Structural properties and in vitro and in vivo immunomodulatory activity of an arabinofuranan from the fruits of Akebia quinata

In our continuous searching for natural active polysaccharides with immunomodulatory activity, an arabinofuranan (AQP70-3) was isolated and purified from the fruits of Akebia quinata (Houtt.) Decne. by using ion exchange chromatography and gel permeation chromatography for the first time. AQP70-3 contained both alpha-L-Araf and beta-L-Araf, and the absolute molecular weight was 1.06 x 10(4) g/mol. The backbone of AQP70-3 comprised -> 5)-alpha-L-Araf-(1 ->, -> 3,5)-alpha-L-Araf-(1 ->, and -> 2,5)-alpha-L-Araf-(1 ->, with branches of -> 1)-beta-L-Arafand -> 3)-alpha-L-Araf-(1 -> residues. Biological assay suggested that AQP70-3 can stimulate phagocytic activity and promote the levels of nitric oxide (NO), interleukin (IL)-6, IL-1 beta, and tumor necrosis factor-alpha (TNF-alpha) of RAW264.7 cells. Furthermore, AQP70-3 was found to increase the production of reactive oxygen species (ROS) and NO in zebrafish embryo model.