Structural characterization of a galactan from Ophiopogon japonicus and anti-pancreatic cancer activity of its acetylated derivative

A galactan ROH05 was isolated from the roots of Ophiopogon japonicus and further purified by DEAE Sepharose™ Fast Flow columns. The molecular weight of ROH05 was estimated to be 16.7 kDa. ROH05 was composed of galactose only. According to the methylation analysis and the results of IR and NMR spectra, the backbone of ROH05 was composed of 1, 4-linked β-D-galactose and 1, 4, 6-linked β-D-galactose, while the branch of this polysaccharide was terminal-linked β-D-galactose attached at C-6 position of 1, 4-linked β-D-galactose directly. The acetylated galactan, ROH05A was prepared by the acetic anhydride-pyridine method. The acetylation modification mainly occurred at C-2, C-3 and C-6 positions of 1, 4-linked β-D-galactose, and C-6 position of terminal-linked β-D-galactose. Bioactivity test showed that ROH05A might inhibit both BxPC-3 and PANC-1 pancreatic cancer cells growth in a dose-dependent manner without significant toxicity to LO2 cells. In addition, the cells apoptosis was triggered since cleaved caspase-3 and FasL were activated while p53, p21, Bax expression were up-regulated by ROH05A as well.