Optimization of preparation conditions, molecular structure analysis and antitumor activity of sulfated sodium alginate oligosaccharides

Sodium alginate is a kind of marine polysaccharide extracted from brown algae, and its degradation products have been widely used in food, medicine and other fields. Sodium alginate oligosaccharide (AOS) was degraded by hydrogen peroxide from sodium alginate and modified by sulfonic acid-chlorosulfonic acid-pyridine to obtain sulfated alginate oligosaccharide (S-AOS). The main research contents included the optimization of the preparation process of S-AOS and the study of its structure characterization and biological activity. First, the optimal reaction conditions of S-AOS were optimized by single factor analysis and response surface analysis. The sulfated derivatives were characterized using Fourier transform infrared spectrum (FTIR), High performance liquid chromatography (HPLC), Nuclear magnetic resonance Hydrogen (1H NMR) spectrum and Electrospray ionization mass spectrometry, and molecular formula and substitutions were determined. Molecular docking, GO and KEGG enrichment analysis were used to predict S-AOS biological activity and possible action targets, and the mechanism of tumor suppression activity of S-AOS was preliminarily investigated. The results showed that, the optimal reaction conditions for S-AOS was finally determined as: Chlorosulfonic acid - pyridine volume ratio was 7:1. Sulfation reagent – AOS volume ratio was 3:1. Reaction time was 3 h. Reaction temperature Was 40 ℃. Under this condition. In contrast to AOS, S-AOS showed two new absorption peaks in the FTIR spectrum and two new chemical shift peaks in the 1H NMR spectrum, suggesting that the sulfate group selectively reacts with the hydroxyl groups on the third carbon and the fourth on the mannoconide. The relative molecular mass of S-AOS was 1566 g/mol and a degree of sulfate substitution was 0.931. Molecular docking screening, GO and KEGG enrichment analysis of S-AOS revealed that it may have a role in apoptosis, oxidative stress, thrombosis, and cellular autophagy. In vitro experiments showed that S-AOS could inhibit the expression of apoptosis and proliferation related proteins, and showed certain anti-tumor activity. S-AOS had more or stronger biological activity by introducing sulfuric acid groups, and its application in the field of biomedicine is expanded.