salicylates and aspalatone

To study the mechanism for the low ulcerogenicity of the antithrombotic agent aspalatone ([3-[2-methyl-4-pyronyl)]-2-acetyloxybenzoate, CAS 147249-33-0), the metabolism and disposition of aspalatone were compared with those of acetylsalicylic acid (ASA) in the gut wall in relation to the salicylate level in the stomach tissues following oral administration in pyrolus-ligated rats. Both aspalatone and ASA were essentially stable in gastric juice and were absorbed in stomach unchanged. In glandular portion of the stomach, salicylate level found at 10 min post-dose in aspalatone (80 mg/kg)-and in ASA (50 mg/kg)-treated group was 67 +/- 43 nmol/g tissue and 2000 +/- 250 nmol/g tissue, respectively. In non-glandular (rumen) tissue, salicylate was not detected in the aspalatone group, whereas it reached a concentration of up to 1100 +/- 130 nmol/g tissue in the ASA group. As a result of the relative stability of the ester bond connecting the salicylic acid and maltol groups towards hydrolysis in the stomach and entrapment of ASA due to ion trapping, a lower salicylate level was observed in the stomach after oral aspalatone administration, and this may, at least in part, be the underlying mechanism for the low ulcerogenicity of aspalatone.

Topics: Animals; Aspirin; Gastric Mucosa; Male; Platelet Aggregation Inhibitors; Rats; Rats, Sprague-Dawley; Salicylates; Stomach Ulcer

In order to determine whether aspalatone ([3-(2-methyl-4-pyronyl)]-2- acetyloxybenzoate, CAS 147249-33-0), a new antiplatelet agent, behaves as a prodrug of acetylsalicylic acid (ASA), metabolism studies in rats were carried out in vivo and in vitro using the whole animal and tissue homogenates. The ASA molecule was not detected in the plasma samples taken after oral administration of aspalatone at 80 mg/kg. Instead, salicylic acid maltol ester (SM), the deacetylated metabolite of aspalatone, was detected in the plasma and it was rapidly hydrolyzed to salicylic acid. In in vitro experiments with rat serum, intestinal fluid, liver and gastric mucosal homogenates, SM was the only compound formed after 4 min incubation at 37 degrees C. From these results it was concluded that aspalatone does not behave as a prodrug of ASA in rats. In addition, the results of experiments using certain esterase inhibitors, suggested the major contribution of B-esterase(s) in the metabolism of aspalatone to SM particularly in serum and intestinal fluid.

Topics: Animals; Aspirin; Biotransformation; Chromatography, High Pressure Liquid; Dealkylation; Esterases; Fibrinolytic Agents; Humans; In Vitro Techniques; Male; Platelet Aggregation Inhibitors; Prodrugs; Rats; Rats, Sprague-Dawley; Salicylates; Spectrophotometry, Ultraviolet