The germicidal activity of some pyridinium salts containing unsaturated hydrocarbon radicals.

The germicidal potency of quatemary ammonium compounds is known to depend mainly on the chemical structure of the cation, the nature of the anion having little if any effect (Glassman, 1948). The relation of structure of the cation to bactericidal activity has been studied extensively insofar as chain length of the hydrophobic or hydrocarbon group is concerned. In compounds with only one long chain aliphatic group the maximum activity is associated almost always with a chain length of 12, 14, or 16 carbon atoms in this radical, the activity decreasing markedly outside this range (Kolloff et al., 1942; Rawlins et al., 1943; Hoogerheide, 1945; Valko and DuBois, 1945; Shelton et al., 1946a, b). No systematic studies, however, have been reported so far on the influence of unsaturation in the hydrocarbon group. In view of the fact that unsaturated fatty acids by themselves possess significant bacteriostatic properties (Kodicek and Worden, 1945; Hirsch, 1947) it was decided to investigate the effect of introducing unsaturated hydrocarbon radicals in quaternary ammonium compounds. In the present investigation the effect of unsaturation in the hydrocarbon group of aliphatic pyridinium salts was examined by studies on stearyl, oleyl, linoleyl, and linolenyl-pyridinium bromides. Pyridinium salts containing hydrocarbon radicals derived from the mixed fatty acids of commercially available hydnocarpus and shark liver oils were synthesized also and assayed for activity, the former being selected on account of its therapeutic application in the treatment of leprosy and the latter on account of its content of polyethenoid fatty acids which are characteristic of fish oils.