Calorimetric Analysis of Antimicrobial Effect of p-Hydroxybenzoic Acid Alkyl Esters

Abstract

Calorimetric studies were conducted on the antimicrobial action of p-hydroxybenzoate alkyl esters (parabens), which are commomly used as preservatives in cosmetic products, and the parameters to quantitatively predict their actions on the microbial strains were determined. The result obtained was that their action on both Saccharomyces cerevisiae and Klebsiella pneumoniae became stronger as the number of carbon atoms in the alkyl chain increased. When comparing the affinity of the drugs to both microorganisms based on the drug concentration required to inhibit growth activity by 50%, a linear relationship was observed to exist between the number of carbon atoms in an alkyl chain and the affinity. In addition, the same drug exhibited a higher effect on S. cerevisiae than on K. pneumoniae, which may be due to the difference in the membrane structures of the microorganisms.