O/W microemulsions with vanillin as vehicles for antiacne actives: preparation, characterization and stability

The aim of this study was to prepare stable O/W microemulsions as topical vehicles for palmitoyl collagen aminoacids (Lipacide PCO) and lauryl pyroglutamate (Lauryl PCA), two active substances that can act as adjuvant in acne treatment. The O/W microemulsions were prepared using low quantities of mild nonionic and amphoionic surfactants, employing percentages of ethanol lower than in commonly used lotions. The diffusion profiles of surfactants through cellulose membrane have been investigated to assess in vitro their irritation potential. Vanillin was added to the emulsified systems as fragrance and its stability against oxidation was investigated. A pseudo-first order mechanism was suggested for vanillin degradation in experimental conditions. Addition of antioxidant and sunscreen agents provided protection to vanillin, reducing its degradation rate and consequently increasing the stability of microemulsions.