Abstract：Objective: The aim of this work was to purify and to identify active antimicrobial peptides from the heterophils of ostrich blood. Method: Ostrich heterophils antimicrobial peptides were isolated by adding of 0.83% ammonium chlorid solution, sonicatingto release the heterophils granules, suspending in acetic acid and mixing overnight to extract the antimicrobial peptides. The crude extractions were obtained. Iox-exchange chromatography and reversed phase high performance liquid chromatography (RP-HPLC) were used to separate the components present in the crude extract. The radial diffusion plate assay method was used to determine antimicrobial activity and the minimum inhibitory concentration (MIC). The molecular weight and amino acid sequence were determined by MS/MS.
Result: The results showed that there were antimicrobial substances in ostrich heterophils, and there were strongly active against Escherichia.coli O78, Staphylococcus.aureus 1056MRSA and Candida.albicans ATCC10231all the bacteria strains above. The peptides were cationic moleculesand have good character of hot stabilization. Peak 6, 16 and 24 were obtained by RP-HPLC. The MIC of peak 6 against Candida.albicans ATCC10231 was 0.065μg/mL. The molecular weight of perk 16 was 4012.472Da, and its MIC against Escherichia.coli O78 and Staphylococcus.aureus 1056MRSA were 3.971μg/mL and 5.245μg/mL respectively. The molecular weight of fractions 24 was 3542.479Da, and the MIC of fraction 16 against Escherichia.coli O78 and Staphylococcus.aureus 1056MRSA were 26.472μg/mL and 21.561μg/mL respectively. Conclusion: The peptides we obtained displayed stronger activity than ostricacins reported by others. Further work need to determine whether they are same substance.
