Stability testing of the anti-skin aging emulsion
Stability profiles of the obtained emulsion containing the optimized extract combination and the emulsion base were evaluated in terms of physical stability and biological properties after storing under various conditions including room temperature with light (RTL) and without light (RTD), 4 °C, 45 °C for three months, and accelerated condition as 6 cycles of heating–cooling (HC). After storing, viscosity and pH value of each formulation were measured and compared with those initially. In addition, DPPH scavenging effect of the extract-loaded formulation was determined and compared with those initially. To evaluate the biological properties, 10% Tween 20 served as an extracting solvent for the extract-loaded formulation in a ratio of 1:1. The mixture was sonicated for 30 min and centrifuged at 10,000 rpm for 30 min (Model: Sorvall ST16R centrifuge, Thermo Fisher Scientific, Osterode am Harz, Germany). Supernatant was then collected and used for the evaluation.