Disinfection performance and synthesis conditions of the EGCG–Cu complex

Abstract Adopting the yield of the epicatechin gallate (EGCG)–Cu complex as an indicator, the impact of four conditions, such as pH, reaction time, temperature and reactant ratio, on the synthesis of the target complex was analyzed to identify the optimal conditions on synthesizing the compound. The reactant ratio between EGCG and Cu2+ was explored, and the characteristic peaks and functional groups of the EGCG–Cu complex were scrutinized by UV–Visible and Fourier-Transform Infrared spectrophotometers. Finally, the efficacy difference of bactericidal properties against Escherichia coli suspensions between EGCG and its complex was evaluated as the criteria. Furthermore, comparative studies were performed to gauge the antimicrobial activity of EGCG and its complex at equivalent concentrations. The results demonstrated that the optimal experimental conditions for the complex reaction were a pH of 7, at 40 °C, in a reaction time of 60 min and a reactant ratio of 1:2. By the molar ratio method, the reactant ratio was determined as n(EGCG):n(Cu2+) = 1:2, and the complex reaction was at the phenolic hydroxyl group on the benzene ring of EGCG. Compared to EGCG, the complex demonstrated significant enhancement in bactericidal properties against E. coli. Complexing enhances its antibacterial properties and the complex solution has lower chromaticity than EGCG during disinfection.