Study On The Extraction And Purification Of Phenolics From Peony Flowers And Their Anti-biofilm Activities Of Escherichia Coli And Staphylococcus Aureus

Tree peony(Paeonia suffruticosa Andr.ostii)is a unique oil peony variety in China.In addition to the ornamental value,peony flowers have antioxidant,anti-inflammatory and antimicrobial activities due to rich phenolics in peony flowers,therefore,it has development and utilization value in the field of food and medicine.Hence,in this paper,the phenolics in peony flowers were extracted and purified,the anti-biofilm activities and mechanism of the phenolics obtained by purification were explored,and the phenolics were applied to the preservation of chicken breast.The main research contents and results were as follows:Extraction of phenolics in peony flowers(PPF)and determination of antimicrobial and anti-biofilm activities.Microwave-assisted extraction(MAE)was used to extract phenolics from peony flowers,and through response surface,the optimum extraction conditions were determined as solvent/solid ratio of 56 mL/g,extraction time of 331 s,ethanol concentration of 56%,and microwave power of 497 W.Compared with CLSE extract,MAE extract has the highest yield(49.26 mg/g),content(12.13%)of phenolics,antimicrobial activities(minimum inhibition concentration value,MIC was 34.00 mg/mL)and antibiofilm activities(minimum biofilm inhibition concentration value,MBIC was 20 mg/m L).Separation and purification of PPF and determination of antimicrobial and anti-biofilm activities.After organic solvent extraction,polyamide column chromatography and silica gel column chromatography,PPF in the eluent of silica gel column chromatography(PPF-ESGCC)was obtained,and main phenolics in PPF-ESGCC was identified as gallic acid(GA),kaempferol-7-O-glucoside(K7G),and apigenin-7-O-glucoside(A7G).Compared with PPF,the content of PPF-ESGCC(83.35%)increased by 7 times,and the antibacterial activities(MIC was 0.88 mg/m L)increased by 39 times,and anti-biofilm activities(MBIC was 0.60 mg/m L)increased by 33 times.The above results showed that the content of phenolics was related to the antimicrobial activities and antibiofilm activities.Inhibition mechanism of PPF in the eluent of silica gel column chromatography(PPFESGCC)on biofilm formation.PPF-ESGCC with sub-minimal inhibitory concentrations(subMICs)can effectively inhibit biofilm formation of Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus),and the inhibition rates of PPF-ESGCC on biofilms of E.coli and S.aureus were 77.93%,and 87.03% respectively,at a very low concentration(0.45 mg/m L).It was found that the biofilm inhibition was achieved by inhibiting their motilities,exopolysaccharide(EPS)production and quorum sensing.Moreover,there was a positive dosedependent relationship(r=0.9137~0.9967)between the inhibition rates and concentrations of PPF-ESGCC during the critical biofilm-formation stage(1-3 d)and strong negative correlations(r=-0.8206~-0.9936)were observed between the incubation time and inhibition rates of biofilm formation at different concentration of PPF-ESGCC.The results of main components of PPF-ESGCC in inhibiting bacterial biofilm showed that the inhibitory effect of A7 G was significantly better than that of GA and K7 G,therefore,A7 G was the main component of PPFESGCC in inhibiting bacterial biofilm.Application of PPF-ESGCC and potassium sorbate in chicken breast preservation.The chicken breast meat was treated with 0.175%(w/v)of potassium sorbate and 0.022%(w/v)of PPF-ESGCC,and the storage period of chicken breast reached 12 days by measuring the color value,pH value,total volatile base nitrogen(TVB-N)value and microbiological index of chicken breast meat.Compared with potassium sorbate group(0.2%(w/v)),the storage period of chicken breast meat was extended for 3 days;compared with the control group(distilled water),the storage period was extended for 6 days.