Selective Antibacterial Activity of Palmitoleic Acid in Emulsions and Other Formulations

In recent years, the selective antibacterial properties of certain fatty acids (FA) against Staphylococcus aureus have received significant attention. In this study, the antibacterial properties of palmitoleic acid (16:1 FA) in oil (triolein), surfactant (Tween® 60), and water ternary systems were evaluated to demonstrate the effects of the mixed states on the biological activity. The 16:1 FA exhibited selective antibacterial activity against Staphylococcus aureus, with a minimum inhibitory concentration (MIC) of 18.8 μg mL−1. In contrast, palmitoleic acid did not display any activity in water‐in‐oil (W/O) emulsions and liquid crystal systems. In some micelle and surfactant‐free oil‐in‐water (O/W) emulsions, the FA showed significant selective antibacterial properties against Staphylococcus aureus. These results suggested that the mixed state of the ternary mixtures affects the antibacterial behavior of FA molecules. The findings of the present study provide a valuable platform for the design of formulations of cosmetics, topical skin products, and skin cleansers.