Preparation and Bacteriostatic Activity of Tea Polyphenol-Metal Complexes

The preparation process of the tea polyphenol-metal complexes was studied based on the preparation technology of tea polyphenol-cadmium(TP-Cd)complex,such as reaction temperature,time,pH and molar ratio. On this basis,12 kinds of metal ion complexes of TP-Cd,TP-Cu,TP-Zn,TP-Fe(Ⅲ),TP-Al,TP-Mn,TP-K,TP-Ca,TP-Se,TP-Cr,TP-W,TP-Pb were prepared,and the antibacterial activity of these complexes on Staphylococcus aureus and Rhizopus stolonifera was compared. The results showed that the optimal technological parameters for the preparation of tea polyphenol-cadmium complex were:TP/Cd²⁺ molar ratio 1:1,pH6.5,reaction at 30 ℃,for 30 min. Under this condition,the rate of tea polyphenols precipitation was the highest at 93.91%. With the exception of Se⁴⁺ and K⁺,tea polyphenols complexed with most metal ions,the antimicrobial activity against Staphylococcus aureus was enhanced,and its bacteriostatic capacity was TP-Cu>TP-Cd>TP-Zn>TP-Pb>TP-Mn>TP-W≈TP-Al>TP-Fe(Ⅲ)>TP-Cr≈TP-Ca>TP. The antifungal activity of tea polyphenols was significantly enhanced after complexation only with Cu²⁺、Cd²⁺、Zn²⁺、Se⁴⁺ and Mn²⁺,and its bacterio-static capacity of Rhizopus stolonifera was TP-Cu≈TP-Cd>TP-Zn>TP-Se>TP-Mn>TP,tea polyphenols was completely lost after complexation with Pb²⁺ and Cr²⁺. It could be seen that the inhibitory activity of tea polyphenols was affected by the com-bination of metal ions with tea polyphenols,among which TP-Cu,TP-Cd and TP-Zn had the strongest bacteriostatic activity. After complexation of Cu²⁺,Cd²⁺,Zn²⁺ plasma with tea polyphenols,it couldn’t only significantly enhance the bacteriostatic activity of tea polyphenols,but also effectively reduce their side effects,which provided a theoretical basis of the development and utilization of safe and efficient new bacteriostatic drugs,and a new idea for the comprehensive utilization of tea resources.