Enzymatic kinetic method for determination of propranolol hydrochloride in pharmaceuticals based on its inhibitory effect on cholinesterase

Propranolol, a widely used beta-blocker, inhibits the hydrolysis reaction of enzyme cholinesterase. Measurements of the difference in rate of hydrolysis rate between uninhibited and inhibited reactions allow the development of a kinetic method for its determination. Both systems, enzyme–substrate–chromogen and enzyme–substrate–chromogen–inhibitor, were characterized through biochemical kinetic parameters (KM, 0.326–0.330 mmol/L; Vmax , 40.0–43.0 μmol/Lmin). The inhibition type was recognized as competitive and the inhibition constant, Ki, was determined to be 22.60 μmol/L. The detection and quantification limits were calculated as 0.004 and 0.0136 μmol/L, respectively. Accuracy and precision of proposed methods were tested. The proposed method showed good sensitivity, selectivity, simplicity and rapidity, thus it is convenient for clinical applications.