Protein Tyrosine Phosphatase 1B Inhibition and Glucose Uptake Potentials of Mulberrofuran G, Albanol B, and Kuwanon G from Root Bark of Morus alba L. in Insulin-Resistant HepG2 Cells: An In Vitro and In Silico Study

Type II diabetes mellitus (T2DM) is the most common form of diabetes and has become a major health problem across the world. The root bark of Morus alba L. is widely used in Traditional Chinese Medicine for treatment and management of diabetes. The aim of the present study was to evaluate the enzyme inhibitory potentials of three principle components, mulberrofuran G (1), albanol B (2), and kuwanon G (3) in M. alba root bark against diabetes, establish their enzyme kinetics, carry out a molecular docking simulation, and demonstrate the glucose uptake activity in insulin-resistant HepG2 cells. Compounds 1–3 showed potent mixed-type enzyme inhibition against protein tyrosine phosphatase 1B (PTP1B) and α-glucosidase. In particular, molecular docking simulations of 1–3 demonstrated negative binding energies in both enzymes. Moreover, 1–3 were non-toxic up to 5 µM concentration in HepG2 cells and enhanced glucose uptake significantly and decreased PTP1B expression in a dose-dependent manner in insulin-resistant HepG2 cells. Our overall results depict 1–3 from M. alba root bark as dual inhibitors of PTP1B and α-glucosidase enzymes, as well as insulin sensitizers. These active constituents in M. alba may potentially be utilized as an effective treatment for T2DM.