Protein tyrosine phosphatase 1B inhibitory activities of ursane-type triterpenes from Chinese raspberry, fruits of Rubus chingii

Protein tyrosine phosphatase 1 B(PTP1 B) has led to an intense interest in developing its inhibitors as anti-diabetes, anti-obesity and anti-cancer agents. The fruits of Rubus chingii(Chinese raspberry) were used as a kind of dietary traditional Chinese medicine. The methanolic extract of R. chingii fruits exhibited significant PTP1 B inhibitory activity. Further bioactivity-guided fractionation resulted in the isolation of three PTP1 B inhibitory ursane-type triterpenes: ursolic acid(1), 2-oxopomolic acid(2), and 2α, 19α-dihydroxy-3-oxo-urs-12-en-28-oic acid(3). Kinetics analyses revealed that 1 was a non-competitive PTP1 B inhibitor, and 2 and 3 were mixed type PTP1 B inhibitors. Compounds 1-3 and structurally related triterpenes(4-8) were further analyzed the structure-activity relationship, and were evaluated the inhibitory selectivity against four homologous protein tyrosine phosphatases(TCPTP, VHR, SHP-1 and SHP-2). Molecular docking simulations were also carried out, and the result indicated that 1, 3-acetoxyurs-12-ene-28-oic acid(5), and pomolic acid-3β-acetate(6) bound at the allosteric site including α3, α6, and α7 helix of PTP1 B.

New triterpenoid saponins from the leaves of Ilex chinensis and their hepatoprotective activity

Seven new triterpenoid saponins,including five ursane-type saponins,ilexchinenosides R–V(1–5),and two oleananetype saponins,ilexchinenosides W–X(6–7),with four known triterpenoid saponins(8–11)were isolated from the leaves of Ilex chinensis.Their structures were elucidated by comprehensive spectroscopic 1 D and 2 D NMR and HR-ESI-MS data.Their sugar moieties were determined by HPLC analysis compared with standards after hydrolysis and derivatization.Compounds 1,2,4,9 and 10 exhibited potential hepatoprotective activity against N-acetyl-p-aminophenol(APAP)-induced Hep G2 cell injury in vitro.