Ursonic acid from Artemisia montana exerts anti-diabetic effects through anti-glycating properties, and by inhibiting PTP1B and activating the PI3K/Akt signaling pathway in insulin-resistant C2C12 cells

Artemisia is one of the largest genera in the plant family Asteraceae and has long been used in traditional medicine for its antitussive, analgesic, antihypertensive, antitoxic, antiviral, antimalarial, and anti-inflammatory properties. However, the anti-diabetic activity of Artemisia montana has not been broadly studied. The goal of this study was to determine whether extracts of the aerial parts of A. montana and its main constituents inhibit protein tyrosine phosphatase 1B (PTP1B) and α-glucosidase activities. We isolated nine compounds from A. montana including ursonic acid (UNA) and ursolic acid (ULA), which significantly inhibited PTP1B with IC50 values of 11.68 and 8.73 μM, respectively. In addition, UNA showed potent inhibitory activity against α-glucosidase (IC50 = 61.85 μM). Kinetic analysis of PTP1B and α-glucosidase inhibition revealed that UNA was a non-competitive inhibitor of both enzymes. Docking simulations of UNA demonstrated negative binding energies and close proximity to residues in the binding pockets of PTP1B and α-glucosidase. Molecular docking simulations between UNA and human serum albumin (HSA) revealed that UNA binds tightly to all three domains of HSA. Furthermore, UNA significantly inhibited fluorescent AGE formation (IC50 = 4.16 μM) in a glucose-fructose-induced HSA glycation model over the course of four weeks. Additionally, we investigated the molecular mechanisms underlying the anti-diabetic effects of UNA in insulin-resistant C2C12 skeletal muscle cells and discovered that UNA significantly increased glucose uptake and decreased PTP1B expression. Further, UNA increased GLUT-4 expression level by activating the IRS-1/PI3K/Akt/GSK-3 signaling pathway. These findings clearly demonstrate that UNA from A. montana shows great potential for treatment of diabetes and its complications.