Synthesis and characterization of a novel soluble neohesperidin-copper(II) complex using Ion-exchange resin column

Abstract

The complexation of a flavonoid with metal ions can help increase its bioactivity or bioavailability. A novel method was designed and developed to synthesize a new neohesperidin-Cu(II) complex using an ion-exchange resin column. The integration of the separation or desorption process of neohesperidin (NH) from the resin and the complexation reaction between neohesperidin and Copper (II) was achieved in the column. The possible synthetic mechanism was analyzed using UV–Vis, FT-IR, XRD, TGA, and Hard and Soft Acid and Base theory. Additionally, the inhibition of the complex on tyrosinase activity was studied. The experimental results showed that the macro-porous strong basic anion-exchange resin D296 can effectively enrich neohesperidin, with a saturated adsorption capacity was 2.38 mg/mL of wet resin. During the integrated method, the CuCl2 concentration was set as 0.2 mol/L. The proposed mechanism for the integration is based on three factors. The first one is the exchange between NH anions and Cl−; the second one is the fact that neohesperidin is a soft base and can form a stable complex with Cu2+ in the stoichiometric ratio of 2:1(neohesperidin: Cu2+), and the third factor is that the “embedding effect” of neohesperidin on Cu2+ and the “concentrate” effect of Cu2+ on neohesperidin increase the solubility of neohesperidin in the complexation process. The neohesperidin-copper(II) complex can inhibit tyrosinase activity, and the findings of this study can offer a reference to the value-added development of effective ingredients like neohesperidin in plants.