Studies on the anti-inflammatory activity and ulcerogenic adverse effect of thiazole derivatives, especially 2-amino-thiazoleacetic acid derivatives.

A series of derivatives of 4-arylthiazole acetic acid and 2-aminothiazole were studied with respect of their antiinflammatory effect in rat carrageenin edema. Some active compounds were found, which suppressed the paw edema formation strongly, and two compounds were selected, 4-(4-chlorophenyl)-2-phenylaminothiazole acetic acid (Compd. 29) and 4-(4-chlorophenyl)-2-diethylaminothiazole acetic acid (Compd. 71) for further detailed studies. These compounds (Compd. 29 and Compd. 71) moderately inhibited the denaturation of albumin with heat-treatment. Hyperthermic lysis of erythrocytes were strongly inhibited with both Compds. 29 and 71 in the wide range of concentrations (5 X 10(-5) mol/l-5 X 10(-4) mol/l), while their related compound, Compd. 2 (fentiazac) and the reference drugs, ibuprofen, phenylbutazone and flufenamic acid, were either ineffective or stimulatory at the higher concentration. Compds. 29 and 71 inhibited strongly both trypsin and chymotrypsin activities, which differed from the above reference drugs qualitatively and quantitatively. The adverse effect on the gastrointestinal membrane was less with Compd. 29 and Compd. 71 compared with fentiazac and ibuprofen. Compd. 29 especially gave the preferable results with almost no gastric damage at the higher dosage together with its good anti-edematous activity. The characteristics of Compds. 29 and 71 are discussed in terms of the correlation between anti-inflammatory effect and ulcerogenic effect and also of the clinical application.