In vitro hemolysis of human erythrocytes -- by plant extracts with antiplasmodial activity.

Human erythrocytes were exposed in a dose dependent manner to various ethanolic plant extracts, and fractions obtained from plant parts of Calotropis procera (Ait.) R. Br. and the gum--oleo resin of Commiphora wightii (Arnott.) Bhand. These have been screened for in vitro schizontocidal activity and graded with respect to their 50% inhibitory concentration (IC(50)) derived from the twofold serial dilution of the dose range 0.0625--2 mg/ml. An attempt had been made to relate their antiplasmodial activity with their cytotoxicity as represented by the in vitro rate of hemolysis. Intact erythrocytes were found to respond with a dose--time-integral and fitted to models of pseudo first-order reaction, Michaelis--Menten equation and Hill equation with k(1), k(2) and k(3) as their rate constants, respectively. Hemolysis isotherms of flower and root of C. procera and gum--oleo resin of C. wightii extracts were representative. Erythrocytic membrane instability is possibly a major factor as has been earlier reported with ethanol and chloroquine for the cytotoxicity of these plant extracts.