Inclusion complexes of laccaic acid A with β-cyclodextrin or its derivatives: Phase solubility, solubilization, inclusion mode, and characterization

Abstract

This study aimed to investigate the formation of three inclusion complexes of laccaic acid A (the main component of the lac dye, named as LA) with β-cyclodextrin (β-CD), methyl-β-cyclodextrin (M-β-CD), or (2-hydroxyethyl)-β-cyclodextrin (HP-β-CD), exploring particularly the effects of CDs on the solubility of LA and the binding ability of the final inclusion complexes. Lac dye, a natural colorant, had been widely used in food and textile industry. Because of its low water solubility, the application of this nontoxic dye was restricted. This study employed β-cyclodextrin and its derivatives to encapsulate the hydrophobic part of LA and resolve the aforementioned limitation. The binding constants (Kc) and solubility of LA were determined with the three β-CDs using the phase-solubility method, which followed the rank order of HP-β-CD > M-β-CD > β-CD. The inclusion interactions between LA and β-CDs were detected using the Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance. Moreover, the scanning electron microscope and transmission electron microscope were applied to characterize the appearance of the inclusion complexes. This study would provide a useful approach for obtaining novel LA-based products with high water solubility and low toxicity.