Abstract: The antibacterial activity of chelates formed by ferrous ions with peach kernel peptides with different molecular masses or peptides from other plant sources and chelates of ferrous, zinc, calcium or magnesium with peach kernel peptide were compared. Then, the structures of all chelates were characterized by Fourier transform infrared (FTIR) spectroscopy. Results indicated that the antibacterial activity of low-molecular-mass peach kernel peptide-ferrous chelate (PKP3, < 5 000 Da) was stronger than that of high-molecular-mass peptide-ferrous chelate (> 10 000 Da). Peach kernel peptide chelates with ferrous and zinc both had strong antibacterial activity. There were significant differences (P < 0.05) in the antibacterial activity of the ferrous-chelating peptides from peach kernel, soybean, corn and wheat. Among them, peach kernel peptide-ferrous and wheat peptide-ferrous chelates had the strongest antibacterial activity, with minimum inhibitory concentrations (MICs) of 5.0 mg/mL for Escherichia coli, and MICs of 2.5 and 5.0 mg/mL for Staphylococcus aureus, respectively. FTIR spectra illustrated that –COO-, N–H and C═O in each of the four peptides were involved in the chelation reaction with ferrous ions to form ferrous-chelating peptides.

Key words: peach kernel, peptide, chelating, antibacterial activity, Fourier transform infrared spectroscopy