Antimicrobial properties of phenolic compounds from berries

Aims: To investigate the antimicrobial properties of phenolic compounds pre sent in Finnish berries against probiotic bacteria and other intestinal bac teria, including pathogenic species. Methods and Results: Antimicrobial activity of pure phenolic compounds repr esenting flavonoids and phenolic acids, and eight extracts from common Finn ish berries, was measured against selected Gram-positive and Gram-negative bacterial species, including probiotic bacteria and the intestinal pathogen Salmonella. Antimicrobial activity was screened by an agar diffusion metho d and bacterial growth was measured in liquid culture as a more accurate as say. Myricetin inhibited the growth of all lactic acid bacteria derived fro m the human gastrointestinal tract flora but it did not affect the Salmonel la strain. In general, berry extracts inhibited the growth of Gram-negative but not Gram-positive bacteria. These variations may reflect differences i n cell surface structures between Gram-negative and Gram-positive bacteria. Cloudberry, raspberry and strawberry extracts were strong inhibitors of Sa lmonella. Sea buckthorn berry and blackcurrant showed the least activity ag ainst Gram-negative bacteria. Conclusions: Different bacterial species exhibit different sensitivities to wards phenolics. Significance and Impact of the Study: These properties can be utilized in f unctional food development and in food preservative purposes.