Protective effect of Millettia pulchra polysaccharide on cognitive impairment induced by D-galactose in mice.

A polysaccharide (PMP) was isolated from Millettia pulchra and purified by DEAE-cellulose and Sephadex G-75 chromatography. The results showed that PMP was composed of d-glucose and d-arabinose in a molar ratio of 90.79% and 9.21%, with an average molecular weight of about 14,301 Da. Furthermore, the effect of PMP on cognitive impairment induced by d-galactose in mice was evaluated. Treatment with PMP significantly reversed d-galactose-induced learning and memory impairments, as measured by behavioral tests. One of the potential mechanisms of this action was to reduce oxidative stress and suppress inflammatory responses. Furthermore, our results also showed that PMP markedly reduced the content and deposition of β-amyloid peptide, improved the dysfunction of synaptic plasticity, increased the levels of acetylcholine, but decreased cholinesterase activity. These results suggest that PMP exerts an effective protection against d-galactose-induced cognitive impairment, and PMP may be a major bioactive ingredient in M. pulchra.