Structure of a polysaccharide from Gastrodia elata Bl., and oligosaccharides prepared thereof with anti-pancreatic cancer cell growth activities

To discover anti-pancreatic cancer cells growth inhibitor, a new water-soluble glucan, WTMA, was isolated from the rhizome of Gastrodia elata Bl. The mean molecular weight of the polysaccharide was estimated to be 7.0 × 105 Da by high performance gel permeation chromatography (HPGPC). The structure of WTMA was characterized by GC, GC–MS, NMR and MALDI-TOF. WTMA was deduced as an α-(1 → 4)-glucan with α-(1 → 4) linked branches attached to O-6 at branch points. Bioactivity tests in vitro indicated that WTMA and its partial acid hydrolysis-derived mixture product, WTMA-AD-O, could significantly inhibit the proliferation of pancreatic cancer cells. However, WTMA-DE, the degraded polysaccharide without branch chain by isoamylase, did not inhibit the proliferation of pancreatic cancer cells. Thus side chain on WTMA was deduced to be required for the anti-cancer cell activity. Further study demonstrated that WTMA and all of its hydrolysis products had no inhibition effect on liver LO2 cells.