Encapsulation of difurfuryl disulfide in β-cyclodextrin and release characteristics of the guest from its inclusion complex

Abstract

Difurfuryl disulfide has been widely used as a flavor compound or a pharmaceutical substance. Encapsulation can provide protection and enhance the stability of the entrapped ingredients, while formation of inclusion complex is one of the methods for encapsulation. In this paper, difurfuryl disulfide-β-cyclodextrin inclusion complex was prepared with difurfuryl disulfide as guest and β-cyclodextrin (β-CD) as host respectively. The inclusion complex was characterized by optical microscope, Fourier-transform infrared spectroscopy (FTIR) and thermo gravity analysis. The characteristics and kinetics of difurfuryl disulfide release from the inclusion complex were investigated. Geometries of the inclusion complex were optimized and the binding energies were obtained using molecular mechanics (MM) calculations. The results show that most of the difurfuryl disulfide-β-CD inclusion complexes, with parallelogram, trapezoidal and rhombic shapes, are in the size range of 1 to 5 µm. The difurfuryl disulfide loading capacity is about 19.8% and the molar ratio of difurfuryl disulfide to β-CD for the inclusion complex is approximately 1:1. The FTIR band at 3380 cm−1 of β-CD is blue-shifted after formation of difurfuryl disulfide-β-CD inclusion complex, and a new band appears at 1500 cm−1 in the FTIR of the inclusion complex while the band is absent in the FTIR curve β-CD. Difurfuryl disulfide release characteristics from its inclusion complex with the increase of temperature were obtained by thermo gravity analysis. Difurfuryl disulfide release kinetic parameters (reaction order, activation energy, pre-exponential factor) were calculated. The results of MM2 calculations indicates that the minimum binding energy is − 135.2 kJ/mol when Z coordinate of S1 is 3.7 × 10−10 m. The most stable structure of the inclusion complex was obtained.