Synthesis, characterization and antioxidant activity of EGCG complexes with copper and zinc ions

Polyphenols from various natural products are potent antioxidants and free radical scavengers due to their high tendency to chelate metals. UV and IR spectrum were recorded to determine the structure of (–)-epigallocatechin gallate (EGCG) complexes with copper and zinc ions. Job’s method, formation constants, free energy, and DPPH scavenging capacity were calculated to analyze these complexes. Our results showed the formation of [Cu(EGCG)(H2O)], [Cu(EGCG)2(H2O)2], [Zn(EGCG)(H2O)2], [Zn(EGCG)2(H2O)2] and [Zn2(EGCG)(H2O)4] complexes in pH 7.4 with formation constants (log K) of 5.25, 5.13, 4.05, 4.61 and 4.49, respectively. The DPPH results did not show any significant difference between the EGCG and its complexes. These relatively stable complexes might be considered for use in medical supplements to balance mineral levels in the blood.