Chemical composition of volatile oil from Citrus limettioides and their inhibition of colon cancer cell proliferation

Volatile oil from Palestine sweet lime (PSL) was analyzed for their chemical constituents. A total of 24 compounds were identified in hydro-distilled oil by GC–MS with electron impact mode using Zebron (ZB)-5 and ZB wax columns. The PSL volatile oil included 13 monoterpenes, 9 sesquiterpenes, one acyclic ester and one straight chain hydrocarbon. Four compounds namely d-limonene, myrcene, citronellal and β-citronellol were further confirmed by NMR spectral analysis. In vitro treatment of PSL volatile oil exhibited dose dependent inhibition of colon cancer (SW480) cell proliferation. Induction of apoptosis by the PSL volatile oil was confirmed through Annexin V staining indicating translocation of phosphatidylserine from inner to outer leaflet of plasma membrane, upon incubation of cells with volatile oil at 50 μg/mL. Treatment with PSL volatile oil suppressed the expression of both Cox-2 and IL-6 suggested the potential inhibition of inflammation and activation of apoptosis in human SW480 colon cancer cells. Suppression of Cox-2 and IL-6 expression in the cells treated with PSL volatile oil were significant compared to treatment with d-limonene (50 ppm), one of the major constituent of citrus volatile oils. This is the first report on chemoprofiling and anti-proliferative activities of volatile oil from PSL.