Structural elucidation of a novel arabinogalactoglucan from Polygonum multiflorum and its binding to the m6A reader YTHDF2.

Polygonum multiflorum Thunb. (P. multiflorum) is a traditional Chinese medicinal herb with a long history of use, and its polysaccharide constituents have been reported to possess a range of biological activities. Nevertheless, most existing studies have focused on crude polysaccharide fractions or preliminary bioactivity evaluations, leaving the fine structural features and molecular targets of these polysaccharides insufficiently defined. Here, a homogeneous polysaccharide, FM02 (Mw 12.1 kDa), was isolated from P. multiflorum. Structural characterisation indicated that FM02 is a novel arabinogalactoglucan with a backbone of alternating →4)-α-Glcp-(1→ and →4, 6)-α-Glcp-(1→ residues. Branches at the O-6 position of 1, 4, 6-linked glucosyl residues comprise three distinct types: a terminal T-α-Glcp cap, a trisaccharide branch →1)-α-Glcp-(4 → 1)-β-Galp-(3 → 1)-α-Araf, and a longer chain →1)-α-Glcp-(4→[1)-Galp-(4]3→[1)-α-Glcp-(4]4 → 1)-α-Glcp. Affinity pull-down of LX-2 hepatic stellate cell lysates combined with mass spectrometry identified YTHDF2 as a candidate binding protein. Surface plasmon resonance (SPR) detected a concentration-dependent interaction between FM02 and YTHDF2 (KD 5.47 × 10-7 M). Neither the acid-hydrolysis-resistant fraction FM02I nor the released degradation fragment FM02E showed detectable binding to YTHDF2, suggesting that the intact primary structure of the polysaccharide may be required to sustain this interaction. In summary, this study reports for the first time a novel arabinogalactoglucan, FM02, isolated from P. multiflorum, and reveals its potential direct interaction with the m6A reader protein YTHDF2, thereby providing foundational data for further activity screening, mechanistic studies, and related drug development of this polysaccharide.