Encapsulation of apple polyphenols in β-CD nanosponges

Abstract

Rutin, phloridzin and chlorogenic acid are some of the most important and characteristic polyphenols found in apples and their by-products (cider, apple juice, apple pomace, etc.). Despite their antioxidant power, their low stability under light or heating conditions restricts the use of this kind of molecules as nutraceuticals. To deal with this issue, encapsulation seems to be an alternative solution. Based on the obtained results, it can be concluded that β-cyclodextrin nanosponges (β-CD NS) are promising agents for the encapsulation of polyphenols. Rutin, phloridzin and chlorogenic acid have been included for the first time in β-CD NS in this work. In particular, the highest encapsulation efficiency for rutin (83.7 %) was obtained using 1,1′-carbonyldiimidazole as cross-linker in a 1:3 ratio (nanosponge/cross-linker). However, for smaller molecules as phloridzin and chlorogenic acid, the nanosponge which showed the best results was the one with HMDI in a 1:8 ratio (87.2 and 77.5 %, respectively). In vitro dissolution studies of encapsulated polyphenols showed that rutin and phloridzin are better dissolved in ethanol, while chlorogenic acid is better dissolved in water. Besides, TGA, DSC, FTIR and XRPD were used as characterization techniques. Individual polyphenols and nanosponges, equimolar physical mixtures and synthesized complexes were characterized. Taking into account the obtained results, it can be confirmed that the solid products were not physical mixtures, but inclusion complexes. Thus, using these encapsulating agents, other polyphenols from apple and its by-products could be encapsulated in order to enhance their bioavailability.