Synthesis and Characterization of a Novel Soluble Neohesperidin Copper (Ⅱ ) Complex Using Ion-Exchanging Resin Column

The complexation of a flavonoid with metal ions usually can better the bioactivity or bioavailability of the flavonoid. A new method was designed and developed to synthesize a new neohesperidin-Cu(II) complex using ion-exchanging resin column. On the column, the integration of separation or desorption of neohesperidin on resins and the reaction of neohesperidin with Copper(II) was realized. Possible synthesis mechanism was discussed using UV-Vis, FT-IR, XRD, TGA and the Hard and Soft Acid and Base Principle. In addition, the inhibition of the complex on the tyrosinase activity was also studied. Results shows that Resin D296, as a macro-porous strong basic anion-exchange resin, can enrich neo-hesperidin effectively, and the saturated adsorption capacity is 2.38 mg per mL wet resins. During the integration method, the CuCl2 concentration should be 0.2 mol/L. Possible mechanism for the integration lies on three factors. One is the exchange between NH anions and Cl- ; the second is that neohesperidin as a soft base can form a stable complex with Cu2+ a borderline acid through the stoichiometric ratio of 2:1(neohesperidin:Cu2+ ) ; the third is that the “embedding effect” of neohesperidin on Cu2+ and the “concentrate effect of Cu2+ on neohesperidin, and the aforesaid two effects helps to better the neohesperidin solubility through the complexation process, since the glycosyl part is outside neohesperidin because of the “concentrate effect” of Cu2+ for hydrophobic aglycone part. The complex of neohesperidin-copper(II) can inhibit the tyrosinase activity，and our research findings can offer a reference to the value-added development of effective ingredients in plants.