Chemical stability and degradation mechanisms of ferulic acid (F.A) within various cosmetic formulations.

Ferulic acid (F.A) receives significant interest in the beauty industry with regard to its skin-whitening and anti-oxidant properties. However, its use in cosmetics is limited due to pH- and temperature-related instabilities. In this study, we investigated the stability of F.A in eight different prototype formulae. The results confirmed that in our conditions the stability of F.A is pH- and temperature-related. Additionally, the nature of the solvent dipropylene glycol (DPPG) showed a capacity to stabilize F.A. A series of experiments was further planned for studying the mechanism of degradation of F.A. In a prototype of a cosmetic medium, F.A degrades first through a decarboxylation step, leading to 4-hydroxy-3-methoxystyrene (PVG). Further, F.A and PVG are both involved in an additional reaction, resulting in the trans-conjugation dimer of PVG. The consequences of these results in formulating F.A are discussed.