Chemical characteristics and bioactivity potential of polysaccharide extracts and purified fractions from Arctic brown macroalgae

Abstract

Macroalgae growing in the polar regions are exposed to extreme environment conditions and may induce differences in the structural and bioactive properties of their polysaccharides. Six brown macroalgae viz. kelp species - Saccharina latissima, Laminaria digitata, and Alaria esculenta; rockweed Fucus distichus; and filamentous macroalgae - Chorda filum and Chordaria flageliformis, from the Arctic were investigated for polysaccharides and their bioactivity. Among them, C. filum and C. flageliformis are least studied. Crude polysaccharide extracts (CPEs), extracted in water using ultrasonication, were found be dominated by fucoidan and alginate based on their monosaccharide composition analyzed using HPAEC-PAD. The CPEs showed up to 66 % radical scavenging activity in DPPH, ABTS and H₂O₂ antioxidant assays, while 93 % inhibition activity was observed in α-glucosidase anti-glycemic assay. The CPEs lacked pigments but contained minor amount of polyphenols. Purified polysaccharide fractions (PPFs) were obtained from the CPEs by ion-exchange chromatography. The monosaccharide composition and colorimetric analysis indicated enhanced purity of polysaccharides and absence of polyphenols in the PPFs. However, the antioxidant and antiglycemic activities of PPFs were lower than CPEs. We attributed the higher bioactivities in the crude extracts to synergistic interactions that may stabilize key active constituents.

Keywords: Alginate; Antiglycemic; Antioxidant; Fucoidan; HPAEC-PAD; Monosaccharide composition.