ABSTRACT
In this study, we attempt to isolate the polysaccharides from the brown seaweed Dictyopteris polypodioides (Dp) growing on the Lebanese coast. The percentages of the main polysaccharide alginic acid were 4.6% in May and 6.25% in July. The extracted yields of Fucoidan, Laminaran and Mannuronan (FLM) and Mannuronan (M) alone were respectively 0.75% and 0.38% in May and 1.15% and 0.67% in July. We performed the infrared spectroscopy in order to reveal the functional groups of alginate and mannuronan. Moreover, a non-destructive technique ¹ H NMR was used to determine the structure of alginate and the distribution of guluronic (G) and mannuronic acid (M) in the chain, allowing us therefore to calculate the ratio M/G. The latter was 0.96 showing a strong ability of alginate to capture heavy metals. The analysis of trace elements showed great amounts of K, Si, Na and Mg in both seasons. Moreover, Dictyopteris appears to be rich in fatty acids (10 items) with palmitic and oleic acids as main fatty acids. Furthermore, the anticoagulant activity of polysaccharides was investigated by activated partial thromboplastin time (APTT) clotting assay and the antioxidant activity was studied by electrolysis method. It has been shown that the FLM and M fractions of Dictyopteris polypodioides have a significant antioxidant and anticoagulant activities. Further investigations are imperative in order to develop new molecules based on these polysaccharides to be used as drugs or for healthcare in general.