Isolation and characterization of three new anti- proliferative Sesquiterpenes from Polygonum barbatum and their mechanism via apoptotic pathway

Background: The emergence of chemoresistant cancers and toxicity related to existing chemotherapeutic agents, demand the search for new pharmacophore with enhanced anti-cancer activity and least toxicity. For this purpose, three new sesquiterpenes were isolated from ethyl acetate fraction of the aerial parts of the plant Polygonum barbatum and evaluated for their anti-cancer potential. Methods: The structural elucidation and characterization of the isolated compounds 1-3 were performed using various spectroscopic techniques such as mass, UV, IR, and extensive 1D/2D-NMR spectroscopy. Furthermore, the compounds 1-3 were subjected to screening of anti-cancer activity against different cell lines followed by brief analysis of apoptotic and anti-angiogenic potentials of the potent hit against non-small cell lung carcinoma cell line. Results: All the compounds 1-3 were subjected to anti-proliferative potential against non-small cell lung carcinoma (NCI-H460), breast cancer (MCF-7), cervical cancer (HeLa) and normal mouse fibroblast (NIH-3 T3) cell lines. Among these, compound 3 was found to be more cytotoxic against NCI-H460 and MCF-7 cells (IC50 = 17.86 +/- 0.72 and 11. 86 +/- 0.46 mu M respectively). When compared with the standard drug cisplatin compound 3 was found to have more potent activity against NCI-H460 (IC50 = 19 +/- 1.24 mu M) as compared to MCF-7 cell lines (IC50 = 9.62 +/- 0.5 mu M). Compound 3 induced apoptosis in NCI-H460 cells in a dose dependent manner. It significantly downregulated, the expression of antiapoptotic (BCL-2 L1 and p53) and increased the expression of pro-apoptotic (BAK and BAX) genes. Besides apoptosis, it also significantly reduced the cell migration and downregulated the angiogenic genes (i.e. VEGF and COX-2), thereby, inhibiting angiogenesis in NCI-H460 cells. Conclusion: Compound 3 possesses potent anti-proliferative potential as well as induced apoptosis and inhibited the cell migration of the cancerous cells by altering the gene expression, responsible for it.