The red beetroot extract antioxidant activity and adsorption kinetics onto hydroxyapatite-based materials

Hydroxyapatite-based materials are known to have several applications, most widely are used as implant coatings, but also as support in drug delivery. The impregnation of apatite with antioxidant substances could have a positive effect in both application areas, due to antioxidant-free radical scavenging properties, antimicrobial and antiviral effect, as in the case of red beetroot extract. By the variation of preparation parameters it is possible to control the properties of synthesized materials in function of the application field. In order to obtain hydroxyapatite-based materials with increased adsorption capacity different amounts of silica and copper ions were incorporated in the materials structure. These materials were analyzed by IR spectroscopy and TEM; particle size variation during synthesis was also monitored. Red beetroot is ranked among the ten most potent antioxidant vegetables, and their extract exhibits high antioxidant properties. The extract was examined by UV-Vis spectroscopy, and their degradation in time was monitored. The antioxidant capacity was determined by means of the Briggs-Rauscher oscillating reaction. The antioxidant activity was measured and expressed in Trolox units. The amount of adsorbed substance and adsorption efficiency was determined for the substituted materials. The adsorption mechanism was elucidated by kinetic studies involving different kinetic model evaluation. The kinetic data correlate best with the pseudo-second-order model, and the principal mechanism is the formation of chemical bonds between the active centers on the material surface and the antioxidant molecules.