Quantitative relationships between structure and antimicrobial activity of new "soft" bisquaternary ammonium salts

New surface-active bisquaternary ammonium salts derived from bis-(2-dimethylaminoethyl) ester of glutaric acid are highly effective against representatives of Gram-positive, Gram-negative bacteria and yeasts. Relationships between structure, lipophilicity and antimicrobial effectiveness were demonstrated by quantitative structure-activity methodology. The non-linear dependence of biological activity on the structure as well as lipophilicity (expressed as critical micelle concentration-CMC) was shown using Kubinyi's bilinear model. The most effective compounds were those with the alkyl chain of 11-12 carbon atoms and with the CMC values around 0.7-1.0 mmol/L. These derivatives possessed higher antimicrobial activity particularly to Gram-negative bacteria.