Antiproliferative activity of new pentacyclic triterpene and a saponin from Ker-Gawl corms supported by molecular docking study.

A new triterpenoidal saponin identified as 3--[β-d-glucopyranosyl-(1 → 2)-β-d-glucopyranosyl-(1 → 4)-β-d-xylopyranosyl]-2β,3β,16α-trihydroxyolean-12-en-23,28-dioic acid-28--α-l-rhamnopyranosyl-(1 → 4)-α-l-rhamnopyranosyl-(1 → 2)-β-d-glucopyranosyl-(1 → 2)-α-l-arabinopyranoside 1 together with a new oleanane triterpene identified as 2β,3β,13α,22α-tetrahydroxy olean-23,28-dioic acid 2 and 6 known compounds (3-8) have been isolated from Ker-Gawl corms. The structural elucidation of the isolated compounds was confirmed using different chemical and spectroscopic methods, including 1D and 2D NMR experiments as well as HR-ESI-MS. Moreover, the cytotoxic activity of the fractions and that of the isolated compounds 1-8 were investigated against five human cancer cell lines (PC-3, A-549, HePG-2, MCF-7 and HCT-116) using doxorubicin as a reference drug. The results showed that the saponin fraction exhibited potent cytotoxic activity against the five human cancer cell lines, whereas the maximum activity was exhibited against the PC-3 and A-549 cell lines with the IC values of 1.13 and 1.98 μg mL, respectively. In addition, compound 1 exhibited potent activity against A-549 and PC-3 with the IC values of 2.41 μg mL and 3.45 μg mL, respectively. Interestingly, compound 2 showed the maximum activity against PC-3 with an IC of 2.01 μg mL. These biological results were in harmony with that of the molecular modeling study, which showed that the cytotoxic activity of compound 2 might occur through the inhibition of the HER-2 enzyme.