Citrus aurantium L. (Rutaceae), commonly known as bitter orange, is used in folklore medicine for the treatment of cancer, diabetes, malaria, painful swellings, typhoid and wounds [1]. In our search for cytotoxic agents from natural sources, we have recently carried out an ethnobotanical survey of plants used for cancer treatment amongst the Ijebu ethnic group of South-Western Nigeria, and C. aurantium has been frequently mentioned as a cancer remedy by several traditional healers.
The ground bark of this plant was Soxhlet-extracted, successively, with n-hexane, dichloromethane and methanol. As the dichloromethane extract showed significant cytotoxic activity (IC50 = 11.5 – 14.3 µg/mL) against the breast (MCF7), the cervix (HeLa) and the urinary bladder (EJ138) carcinoma cells in the MTT assay, it was subjected to Vacuum Liquid Chromatography (VLC) to obtain six (F1-F6) different fractions. Since F2-F3 displayed the highest activities amongst the fractions (IC50 = 8.55 – 10.38 µg/mL), the combined fractions were subjected to column chromatography and repeated preparative thin layer chromatography on silica gel leading to the isolation of an acridone alkaloid, citracidone-1. The structure of the alkaloid was elucidated by spectroscopic means. It could be assumed that citracidone-1, at least to a certain extent, accounts for the cytotoxic activity of C. aurantium, as its cytotoxic activity was documented in a previous study[2]. This study has demonstrated the cytotoxic property of C. aurantium and further investigations on citracidone-1 in relation to its anticancer potential and possible mechanism of action are underway.
References:
1. Arias BA, Ramón-Laca L. Pharmacological properties of citrus and their ancient and medieval uses in the Mediterranean region. J. Ethnopharmacol. 2005; 97: 89-95
2. Teng WY, Huang YL, Shen CC, Huang RL, Chung RS, Chen CC. Cytotoxic acridone alkaloids from the stem bark of Citrus maxima. J. Chin. Chem. Soc. 2005; 52: 1253–1255