Characterization and macrophage immunomodulatory activity of two polysaccharides from the flowers of Paeonia suffruticosa Andr.

Paeonia suffruticosa Andr. has a long history of cultivation in China and its flower possesses high nutritional and medicinal value. Characterization and macrophage immunomodulatory activity of the two polysaccharides from the flowers of Paeonia suffruticosa Andr., PSAP-1 and PSAP-2, purified by anion exchange chromatography followed by size exclusion chromatography, were investigated in the present study. Results showed that PSAP-1, with a molecular weight of 155 kDa, was mainly composed of glucuronic acid, glucose, arabinose and galactose with molar percentages of 0.83, 11.53, 18.98 and 68.96% respectively, and PSAP-2, with a molecular weight of 210 kDa, consisted of rhamnose, galacturonic acid, glucose, arabinose and galactose with molar percentages of 9.13, 8.35, 12.20, 14.75 and 55.57% respectively. Immunostimulatory activity evaluation in vitro revealed that the PSAP-1 and PSAP-2 could significantly stimulate the proliferation of Raw264.7 cells in dose-dependent manner and further activate Raw264.7 cells by releasing immunoactive molecules such as nitric oxide, tumor necrosis factor (TNF)-α and interleukin (IL)-6. In addition, PSAP-2 had higher immunomodulatory activity than PSAP-1. The above results suggested that both PSAP-1 and PSAP-2 had potent immunostimulatory activity and could be explored as a potential natural immunomodulatory agent in medicine or functional food fields.