Arabinogalactans from Larix principis-rupprechtii: An investigation into the structure-function contribution of side-chain structures

Certain polysaccharides can serve as bio-active natural polymers that provide health benefits, however their complex structures tend to induce dramatically different activities. In this work, the immunomodulatory activity of the two arabinogalactans from larch was investigated, based upon comparison of native arabinogalactans and those modified to have lesser quantities of side-chain paraphernalia. Various in vitro assays demonstrated that the native arabinogalactans increased the secretion of macrophage-derived biological factors including NO, TNF-alpha, IL-1 beta and IL-6. Methylation analysis and nuclear magnetic resonance spectra results indicated that part side chains of arabinogalactan were successfully removed. Partial removal of the side-chains enhanced immunomodulatory activity, while excessive removal resulted in a sharp decrease in immunomodulatory activity. These results provide new evidence that alludes to the structure-function relationship of bio-active polysaccharides, furthering the case for development of a universal assessment of polysaccharide structure-function proclivities.