Blessing Mabate1, Chantal D. Daub1, Samkelo Malgas2, Adrienne L. Edkins3 and Brett I. Pletschke1
1Enzyme Science Programme (ESP), Department of Biochemistry and Microbiology, Faculty of Science, Rhodes University, Makhanda 6140, South Africa
2Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Pretoria 0028, South Africa
3Biomedical Biotechnology Research Unit, Department of Biochemistry and Microbiology, Faculty of Science, Rhodes University, Makhanda 6140, South Africa
Fucoidans are sulphated polysaccharides derived from brown seaweeds, consisting of considerable proportions of L-fucose and other monosaccharides. The search for novel natural compounds as potential drugs, due to the side effects associated with some currently available synthetic drugs, has led to an extensive study of fucoidans. Fucoidans are reported to display several bioactivities, including anti-diabetic and anti-cancer properties. Our study sought to investigate the anti-diabetic (viz., inhibition of amylolytic enzymes) and anti-cancer activities of fucoidan. Firstly, fucoidans were hot water extracted from Ecklonia maxima, Ecklonia radiata and Sargassum elegans. These fucoidans were structurally and chemically profiled using FTIR, NMR, HPLC and colourimetric assays. Thereafter, the fucoidans were investigated for their anti-diabetic and anti-cancer activities. Our results show that fucoidans extracted from South African seaweeds inhibit α-glucosidase, with the most potent fucoidan exhibiting an IC50 of 19 µg/ml, compared to acarbose (a commercial anti-diabetic drug) with an IC50 of 332 µg/ml. Interestingly, fucoidans and acarbose also synergistically inhibited this enzyme, which enabled a remedial combination approach in a proposed new strategy to control Type-2 diabetes mellitus (T2DM). This combination strategy may reduce the amount of acarbose used and, therefore, the associated side effects. The fucoidans also exhibited anti-cancer activities – including inhibiting cancer cell adhesion to surfaces, anti-spheroid migration and anti-colony formation properties using a HCT116 human colorectal cancer cell line. In summary, fucoidans are seaweed polysaccharides that show potential application in alleviating T2DM and cancer progression.