Nafiseh Sadat Mousavi, Mehdi Tabarsa, Hassan Ahmadi,
Volume 11, Issue 2 (5-2022)
Abstract
Polysaccharides possess diverse biological properties, mostly owed to their structural complexity and molecular heterogeneity, that could be improved through engineering methods and application of structural modifications. The objective of the present study was the assessment of antioxidant properties of hydrolyzed fucoidan from seaweed Nizamuddinia zanardinii and the correlation of molecular weight with biological function. After the removal of pigments and low molecular weight compounds, crude extracted polysaccharide was hydrolyzed at 100 C for 10, 20, 40 and 60 minutes using 0.01N HCl. The average molecular weight of crude fucoidan 1254.4 × 103 g/mol and for hydrolysates FH10, FH20, FH40 and FH60 was 974.5, 891.8, 806.5 and 705.5 × 103 g/mol, respectively. With the decrease of molecular weight, hydrolysates, compared with the crude fucoidan, exerted considerable DPPH (61.27-84.54%) and ABTS (40.1-88.5%) radical scavenging and Fe3+ reducing power (0.49-0.81 Abs) activities. Among different samples, hydrolysate FH20 showed the greatest capacity for DPPH radical scavenging activity (70.45-84.54%) and Fe3+ reducing power (0.49-0.81 Abs). Overall, the results of the current study showed that hydrolysis and reduction of molecular weight significantly improved the antioxidant activities of the fucoidan while time did not result any significant differences in antioxidant properties of hydrolysates which could be due to alterations in functional groups. Hence, fucoidan isolated from the examined species could be utilized as antioxidant agents in forms of native or hydrolysates.
Masoumeh Ghanbari Kiasara, Mehdi Tabarsa, Hassan Ahmadi, Amin Mokhlesi,
Volume 11, Issue 4 (12-2022)
Abstract
The aim of the current study was the evaluation of stepwise recovery of fucoidan extracted from seaweed Nizamuddinia zanardinii and the assessment of relationship between sulfate content and molecular weight with its antioxidant activity. After the removal of pigments and low molecular weight compounds, fucoidan extracted with water was precipitated using different concentrations of ethanol at three levels (30, 50 and 70%). Three fractions of Fuc30, Fuc50 and Fuc70 showed molecular weights of 731.62, 655.76 and 10.41 × 103 g/mol, respectively. The content of sulfate esters in the obtained fractions were measured between 6.49-25.03%. The color evaluation of produced fucoidans by a digital chroma meter indicated the highest lightness index for Fuc50 fraction. Antioxidant results were varying in DPPH radical (43.93-89.40%) and ABTS radical (25.05-96.10%) scavenging activities as well as Fe3+ reducing power (Abs of 0.142-0.259). Overall, the findings of the present study indicated that stepwise precipitation of fucoidan from N. zanardinii leads to production of fractions with different chemical and molecular weight characteristics and antioxidant activities. Besides, although all isolated fucoidan fractions are introduced as potent antioxidant compounds, polymers possessing lower molecular weight and greater sulfate content exert higher antioxidant activities.
