A Novel Hypoglycemic Polysaccharide DOP 3-1 Purified from Danxia  Dendrobium officinale

Ethnopharmacological relevance Dendrobium officinale is a prized traditional Chinese medicinal herb, which has long been esteemed in clinical practice. Recently discovered in Guangdong Province, Danxia Dendrobium officinale represents a novel germplasm resource. Preliminary studies have demonstrated that its aqueous extract significantly reduces blood glucose levels in diabetic rat models, suggesting its potential application in hypoglycemic therapy.Aim of the study Polysaccharides represent one of the primary active constituents of Danxia Dendrobium officinale, but the structure-function relationship underlying this activity remains unclear and requires further elucidation. Materials and methods Danxia Dendrobium officinale polysaccharides (DOP 3-1) were purified using DEAE-Sepharose Fast Flow and Sephacryl S-200 HR column chromatography. Hypoglycemic effect was evaluated by α-amylase, α-glucosidase inhibition assays and HepG2 insulin-resistant cell model, and IRS1/PI3K/AKT axis-related mRNAs were detected by RT-qPCR.Results DOP 3-1 was found to have the best hypoglycemic activity. DOP 3-1 (144.905 kDa) is mainly composed of D-glucose and D-mannose in a ratio of 3:17. Its backbone is composed of alternating →4)-β-D-Glcp-(1→ and →4)-α-D-Manp-(1→ linkages. In vitro hypoglycemic assays demonstrated that DOP 3-1 effectively inhibited α-amylase and α-glucosidase, with IC50 values of 2.175 mg/mL and 2.727 mg/mL, respectively. At the cellular level, DOP 3-1was found to regulate glucose metabolism via IRS1/PI3K/AKT signaling pathway.Conclusions These findings provide initial insights into the structure–activity relationship and the hypoglycemic mechanism of DOP 3-1.