Abstract: Ascophyllum nodosum (Linnaeus) Le Jolis (AN) is a brown alga from the Fucaceae family and the unique species from the Ascophyllum genus. This brown alga is an edible macroalga from the North Atlantic Ocean, commonly found on the European north-western coast. High-value bioactive molecules such as pigments, polyphenols, and phlorotannin [1,2] have been found in the macroalgae composition, which turns this alga particularly interesting for exploring potential biological activities. Among sustainable extraction technologies, microwave-assisted extraction (MAE) has many advantages such as short extraction time and less solvent requirement. On the other hand, ethanol and water are eco-friendly solvents that have already been proven to be effective for obtaining bioactive compounds with antimicrobial capacity [3]. Therefore, in this work, MAE t=5 min; P=10.5 bar; using ethanol (37% ) as solvent was applied to obtain a polyphenol-rich extract from AN. The antimicrobial effect of the resulting extract against five foodborne microorganisms (Bacillus cereus, Escherichia coli, Salmonella enteritidis, Pseudomonas aeruginosa, Staphylococcus aureus), and the opportunistic bacteria Staphylococcus epidermidis was tested. The antimicrobial activity was performed through Kirby-Bauer disk diffusion susceptibility test protocol and the microdilution method. The analytical results indicated that the AN extract was effective against all tested bacteria except for Escherichia coli. The highest antimicrobial activity was found against Staphylococcus aureus presenting a minimal inhibitory concentration of 400µg/mL and an inhibition halo of 11,79±1,92 mm.

Acknowledgments: The research leading to these results was supported by MICINN supporting the Ramón y Cajal grant for M.A. Prieto (RYC-2017-22891) and the Juan de la Cierva Incorporación for Hui Cao (IJC2020-046055-I), Xunta de Galicia for supporting the program EXCELENCIA-ED431F 2020/12, the post-doctoral grant (ED481B-2019/096), and L. Cassani (ED481B-2021/152), and the pre-doctoral grants of P. Garcia-Oliveira (ED481A-2019/295), and M. Carpena (ED481A 2021/313). The research leading to these results was supported by the European Union through the “NextGenerationEU” program supporting the “Margarita Salas” grant awarded to P. Garcia-Perez. Authors are grateful to Ibero-American Program on Science and Technology (CYTED—AQUA-CIBUS, P317RT0003), to the Bio Based Industries Joint Undertaking (JU) under grant agreement No 888003 UP4HEALTH Project (H2020-BBI-JTI-2019) that supports the work C. Lourenço-Lopes and to AlgaMar enterprise (www.algamar.com) for the collaboration and algae material provision. The authors would like to thank the EU and FCT for funding through the programs UIDB/50006/2020; UIDP/50006/2020.

References:

1. Sardari, R.R.R.; Prothmann, J.; Gregersen, O.; Turner, C.; Karlsson, E.N. Identification of phlorotannins in the brown algae, saccharina latissima and ascophyllum nodosum by ultra-high-performance liquid chromatography coupled to high-resolution tandem mass spectrometry. Molecules 2021, 26, doi:10.3390/MOLECULES26010043.
2. Garcia-Perez, P.; Lourenço-Lopes, C.; Silva, A.; Pereira, A.G.; Fraga-Corral, M.; Zhao, C.; Xiao, J.; Simal-Gandara, J.; Prieto, M.A. Pigment Composition of Nine Brown Algae from the Iberian Northwestern Coastline: Influence of the Extraction Solvent. Mar. Drugs 2022, 20, 113, doi:10.3390/md20020113.
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