Antibacterial activity and cytotoxicity of l‑phenylalanine-oxidized starch-coordinated zinc (II).

Zn (II) coordination compounds have aroused growing attentions as antibacterial entities. In the present work, we fabricated a new antibacterial complex of l‑phenylalanine‑oxidized starch-coordinated zinc (II) (l‑Phe-OSt→Zn (II)) by successive reactions of oxidization, Maillard and coordination. Maillard reaction occurred between l‑Phe and OSt to form l‑Phe-OSt, which was then coordinated with Zn (II) by carboxyl groups for l‑Phe-OSt→Zn (II). The complex showed good antibacterial activity and the antibacterial activity against E. coli was slightly poorer than B. subtilis. The presence of complex favored the generation of reactive oxygen species (ROS) in bacteria and the ROS level in B. subtilis was higher than that in E. coli. Furthermore, the toxicity of l‑Phe-OSt→Zn (II) towards HT-29 cells was very low. The characteristics of better antibacterial activity and less cytotoxicity endow l‑Phe-OSt→Zn (II) a great potential of application as a food additive.