A BIOASSAY FOR EVALUATING ANTIMALARIAL ACTIVITY AND FOR MEASURING CONCENTRATION IN PLASMA

Our objective was to develop a bioassay method based on the isotopic m icrotest of Desjardins and to validate it by comparing the results wit h high performance liquid chromatograph (HPLC). The bioassay was devel oped using a continuous culture of P. falciparum, and the test materia l consisted of 32 human serum samples from 22 Filipino patients treate d only with chloroquine (CQ) for noncomplicated malaria. A blind assay of the serum was done using the Desjardins method and HPLC. A good co rrelation (r = 0.90, n = 32) was observed between the CQ plus monodese thylchloroquine (DCQ) concentrations obtained by HPLC and the equivale nt CQ by bioassay. It was also shown that the antimalarial activity of CQ is practically identical to that of its main metabolite DCQ, the a ctivity of DCQ being 0.9 times the activity of CQ. The bioassay is rel iable, semi-automated, and reproducible. This method may be used as a complementary technique to HPLC for determining biological activity in serum and for measuring the kinetics of this activity, as well as to indicate the existence of new metabolites. The bioassay can be applied to other protozoans for which an in vitro model is available.