2.2.5. Evaluation of in vitro skin retention of curcumin

Extraction of the curcumin retained in the porcine ear skin discs was based on the methodology described by Sato et al. (2007). After 12 h of in vitro permeation, the porcine ear skin discs were removed from the diffusion apparatus and the skin area exposed to the receiving fluid was cleaned with aqueous ethanol (50% (v/v)), and cut and shredded. The skin fragments thus produced were processed with 25 mL of absolute ethanol using an UltraTurrax tissue homogenizer (model LR 5/10 from IKA Werke GmbH & Co. KG, Staufen, Germany) until total tearing of the skin. The resulting suspension was further subjected to sonication via ultrasounds to disrupt the cells, the resulting suspension was filtered into a 50 mL volumetric flask, and the volume made up with aqueous ethanol (50% (v/v)). Determination of the amount of curcumin retained in the porcine ear skin samples was carried out by spectrophotometry as described earlier.