An in vitro approach to study the absorption of a new oral formulation of berberine

Background Berberine (BBR) possesses several biological activities in humans, but the poor water solubility and low oral bioavailability preclude its pharmacological use. To overcome these limitations, several formulations have been prepared including encapsulation, micro- and nano-emulsion. The aim of this study was to develop a nanoemulsion delivery system of BBR and to evaluate its membrane permeability using Caco-2 cell model. Methods Nanoemulsions containing different ratios BBR:Compritol ATO 888 (a lipid excipient) were formulated at 25 and 80 °C. The controls consisted of BBR and carboxymethylcellulose. Absorption of BBR nanoemulsions delivery systems was evaluatedin vitro by using human colon adenocarcinoma cells (Caco-2) Transwell model. The amount of permeated BBR was determined by LC-HR-MS at time zero and every 30 min for 180 min. Results Nanoemulsions significantly improved apical-to-basal transport of BBR compared to the control formulation. Kinetics of BBR uptake showed that the maximum amount absorbed was reached after 90-120 min and the percentage of BBR absorbed by Caco-2 cells increased with increasing BBR-to-Compritol ratio (1:20 > 1:10 > 1:5 > 1:1). Moreover, the formulation prepared at 80 °C showed a higher absorption rate (6-fold increment compared to control) than that developed at 25 °C (4.5-fold increment compared to control). Furthermore, demethyl-BBR was detected after 120 min of incubation as partial metabolism of berberine in the intestine. Conclusions Overall, in ourin vitro model, these new nanoemulsions seem to potentially improve the absorption of BBR. However, in vivo studies are required in order to demonstrate the bioavailability of BBR from this new formulation.