Comparative study of Salvia miltiorrhiza polysaccharides prepared by different extraction methods: physicochemical...

Extraction methods significantly affect the physicochemical characteristics and biological activities of polysaccharides. This study compared the effects of five extraction techniques (hot water, acid, alkali, enzyme and ultrasound-assisted extraction) on the physicochemical characteristics of Salvia miltiorrhiza polysaccharides (SMPs, SMP-W, SMP-A, SMP-B, SMP-E and SMP-U) and their protective effects against ulcerative colitis (UC) in mice. The extraction methods significantly affected polysaccharide yield, molecular weight distribution, monosaccharide composition and uronic acid content. SMP-W exhibited the lowest yield (13.06%) but the highest molecular weight (1571.40 kDa) and uronic acid content (7.57%), along with a Congo red λ_max red shift suggestive of triple-helix-like features. SMP-U showed the highest yield (18.56%) but lower molecular weight (1053.18 kDa) and uronic acid content (1.13%). SMP administration was associated with barrier repair, anti-inflammatory and antioxidant effects, and gut microbiota - tryptophan metabolism remodeling. Specifically, SMP-W was closely associated with intestinal barrier repair, tight junction protein restoration, and IL-10 promotion, whereas SMP-U showed a stronger association with restored microbial diversity, pro-inflammatory cytokine suppression and oxidative stress alleviation. Correlation analysis indicated that SMP administration was associated with enrichment of beneficial Akkermansia and Lachnospiraceae, inhibition of Desulfovibrio, and a shift of tryptophan metabolism from the pro-inflammatory kynurenine pathway toward beneficial metabolites. These findings suggest that the extraction method influences SMP bioactivity, likely through alterations in molecular weight distribution and monosaccharide composition, offering a comparative basis for their application as functional food ingredients.