Metabolite Profiling and Antioxidant Activities in Seagrass Biomass

In this work, metabolite profiling of seeds and antioxidant analysis of fragments of two marine seagrasses, <i>Posidonia oceanica</i> and <i>Cymodocea nodosa,</i> were carried out to identify metabolite signature involved in seed viability and to evaluate the potential of fragments as a source of bioactive compounds. Using HILIC/QTOF-MS, UHPLC-MS and spectrophotometric analysis, seed metabolites and polyphenols and antioxidant activities, such as those of radical scavenging (RSA), reduction (FRAP, CUPRAC) and complexation (CCA), of rhizome fragments were evaluated. Metabolite comparison between seeds revealed differences across development stages (germinated and non-germinated) and seed types (dormant and non-dormant), providing insights into metabolic activity potentially associated with germination processes and seed viability. Furthermore, polyphenol analysis showed the highest content of caffeic acid in mature leaves (17.00 ± 0.02 μg g^-1 dw for <i>P. oceanica</i> and 98.00 ± 0.03 μg g^-1 dw for <i>C. nodosa</i>). Total phenolic content was correlated with flavonoids and with reduction and complexation activities. The combination of radical scavenging activity and t_1/2 was higher in <i>P. oceanica</i> than <i>C. nodosa</i> and also surpassed the commercial synthetic antioxidant BHA. We conclude <i>P. oceanica</i> and <i>C. nodosa</i> exhibit distinct seed metabolite profiles related to germination and type of seeds, and that fragments are rich in antioxidants, with potential as sustainable sources of bioactive compounds.