Centrifugation-based stability evaluation of creams containing resveratrol and ferulic acid

Introduction. Photoprotective formulations are used to decrease the deleterious effects of solar radiation [2]. As emulsion-based products, their stability affects shelf life and quality [1], making assessment crucial, especially with novel, plant-derived photoprotective ingredients like resveratrol and ferulic acid. Materials and methods. Creams consisted of a lipophilic phase (pumpkin seed oil, Olivem-1000) and a hydrophilic phase (water, glycerol, phenoxyethanol). Resveratrol was dispersed into a hydrophlic phase, while ferulic acid was dispersed into a lipophilic phase. Code names for each formulation were assigned. Resveratrol and ferulic acid content in each cream is provided in Table 1. Stability was assessed via centrifugation (centrifuge Sigma 3-18 KS, Germany): samples were spun at 3000 rpm for 5 min, followed by 10000 rpm for 5 min if remained stable. Results and their discussion. Results of the centrifugation test are provided in Table 2. (+ = remained stable;  = became unstable; NP = not performed) It is apparent that creams with resveratrol only remained stable at both lower stress and higher stress conditions, whereas no creams with ferulic acid remained stable after centrifugation at 10000 rpm, some of them separating even at 3000 rpm (F2, R1F1, R1F2). This suggests that both the presence and concentration of resveratrol and ferulic acid affect the physical stability of the emulsion and may require careful consideration while formulating photoprotective creams.