Development of a method for evaluating the entrapment efficiency of andrographolide

Abstract

Objective: This study aimed to develop a method for evaluating the entrapment efficiency of andrographolide (AG) during the preparation of AG phytosomes (AG-P). Methods: AG-P was prepared using the solvent evaporation technique. A selective dissolution technique employing different solvents was used to remove free AG. The effects of solvent type and sonication time were investigated to optimise the dissolution conditions for AG in phytosome form. The formation of the AG-phosphatidylcholine complex was confirmed by Fourier-transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy (¹H-NMR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). Results: Benzene was selected as the selective dissolution solvent for AG in phytosome form while exhibiting minimal solubility for free AG. The optimal sonication time of the phytosome in the selective solvent was 60 minutes. Under these conditions, the solubility of andrographolide in phytosome form was 1495.18±24.66 µg/ml, which was markedly higher than that of free AG (19.83±0.07 µg/ml). FT-IR, ¹H-NMR, XRD and DSC analyses confirmed the formation of a complex between AG and phosphatidylcholine in the obtained phytosome. Conclusions: A method for evaluating the entrapment efficiency of AG during the preparation of AG-P was successfully developed. This method is simple, easy to perform, and useful for the formulation development and production of AG-P-based pharmaceutical products.