Comparison of structure and neuroprotective ability of low molecular weight galactomannans from Sesbania cannabina obtained by different extraction technologies

Study on structure and properties of galactomannan and enzyme changes during fenugreek seeds germination

Fenugreek (Trigonella foenum-graecum L) galactomannan play an important role in the food and pharmaceutical sectors due to its attractive physicochemical properties. In this study, the changes of structure, properties and biological activity of fenugreek galactomannan (FG) during germination are analyzed by the activity and mechanism of endogenous enzymes (α-D-galactosidase and β-D-mannanase). The enzymes generally increased during germination and synergistically altered the structure of GM by cutting down the main chains and removing partial side residues. The mannose to galactose ratio (M/G) increased from 1.11 to 1.59, which is accompanied by a drastic decrease in molecular weight from 3.606 × 106 to 0.832 × 106 g/mol, and the drop of viscosity from 0.27 to 0.06 Pa·sn. The degraded macromolecules are attributed to the increase in solubility (from 64.55 % to 88.62 %). In terms of antioxidation and antidiabetic ability, germinated fenugreek galactomannan has the ability to scavenge 67.17 % ABTS free radicals and inhibit 86.89 % α-glucosidase. This galactomannan with low molecular weight and excellent biological activity precisely satisfies the current demands of pharmaceutical reagents and food industry. Seeds germination holds promise as a means of industrial scale production of low molecular weight galactomannans.

Structure and properties of acidic polysaccharides isolated from Massa Medicata Fermentata: Neuroprotective and antioxidant activity

Massa Medicata Fermentata (MMF) is a fermented food with therapeutic effects. Previous studies suggested that after stir-frying, the uronic acid content in MMF crude polysaccharides increases, and the pH value decreases, which is caused by the change in acidic polysaccharides. However, the detailed physicochemical properties and structure-activity correlation of the acidic polysaccharides in MMF have not been fully explored. In this study, two acidic polysaccharides (SMMFAP and CMMFAP) were isolated from the MMF and its stir-fried product, respectively. Their structural characteristics and bioactivities were comparatively studied, and the structure-activity correlation was examined. Our findings revealed that the SMMFAP had a higher average Mw and higher Gal and Man content than the CMMFAP. Both the SMMFAP and CMMFAP were mainly composed of Xyl, Man, and Gal residues, whereas the CMMFAP had fewer linkage types. Additionally, the CMMFAP exhibited stronger neuroprotective activity than the SMMFAP owing to its higher content of 1,6-linked-Galp, while the SMMFAP exhibited better antioxidant activity, which might be related to its higher average Mw. Our findings suggest that acidic polysaccharides may be the active substances that cause differences in effectiveness between the sheng and chao MMF. Furthermore, the research qualified the SMMFAP and CMMFAP with different potential applications.