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

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 ( K c ) 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 1 H 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.