Determining the Chain Conformation, Microstructure, and Antioxidant Activity of Fucoidan from Dictyota dichotoma Growing in the Sea of Cortez, Mexico

Abstract

Brown algae, such as Dictyota dichotoma, contain fucoidan, whose bioactivity is linked to its molecular characteristics, which are in turn defined by environmental conditions. D. dichotoma fucoidan from the Sea of Cortez in Mexico (DDFSC) has not been previously investigated. This study aimed to extract DDFSC and investigate its chain conformation, microstructure, and antioxidant activity. The extraction yield was 3.6% (w DDFSC/w lyophilized seaweed). Fourier-transform infrared spectroscopy recorded bands characteristic of fucoidan. Fucose represented the main monosaccharide in DDFSC (49.52% w/w). The sulfate content was 3.40% (w/w). Size-exclusion chromatography with multi-angle light scattering determined the molecular weight, intrinsic viscosity, radius of gyration, and hydrodynamic radius as 880 kDa, 260 mL/g, 34 nm, and 32 nm, respectively. The characteristic ratio (C∞) and the persistence length (q) were 4.5 and 1.5 nm, respectively, suggesting a branched random coil conformation. Dynamic light scattering determined polysaccharide diameters of 27.6 and 173.1 nm. Scanning electron microscopy and atomic force microscopy revealed an irregular morphology and aggregates with rough topography, respectively. The IC50 values for ABTS+ and DPPH radical scavenging assays were 4.21 and 5.64, respectively. The present study constitutes the first insight into DDFSC characterization and establishes a starting point for the development of sustainable future applications using this polysaccharide.