*3.7. Conclusive Words*

This study was well equipped to compare the biological activities of ten fucoidans, with several extract variables. We investigated three different species, from which SL seems most promising. We could demonstrate that the use of acid for alginate precipitation is not recommended and CaCl2 should be used. In the four different tested enzymatic treatments, no significant difference could be determined in the biological activities, but the used SAT2 enzyme mix seems very promising considering the activities of the SL\_F2 and SL\_F3 fractions, that were purified with these enzymes. Also a three-step fractionation after the enzyme treatment with IEX was conducted and we could clearly show that fractionation is recommended to achieve fucoidan extracts with high fucose and low alginate content. The extract SL\_F2 which resulted from IEX fractionation after an enzyme assisted extraction with CaCl2 precipitation is the most promising extract regarding oxidative stress protection and VEGF inhibition. Considering all tested brown seaweed extracts so far, fractionated SL extracts SL\_F2 and SL\_F3 are the most efficient regarding VEGF inhibiting effect in ARPE-19. They lowered VEGF nearly to 40%. In previous studies we could determine inhibitory effects of a pure LH fucoidan with nearly 50% at 50 and 100 μg/mL [17] and another SL extract which also lowered the VEGF secretion to nearly 50% at 100 μg/mL [19]. The latter extract contained a very high fucose content of 83.8% and only 6% uronic acids [21] (comparable to SL\_F2/F3). Surprisingly, the SL extracts from this study lowered VEGF in all concentrations, already very efficiently at 1 μg/mL. So we can conclude that SL is a promising fucoidan source besides *Laminaria hyperborea* [17] regarding potential treatment of AMD. The enzymatically-assisted extraction method, followed by IEX fractionation seem very promising to obtain highly pure and large sized fucoidans with high content of fucose and low content of alginates. With this novel method fucoidans were produced that showed promising VEGF reducing and anti-oxidative properties. Further research is warranted to confirm the beneficial e ffects in primary in vitro, ex vivo and in vivo models.
