THE ABSORPTION OF CINCHONA ALKALOIDS IN THE CHICK AND ITS RELATIONSHIP TO ANTIMALARIAL ACTIVITY

¹ From the Wellcome Laboratories of Tropical Medicine, 183 Euston Road, London, England

1. Determinations of the rate of absorption from the gut, red cell concentrations and antimalarial activity in chicks of the four natural alkaloids of cinchona and four derivatives showed that antimalarial activity was, in most cases, correlated with rate of absorption and red cell concentrations.

2. In three optically active pairs of alkaloids, the d-isomers showed a greater rate of absorption, higher red cell concentrations and higher antimalarial activity than the l-isomers.

3. The rate of "destruction" of the alkaloids by chick liver suspensions was not related to optical configuration. Cinchonine and cinchonidine, unlike the other alkaloids, were not metabolized at all.

4. Saturation of the double bond in quinine doubled the antimalarial activity. Dihydroniquidine, however, showed no greater activity than niquidine.