Structural Characterization and Anti-Inflammatory Effects of Oligosaccharides in Psidium guajava Linn.

Guava (Psidium guajava Linn.) is a tropical fruit rich in carbohydrates, and its polysaccharides have been deeply studied. However, the extraction of guava oligosaccharides and the molecular mechanisms of anti-inflammatory activity are still inadequately explored. Herein, a water-soluble oligosaccharide (GPO) separated from guava was purified and obtained by ultrafiltration and DEAE-52 cellulose column chromatography, with a molecular weight of 1054 Da. Ion chromatography analysis of GPO indicated the presence of glucose and xylose in a ratio of 5:1, respectively. The structure of GPO was characterized by GC-MS, NMR, and MS, deduced as α-d-Glcp-(1,4)-α-d-Glcp-(1,6)-α-d-Glcp-(1,3)-β-d-Glcp-(1,4)-β-d-Xylp-(1,3,6)-α-d-Glcp, with a sulfate ester group bound to carbon 3 of →3,6)-α-d-Glcp-(1→. Bioactivity tests in vitro indicated that GPO (25 μg/mL) could significantly inhibit the release of nitric oxide (NO), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α), exhibiting anti-inflammatory activity. Subsequent metabolomics and ferroptosis-verification experiments further revealed that GPO mediated ferroptosis to exert anti-inflammatory activity on macrophage RAW264.7 cells. Our research introduced an innovative approach for isolating oligosaccharides and provided a detailed elucidation of the structure of GPO, indicating its potential as a natural anti-inflammatory agent.