Galactofuranose-rich heteropolysaccharide from Trebouxia sp., photobiont of the lichen Ramalina gracilis and its effect on macrophage activation

A structural study of the carbohydrates from Trebouxia sp., the algal symbiont of the lichen Ramalina gracilis demonstrated a galactofuranan-rich heteropolysaccharide, which was predominated by (1 → 5)-linked galactofuranosyl units with side-chains in position 6 on approximately 11.0% of the units. The side-chains have very complex branched structures. This polysaccharide showed cell eliciting activity on peritoneal macrophages in vitro at all concentrations tested (1–150 μg/mL), and at 150 μg/mL an increase of 60% of macrophage activation in comparision to the control group was observed. A potential role of these carbohydrates in lichen recognition process is also discussed.