Antimicrobial Activity and Mechanism of Flavonoids from Litchi Pericarp

The concentration of total flavanoids from litchi pericarp(LPF) was determined by spectrofluorimetry,and its antimicrobial and bactericidal activities against microbes,as well as the mechanisms were investigated.The purity and yield of extract was 48.56% and 13.61%,respectively.Meanwhile,the diameter of inhibition zone of Escherichia coli,Staphylococcus aureus and Saccharomgces cerevislac by oxford plate assay were 15.1,14.0 and 13.8 mm,respectively.The maximum inhibitory rate of Aspergillus niger reached 28.75% under the concentration of 10 mg/mL.The minimal inhibitory concentration(MIC) and minimal bactericidal concentration(MBC) of LPF were also measured by plate dilution method.As the results,the MIC of LPF against E.coli and St.aureus were 2.5 mg/mL and MBC were 5 mg/mL,while those of Sa.cerevislac and A.niger were 5 mg/mL and no bactericidal activity observed.Observation under scanning electron microscope revealed that the antimicrobial activity and the bactericidal function of LPF against St.aureus were directly relevant to the structure destruction of cells membrance and wall.