(浙江农林大学动物科技学院、动物医学院 浙江省畜禽绿色生态健康养殖应用技术研究重点实验室 杭州 311300)
(College of Animal Science and Technology·College of Veterinary Medicine， Zhejiang A＆F University， Key Laboratory of Applied Technology on Green-Eco-Healthy Animal Husbandry of Zhejiang Province， Hangzhou 311300)
In order to study the antibacterial effect of curcumin combined with phloretin against Escherichia coli and explore the antibacterial mechanism， the sub-inhibitory concentrations of curcumin and phloretin were determined by the micro broth dilution method. The effects of each drug on the growth curve， extracellular nucleic acid protein， lactate dehydrogenase (LDH)， alkaline phosphatase (AKP) and total protein content of Escherichia coli were determined by bacterial culture at sub-inhibitory concentration doses. The Oxford cup method was used to analyze the combined antibacterial effect of curcumin and phloretin at the sub-inhibitory concentration of each drug. These results showed that: 1) Curcumin and phloretin had a significant inhibitory effect on the growth of Escherichia coli when both concentrations were 250 μg/mL， and this concentration was determined as the sub-inhibitory concentration of curcumin and phloretin. 2) The combined action of curcumin and phloretin at sub-inhibitory concentrations could effectively inhibit the growth of Escherichia coli， and the antibacterial effect was better than that of curcumin and phloretin alone(P<0.05). 3) The combined use of curcumin and phloretin at sub-inhibitory concentrations has a strong destructive effect on the cell wall and cell membrane of Escherichia coli， resulting in the increase of nucleic acid， protein and AKP index in the supernatant of bacterial liquid. At the same time， the combined use of sub-inhibitory concentrations of curcumin and phloretin reduced the expression of total proteins (including LDH) in bacteria， and the effect was significantly better than that of curcumin and phloretin alone (P<0.05). It can be seen that the antibacterial effect of curcumin and phloretin is better than that of curcumin and phloretin alone.