Cucurbitane triterpenoids from Momordica charantia L. and their inhibitory activity against α-glucosidase, α-amylase and protein tyrosine phosphatase 1B (PTP1B)

Momordica charantia L. has been widely used in different countries as a functional food source, particularly as a remedy for type 2 diabetes. In the present study, 21 cucurbitane-type triterpenoids, including two new compounds named charantoside IX and X (1−2), were isolated from the extract of M. Charantia L. Their chemical structures were identified by 1D, 2D-NMR and FT-ICR-MS techniques. Three anti-diabetes target assays of all triterpenoids were carried out, with all compounds exhibiting α-glucosidase inhibitory activity. Particularly, compounds 6, 9 and 11 exhibited excellent α-glucosidase inhibitory activity with IC50 values of 10.19, 28.55, and 20.20 μM, respectively. Some of the tested isolates showed inhibitory activity against the protein tyrosine phosphatase 1B (PTP1B) and α-amylase, with compound 6 exhibiting the strongest activity against PTP1B. These chemical and biological results indicated that cucurbitane triterpenoids in functional foods may represent attractive candidates for regulation of blood glucose levels.