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.