Physicochemical and biopharmaceutical characterization of amorphous solid dispersion of nobiletin, a citrus polymethoxylated flavone, with improved hepatoprotective effects

Abstract

The present study aimed to develop an amorphous solid dispersion (SD) of nobiletin (NOB), a citrus polymethoxylated flavone, with the aim of improving its biopharmaceutical and hepatoprotective properties. SD formulation of NOB (NOB/SD) was prepared by wet-milling and subsequent freeze drying, and its stability and dissolution properties were characterized. The hepatoprotective effects and pharmacokinetic behavior of orally dosed NOB/SD were evaluated in rats. During the storage of NOB/SD for 4 weeks under accelerated conditions, there were no significant transitions in the appearance, particle size, and amorphousity of wet-milled NOB. In comparison with crystalline NOB, the NOB/SD exhibited significant improvement in the dissolution with a 10-fold higher dissolution rate. In a rat model of acute liver injury, repeated treatment with NOB/SD (2 mg NOB/kg) every 4 h led to marked attenuation of hepatic damage as evidenced by decreased ALT and AST, surrogate biomarkers for hepatic injury; however, crystalline NOB was found to be less effective. After oral administration of NOB/SD (2 mg NOB/kg) in rats, compared with crystalline NOB, improved pharmacokinetic behavior was observed with increases of bioavailability and hepatic delivery by ca. 7- and 6-fold, respectively, possibly leading to better hepatoprotection. Given the improved physicochemical and biopharmaceutical properties, the SD formulation strategy might be efficacious for enhancing the therapeutic potential of NOB.

Keywords: ALT; ANOVA; AST; CCl(4); CYP; Ceq; DLS; DSC; Dissolution; H&E; HPC; Hepatoprotection; NAD; NOB; Nobiletin; Oral absorption; PBS; PLM; PM; PXRD; RH; SD; SEM; SIR; Solid dispersion; UPLC/ESI-MS; alanine aminotransferase; analysis of variance; aspartate aminotransferase; carbon tetrachloride; cytochrome P450; differential scanning calorimetry; dynamic light scattering; equilibrium solubility; hematoxylin and eosin; hydroxypropyl cellulose; nicotinamide adenine dinucleotide; nobiletin; phosphate-buffered saline; physical mixture; polarized light microscopy; powder X-ray diffraction; relative humidity; scanning electron microscopy; selected ion recording; solid dispersion; ultra-performance liquid chromatography equipped with electrospray ionization mass spectrometry.