•The precise structure of a dragon fruit pulp polysaccharide (DFPP) was identified.•DFPP had a molecular weight of 2.2 × 103 kDa.•→4-β-d-GlcpA-1→, →6-β-d-Galp-1→ and →4-α-l-Rhap-1→ constituted the backbone.•α-l-Araf-1→5-α-l-Araf-1→ formed the branch chain.Dragon fruit is a tropical fruit with good taste. It can bring health benefits to human body. As one of the major bioactive components in this fruit, the polysaccharides might contribute to the health benefits. However, the precise structure information remains unknown. A leading polysaccharide of dragon fruit pulp, DFPP, was purified and identified by NMR and GC–MS. →4-β-d-GlcpA-1→, →6-β-d-Galp-1→ and →4-α-l-Rhap-1→ constituted the backbone and α-l-Araf-1 → 5-α-l-Araf-1→ formed the branch chain. The precise structure was putatively identified as below. The molecular weight was 2.2 × 103 kDa. The structure information of polysaccharides will be helpful to understand this fruit.Figure options

•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.