Isolation and structural elucidation of immunomodulatory oligosaccharides from Trillium tschonoskii

Six oligosaccharides with the degree of polymerization (DP) 2 to 7 were isolated from the active fraction of Trillium tschonoskii using a high-temperature semi-preparative porous graphitic carbon (PGC) column based on high-performance liquid chromatography coupled with a charged aerosol detector and vanquish fraction collector (HPLC-CAD-VFC) system. The structures of DP2 - 7 were determined as maltose, maltotriose, maltotetraose, maltopentaose, maltohexaose, and maltoheptaose with (1→4)-α-D-glucopyranose residues by relative quantitative ¹H nuclear magnetic resonance (qHNMR) spectroscopy with anomeric protons integration and NMR structural-reporter-group resonances. The immunomodulatory activities of this series of maltooligosaccharides (MOS) were tested on RAW264.7 cells. All samples on cells had no cytotoxicity, and the oligosaccharide fraction (TOS1) could increase the phagocytic capacity and production of nitric oxide (NO) and cytokines to a much higher level than monomers. In particular, maltopentaose (DP5) showed a relatively higher capacity for stimulating proliferation, NO, and cytokine production than other purified oligosaccharides. The immunomodulatory activity of MOS investigated in this study is beneficial for utilizing MOS as a functional ingredient in novel product development.