Dehydroacetic acid sodium salt stability in cosmetic preservative mixtures

Abstract

Synopsis Dehydroacetic acid sodium salt Prevan (DHANa) stability in presence of other cosmetic preservatives as Bronopol, Germall 115 and Kathon CG was investigated through a HPLC method that permits simultaneous determination of binary and ternary mixtures of the above preservatives. A new molecule coresponding to 3,7-dimethyl-1H, 9H, 10H, dipyrano (4,3-b: 3',4'-e) pyran-1, 9-dione has been discovered to be spontaneously formed between DHA and free or released formaldehyde. Its structure has been established by means of elemental analysis, NMR and mass spectrometry aswell as its chromatographic and antimicrobial behaviour. The magnesium salt present as stabilizer in the Kathon CG solution can also cause the formation of insoluble magnesium salt from DHANa. The ascertained chemical interaction among these preservatives is therefore discussed as a function of their cosmetic application.