Palmitoleic acid calcium salt: a lubricant and bactericidal powder from natural lipids

Palmitoleic acid is a promising bactericidal agent for cleansing products with alternative bactericidal abilities. In this study, we focus on the physical and biological activity of palmitoleic acid calcium salt (C16:1 fatty acid Ca salt) because it forms via an ion-exchange reaction between palmitoleic acid and Ca ions in tap water, and remains on the skin surface during the cleansing process. Here, we prepared C16:1 fatty acid Ca salt to investigate its crystal structure and physical and bactericidal properties. The Ca salt was a plate-shaped lamellar crystalline powder with a particle diameter of several micrometers to several tens of micrometers; it exhibited significant lubricity and alternative bactericidal activity against Staphylococcus aureus (S. aureus) and Propionibacterium acnes (P. acnes). We also examined other fatty acid Ca salts prepared from lauric acid (C12:0 fatty acid), palmitic acid (C16:0 fatty acid), and oleic acid (C18:1 fatty acid). The bactericidal activities and lubricity of the fatty acid Ca salts changed with the alkyl chain length and the degree of unsaturation. The C16:1 fatty acid Ca salt exhibited the strongest selective bactericidal ability among the four investigated fatty acid Ca salts. These findings suggest that C16:1 fatty acid and its Ca salt have potential applications in cleansing and cosmetic products.