Synergistic Antibacterial and Antioxidant Effects of Different Molecular Weight Chitosan with Cosmetic Ingredients

Abstract

This study investigates the properties of chitosan in cosmetic formulations, by examining the antibacterial and antioxidant effects when used alongside other cosmetic ingredients. Three types of chitosan with different molecular weights were examined, and five representative cosmetic ingredients used as raw materials in cosmetic formulations (1,2-hexanediol, 1,3-butylene glycol, EDTA-2Na, ethanol, and glycerol) were selected. Disc diffusion and broth microdilution assays were conducted to determine the antibacterial activity of chitosan and the cosmetic ingredients. Synergistic antibacterial effects were evaluated by applying the checkerboard synergy assay. Bacterial strains used for the experiments were Gram-positive bacteria (Staphylococcus aureus, methicillin-resistant Staphylococcus aureus) and a Gram-negative bacterium (Escherichia coli). Antioxidant activity was measured by the DPPH radical scavenging assay. LMWC showed potent antibacterial and antioxidant activities. Synergistic antibacterial effects (in order of potency) were determined for LMWC, HMWC, and MMWC. In particular, EDTA-2Na and ethanol showed remarkable synergistic antibacterial effects with chitosan; none of the compounds showed antagonistic effects. Our data indicate that chitosan has strong potential for use as a natural material in cosmetic formulations, and may be useful in a wide range of applications in the cosmetic industry.