Enhanced oral bioavailability of magnolol via mixed micelles and nanosuspensions based on Soluplus®-Poloxamer 188

Magnolol, known to have extensive biological activities, is the major bioactive ingredient isolated from the root and stem bark of Magnolia officinalis. However, the clinical application of magnolol is limited by poor aqueous solubility and absorption. The aim of this study is to develop novel mixed micelles and nanosuspensions composed of two biocompatible copolymers, Soluplus^® and Poloxamer 188, and to improve the solubility and oral bioavailability of magnolol. The magnolol-loaded mixed micelles (MMs) and magnolol nanosuspensions (MNs) were prepared to use film hydration and antisolvent methods, respectively. The optimal MMs and MNs formulations were prepared to use magnolol, Soluplus^®, and Poloxamer 188 in ratios of 1:12:5 and 2:1:1, respectively. The average particle size of MMs was 111.8 ± 14.6, and MNs was 78.53 ± 5.4 nm. The entrapment and drug loading efficiency for MMs were 89.58 ± 2.54% and 5.46 ± 0.65%, correspondingly. The drug loading efficiency of MNs was 42.50 ± 1.57%. In the in vitro release study, MMs showed a slow drug release while that of MNs was fast. The results of the Caco-2 transcellular transport study indicated that both MMs and MNs increased the permeation of magnolol. MMs and MNs markedly promoted gastrointestinal drug absorption by 2.85 and 2.27-fold, respectively, as shown in the pharmacokinetics study. These results indicated that both MMs and MNs formulations prepared with Soluplus^® and Poloxamer 188 are promising drug delivery systems for improving the oral absorption of insoluble drugs in the gastrointestinal tract.