Insulin-Mimetic Selaginellins from Selaginella tamariscina with Protein Tyrosine Phosphatase 1B (PTP1B) Inhibitory Activity

As part of an ongoing search for new antidiabetic agents from medicinal plants, three new (2, 4, and 5) and two known selaginellin derivatives (1 and 3) were isolated from a methanol extract of Selaginella tamariscina. The structures of the new compounds were determined by spectroscopic data analysis. All isolates showed strong glucose uptake stimulatory effects in 3T3-L1 adipocyte cells at a concentration of 5 mu M. Furthermore, these compounds were found to possess inhibitory effects on PTP1B enzyme activity with IC50 values ranging from 4.6 +/- 0.1 to 21.6 +/- 1.5 mu M. Compound 2 showed the greatest potency, with an IC50 value of 4.6 +/- 0.1 mu M, when compared with the positive control (ursolic acid, IC50 = 3.5 +/- 0.1 mu M). Therefore, these selaginellin derivatives may have value as new lead compounds for the development of agents against type 2 diabetes.