Inclusion complexes of capsanthin with acyclic cucurbit[n]urils to improve its stability and antioxidant capacity

Capsanthin is a natural red pigment widely used in the food industry, but its pigment is severely lost during use and storage. Supramolecular chemistry-based macrocyclic hosts can encapsulate small molecule pigments to improve their stability and solubility. Herein, we synthesized two acyclic cucurbit[n]urils (ACBs, M1 and M2) as carriers for encapsulating capsanthin, and we expect this strategy to generate some positive improvements on the properties of capsanthin, extending its use by the food industry. Successful host-guest inclusion complexes (IC) formation was confirmed via 1H NMR, 2D-ROESY NMR, 13C NMR, XRD, and FT-IR. After encapsulation, the solubility of capsanthin was increased by 75.8 times and 62.3 times, respectively. Furthermore, the storage and utility of capsanthin was enhanced due to the phase transition from oil to solid powder. IC exhibited enhanced stability for capsanthin in challenging environments, such as high temperature, light exposure, acidity, metal ions, food additives, and extreme oxidation.