Pentacyclic triterpenoids from spikes of Prunella vulgaris L. inhibit glycogen phosphorylase and improve insulin sensitivity in 3T3-L1 adipocytes.

Phytochemical investigation of methanol extract from the spikes of Prunella vulgaris L. led to the isolation of two new pentacyclic triterpenoid glycosides Vulgasides I (1) and II (2) along with 13 known compounds (3-15). Their structures were established on the basis of nuclear magnetic resonance (1D and 2D) and mass spectroscopic data analysis. All the isolated compounds were screened for glycogen phosphorylase inhibitory activity and also evaluated for their effect on insulin sensitivity in 3T3-L1 adipocytes. Two new compounds (1, 2) did not demonstrate the glycogen phosphorylase inhibitory activity, but other compounds (3-11) exhibited varying degrees of glycogen phosphorylase inhibitory activity with IC50 values in the range from 30.69 to 68.85 μM. Compounds 3, 6, 7, 11, and 13 demonstrated markedly increased insulin-mediated glucose consumption in 3T3-L1 adipocytes.