The homogenous polysaccharide SY01-23 purified from leaf of Morus alba L. has bioactivity on human gut Bacteroides ovatus and Bacteroides cellulosilyticus.

Function of mulberry leaf (Morus alba L.) polysaccharide has been reported on antitumor, immunostimulatory and anti-inflammatory effects. However, the bioactivity on human gut microbiota is unclear so far. Here, three homogenous polysaccharides named SY01-21, SY01-22, SY01-23 were isolated from mulberry leaf with molecular weight 57 kDa, 25 kDa and 7.2 kDa, respectively. The monosaccharide composition of SY01-21 contained rhamnose, galactose and arabinose in a molar ratio of 7.60:43.52:48.88. SY01-22 contained rhamnose, galacturonic acid, glucose, galactose, xylose and arabinose in a molar ratio of 14.61:9.06:1.35:34.65:2.99:37.34. SY01-23 contained rhamnose, glucuronic acid, galacturonic acid, glucose, galactose, xylose and arabinose in a molar ratio of 23.00:4.12:24.60:5.74:17.28:1.12:24.13. Bioactivity test showed SY01-21 promoted the growth of Bacteroides cellulosilyticus (BC) while SY01-22 benefited the growth of Bacteroides ovatus (BO). Interestingly, SY01-23 boosted the growth of both BO and BC. However, Bacteroides thetaiotamicron (BT) only grew on 5 mg/mL SY01-21. Intriguingly, the growth of co-culture of BT with BO or BC was better than monoculture. This suggested that cross-feeding might exist between them. Besides, we found BO and BC generated acetate and propionate by utilizing SY01-23. The above results suggested that SY01-23 might modify human gut microbiota by driving colonization of Bacteroides in the gut to improve wellness.