Structural Characterization and in vitro Activity Changes of Sulfated Helianthus annuus L. Pollen Polysaccharides

Abstract:

A macromolecular polysaccharide (SPP) with a molecular weight of 1.93×106 Da was extracted from Helianthus annuus L. pollen and modified using the sulfur trioxide-pyridine method, yielding sulfated SPP (SPP-S) with a molecular weight of 1.58×106 Da. Through single-factor and response surface experiments, the optimal conditions for sulfation were identified as 3 g of sulfur trioxide-pyridine complex, a reaction time of 2 h, and a temperature of 55 ℃, achieving a substitution degree of 1.73. Basic component analysis revealed that SPP and SPP-S contained 93.03% and 45.33% total sugars and 35.55% and 84.48% sulfate mass fractions, respectively. The monosaccharide compositions of SPP and SPP-S were comparable, both containing rhamnose, arabinose, galactose, glucose, and a small amount of galacturonic acid, with molar ratios of 0.125:3.368:1:0.725:0.063 in SPP and 0.084:3.588:1:1.369:0.004 in SPP-S. NMR hydrogen spectroscopy confirmed the presence of both α- and β-glycosidic linkages. In vitro assays showed that the IC50 values (mg/mL) for SPP against DPPH, •OH, and ABTS+• free radicals were 8.19, 17.42, and 11.26, while those for SPP-S were 0.78, 1.912, and 1.378, respectively. Furthermore, the IC50 values (mg/mL) for α-amylase and α-glucosidase inhibition were 2.37 and 4.737 for SPP and 0.123 and 0.795 for SPP-S, respectively. In summary, sulfation reduces the content of various basic polysaccharide components while increasing the sulfate content. This modification significantly enhanced the in vitro antioxidant and hypoglycemic capabilities of SPP, suggesting its potential for other future applications in the field.