Antimicrobial and antibiofilm activity against Staphylococcus aureus of Opuntia ficus indica (L.) Mill. cladode polyphenolic extracts

Plant extracts are a rich source of natural compounds with antimicrobial properties, which are able to prevent, at some extent, the growth of food-borne pathogens. The aim of this study was to investigate the potential of polyphenolic extract from cladodes of Opuntia ficus-indica (L.) Mill. to inhibit the growth of some enterobacteria and the biofilm formation by Staphylococcus aureus. Opuntia ficus-indica cladodes at two stages of development were analysed for total phenolic content and antioxidant activity by ORAC and TEAC (in vitro assays) and by CAA-RBC (ex vivo assay). The LC/MS-TOF analysis of the polyphenolic extract revealed high levels of p-hydroxybenzoic acid derivatives, isorhamnetin derivatives and rutin, particularly in the immature cladode extract. Opuntia cladodes extracts showed a remarkable antioxidant activity (in vitro and ex vivo), a selective inhibition of the growth of Gram-positive bacteria, and an inhibition of Staphylococcus aureus biofilm formation. Our results suggest that Opuntia ficus-indica cladode extracts could be employed as functional food, due to the high polyphenolic content and antioxidant capacity, and used as natural additive for food process control and food safety.