Antimicrobial Effects of Various Flavonoids on Escherichia coli O157:H7 Cell Growth and Lipopolysaccharide Production

Flavonoids have biofunctional effects as antioxidant and antimicrobial agents. The objective of this study was to evaluate the bactericidal activity and antilipopolysaccharide (LPS) effects of flavonoids on Escherichia coli O157:H7. The effects of flavonoids on the growth of E coli O157:H7 were bacteriostatic rather than bactericidal at concentrations below 200 mu M, and there was no significant difference among the flavonoids tested (p<0.05). LPS production in E coli O157:H7 treated with 200 mu M quercetin and naringenin decreased by 34.06 +/- 1.03 and 19.90 +/- 1.51%, respectively, relative to the control (no flavonoid). Luteolin, genkwanin, hesperetin, and apigenin caused decreases in LPS production of 69.85 +/- 1.03, 61.18 +/- 1.15, 60.74 +/- 1.10, and 58.93 +/- 0.98%, respectively, relative to the control. Based on these results, luteolin had the greater inhibitory effect on LPS production by E. coli O157:H7 than other flavonoids tested in this study.