Effect of polyols on interaction of paraben preservatives with polysorbate 80.

A quantitative study of the interaction of the methyl, ethyl, propyl, and butyl esters of p-hydroxybenzoic acid with polysorbate 80 in the presence and absence of two polyols (propylene glycol and glycerol), which were potential competitors, was performed. The results indicate that neither competitor displaced significant amounts of the parabens from their binding sites on polysorbate 80. The previously observed synergistic antimicrobial effects of these polyols appear to be due to a mechanism other than the displacement of the parabens from their micellar binding sites.