Investigation of the Absorption Mechanism of Solubilized Curcumin Using Caco-2 Cell Monolayers

Curcumin is a bioactive compound with poor oral bioavailability. Low water solubility and rapid metabolism are two known limiting factors, but the absorption mechanism of solubilized curcumin remains unclear. This study investigated the permeation mechanism of solubilized curcumin using an in vitro Caco-2 cell monolayer model. It was shown that curcumin permeated across the monolayers fairly rapidly [P app(A–B) = (7.1 ± 0.7) × 10–6 cm/s] and the permeation mechanism was found as passive diffusion [P app(B–A)/P app(A–B) = 1.4]. Furthermore, the permeation rates of curcumin complexed with bovine serum albumin and in the bile salts–fatty acids mixed micelles were also determined as P app(mixed micelle) > P app(DMSO) > P app(protein complex). These results suggested that solubilization agents play an important role in the permeation of solubilized curcumin, and stronger binding between the solubilization agents and curcumin may decrease the permeation rate. The results further suggest that lipid-based formulations, which solubilize curcumin in mixed micelles after lipid digestion, are promising vehicles for curcumin oral delivery.