Study On The Extraction Of Total Flavonoids From Ilex Rotunda Thunb And The Antimicrobial Mechanism Against Esbls-Producing Escherichia Coli

In this paper, the method of ultrasonic-assisted extraction of total flavonoids from Illex Rotunda Thunb was optimized by response surface methodology (RSM). The MIC of flavonoids and antibiotics were determined by two times dilution method, the effect of flavonoids on the growth curve of ESBLs-producing Escherichia coli was determined by colony counting method. The antimicrobial effect of flavonoids combined with antibiotics was deter-mined by checkerboard method and passage method. TEM, determination of AKP activity and soluble protein concentration, total protein synthesis and the fluorescence intensity of DNA were used to study the mechanism of flavonoids from Ilex Rotunda Thunb against ESBLs-producing E.coli. The main result were as following:1. Based on the results of single factor test, the optimized extraction conditions for total flavonoids from Ilex Rotunda Thunb by RSM was ethanol concentra-tion of 60%, the ratio of liquid to material of 40:1(mL/g), power 60%(420W), temperature 55 ℃ and time duration 40 min.2. The strain was identified as ESBLs-producing Escherichia coli. It was re-sistant to Ceftriaxone, Ceftazidime, Ceftiofur, Cefotaxime, Amoxicillin, Fosfomycin, Lincomycin, Amikacin, Azithromycin, Mequindox, and Florfenicol, but sensitive to Meropenem and Colistin. The flavonoids from Ilex Rotunda Thunb could inhibit the growth of E.coli and showed antibacterial and bactericidal action. The fractional inhibitory concentrations index(FICI) of fla-vonoids from Ilex Rotunda Thunb, in combination with Ceftriaxone, Ceftazidime, Ceftiofur, Cefotaxime, Amoxicillin, Fosfomycin, Amikacin, Florfenicol, Azithromycin showed marked synergism in the value range of 0 to 0.5; in combination with Lincomycin, Mequindox, Sulfamonomethoxine, showed additive effect in the range of 0.5 to 1.0.3. The result of the antimicrobial mechanism of flavonoids from Ilex Rotunda Thunb were as follows:The TEM imagine showed that flavonoids could dam-age the cell wall and membrane; the increase of AKP activity and soluble pro-tein content in the medium,which showed the damage of cell wall and cell membrane further. The flavonoids could inhibit the synthesis of the total protein and DNA.