Characterization of halogen species in seaweeds from the Antarctic using a multi-technique approach

Background: Despite the recognized importance, the determination of halogens in Antarctic seaweeds remains understudied. Limited research exists due to challenges associated with sample preparation, and reliable analytical techniques for this type of analysis. Therefore, further investigations are necessary to bridge this knowledge gap and gain a comprehensive understanding of halogen metabolism in Antarctic seaweeds. Methods: In this study, seaweeds from the coast of the Antarctic continent were characterized concerning the total content of halogens and their species. For this purpose, different sample preparation methods, based on extraction and combustion, combining highly selective and sensitive chromatographic and spectrometric multitechnique approaches were used. Results: By using optimized methods, it was possible to determine total halogens content, the distribution of bromine and iodine in different classes of species (lipids, water-soluble, proteins, carbohydrates, and residue), as well as the identification of iodinated amino acids (MIT and DIT) in ten brown and red seaweeds. Bromate and iodate were not detected in the samples, which presented only bromide and iodide species in their composition. Additionally, unknown bromine and iodine species were observed in different extracts evaluated. Furthermore, 25 halogenated polyphenols were identified in seaweeds, of which only four were already reported in the literature. Conclusion: The results obtained in this study comprise unprecedented data in the literature on species of halogens present in seaweeds from the Antarctic environment.