The action of the cinchona and certain other alkaloids in bird malaria. III

Abstract

An extensive series of isomerides and transformation products of quinine and quinidine has been prepared[long dash]many of them for the first time, purified, and tested in bird malaria. Quinine was used as a standard of comparison. A detectable anti-malarial effect is produced in infected canaries with as little as 0.1 mg. of this alkaloid. To facilitate a roughly quantitative comparison the results are expressed as quinine ratios, i.e.. the ratios of the times of retardation of onset of attack, due to quinine and to the drug under test. The results show that interference with the central, secondary carbinol group, even to the extent of a change in spatial distribution at this point, as in the conversion of quinine and quinidine to epi-quinine and epiquinidine respectively, destroys the anti-malarial activity. Activity is diminished by the conversion of the vinyl side-chain, CH2CH, into CH3 CH(OH). and may be either reduced or increased by the change CH2:CH [forward arrow] CH3 CH:, depending on the configuration of the rest of the molecule. Homologous series of apoquinine and dihydro-cupreine alkyl ethers from C20 to C30 have also been prepared and tested. Such a series divides itself into 2 sub-series consisting of members with odd and even number of atoms respectively. In each, activity rises to a maximum as the sub-series is ascended and then falls.