Abstract: This study was to investigate the antibacterial activity and stability of hydroxytyrosol on Escherichia coli,Staphylococcus aureus,Pseudomonas aeruginosa and Bacillus subtilis.MIC and MBC of hydroxytyrosol on four bacteria were determined by the method of tube dilution.Besides,the effects of hydroxytyrosol on the growth and membrane integrity of four bacteria were estimated.In addition,the antimicrobial stability of hydroxytyrosol was evaluated under NaCl and sucrose mediums.The results showed that hydroxytyrosol demonstrated a great antibacterial activity.The MIC for E.coli,S.aureus,P.aeruginosa and B.subtilis was 0.625,0.625,1.250 and 2.500 mg/mL,respectively.The MBC was 1.250,1.250,2.500 and 5.000 mg/mL,respectively.Compared with blank control,nucleic acid and soluble protein of four bacteria had leaked significantly when the culture medium was added with hydroxytyrosol.So the bacteriostasis mechanism of hydroxytyrosol might be through destroying the cell membrane integrity.Under different concentrations of NaCl,the antibacterial activity of hydroxytyrosol on B.subtilis was still stable.Under 1.0% and 2.0% NaCl medium,antibacterial activities of hydroxytyrosol on E.coli and P.aeruginosa were stable.Under 2.0% NaCl medium,the antibacterial activity was stable with lower concentration of hydroxytyrosol on S.aureus.While under 0.5,1.5 and 2.0% NaCl medium the antibacterial activity was stable with high concentration of hydroxytyrosol.Under sucrose medium,antibacterial activities on the four bacteria were unstable.Therefore,hydroxytyrosol can be used as a novel preservative.  

Key words: hydroxytyrosol, antibacterial activity, antibacterial stability