Modification of ulvans via periodate-chlorite oxidation: Chemical characterization and anticoagulant activity

•Ulvans (Ulva fasciata) were oxidized via NaIO4 originating dialdehyde derivatives.•Oxidation of aldehyde groups with NaClO2 produced polycarboxyl ulvans.•Periodate-chlorite oxidation increased the anticoagulant activity of ulvans.•Anticoagulant activity of polycarboxyl ulvans depends of the native sulfate groups.•Increase of anticoagulant activity was paralleled to increase of carboxyl content. Native (F2) and carboxyl-reduced (R) ulvans from Ulva fasciata were sequentially oxidized with periodate-chlorite affording the polycarboxyl ulvans C1, C2 and C3 (1.20, 1.41 and 1.81 mmol g−1 of COOH, respectively; 19.7, 21.3 and 21.0% of NaSO3, respectively) and R-C3 (1.86 mmol g−1 of COOH; NaSO3 = 22.7%), respectively. APTT assay (polysaccharide fractions at 150 μg mL−1) showed clotting time of 45.6 s for F2 fraction. For polycarboxyl ulvans C1, C2, C3 and R-C3 the clotting times were 101.0, 122.2, 222.0 and 227.0 s, respectively. Comparison of the APTT assay results using ulvans chemically modified by carboxyl-reduction, desulfation, periodate oxidation and/or chlorite oxidation showed the anticoagulant activity of polycarboxyl ulvans is dependent of the sulfate groups present in the native polymer. In addition, the increase of the anticoagulant activity was accompanied by the increasing of the carboxyl groups and the content of this acidic substituent seems to be more important than its positioning.