Partial purified extract consisted of a mixture of oligosaccharides having molecular weights of 716, 700, 490 and 474 Da with a degree of polymerisation of 3–4. Pitaya oligosaccharides showed prebiotic properties, which included resistance to acid conditions in human stomach, partial resistance to human salivary a-amylase and the capability to stimulate the growth of lactobacilli and bifidobacteria