Chemical characterization, antioxidant properties, cholinesterase inhibitory and anti-amyloidogenic activities of sulfated polysaccharides from some seaweeds

Abstract

Sulfated polysaccharides were extracted from Ecklonia maxima (PKPM), Gelidium pristoides (PMNP) and Ulva rigida (PURL) and characterized using scanning electron microscope with energy dispersing x-ray (SEM-EDX), Fourier transform infrared spectroscopy (FTIR) and Gas Chromatography-coupled with mass spectrometry (GC-MS). The radical scavenging activity, metal chelating effects, enzyme inhibitory potentials and anti-amyloidogenic activities of the sulfated polysaccharide samples were also evaluated. The elemental analysis and FTIR results confirmed the presence of sulfate groups in the polysaccharides. Furthermore, GC-MS analysis revealed the presence of glucose, galactose, fucose, arabinose and xylose as the main monosaccharides present in the samples. PKPM, PMNP and PURL exhibited radical scavenging activities against DPPH, ABTS and OH radicals and were able to chelate Fe2+. The sulfated polysaccharides also showed inhibitory effects on acetylcholinesterase, butyrylcholinesterase and β-secretase activities. PKPM showed higher cholinesterase and β-secretase inhibitory activities than PURL and PMNP. Thioflavin-T assay revealed that incubation of β-amyloid (Aβ1-42) peptide without the polysaccharides showed high fluorescence intensity compared to Aβ1-42 treated with PMNP, PKPM and PURL which showed drastic reduction in fluorescence intensity. Electron micrographs also revealed continuous aggregation of amyloid fibrils in the control (Aβ1-42 alone). However, Sulfated polysaccharides samples incubated with Aβ1-42 showed disappearance of Aβ1-42 fibrils which connotes disaggregation and inhibition of aggregation of the fibrils. These results suggest that the sulfated polysaccharide samples exhibit antioxidant and neuroprotective potentials which could be explored as nutraceuticals for the management of AD.