Structure characterization and lipid-lowering activity of a homogeneous heteropolysaccharide from sweet tea (Rubus Suavissmus S. Lee)

Sweet tea (Rubus Suavissmus S. Lee) is consumed as herbal tea in southwestern China, which has multiple functions such as relieving cough, alleviating allergic responses, and clearing away heat. Here we report the structure and lipid-lowering activity of a sweet tea polysaccharide (STP-60a). STP-60a is a homogeneous heteropolysaccharide with a molecular weight of 9.16 × 10⁴ Da, and composed of rhamnose, arabinose, glucose, galactose and glucuronic acid. The main backbone of STP-60a consists of β-L-Rhap-(1→, →3)-β-D-Galp-(1→, →4)-β-D-Glcp-UA-(1→, →3,6)-β-D-Galp-(1→, →6)-β-D-Galp-(1→, →3)-4-OAc-β-L-Arap-(1→, →3)-α-L-Araf-(1→ and the side chain are α-L-Araf-(1→ and →3)-α-D-Glcp-(1→. Using Caenorhabditis elegans (C. elegans) in a high-sugar diet as a model, we found that STP-60a significantly reduced the fat accumulation in the intestine of C. elegans, and extensively affected lipolysis, fatty acid synthesis and β-oxidation processes. In addition, sbp-1 and nhr-49 were essential for STP-60a to exert a lipid-lowering effect.