The HPCCC method used in this study provided a sufficient amount of procyanidins to screen defined fractions against a large panel of indicator strains. HPCCC methods also provided high yields of procyanidin fractions from other plant sources. The polymeric and oligomeric procyanidin fractions tested in this study also exhibited a highly selective inhibitory activity. The resistance of lactic acid bacteria against flavan-3-ols has previously been reported. Many lactobacilli are adapted to plant habitats, express metabolic pathways to detoxify phenolic acids, and exhibit multiple antimicrobial resistance mechanisms that protect against plant secondary metabolites, and are significantly more resistant to phenolic compounds compared to gram negative organisms. Grape seed extracts exhibited antimicrobial activity against pathogenic bacteria including H. pylori, E. coli, S. Typhimurium.