Characterization and in vitro simulated gastrointestinal digestion and fermentation of Mentha haplocalyx polysaccharide

An acidic polysaccharide (PMHP-3) obtained from the Mentha haplocalyx was structurally characterized, and in vitro simulated digestion and fermentation were investigated. PMHP-3 was mainly composed of mannose, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose and arabinose with molecular weight of 21.82 kDa. After digestion in saliva and simulated gastric juice, the molecular weight, reducing sugar, total sugar and uronic acid contents of PMHP-3 did not change significantly (p > 0.05). After digestion in simulated intestinal juice, the molecular weight and uronic acid content of PMHP-3 did not change significantly, and there was no free monosaccharide production, but the total sugar and reducing sugar contents slightly decreased. During fermentation, the molecular weight, carbohydrate residue and free monosaccharides of PMHP-3 were decreased, suggesting that PMHP-3 could be degraded by microorganism and metabolized into a variety the short-chain fatty acids (SCFAs) such as acetic, propionic. Meanwhile, PMHP-3 modulated the gut microbiota by reducing the ratio of Firmicutes/Bacteroidetes, promoting the proliferation of beneficial bacteria such as Bacteroidaceae and Bifidobacteriaceae, and inhibiting harmful bacteria such as Lachnospiraceae and Enterobacteriaceae. These results indicate that PMHP-3 is beneficial to the gut health and can be developed as a potential prebiotic to prevent diseases by improving intestinal health.