In vitro macrophage nitric oxide production by Pterospartum tridentatum (L.) Willk. inflorescence polysaccharides

[Display omitted] •Hot water soluble polysaccharides from P. tridentatum dried inflorescences were characterized.•High proportions of pectic polysaccharides were observed.•Type I and type II arabinogalactans, galactomannans and xyloglucans were also present.•Macrophage NO production was mostly due to acetylated galactomannans.•Arabinogalactans, low molecular weight galacturonans and xyloglucans also contributed to NO production. Pterospartum tridentatum (L.) Willk. decoctions of dried inflorescences are used in Portugal due to their claimed beneficial properties for various health disorders. To disclose the potential contribution of its polysaccharides to health benefits, in this work, hot water extracts from P. tridentatum inflorescences were prepared and fractionated by ethanol precipitation and anion exchange chromatography. The fraction rich in acetylated galactomannans evidenced an increase in nitric oxide (NO) production by macrophages. This activity decreased 60–75% after saponification, confirming that acetylation is an important structural feature for this biological property. In addition, the treatment of pectic polysaccharides with endo-polygalacturonase showed that type-I and type-II arabinogalactans, as well as low molecular weight galacturonans and xyloglucans, may also contribute to macrophage NO production. Thus, the polysaccharides present in P. tridentatum dried inflorescences may contribute to the health beneficial properties frequently attributed to the decoctions of this plant.