Radiosensitivities of parabens and characterization of the radical species induced in this class of antimicrobial agents after gamma irradiation

Abstract

Radiosensitivities of methyl, ethyl, propyl and butyl parabens and sodium salts of methyl and propyl parabens (hereafter, MP, EP, PP, BP, SMP and SPP, respectively) were investigated by monitoring, through electron spin resonance (ESR) spectroscopy, the evolution under different experimental conditions of characteristic features of the radicalic species produced upon irradiation by gamma radiation. While ESR spectra of the studied parabens consisted of the sum of broad and narrow resonance lines of different microwave saturation and thermal characteristics, those of sodium salts appeared to consist of the sum of two overlapping narrow resonance lines. Radical species presented different room and high-temperature decay characteristics, depending on the extent of the cage effect created by the lattice networks on these species. A model based on the presence of two radical species presenting different spectroscopic and kinetic features described best the experimental data collected for parabens and their sodium salts. Radiation yields of the studied parabens towards gamma radiation were calculated to be low (G≤10⁻²), providing the opportunity of using these antimicrobial agents in food, cosmetics and drugs to be sterilized by radiation without much loss from their antimicrobial activities.

Keywords:

• parabens
• sterilization
• ESR
• dosimetry
• radical kinetics