Structural characterization of a broccoli polysaccharide and evaluation of anti-cancer cell proliferation effects

•The precise structure of a broccoli polysaccharide (BPCa) was identified.•BPCa showed anticancer activities.•BPCa could be a candidate for nutraceuticals. Broccoli is a widely consumed vegetable with abundant amount of nutrients, which bring numerous beneficial effects on human health. The structural information of water-soluble polysaccharides in broccoli was eludicated for the first time in this work. A purified polysaccharide fraction (BPCa) was obtained by column chromatography. It comprised of arabinose (Ara), galactose (Gal), rhamnose (Rha) with a molar ratio of 5.3:0.8:1.0. Nuclear magnetic resonnance spectra data revealed that α-l-1,5-Araf and α-l-1,3,5-Araf are present in the backbone, while α-l-Araf terminal was attended in side chain. α-l-1,2-Rhap was found to be linked to α-l-1,5-Araf in heteronuclear multiple bond correlation spectra. The presences of β-d-1,4-Galp and α-d-1,4-GalpA were also detected. Furthermore, BPCa showed significant anti-cancer cell proliferation activities against HepG2, Siha and MDA-MB-231 carcinoma cell lines. The results indicated that BPCa had a good potential to be applied as functional food additives.