Isolation, structural elucidation, and immunoregulation properties of an arabinofuranan from the rinds of Garcinia mangostana

In our search for bioactive polysaccharides as immunomodulatory agents, an arabinofuranan (GMP90-1) was purified and characterized from the rinds of Garcinia mangostana L. GMP90-1 (absolute molecular weight: 5.30 x 10(3) g/mol) was found to be composed of arabinose, galactose, and rhamnose. The backbone of GMP90-1 was determined as (1 -> 5)-linked alpha-L-Araf, (1 -> 2,3,5)-linked alpha-L-Araf, (1 -> 3,5)-linked alpha-L-Araf, (1 -> 6)-linked beta-D-Galp, and (1.2)-linked alpha-L-Rhap. Conformational analysis revealed GMP90-1 to exist as a rigid rod structure in sodium chloride solution. To explore its potential as immunomodulatory agents, an in vitro cell screening was performed and GMP90-1 was found to significantly enhance the phagocytic uptake of neutral red and improve the secreted level of nitric oxide (NO), interleukin (IL)-6, IL-1 beta, and tumor necrosis factor-alpha (TNF-alpha) of macrophages. Furthermore, the cellular immunomodulatory activities were confirmed by the in vivo zebrafish experiment, which suggested that GMP90-1 with immunomodulatory effects could be considered as a potential immunomodulatory for immune diseases.