Abstract

This study elucidates the structure and antioxidant activity of a galactomannan (EGSP) from the unique Chinese endemic species Gleditsia japonica var. delavayi. Structural analysis characterized EGSP as a polysaccharide (1.054 × 10 6  Da) with a backbone of →4)- β -D-Manp-(1 → residues, bearing side chains of α -D-Galp-(1 → 6) at the O-6 position, consistent with its Man:Gal:Glc molar ratio of 70.74:28.28:0.35. In vitro assays demonstrated its potent, concentration-dependent scavenging activity against DPPH•, ABTS• + , and •OH radicals, as well as considerable reducing power. Moreover, in a cellular model, EGSP protected RAW 264.7 macrophages from H 2 O 2 -induced oxidative damage by significantly reducing reactive oxygen species (ROS) and malondialdehyde (MDA) levels, while enhancing the activities of superoxide dismutase (SOD) and catalase (CAT). Mechanistic studies further associated this cytoprotective effect with the activation of the Nrf2 antioxidant signaling pathway. The well-defined structure-activity relationship established herein positions EGSP as a promising natural antioxidant candidate for functional foods and therapeutics.