Stabilization of oxidable vitamins by flavonoid-based hydrogels

This study has the goal to evaluate the stability of B complex vitamins, loaded into catechin-based 22crosslinked hydrogels, in aqueous medium at accelerated conditions of oxidative stress. The formulations 23were prepared by coupling polyacrylic acid with catechin in the presence of dicycloexylcarbodiimide. 24Folic acid (FA) and Thiamine (TH) were chosen within the B complex vitamins because of the well-known 25oxidative degradation characteristics. The protective role of the hydrogels against the oxidation damage 26was monitored inducing oxidative stress, by means of UV irradiation and t-butyl hydroperoxide treat- 27ment for FA and TH, respectively. The characterization of the hydrogels was obtained by morphological, 28calorimetric, FT-IR analyses, antioxidant assays and evaluation of the swelling behavior in aqueous media 29at different pH. The experimental results confirmed the suitability of the hydrogels as pH-responsive 30devices, furthermore the presence of oxidative condition proved the protective effect of the hydrogels. 31Catechin-based polymers gave a pronounced improvement in the stability of vitamins compared to 32hydrogels prepared by the coupling reaction of polyacrylic acid in the presence of 1,6-hexandiol. Under 33oxidative conditions, FA and TH were preserved by 96% and 60% respectively.