Multiscale Structural Characterization of the Assembly Mode of Amylose-Lycopene Complexes

Abstract

The formation and supramolecular structures of inclusion complexes between amylose and lycopene (amylose-lycopene complexes, ALCs) were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, and 13C CP/MAS nuclear magnetic resonance (NMR). The results showed that the complex index of amylose to lycopene in ALCs was (17.10 ± 0.01)%, indicating that lycopene could enter the spiral cavity of starch to form a complex. ALCs exhibited a type II composite structure consisting of spherical V-shaped sub-microcrystals with a crystallinity of (65.32 ± 0.22)% and a T0 of (106.72 ± 0.63) ℃. Moreover, no characteristic absorption of lycopene at 960 cm-1 was observed, indicating complexation between the host and guest molecules. Furthermore, the structural components of ALCs were ranked as follows: double helix > amorphous form > V-shaped single helix. Among them, the proportions of double and V-shaped single helix structures in ALCs were (55.95 ± 3.25)% and (17.84 ± 0.96)%, respectively. These results indicated that amylose can include and twine around lycopene to form a thermally stable composite structure. This study provides a theoretical basis for expanding the prospective pharmaceutical and nutraceutical applications of lycopene as a functional pigment.

Keywords

• amylose-lycopene complexes; structural characterization; crystal structure; inclusion; assembly mode