Preparation of phillyrin/cyclodextrin inclusion complexes and study of their physical properties, solubility enhancement, molecular docking and antioxidant activity

Abstract

Phillyrin has good biological activity, but it is insoluble in water, which restricts its use in various industries. In our work, we prepared phillyrin using a green and rapid method from Forsythia suspensa leaves, and its purity is greater than 93%. Then, phillyrin was made to interact with different kinds of cyclodextrins (CDs) as a way to improve the water solubility of phillyrin, and the interaction mechanism between CDs and phillyrin was speculated by various characterization methods. First, phase solubility experiments showed that the phase solubility curves of all three CD inclusion complexes were A_L-shaped, indicating that all three inclusion complexes were prepared using phillyrin with CDs in a 1 : 1 stoichiometric ratio. And based on this result, three cyclodextrin inclusion compounds, phillyrin/HP-β-CD (complexation efficiency (CE): 82.58%, the loading efficiency (LE): 22.27%), phillyrin/DM-β-CD IC (CE: 89.31%, LE: 24.83%) and phillyrin/β-CD IC (CE: 68.59%, LE: 23.67%), were prepared. Then, phillyrin was successfully encapsulated as determined by various characterization analyses, after which the conformations of the inclusion complex interactions were analyzed by NMR and molecular docking. The result also indicated that the water solubility of the phillyrin/HP-β-CD, phillyrin/DM-β-CD IC and phillyrin/β-CD IC has significantly improved, which was 30.02, 41.91 and 14.56 times higher than that of pure phillyrin. And the inclusion of CDs also considerably improved the antioxidant capacity of phillyrin, and the DPPH clearance rates of the three inclusion compounds were 4.34, 4.46 and 4.79 times higher than those of pure phillyrin, respectively, and the ABTS clearance rates were 1.35, 1.70 and 1.62 times higher than that of pure phillyrin. The prepared inclusion complexes can be applied in the functional food industry as active ingredients.