Raman study for β-ring positioning in β-carotene complexes with cyclodextrins and chitooligosaccharides

Abstract

β-Carotene is insoluble in water, and the complexation of β-carotene with chitooligosaccharides or 2-hydroxypropyl-β-cyclodextrin is one of the strategies to resolve the problem. We present both experimental and theoretical studies for three type solid-state samples: β-carotene, β-carotene/chitooligosaccharides and β-carotene/2-hydroxypropyl-β-cyclodextrin. The prepared samples were analysed by using Raman spectroscopy. The Raman ν1 band shift of β-carotene molecules in cyclodextrins or chitooligosaccharides were observed. The β-ring dihedral angle analysis showed there were three major typical all-trans-β-carotene conformers (trans-trans, trans-cis, cis-cis) which have ν1 shifted by 4 cm−1 according to each other. The study is helpful for better understanding of correlations between Raman ν1 band and Cars distortions.