Chemical characterization of soluble polysaccharides in the red alga Acanthophora spicifera from La Paz Bay, Baja California Sur, Mexico

Acanthophora spicifera is an invasive red alga that was recently detected in La Paz Bay, Baja California Sur, Mexico, where it has developed into a large biomass. Because it is a new species in the region, the characteristics and properties of the soluble polysaccharides (SPs) that it contains are unknown. To determine the content, chemical composition, and properties of SPs in A. spicifera, monthly samplings were carried out in 2013 at Point Roca Caimancito in La Paz Bay, and native and alkali-treated polysaccharides were extracted and characterized. The alkaline treatment produced lower yields and modified the composition of A. spicifera SPs. The polysaccharides obtained before or after the alkaline treatment had low viscosity and did not have gelling properties. In line with the obtained results, the molar ratio of components (galactose, 3,6-anhydrogalactose, sulfates [Gal:3,6-AG:sulfates]) for native (1.00:0.30:0.23) and alkali-treated (1.00:0.30:0.17) polysaccharides showed that A. spicifera SPs have a lower proportion of sulfates than that in polysaccharides belonging to carrageenans but greater than that in polysaccharides belonging to true agar. The Fourier-transform infrared spectra of SPs showed characteristic signals for sulfated galactans, with the presence of pyruvic acid; after the alkaline treatment, characteristic signals for agar-type polysaccharides (agaroid) were observed. Although A. spicifera polysaccharides have no gelling properties, additional studies are needed to clarify the structure of the SPs it contains to find appropriate uses for this resource.