Study on the structure and lipid-lowering activity of different components of lotus root polysaccharides

Lotus root is a widely popular aquatic vegetable with edible and medicinal values. Here we report the structure and lipid-lowering activity of two lotus root polysaccharides LRW (lotus root polysaccharide by water extraction) and LRA (lotus root polysaccharide by alkali extraction), that were extracted by aqueous and alkaline solution respectively. The results showed that the yield of polysaccharide from lotus root could be significantly improved by alkali extraction. Basic composition and structural characterization showed that the total sugar contents of LRW and LRA were 96.83 % and 73.66 %, and the molecular weights were 2.464 × 10⁵ Da and 1.727 × 10⁵ Da, respectively. LRW and LRA had the similar structure that the main backbone consisted of →4)-α-D-Glcp-(1→ with branches at C-6 site. Both LRW and LRA could scavenge DPPH and hydroxyl radicals effectively, and have strong adsorption capacity to cholate salts in a concentration-dependent manner. In HepG2 cells, LRW and LRA inhibited the accumulation of lipid droplets induced by oleic acid, and increased the activity of T-SOD and CAT, meanwhile, reduced the level of MDA, TC and TG, showing good lipid-lowering activity. In comparison, the lipid-lowering effect of LRA was better than that of LRW. In addition, gene sequencing and RT-PCR showed that AMPK, ACC, PPARα and CPT-1 were essential for LRA to exert a lipid-lowering effect. This study provides a theoretical basis for the extraction and lipid-lowering application of lotus root polysaccharides.