Structural elucidation and antidiabetic activity of polysaccharides from the parasitic plant Orobanche cumana

Introduction This study systematically evaluated the therapeutic potential of polysaccharides from the agricultural plant Orobanche cumana for diabetes management. Methods Three polysaccharide fractions (OCP-1, OCP-2, OCP-3) with distinct structural profiles were obtained through sequential extraction using water at room temperature, high-temperature water, and alkaline solution, respectively. Results Among them, the alkaline-extracted OCP-3 exhibited the most favorable properties, which was characterized as a rhamnogalacturonan-I-rich polysaccharide with a low molecular weight of 66,273 Da. OCP-3 demonstrated strong antioxidant activity by effectively scavenging 2,2-diphenyl-1-picrylhydrazyl, hydroxyl, and superoxide anion radicals, and significantly inhibited both α -amylase (IC₅₀ = 98.5 μg/mL) and α-glucosidase (IC₅₀ = 56.1 μg/mL). In streptozotocin-induced type 2 diabetic male C57BL/6 mice, OCP-3 treatment alleviated hyperglycemic symptoms, improved insulin sensitivity, and provided substantial protection against pancreatic, hepatic, and renal damage. Specifically, OCP-3 reduced fasting blood glucose from 31.3 to 17.2 mM and restored insulin levels to 10.34 mU/L, and improved oral glucose tolerance (AUC = 39.83 h·mmol/L), while maintaining an excellent safety profile in toxicological assessment. Discussion These findings not only validate the traditional use of Orobanche cumana but also establish OCP-3 as a safe and effective candidate for diabetes treatment, offering a sustainable approach to valorizing this agricultural plant.