Euterpe edulis BY-PRODUCT EXTRACT COMBINED WITH SODIUM NITRITE AGAINST Salmonella enterica SEROVAR TYPHI

Euterpe edulis Martius (juçara) is a palm species native to the Atlantic Forest whose industrial fruit processing generates by-products rich in bioactive compounds with potential applications in the food preservation. The growing demand for natural preservatives has driven the search for alternatives to sodium nitrite, a synthetic additive associated with the formation of potentially harmful compounds. In this context, controlling Salmonella spp., one of the leading bacterial pathogens associated with foodborne illness, remains a major challenge for food safety. Thus, this study aimed to evaluate the antibacterial activity of the E. edulis by-product extract against Salmonella enterica serovar Typhi and investigate its synergistic interaction with sodium nitrite. The E. edulis pulp by-product, obtained from a food processing industry in Ivaiporã, Paraná, Brazil, was dried at 50 °C for 48 h, ground, and sieved (48 mesh). The ethanolic extract was prepared using a solid-to-solvent ratio of 1:20 (w/v) with 70% ethanol at 25 °C under agitation (180 rpm) for 30 min. The minimum inhibitory concentration (MIC) was determined by the broth microdilution method using 96-well microplates against Salmonella enterica subsp. enterica serovar Typhi ATCC 19214. The E. edulis by-product extract was tested at concentrations ranging from 0.078 to 40.00 mg/mL, whereas sodium nitrite was evaluated from 1.25 to 50.00 mg/mL. Microplates were incubated at 35 °C for 24 h. The minimum bactericidal concentration (MBC) was determined by plating 10 μL aliquots from each well onto Mueller Hinton agar plates, which were incubated at 35 °C for 24 h. The combination of the E. edulis by-product extract and sodium nitrite was evaluated at a 1:1 (w/w) ratio based on the previously determined MIC values using the broth microdilution assay. The MIC and MBC values of the E. edulis by-product extract were 10.00 ± 0.00 and >40.00 mg/mL, respectively, whereas those of sodium nitrite were 12.50 ± 0.00 and 100.00 ± 0.00 mg/mL. When combined, the MIC of the extract decreased to 5.00 mg/mL, whereas the MIC of sodium nitrite remained unchanged at 12.50 mg/mL. The by-product extract exhibited MIC values comparable to those of sodium nitrite, highlighting its potential as a natural alternative to reduce the use of synthetic preservatives in food products. The antibacterial activity is likely associated with flavonoids previously reported in E. edulis, which have been linked to multiple mechanisms of action, including disruption of cytoplasmic membrane integrity, inhibition of nucleic acid synthesis, biofilm formation, and bacterial adhesion. Overall, the results demonstrate that the by-product extract has promising antibacterial potential, either alone or in combination with sodium nitrite, for food preservation applications.