Phytochemistry and activity against digestive pathogens of grape (Vitis vinifera L.) stem's (poly)phenolic extracts

- Grape stems from red and white varieties are an valuable source of (poly)phenols.
- Bioactive (poly)phenols from grape stems show antibacterial activity.
- Gram positive intestinal pathogens are more sensible that Gram negative strains.

Winemaking industry produces huge amounts of organic residues including grape pomace, grape stems and wine lees, with deleterious impact on the environment and concerning the sustainability of this socio-economic activity, being grape stem the less explored material. The content in phytochemicals of grape and vinification residues as well as the antimicrobial efficiency described for the identified compounds, prompted us to the evaluate the capacity of grape stem's extracts to inhibit the growth of digestive pathogens, and therefore, their potential as a functional ingredient that could prevent microbial disturbance. The phytochemical composition was determined by HPLC-DAD-ESI-MSn and was correlated with the antimicrobial activity in vitro, against Gram positive (Listeria monocytogenes, Staphylococcus aureus and Enterococcus faecalis) and Gram negative (Pseudomonas aeruginosa, Escherichia coli and Klebsiella pneumoniae) digestive pathogens. Antimicrobial activity was determined by the assessment of the Minimum Inhibitory Concentration and the capacity of grape stem's extracts to inhibit microbial growth. The correlation analyses performed pointed out kaempferol-3-O-rutinoside, kaempferol-3-O-glucoside and caftaric acid as compounds responsible for the antimicrobial effect. The confirmation of the inhibitory effect grape stem's extracts on digestive pathogens in vitro encourages further evaluations in vivo on their capacity to prevent the disturbance of intestinal homeostasis.