Phytoglycogen improves the water solubility and Caco-2 monolayer permeation of quercetin

• Quercetin (QC) was incorporated with phytoglycogen (PG) to generate PG-QC solid formulations.
• PG-QC formulations showed much enhanced QC solubility than QC alone.
• PG-QC formulations showed negligible QC crystallinity and the formation of hydrogen bonding between QC and PG.
• PG-QC formulation solutions showed much enhanced Caco-2 monolayer permeation of QC.

The study examined the capability of phytoglycogen (PG) to improve the water solubility of quercetin (QC). PG-QC formulations were prepared by mixing a QC ethanol solution with a PG aqueous solution followed with vacuum drying of the supernatant. PG-QC formulations with various PG to QC ratios were prepared; the solubility of QC reached 241.76 μg/mL at PG/QC ratio of 30/1 compared with approximately 4.32 μg/mL of QC alone. The X-ray powder diffraction and FTIR analyses showed a significant reduction of QC crystallinity upon formulating with PG that was associated with the intermolecular hydrogen bonding between the hydroxyl groups of QC and PG. The Caco-2 cell monolayer permeation tests showed that PG-QC formulations resulted in substantially enhanced cellular uptake and transepithelial permeation of QC, which was related to the much-enhanced QC solubility. This study showed the potential of using PG to formulate poorly water-soluble ingredients such as QC.