Highlights

• Novel Gastrodiaelata polysaccharides with different molecular weights were purified. 
• GEP1-2 (3.21 × 106 Da) had α-1,4-Glcp, α-1,6-Glcp, β-1,6-Galp, β-1,2-Frucf, and p-HAC.
• GEP3-3 (1.91 × 104 Da) was an α-1,4- and α-1,4,6-glucan.
• All GEPs showed immune-enhancing effects on macrophages in a dose-dependent manner. 
• The macromolecular GEP1-2 improved immunity by increasing cytokine levels in vivo. 

Summary

Gastrodia elata Blume is a traditional medicinal plant known for its health-related uses. However, many researchers focus mainly on smaller compounds, partly because very large polysaccharides are often assumed to have limited effectiveness when taken orally. 

In this study, researchers purified a newly identified polysaccharide called GEP1-2 with an unusually high molecular weight of 3.2 million Daltons, and compared it with a much smaller polysaccharide (GEP3-3, 19,000 Daltons). Structural analysis showed that GEP1-2 contains distinctive sugar branching patterns and phenolic components that may influence how it interacts with biological systems. 

In laboratory immune cell tests, the polysaccharides stimulated immune activity by increasing signaling responses. In mice, daily oral administration of GEP1-2 at 200 mg/kg increased the relative size of the thymus—an organ involved in immune cell development—and significantly raised serum levels of TNF-α and IL-6. 

These results suggest that ultra-large plant polysaccharides can still show measurable immune-related activity after oral intake, and that molecular size alone should not be used to rule out polysaccharides as candidates for future functional food or health-related research. 

Reference

J.Q. Chen et al., “In vitro and in vivo immune-enhancing effects of polysaccharides with different molecular weights and structural characteristics from Gastrodia elata Blume,” International Journal of Biological Macromolecules, vol. 295, art. no. 139526, 2025, doi: 10.1016/j.ijbiomac.2025.139526.