**5. Conclusions**

Fucoidans or sulfated fucans are very promising marine polysaccharides for a possible new treatment development for AMD. With this study we wanted to test the influence of a new enzymatic purification method on the biological activity of fucoidans from di fferent algal species. We tested ten di fferent fucoidans, from the brown seaweed species LD, SL and FE and compared them with regards to toxicity, oxidative stress protection against H2O2 or TBHP and VEGF secretion. Furthermore, we assessed which enzymatic purification method (testing five di fferent FE extracts) and how IEX fractionation (testing four di fferent SL extracts) were most promising for these biological activities. No fucoidan displayed a negative e ffect on viability after 24 h. Some FE fucoidans were slightly (but not relevantly) protective in ARPE-19 cells. SL\_F2 and some of the FE extracts showed protective e ffects in the melanoma cell line OMM-1. E ffective extracts reducing VEGF were LD\_SiAT2, FE\_SiAT2 and SL\_F2 and SL\_F3 fucoidans. The enzymatic method SAT2 without acid dialysis seems most promising for biological e ffects, which could be confirmed for with the SL fractions SL\_F2 and F3. They were the most e ffective fucoidans regarding VEGF inhibition, which correlated with a high fucose and low alginate content. SL fucoidans, which were treated with SAT2 enzymes and further processed with ion-exchange chromatography, are the most promising extracts for a potential application in AMD.

**Author Contributions:** Conceptualization, A.K., A.S.M.; Methodology, A.K., M.D.M., P.D., T.N.T.; Validation, M.D.M., P.D., T.N.T.; Formal Analysis, P.D.; Investigation, M.M., P.D., T.T.; Resources, A.K., A.M., J.R.; Data Curation, A.K., M.M., P.D.; Writing—Original Draft Preparation, M.D.M., P.D.; Writing—Review and Editing, A.K., A.S.M., M.D.M., P.D.; Visualization, M.D.M., P.D.; Supervision, A.K., A.S.M., J.R. All authors have read and agreed to the published version of the manuscript.

**Funding:** This study is part of the FucoSan-Health from the Sea Project and is supported by EU InterReg-Deutschland-Denmark and the European Fund of Regional Development. This work was part of the BioValue SPIR Platform funded by Innovation Fund Denmark, case no. 0603-00522B.

**Acknowledgments:** We thank the Coastal Research & Management for the provision of the algae.

**Conflicts of Interest:** The authors declare no conflict of interest.



\* Nguyen et al. 2020 [15].

**Table A1.** Monosaccharide composition of fucoidans determined by HPAEC, including standard deviations (%mol).
