Antibacterial activity of isolated phenolic compounds from cranberry (Vaccinium macrocarpon) against Escherichia coli

Abstract

Phenolic compounds from a cranberry extract were isolated in order to assess their contribution to the antibacterial activity against urophatogenic strains of Escherichia coli (UPEC). With this purpose, a total of 25 fractions from a cranberry extract were isolated using semipreparative high performance liquid chromatography (HPLC) and characterized based on the results obtained by reversed-phase HPLC coupled to mass spectrometry detection. Then, the effect on UPEC surface hydrophobicity and biofilm formation of the cranberry extract as well as the purest fractions (a total of 13) was tested. As expected, the whole extract presented a powerful antibacterial activity against UPEC while the selected fractions presented different behavior. Myricetin and quercitrin significantly decreased (p < 0.05) E. coli biofilm formation compared with the control, while dihydroferulic acid glucuronide, procyanidin A dimer, quercetin glucoside, myricetin and prodelphinidin B led to a significant decrease on the surface hydrophobicity compared with the control. The results suggest that apart from procyanidins, other compounds, mainly flavonoids, can act against E. coli biofilm formation and also modify UPEC surface hydrophobicity in vitro, one of the first steps of adhesion.