Marine lipids as building blocks for soft quaternary ammonium compounds and their antibacterial activity

Environmental friendly antibacterial agents have to degrade relatively rapid to non-toxic and inactive products after they have had their desired effect. Environmental friendly quaternary ammonium agents were designed according to Bodor's soft drug approach and evaluated in vitro. Structure-activity relationship (SAR) studies showed that the antibacterial activity of a given soft agent will only be acceptable if its chemical stability is adequate to allow the agent to express its activity for sufficient duration of time. However, the studies also showed that increasing the lipophilicity of a chemically labile antibacterial agent could increase its potency. Two of the lipophilic quaternary ammonium antibacterial agents evaluated had minimum inhibitory concentration (MIC) against Staphylococcus aureus as low as 2 microg/ml and estimated degradation half-life less than 4 to 6 days at room temperature. Decreased MIC could only be obtained by increasing the degradation half-life of the agents.