Improved Oral Absorption of Poorly Soluble Curcumin via the Concomitant Use of Borneol

In this study, borneol, a natural active compound was applied to improve the bioavailability of curcumin (CUR). In order to increase CUR solubility and dissolution, solid dispersions (SDs) were prepared with the matrix of polyvinylpyrrolidone (PVP) at various ratios by solvent evaporation method. CUR was evidenced to exist as amorphous state in solid dispersion by differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). Fourier-transform infrared spectroscopy (FT-IR) was utilized to confirm intermolecular hydrogen bonding. The SD at the ratio of 1:3 (CUR:PVP) exhibited the optimal solubility and dissolution rate in various media. The results of ex vivo permeability studies by everted gut sac method showed that the apparent permeability coefficients (Papp) of CUR in SD across the duodenum, jejunum, and ileum had been significantly improved by co-incubation of borneol, and the improvement degree relied on the concentration of borneol. The pharmacokinetic results in rats indicated that the AUC0-t of CUR-SD (40 mg/kg) co-administration of borneol (90 mg/kg) were 2.53-fold higher than CUR-SD alone, and 19.41-fold higher than pure CUR (200 mg/kg) with borneol (90 mg/kg). Therefore, the combination of borneol and solid dispersion strategy provide a potential approach to enhance the oral bioavailability of CUR.