Salicylic acid mechanism

Mechanism I was ruled out by an isotopic labeling experiment. The mixed anhydride of salicylic acid and acetic acid is an intermediate if nucleophilic catalysis occurs by mechanism 1. This molecule is known to hydrolyze in water with about 25% incorporation of solvent water into the salicylic acid. 

Hydrolysis of aspirin in H2 0 leads to no incorporation of into the product salicylic acid, ruling out the anhydride as an intermediate and thereby excluding mechanism 1. The general acid catalysis of mechanism III can be ruled out on the basis of failure of other nucleophiles to show evidence for general acid catalysis by the neighboring carboxylic acid group. Because there is no reason to believe hydroxide should be special in this way, mechanism III is eliminated. Thus, mechanism II, general base catalysis of hydroxide-ion attack, is believed to be the correct description of the hydrolysis of aspirin. 

The author has observed enhanced improvement of oily skin, enlarged pores, and acne vulgaris with the use of salicylic acid peels compared with glycolic acid peels. Possible mechanisms for this observation include salicylic acid s effect on lipid solubility and microcome-odone formation. 

Another limitation to the studies in Table 1 is the small number of plant species tested. Primarily monocotyledonous plants have been studied, although McClure et al. (26) found ferulic acid inhibitory in soybean. The restriction of studies to monocots is probably because the mechanism of mineral absorption has been more fully elucidated with monocots. Harper and Balke (32) reported some minor differences in the inhibition of K+ absorption by salicylic acid among oats (Avena sativa L.), wheat (Triticum aestlvum L.), barley, and maize roots. 

Figure 5 Dissolution rates of salicylic acid-benzoic acid mixtures. ( ) Benzoic acid from melt (O) salicylic acid from melt (A) salicylic acid from mechanical mix ( ) Benzoic acid from mechanical mix. (From Ref. 19.)... 

Recently, Prasad et al. cloned a mammalian Na+-dependent multivitamin transporter (SMVT) from rat placenta [305], This transporter is very highly expressed in intestine and transports pantothenate, biotin, and lipoate [305, 306]. Additionally, it has been suggested that there are other specific transport systems for more water-soluble vitamins. Takanaga et al. [307] demonstrated that nicotinic acid is absorbed by two independent active transport mechanisms from small intestine one is a proton cotransporter and the other an anion antiporter. These nicotinic acid related transporters are capable of taking up monocarboxylic acid-like drugs such as valproic acid, salicylic acid, and penicillins [5], Also, more water-soluble transporters were discovered as Huang and Swann [308] reported the possible occurrence of high-affinity riboflavin transporter(s) on the microvillous membrane. 

The answer is b. (Hardman, p 1061.) Sulfasalazine consists of sul-fapyridine with 5-aminosalicylic acid linked by an azo- bond. This bond is broken by bacteria that release the salicylic acid, which is believed to be the active agent. Sulfa drugs or salicylic acid used alone is not as effective. The mechanism of action is unknown, but it is believed to be protective action on the mucosa by inhibition of the synthesis of prostaglandins and leukotrienes. 

In a bidentate ligand system, three molecules of a dye containing either a terminal salicylic acid unit (as in 5.2) or an o-nitrosonaphthol residue are able to chelate simultaneously with a trivalent metal ion of CN6, such as chromium (III) or iron(III), to form a 1 3 metal-dye complex (as in 5.8). Historically, the most important bidentate ligand system was alizarin (5.1). It has been suggested that both hydroxy groups and the keto group in the peri position are all involved with the metal atom in the chelation mechanism. 

Spectroscopic techniques may provide the least ambiguous methods for verification of actual sorption mechanisms. Zeltner et al. (Chapter 8) have applied FTIR (Fourier Transform Infrared) spectroscopy and microcalorimetric titrations in a study of the adsorption of salicylic acid by goethite these techniques provide new information on the structure of organic acid complexes formed at the goethite-water interface. Ambe et al. (Chapter 19) present the results of an emission Mossbauer spectroscopic study of sorbed Co(II) and Sb(V). Although Mossbauer spectroscopy can only be used for a few chemical elements, the technique provides detailed information about the molecular bonding of sorbed species and may be used to differentiate between adsorption and surface precipitation. 

More recently, polyesters with beneficial degradation products (salicylic acid) have been produced to promote healing through enhanced regeneration of tissue [10]. Degradation mechanisms relevant to medical applications include... 

Gandhi R, Robinson J (1992) Mechanisms of penetration enhancement for trans-buccal delivery of salicylic acid. Int J Pharm 85 129-140... 

Wilkins. S.J., Coles, B.A., Compton, R.G., and Cowley, A. Mechanism and kinetics of salicylic acid dissolution in aqueous solutionunder defined hydrod3mamic conditions via atortric force trricrosopy the effects of the ionic additives NaCl, LiCl, and MgCb, the organic additives 1-propanol, 2-propanol, and the surfactant sodium dodecyl sulfate. J. Rhys. Chem. B, 1061(106) 4763-4774, 2002. 

The purposes of this paper are to review one of the common mechanisms of detoxication in plants, namely conjugation, and to present data showing that salicylic acid, an allelopathlc phenolic acid, is enzymatically conjugated by oat roots. 

Drugs that are used to treat hyperkeratosis, a thickening of the stratum corneum, are called keratolytics. Examples of these agents are salicylic acid, urea, lactic acid, and colloidal or precipitated sulfur. The precise mechanisms by which these agents treat hyperkeratosis are not known. Presumably, a common property is the ability to denature keratin, the major structural protein of the epidermis. Other beneficial effects vary among the different drugs. All of them have antimicrobial or... 

Mechanism of Action A salicylic acid derivative that locally inhibits arachidonic acid metabolite production, which is increased in patients with chronic inflammatory bowel disease. Therapeutic Effect Blocks prostaglandin production and diminishes inflammation in the colon. 

Salicylic acid has been extensively used in dermatologic therapy as a keratolytic agent. The mechanism by which it produces its keratolytic and other therapeutic effects is poorly understood. The drug may solubilize cell surface proteins that keep the stratum corneum intact, thereby resulting in desquamation of keratotic debris. Salicylic acid is keratolytic in concentrations of 3-6%. In concentrations greater than 6%, it can be destructive to tissues. 

A number of 2,3-fused chromones have been prepared from ethyl chloroformate and acetylsalicylic acid, a source of the mixed anhydride of formic and salicylic acids, and piperidinocycloalkenes (69JCS(C)935). A plausible mechanism is outlined in Scheme 165. It has not proved possible to isolate the chromanone (460) but the formation of 3-acetyl-2-methylchromone from 2-pyrrolidinopropene lends support to the intermediacy of the chromanone. The migration of the acyl group from oxygen to carbon is supported by the synthesis of 3-benzoyl-2-methylchromone rather than 3-acetylflavone from benzoylsalicylic acid and the pyrrolidinopropene. 

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