Structural elucidation of a novel xylylogalactan from Alpinia oxyphylla and the GREM1-binding-associated anti-colorectal cancer activity of its sulfated derivative.

While extracts of Alpinia oxyphylla Miq. have demonstrated promise in the prevention and treatment of colorectal cancer (CRC), the specific bioactivity and underlying molecular mechanisms of its constituent polysaccharides remain largely elusive. Inspired by the capacity of heparin to modulate the BMP signaling pathway through sulfate-mediated binding to the antagonist GREM1, we hypothesized that the targeted introduction of sulfate groups into A. oxyphylla polysaccharides would confer analogous GREM1-binding affinity and anti-tumor efficacy. In this study, a novel homogeneous polysaccharide, YZR111 (191.9 kDa), was isolated and purified. Structural elucidation revealed a well-defined fine structure characterized by a xylylogalactan backbone substituted with arabinoxylan side chains, with terminal glucuronic acid (T-GlcA) residues predominantly localized at branch termini. The subsequent sulfated derivative, SYZR111, exhibited robust, dose-dependent inhibitory activity against multiple CRC cell lines (SW1116, SW620, HCT-116, and HT-29) over the concentration range of 0.008-1 mg/mL. Notably, SYZR111 achieved an inhibition rate of approximately 70% in HCT-116 cells, significantly outperforming the native YZR111. Surface plasmon resonance (SPR) analysis confirmed a high-affinity interaction between SYZR111 and GREM1 (KD: 6.14 × 10-8 M), suggesting that SYZR111 potentiates the antagonistic function of GREM1 to attenuate BMP signaling, thereby suppressing CRC cell proliferation, migration, and invasion. This study provides the first detailed structural elucidation of YZR111 and identifies sulfation as the critical modification for targeting GREM1 to exert anti-CRC activity, offering a novel paradigm for the development of natural polysaccharide-derived BMP signaling inhibitors.