Purification and Molecular Characterization of Fucoidan Isolated from Ascophyllum nodosum Brown Seaweed Grown in Ireland

Abstract

The present study investigates the molecular characteristics of fucoidan obtained from the brown Irish seaweed Ascophyllum nodosum, employing hydrothermal-assisted extraction (HAE) followed by a three-step purification protocol. The dried seaweed biomass contained 100.9 mg/g of fucoidan, whereas optimised HAE conditions (solvent, 0.1N HCl; time, 62 min; temperature, 120 °C; and solid to liquid ratio, 1:30 (w/v)) yielded 417.6 mg/g of fucoidan in the crude extract. A three-step purification of the crude extract, involving solvents (ethanol, water, and calcium chloride), molecular weight cut-off filter (MWCO; 10 kDa), and solid-phase extraction (SPE), resulted in 517.1 mg/g, 562.3 mg/g, and 633.2 mg/g of fucoidan (p < 0.05), respectively. In vitro antioxidant activity, as determined by 1,1-diphenyl-2-picryl-hydrazyl radical scavenging and ferric reducing antioxidant power assays, revealed that the crude extract exhibited the highest antioxidant activity compared to the purified fractions, commercial fucoidan, and ascorbic acid standard (p < 0.05). The molecular attributes of biologically active fucoidan-rich MWCO fraction was characterised by quadruple time of flight mass spectrometry and Fourier-transform infrared (FTIR) spectroscopy. The electrospray ionisation mass spectra of purified fucoidan revealed quadruply ([M+4H]4+) and triply ([M+3H]3+) charged fucoidan moieties at m/z 1376 and m/z 1824, respectively, and confirmed the molecular mass 5444 Da (~5.4 kDa) from multiply charged species. The FTIR analysis of both purified fucoidan and commercial fucoidan standard exhibited O-H, C-H, and S=O stretching which are represented by bands at 3400 cm−1, 2920 cm−1, and 1220–1230 cm−1, respectively. In conclusion, the fucoidan recovered from HAE followed by a three-step purification process was highly purified; however, purification reduced the antioxidant activity compared to the crude extract.

Fucoidan from Ericaria crinita Alleviates Inflammation in Rat Paw Edema, Downregulates Pro-Inflammatory Cytokine Levels, and Shows Antioxidant Activity

“…Moreover, Sellimi et al [35] observed the highest reducing activity of Gongolaria barbata fucoidan at concentrations of 1 mg/mL and 24.62 mg ascorbic acid equivalents/g of the sample. Correlating with our results, Rajauria et al [44] reported FRAP values for A. nodosum crude fucoidan and commercial fucoidan from F. vesiculosus to be 38.6 and 13.9 mg TE/g, respectively. The reducing capacities of fucoidans are supposed to be due not only to their sulfate content and molecular weight but also to the presence of hydroxyl and carboxylic groups of the uronic acids in their chain [15].…”

“…The higher scavenging effect of Gongolaria barbata fucoidan compared to Ericaria crinita , Cystoseira compessa , and Ericaria sedoides fucoidan could be related to its higher content of sulfate groups. Fucoidans isolated from Cystoseira / Eicaria / Gongolaria species resulted to be more effective radical scavenging agents compared to other brown algae such as Ascophyllum nodosum (43.0%, IC 50 = 1.16 mg/mL) [ 44 ], Undaria pinnatifida (86.80% at concentration 1 mg/mL) [ 45 ], Sargassum pallidum (19.1%), S. vulgare (22.5%), and S. tenerrimum (64.66%) at concentrations of 2.5 mg/mL, 3.8 mg/mL, and 1 mg/mL, respectively [ 15 ]. Compared to crude fucoidans, the established lower scavenging effect of the commercial fucoidan from F. vesiculosus (IC 50 = 1.66 mg/mL), also reported by other authors (IC 50 = 2.30 mg/mL [ 44 ]; 76.61% at 4 mg/mL [ 46 ]), could be related to its higher purity and the absence of residual substances such as phenols, pigments, and proteins.…”

“…The crude fucoidan from E. crinita displayed the potential to reduce the Fe 3+ /ferricyanide complex at concentrations of 1 mg/mL ( Table 1 ). Several studies on the FRAP capacity of fucoidan isolated from Cystoseira / Eicaria / Gongolaria species have been conducted [ 15 , 35 , 43 , 44 ]. However, the application of different variations of the FRAP method and the use of different standards, equivalents, and units complicate the comparison of the antioxidant values.…”

Bioactivity of Fucoidan-Rich Extracts from Fucus vesiculosus against Rotavirus and Foodborne Pathogens

“…In studies performed in other types of algae, fucoidan content has also been determined. Thus, fucoidan extracted from Ascophyllum nodosum using a MWCO of 10 kDa showed a content of 562.3 ± 0.08 mg/g of dry seaweed extract [ 33 ]. Another report on Padina boryana showed a fucoidan content of 1.59 ± 0.16%, expressed in dry weight, in an extract obtained by using a 10 kDa MWCO fractionation [ 34 ].…”