Application of the carbonic anhydrase inhibitory effect of furosemide to the study of furosemide release from two of its diuretic derivatives.

Bovine carbonic anhydrase B (CA) inhibitory effect of furosemide was established in two pH values at 26 degress. FFBu [N-furfuryl-4-chloro-5-(butoxymethylsulfamoyl)anthranilic acid] and FFMe [N-furfuryl-4-chloro-5-(methoxy-methylsulfamoyl)anthranilic acid], two of its alkoxymethyl derivatives, did not exert any CA inhibitory effect at those conditions but were found to inhibit the CA activity after their hydrolysis, which yielded the furosemide molecule. The CA inhibitory effect of furosemide was utilized for determining the kinetic rate constants for the hydrolysis of FFBu and FFMe at various pH and temperature levels.