2-aminopyridine and salicylic acid (49 Scheme 14) (80CPB465). 

Since OH is strongly electrophilic, the OH group directs OH into its ortho- and para-positions [reactions (51)—(53)]. One of the ortho-positions is occupied by the somewhat bulky carboxylate group which renders reaction (51) less likely than reaction (52). An addition to the meta-position can be largely neglected. Upon oxidation of the OH-adduct radicals, cyclohexadienones are formed [reactions (54)-(56)] which either decarboxylate [reaction (57)] or rearrange into the corresponding phenols [reactions (58) and (59) e.g., Bausch et al. 1976]. Product yields from hydroxybenzoic acids are compiled in Table 3.5 from salicylic acid in Table 3.6. 

Capelle S, Planckaert B, Cotelle P, Catteau JP (1992) Hydroxyl radical scavenging activity of salicylic acid and its hydroxylated metabolites. An ESR study. J Chim Phys 89 561-566 Castro GD, Delgado del Layno AMA, Castro JA (1997) Hydroxyl and 1-hydroxyethyl free radical detection using spin traps followed by derivatization and gas chromatography-mass spectrometry. Redox Rep 3 343-347... 

Kaur H, Halliwell B (1996) Salicylic acid and phenylalanine as probes to detect hydroxyl radicals. In Punchard NA, Kelly FJ (eds) Free radicals, a practical approach. IRL Press at Oxford University Press, Oxford, pp 101-116... 

By using the S0D/H202 biosensor set up in our laboratory, we recently evaluated the scavenging properties in vitro of important molecules such as cysteine, melatonin, /(-carotene and acetyl salicylic acid to be considered as antitoxic agents against radicals as well as of fresh vegetal and fruit tissues, or else of extracts of the same fruits and vegetals present on the market and available in the chemists or herbalists shops. 

Qualitative inorganic analysis of compounds containing lead and salicylate radicals can lead to the formation of explosive lead picrate. This occurs due to conversion of salicylic acid to picric acid during evaporation with nitric acid.21... 

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

The mechanism of action of aspirin may be more involved than is indicated above. Aspirin also induces the formation of NO-radicals in the body, which in mice have been shown to have an independent mechanism of reducing inflammation salicylic acid and its derivatives can modulate signalling through NF-kB, a transcription factor complex that plays a central role in many processes, including inflammation. 

Initial reports (Dumer and Klessig, 1995) indicating that salicylic acid acts as an inhibitor of APX activity were later questioned (Kvaratskhelia et al., 1997a). In fact, it seems more likely that salicylic acid acts as a reducing substrate for Compound I and Compound II (second order rate constants, Jc2 and ks, of 4.0 X 10 and 1.5 x 10 M s respectively), although the nature of the radical products has not been identified (Kvaratskhelia et al., 1997a). 

Tomita M, Okuyama T, Watanabe S, Watanabe H. Quantitation of the hydroxyl radical adducts of salicylic acid by micellar elec-trokinetic capillary chromatography oxidizing species formed by a Fenton reaction. Arch Toxicol 1994 68 428-433. 

Derivative benzoates and parabenzoates have been used primarily in fruit juices, chocolate syrup, pie fillings, pickled vegetables, relishes, horseradish, and cheese (Barbosa-Canovas et al., 2003). Other foodstuffs where sodium benzoate is used include soft drinks, baked goods, and lollipops (Poulter, 2007). Benzaldehyde and benzoic alcohol are better known to be yeast inhibitors. Benzoic acid has been found to release fewer protons than sulphite, nitrite, or acetic acid and it may be speculated that benzoic acid is not a classic weak-acid preservative. However, due to a lower pKa value, benzoic acid releases three to four times more protons than sorbic acid. This is a sizable concentration of protons although not as much as other weak-acid preservatives (Stratford and Anslow, 1998). Inhibition of growth is strongly pH-dependent and most effective under acidic conditions. Under these conditions the protonated form of the acid is predominantly found (Visti, Viljakainen, and Laakso, 2003). Another unexpected discovery was that benzoic acid appears to be a pro-oxidant. This was unexpected as it is a well-known fact 2-hydroxybenzoic acid (or salicylic acid) acts as a scavenger of free radicals in vivo (Piper, 1999). 

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