Host-guest interaction between brazilin and hydroxypropyl-β-cyclodextrin: Preparation, inclusion mode, molecular modelling and characterization

Brazilin, the major constituent from the heartwood of Caesalpinia sappan, has been widely used as a natural red color dye or food ingredient and drug. However, the application of brazilin is greatly restricted by its low stability. In this study, the preparation, characterization, inclusion mode, stability and solubility of brazilin with hydroxypropyl-beta-cyclodextrin (HP beta CD) were studied for the first time in both the solid state and solution by means of XRD, DSC, SEM, H-1 and 2D NMR and UV-vis spectroscopy. The molecular modelling demonstrated the most stable inclusion model of brazilin/HP beta CD complex. The results illustrated that the stability of brazilin were improved in the inclusion complex with HP beta CD. This satisfactory characterization and stability of the brazilin/HP beta CD complex should be possibly useful for its utilization as dye, food or drug.