Hypoglycemic effect and mechanism of a pectic polysaccharide with hexenuronic acid from the fruits of Ficus pumila L. in C57BL/KsJ db/db mice

In this study, a particular pectic polysaccharide (FPLP) was extracted and purified from the fruits of Ficus pumila Linn. through boiling water extraction, alcohol precipitation, diethylaminoethyl-Sepharose Fast Flow chromatography and Superdex™ G-75 gel filtration chromatography. Analysis of high-performance gel permeation chromatography, FTIR, GC-MS, methylation and 1D/2D NMR spectroscopy revealed that FPLP (Mw: 34.69 kDa) is a linear (1,4)-α-d-galacturonic acid binding 1.30% branched chain hexenuronic acid with 23.34% methyl esterification. Treatment with FPLP ameliorated hyperglycaemia in association with an improvement in hepatic glycogen metabolism in C57BL/KsJ db/db mice. The activation of IRS-1/PI3K/Akt/GSK3β/GS insulin signalling pathway and AMPK/GSK3β/GS signalling pathway and the regulation of glucokinase, phosphoenolpyruvate carboxykinase and glucose-6-phosphatase expressions involved in hepatic glycogenesis and glycogenolysis were considered the therapeutic mechanisms of FPLP. These results provide a new insight for investigating the effects of pectic polysaccharides on blood glucose control and suggest that FPLP is a promising nutraceutical for treatment of T2DM.