Alkaloids of Papaver libanoticum and their Cytotoxic Activity

Papaver libanoticum (family Papaveraceae) is an endemic Lebanese plant that has not been investigated before. The plant extract was found to possess a potent opioid analgesic activity with characteristic profile that suggest its potential use for the treatment of opioid abuse and withdrawal symptoms. The present study aims at exploring the cytotoxic activities of the plant extract and the isolated alkaloidal compounds. Chromatographic separation of Papaver libanoticum extract resulted in the isolation of; dehydroremerine (1), roemerine (2), berberine (3), alborine (4), remrefidine (5), and mecambrine (6). Their chemical structures were determined based on different recorded spectroscopic data in addition to comparison with those published in literature. The cytotoxic activity of the plant extract and its alkaloids (2-5) were determined by MTT assay on human breast cancer (MCF7) and human colon cancer cells (HCT116). The results indicated that berberine exhibited the highest inhibitory effect against both cell lines with IC 50 of 22 and 106 µM on MCF7 and HCT116 cells, respectively. Other compounds (including the crude extract) showed different dose-dependent inhibitory effects on the two cell lines indicating cell type specificity and suggesting different cell-alkaloid interactions. Further studies are needed to explore the structure-activity relationships (SAR) of alkaloids derived from P. libanoticum .