Human Sebaceous Cis -6-Hexadecenoic Acid: Possible Application of an Innate Antimicrobial Substance to Cosmetic Products for Mucous Membrane

The antimicrobial properties of cis-6-hexadecenoic acid (C16:1Δ6), a component of the innate human metabolome, were studied and its application to cosmetic products was investigated in detail. A variety of the resident and transient microbial flora of the skin, oral cavity, and intestine was applied to an investigation of the antimicrobial activity of C16:1Δ6. C16:1Δ6 showed selective antibacterial activity against human microbial pathogens such as Clostridium perfringens (one of the most common causes of food poisoning) and Streptococcus mutans (one of the tooth-decaying bacteria), as well as Staphylococcus aureus. C16:1Δ6 seemed to possess a “species-selective” antibacterial activity against bacteria belonging to the genera Staphylococcus and Clostridium. We performed a preliminary assessment of the application of C16:1Δ6 as an antimicrobial component in a liquid lip gloss by performing preservation efficacy and home-use tests. We noted that the amount of p-hydroxybenzoate was needed in an oily cosmetic, especially liquid lip gloss, could be reduced by replacing p-hydroxybenzoate with C16:1Δ6. We suggest that C16:1Δ6 may find application as a stable antimicrobial substance gentle enough for use in consumer products by its selective antimicrobial characteristics.