Structural Characterization and Antioxidant Properties of a Novel Polysaccharide Isolated from <i>Gymnopetalum cochinchinense</i>

In this investigation, a novel heteropolysaccharide, denoted as PS-HW1, is isolated from <i>Gymnopetalum cochinchinense</i>. The achieved PS-HW1 polymer exhibits a molecular weight of 1.22 × 10² kDa and composes the residues of d-glucose, d-fructose, and d-galactose in a 1:1:2 ratio. The structure of PS-HW1 is elucidated via gas chromatography-mass spectrometry, infrared spectroscopy, and nuclear magnetic resonance spectroscopy, revealing a backbone consisting of (1→4)-d-glucopyranose, (1→4)-d-galactopyranose, and (1→3)-d-fructopyranose residues. Furthermore, PS-HW1 demonstrates remarkable antioxidant activity, with low IC₅₀ values of 0.88 and 3.51 mg·mL^-1 in the DPPH and ABTS assays, respectively. Its total antioxidant capacity is determined to be 0.2672 ± 0.0042 mg of GA·g^-1 or 0.1765 ± 0.0028 mg of AS·g^-1. Additionally, PS-HW1 shows significant inhibitory effects on nitric oxide, acetylcholinesterase, and cytotoxicity against HepG2, MCF-7, KB, and SK-LU-1 cancer cells. Such findings emphasize the considerable potential of PS-HW1 from <i>G. cochinchinense</i> for pharmaceutical applications.