Lubricant and Bactericidal Properties of Calcium Salts of Fatty Acids: Effect of Degree of Unsaturation

Fatty acids containing a C18 alkyl chain such as stearic acid (C18:0 fatty acid), oleic acid (C18:1 fatty acid) and linoleic acid (C18:2 fatty acid) are common emulsifiers in skin-care products and cosmetics and are also used in skin cleansers. In this study, we prepared calcium salts (Ca salts) of the above fatty acids to determine the effect of the degree of unsaturation of the alkyl chain. Scanning electron microscopy images and X-ray diffraction patterns show that C18:0 and C18:1 fatty acid Ca salts are plate-shaped, lamellar-crystalline powder, while C18:2 fatty acid Ca salt is amorphous powder. Therefore, C18:2 fatty acid Ca salt exhibits a lower lubrication ability than do C18:0 and C18:1 fatty acid Ca salts. In addition, the bactericidal ability against Staphylococcus aureus, Staphylococcus epidermidis and Propionibacterium acnes improved with increasing degree of unsaturation. These findings suggest that Ca salts of unsaturated fatty acids have potential applications in cleansing and cosmetic products.