Physicochemical Characterization and In Vitro Hypoglycemic Activity of a Low-Molecular-Weight Extracellular...

Deep-sea microorganisms constitute a valuable source of structurally diverse natural products. In this study, an extracellular polysaccharide was isolated from the deep-sea fungus Beauveria bassiana T2-2 by ultrasonic-assisted hot water extraction followed by Sephadex LH-20 chromatography, yielding a fraction designated BPS-2. Physicochemical characterization revealed that BPS-2 is a glucose-rich polysaccharide (>90% molar ratio) with a weight-average molecular weight of approximately 3.62 kDa and moderate levels of uronic acid (2.84%) and sulfate (3.15%). In vitro enzyme assays demonstrated that BPS-2 inhibited α-amylase and α-glucosidase in a concentration-dependent manner, with an IC₅₀ value of 1.3 × 10^-4 M for α-glucosidase. Within the tested range, its inhibitory activity was stronger than that of Astragalus polysaccharide (APS) but weaker than that of acarbose. In a palmitic acid-induced insulin-resistant HepG2 model, BPS-2 significantly enhanced glucose consumption and increased 2-Deoxy-2-[(7-nitro-2,1,3-benzoxadiazol-4-yl) amino]-D-glucose (2-NBDG) uptake by 44.9% at 0.75 mg/mL without detectable cytotoxicity, suggesting a potential role in improving cellular glucose utilization under insulin-resistant conditions. To the best of our knowledge, this is the first report describing hypoglycemic-related activity of extracellular polysaccharides derived from deep-sea B. bassiana. These findings provide initial evidence linking the structural features of BPS-2 to glucose metabolism-associated bioactivity, while further studies are required to clarify detailed structural characteristics and underlying molecular mechanisms.