Abstract:
Almost all adult leukemia patients suffer from acute myeloid leukemia with around 20,830 new cases and 10,460 deaths expected in the United States in 2015 due to poor prognosis. Daucus carota L. ssp. carota (Apiacea) is a medicinal plant used in folk medicine worldwide. In Lebanon, the plant has been used for the treatment of several ailments including cancer. Earlier studies in our lab revealed that Daucus carota oil extract (DCOE) composition varied significantly between Lebanon and European countries. Also, the oil extract and its fractions were shown to have strong antioxidant and anticancer activities. In the present work, GC-MS was used to study the composition of DCOE obtained from roots, stems, leaves and umbels which are collected from two different regions in Lebanon (North and Mount Lebanon). β-2-himachalen-6-ol, the major component of F2 fraction, was also assessed in opened and closed umbels and at three different altitudes. Daucus carota oil extract was subjected to silica gel column chromatography in order to isolate the major compound β-2-himachalen-6-ol and test its anticancer activity against five AML cell lines: Mono-Mac-1, HL60, KG1, ML2, and U937. Results revealed that the chemical composition of the Lebanese DCOE varied drastically among different plant parts and between different locations. In addition, β-2- himachalen-6-ol seems to be only present in the Lebanese wild carrot, and it is prevalent in closed umbels collected from Mount Lebanon without significant changes with altitude. All AML cells were sensitive to the major compound with Mono-Mac-1 being the most sensitive (12 μg/mL), and U937 the least sensitive (30 μg/mL). Cell cycle analysis using flow cytometry revealed an increase in the sub-G1 population. Analysis of cell death after treatment with various drug concentrations showed that cells were positive for annexin V, PI, and active caspase staining, indicating a caspase dependent apoptotic cell death. There was no sign of cell cycle arrest. Co-incubation of AML cells with β-2-himachalen-6-ol and a MEK1/2 inhibitor (U0126) revealed an additive effect in Mono-Mac-1 and U937; the effect was mild in HL60. In conclusion, Daucus carota chemical composition varies drastically among different locations in Lebanon with β-2-himachalen-6-ol being present mainly in the mature closed umbel. β-2-himachalen-6-ol possesses potent anticancer activity against a panel of AML cells, an effect that may be mediated via a suppression of the MAPK/Erk and PI3K/Akt pathways.
