Nanoencapsulation of lutein and its effect on mice's declarative memory

Lutein is a xanthophyll carotenoid widely known by its biological properties and low toxicity. When located in the brain, lutein may inhibit damage mechanisms, acting in neural cells maintenance. However, this carotenoid is very sensitive to external agents such as heat, light, pH and oxidation, besides presenting low absorption in gastrointestinal tract due its low solubility in water. Encapsulation procedures have shown promising results to increase lutein stability and bioavailability. In this work, lutein was encapsulated in polyvinylpyrrolidone (PVP) matrix by the dissolution in common solvent method. Nanoparticles were characterized in respect to morphology, water solubility, and interactions between PVP and lutein. In vivo tests were carried out in order to investigate the influence of lutein encapsulation on mice's declarative memory. Ex vivo tests were also carried out to determine if nanoparticles may cause any inflammatory process per se. Results indicated that lutein was successfully encapsulated in PVP while nanoparticles presented spherical shape and uniform size. Encapsulation was able to increase water solubility of lutein by more than 43 times, which may be attributed to the formation of soluble complexes trough hydrogen bonds between lutein hydroxyl group and PVP carbonyl group. In vivo studies showed that the administration of free lutein at 100mg·kg^-1 and lutein-loaded PVP nanoparticles at 10 and 1.5mg·kg^-1 significantly increased mice's object recognition index, meaning that significant lower doses of lutein were needed to achieve the same effect when lutein was encapsulated. Ex vivo studies showed that lutein-loaded nanoparticles administration did not alter inflammatory parameters in plasma, liver and brain of mice. In this sense, lutein-loaded PVP nanocapsules showed to be an advantageous alternative to increase water solubility and to improve the memory of mice without causing inflammatory damage per se.