Quantitative structure activity relationships (QSAR) of lipophilic acids and related compounds on bacterial and mammalian cells.

It is shown by means of regression analysis that the lipophilic character of the molecule as expressed by log P in octanol/water is very important in determining the relative activities of these compounds in all of the three systems examined. In addition, molecular weight is also important in some of the systems. In general, activity increases with increasing lipophilicity and molecular weight for the limited number of compounds studied. The role of degree of ionization of these acidic drugs may affect both penetration and intrinsic activity in different ways. The finding by Sheu et al., (1) that long-chain fatty acids inhibit gram-positive bacteria (Bacillus subtilis) but not gram-negative bacteria such as E. coli, due to the protective layer of lipopolysaccharide, is in agreement with the correlations obtained for many different series of antibacterial agents by Lien, Hansch & Anderson (2).