In vitro anti-proliferative activity of the Rubia tinctorum and Alkanna tinctoria root extracts in panel of human tumor cell lines

Cancer is a devastating disease and is considered number one killer worldwide. Herbal formulations had played a key role over the past several decades in the development of anti-cancer drugs. Medicinal plants, which are endemic in Jordan, are known for several biological activities in particular their anti-cancer activity. However, the anti-cancer efficacy of the root extracts of Jordanian Rubia tinctorum and Alkanna tinctoria is not yet reported. To address this issue, this study assessed the anti-cancer activity of some root extracts obtained from Jordanian R. tinctorum and A. tinctoria in different tumor cell lines including the tongue, bladder, colon, gastric, lungs, breast, pancreas, and renal tissue origins by modified propidium iodide (PI) based monolayer assay. Among the tested root extracts obtained by different solvent systems, A. tinctoria in 100 % ethanol and methanol showed prominent anti-cancer activity against MDA-MB-231breast cancer cells (IC₅₀: 2.98 μg/ml, IC₇₀: 6.03 μg/ml), and CAL-27 tongue squamous carcinoma cells (IC₅₀: 3.86 μg/ml, IC₇₀: 5.97 μg/ml) respectively. Different solvent root extracts of R. tinctorum exhibited a similar trend of anti-tumor activity in both CAL-27 and MDAMB-231 cells. The anti-proliferative property of the extracts on CAL-27 and MDA-MB-231 cells is unclear. However, it can be concluded that the observed anti-cancer potential can be attributed to the phenolic compounds of the extracts as high polar solvents were used for extraction. The current study forms the rationale for isolating significant amount of anti-cancer active compounds from R. tinctorum and A. tinctoria.