Structural characterization of an arabinogalactan rich fraction from Bauhinia forficata Link leaves and evaluation of its effect on THP-1 macrophages

Bauhinia forficata is a medicinal plant known as cow's paw, used for many purposes. Although there are studies that aimed to elucidate compounds from the plant leaves, there is no information about its polysaccharides. This study intended to obtain a polysaccharide rich fraction from its leaves, structurally characterize the water-soluble polysaccharides, as well as evaluate their effect on THP-1 cells. From the aqueous extract, followed by purification processes, a polysaccharide fraction (TCA-S) was obtained, constituted mainly of arabinose and galactose. Bidimensional NMR (13C/1H, HSQC) and methylation analyses identified type I and type II arabinogalactans, arabinan and starch as the major polysaccharides of the fraction. TCA-S was then submitted to starch removal process and renamed as TCA-Sα. TCA-Sα (2 to 500 μg/mL) was not cytotoxic to THP-1-cells and exhibited an immunostimulatory effect by increasing the secretion of nitric oxide and both pro-inflammatory cytokine IL-1β and anti-inflammatory cytokine IL-10. Immunomodulatory effect on IL-6 secretion was observed when macrophages were treated with TCA-Sα at 500 μg/mL. Additionally, the ratio between the concentrations of pro and anti-inflammatory cytokines produced by LPS-treated cells was higher than that produced by LPS plus TCA-Sα treated ones, suggesting that the polysaccharide fraction could modulate the LPS inflammation effects. •A polysaccharide fraction (TCA-S) was obtained from Bauhinia forficata Link leaves.•TCA-S contains type I and II arabinogalactans, arabinan and starch.•The starch-free polysaccharide fraction (TCA-Sα) induced IL-1β, IL-10 and nitric oxide secretion by THP-1 macrophages.•TCA-Sα showed immunomodulatory effect on LPS-stimulated macrophages.