Search

Sargassum fusiforme polysaccharides (SFPs), including SFP-3-40, SFP-3-60, SFP-3-80, SFP-7-40, SFP-7-60, SFP-7-80, SFP-10-40, SFP-10-60, and SFP-10-80, were extracted at different pH (3, 7, and 10), and then precipitated with graded precipitation of 40%, 60% and 80% (v /v) ethanol solution, respectively. Their physicochemical properties and α -glucosidase inhibitory activity were determined. Results showed that SFPs significantly differed in the contents of total sugar, protein, uronic acid, sulfate, the zeta potential, and molecular weight distribution. SFPs, including SFP-10-40, SFP-10-60, and SFP-10-80, had bigger absolute zeta potential value and higher respective average molecular weight in the same ethanol concentration precipitate. All samples were mainly composed of fucose, glucuronic acid, and mannose with different molar ratios. The extraction pH and precipitation ethanol solution concentration caused little changes in functional groups, but significantly altered surface morphology of SFPs. Congo red test revealed that all polysaccharides were not helical polysaccharides. Rheological measurements indicated that SFPs were pseudoplastic fluids and showed elastic behavior of the gel. Except SFP-3-40 and SFP-3-60, all other samples had a stronger α -glucosidase inhibitory activity than that of acarbose. The inhibition type of SFPs against α -glucosidase varied owing to different extraction pH and precipitation ethyl concentration. This study shows that extraction pH can significantly affect the structure and hypoglycemic activity of SFPs and provide a data support for the scientific use of Sargassum fusiforme in industrial production. [Display omitted] • Nine polysaccharide fractions were obtained from Sargassum fusiforme (Harv.) Setch at different extraction pH. • The physicochemical properties of SFPs were significant different. • SFP-7-40 showed the strongest α -glucosidase inhibitory activity with IC 50 values of 0.304 mg/mL. [ABSTRACT FROM AUTHOR]

In this study, five Fucus vesiculosus polysaccharides (FVPs; FVP-2, FVP-4, FVP-7, FVP-10, and FVP-13) were extracted by different pH, and their physicochemical characteristics and α -glucosidase inhibitory activity were investigated. Results showed that extraction pH significantly affected the chemical composition, molecular weight, zeta potential, structure characterization, and rheological property of FVPs. The viscosity consistency index of Fucus vesiculosus polysaccharides at high concentration (40 mg/mL) were ranked in decreasing order as FVP-10 > FVP-4 > FVP-7 > FVP-2 > FVP-13, which was strictly in accordance with the order of Mw. Among the five polysaccharides, FVP-13 showed the strongest α -glucosidase inhibitory activity, which might be related to its the lowest Mw and relatively higher xylose content. Fluorescence quenching analysis indicated that the interaction of FVPs and α -glucosidase was predominated by a dynamic mechanism. Thermodynamic analysis showed that the main driving forces for the interaction was hydrophobic interaction. Circular dichroism spectrum analysis found that FVPs could induce the secondary structure of α -glucosidase changes like the decrease of β -sheet content and the increase of β -turn and random coil content to inhibit α -glucosidase activity. These results suggested that extraction with high pH was an efficient method to obtain FVPs with strong α -glucosidase inhibition activity. • Five Fucus vesiculosus polysaccharides were obtained at different extraction pH. • FVP-13 showed the stronger α -glucosidase inhibitory activity. • The α -glucosidase inhibitory mechanism of polysaccharide was studied. • Hydrophobic interaction played a key role in the bonding of FVPs to α -glucosidase. [ABSTRACT FROM AUTHOR]