Betanin loaded nanocarriers based on quinoa seed 11S globulin. Impact on the protein structure and antioxidant activity

The objective of the present contribution was to design and characterize betanin (Bt) loaded 11S quinoa seed protein nanovehicles. 11S was isolated from quinoa seed floor. Protein purification was performed by Size-Exclusion Chromatography. MALDI-TOF (Matrix-Assisted Laser Desorption/Ionization-Time-Of-Flight) analysis confirmed the identity of 11S. Nanocarriers (11S-Bt) were generated at pH 8 at different ionic strength. Globulin intrinsic fluorescence spectra showed a quenching effect exerted by Bt, demonstrating in turn protein-bioactive interaction. Stern-Volmer and Scatchard models application confirmed static quenching and allowed to obtain parameters that described 11S and betanin complexation process. Bt-11S globulin interactions seem to be more probably of physical type. Protein solubility was increased after complexation with Bt. 11S betanin-loaded nanocarrier showed additive effect in terms of both, antiradical or reducing power capacity in comparison to Bt as evaluated by two methods, 2,2 -azino-bis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS), and by ferric reducing antioxidant power (FRAP). Interestingly 11S globulin quaternary structure was modified by the bioactive, experimenting hexamer dissociation. This nanocarrier could have the potentiality to exert the Bt controlled delivery for pharmaceutical and nutraceutical products. Bt could also be protected from light and oxygen in such systems.