<SCP>l</SCP>-Carnitine Esters as “Soft”, Broad-Spectrum Antimicrobial Amphiphiles

A new class of antimicrobial, “soft”, quaternary ammonium <SCP>l</SCP>-carnitine esters, of the type (CH<INF>3</INF>)<INF>3</INF>N⁺-CH<INF>2</INF>-CHOCO(R<INF>1</INF>)-CH<INF>2</INF>-COO(R<INF>2</INF>) Cl^-, has been designed, with R<INF>1</INF> and R<INF>2</INF> being in general long-chain alkyl substituents. The series shows good activity against a wide range of bacteria, yeasts, and fungi. Lipophilicity has been measured by RP-HPLC method to give the logarithm of the experimental capacity factor (log k‘), and a quantitative relationship has been determined between log k‘ and the theoretical partition coefficient (CLOGP); also, bond−dipole descriptors have been introduced into calculations by accounting for polar moieties present within the apolar cores of the molecules, giving a more refined calculated capacity factor (log k‘<INF>calcd</INF>). Finally the latter has been related to the antimicrobial activity (MIC values). The proposed models are predictive for the best broad-spectrum antimicrobial compound within the series.