Isolation, characterization and in vitro anticancer activity of an aqueous galactomannan from the seed of Sesbania cannabina.

As a pioneer plant, Sesbania cannabina is cultivated on a large scale for saline-alkali land improvement in China. Here, a native galactomannan (GalM) and a series of its hydrolysates (GalM40, GalM50 and GalM65) were obtained from S. cannabina seed by water extraction, β-mannanase hydrolysate and ethanol precipitation. As elucidated by HPAEC, NMR, FT-IR and HPGPC, GalM was characterized as a β-1,4-linked d-mannose polymer with single α-1,6-linked d-galactose side chain in a 2.4:1M ratio, and had a molecular weight of 1.42×106Da. MTT assay showed that these four fractions had significant inhibitory effect on A549, Hela, HepG2 and MCF-7 in a dose-dependent manner, and that GalM40 with second-highest MW (1.47×104Da) possessed higher activity amongst those fractions. Such strong inhibition effect on the growth of human cancer cells might derive from its ability to increase caspase-12 expression, as revealed from immunohistochemical analysis. In sum, this paper characterizes the molecular structure of S. cannabina galactomannan with anticancer activity, and this new knowledge will provide a basis for its further structure-properties research and ultimately, develop new possibilities for its use in high-value applications, such as functional food.