PTP1B and α-glucosidase inhibitors from Selaginella rolandi-principis and their glucose uptake stimulation

As part of an ongoing search for new protein tyrosine phosphatase 1B inhibitors and glucose uptake stimulators from nature, a new coumarin, selaginolide A (1) and four known isoflavones (2‒5) were isolated from the ethanol extract of a Vietnamese medicinal plant Selaginella rolandi-principis. The chemical structures of the isolates were elucidated by extensive analysis of spectroscopic and physicochemical data. Compounds 3‒5 have been identified from Selaginella genus for the first time. The antidiabetic properties of the isolates (1‒5) were investigated using in vitro assay on 2-NBDG uptake in 3T3-L1 adipocytes and against PTP1B and α-glucosidase enzyme activities as well. Compounds 1 exhibited the most potency with inhibitory IC₅₀ values of 7.40 ± 0.28 and 7.52 ± 0.37 µM against PTP1B and α-glucosidase, respectively. Compounds 3 and 5 possessed potential inhibitions on PTP1B enzyme with IC₅₀ values of 23.02 ± 1.29 and 11.08 ± 0.92 µM and moderate inhibitions on α-glucosidase with IC₅₀ values of 36.47 ± 1.87 and 55.73 ± 2.58 µM, respectively. Compounds 2 and 4 showed weak PTP1B inhibitory activity (IC₅₀ > 30 µM) but displayed remarkable α-glucosidase inhibition with IC₅₀ values of 3.39 ± 0.87 and 9.72 ± 0.62 µM, respectively. Furthermore, ursolic acid as a positive control (IC₅₀ 3.42 ± 0.26 µM) and compounds 1 and 5 acted as mixed-competitive inhibitors against PTP1B enzyme with K_i values of 6.46, 10.28, and 15.01 µM, respectively. In addition, compounds 1 and 5 also showed potent stimulatory effects on 2-NBDG uptake at a concentration of 10 µM. The obtained result might suggest the potential of new coumarin (1) as a new type of natural PTP1B and α-glucosidase inhibitor for further research and development of antidiabetic and obese agents.Graphic abstract.

Keywords: 2-NBDG; Coumarin; Diabetes; Isoflavone; PTP1B; Selaginella rolandi-principis; Selaginellaceae; α-glucosidase.