Systematic investigation of a Fraxinus mandshurica seed-derived iridoid glucoside fraction as a novel functional ingredient with anti-diabetic potential.

Fraxinus mandshurica (Oleaceae, Fraxinus) seeds serve as food and condiments in traditional American and European diets. This study provides the first systematic evaluation of the therapeutic effects of F. mandshurica seed extract on T2DM. This study evaluated the effects of F. mandshurica seed extract on glucose-lipid metabolism, hepatorenal function, and gut microbiota in an HFD/STZ-induced T2DM mouse model. Through UPLC-Q-TOF-MS chemical characterization and phytochemical analysis, combined with network pharmacology and molecular docking techniques, potential active components and their corresponding targets were predicted. Critically, the predicted activity of 18 iridoid monomers was confirmed by evaluating their ability to enhance glucose consumption in L02 cells. F. mandshurica seed extract significantly reduced body weight, TC, TG, and blood glucose levels, improved insulin sensitivity and glucose tolerance, and alleviated hepatorenal injury. Additionally, it regulated the gut microbiota by reducing the Firmicutes/Bacteroidetes ratio. Network pharmacology analysis identified AGE-RAGE and TNF signaling as core anti-diabetic pathways. Key active components, including bisandrographolide A, ligstroside, reptoside, oleuropein, fraxoside, koaburside, and mudanpioside D, were identified and selected for molecular docking. The results indicate that these active components form stable ligand-receptor complexes with target proteins (HRAS, MAPK1, HSP90AA1, MMP9 and AKT1) via hydrogen bonds, hydrophobic interactions, π-π stacking and salt bridges. Finally, 18 iridoid glucosides from the F. mandshurica seed were shown to promote glucose consumption, with efficacy ranging from 7.27% to 71.52%. This study reveals that F. mandshurica seeds and their characteristic iridoid components possess promising prospects as candidates for developing natural anti-diabetic therapeutics.