Physico- and biochemical properties of alginates extracted from Ecklonia maxima and Sargassum fluitans using a simple cascade process

Alginate fractions from the pelagic Sargassum fluitans (Børgesen) Børgesen and kelp, Ecklonia maxima (Osbeck) Papenfuss sourced from the coastal waters of Ghana and South Africa respectively, were extracted by a simple sequential protocol different from the conventional methods. A total of six different phycocolloids were obtained, with two extracted under ambient conditions (fractions 1A) and the remaining four under hot conditions (fractions 2A and 3A) using ethanol and CaCl₂, respectively, for precipitation. These extracts were assessed for variations in their physicochemical properties, tyrosinase inhibition, antioxidation and anticoagulation activities. Molecular weights of the extracts were ~ 58–1506 kDa with their yields ranging between 4.8 to 11.1%. A sequential reduction (up to tenfold) was observed in their total phenolic compounds, proteins and sulphate contents. ¹H-NMR analysis of their uronic acid block structure revealed M/G ratios less than 1 for all extracts with dominant F_GG and F_GGG units depicting guluronic acid rich alginate fractions. Extracts from S. fluitans, notably, showed distinct antioxidation activity comparable to the well-known antioxidants like ascorbic acid. For tyrosinase inhibition, the highest was from S. fluitans fraction 1A (~ 37.1 ± 4.38%). The variations in properties of extracts reported herein, elucidates the possibility of obtaining series of relatively desirable alginate fractions from E. maxima and Ghanaian sourced S. fluitans via this modified extraction process.