Phytochemicals Isolated from Leaves of Chromolaena odorata : Impact on Viability and Clonogenicity of Cancer Cell Lines

The leaves of Chromolaena odorata (Asteraceae) are exploited extensively in West and Central African ethnopharmacy for the treatment of a wide range of conditions, despite this being a non-native species established in the last 50 years. With the objective of seeking bioactive principles, the nonvolatile compounds, an ethanolic (80% v/v) extract was made and fractionated. From the hexane-soluble fraction, three compounds were isolated. Two of these, 5-hydroxy-7,4'-dimethoxyflavanone and 2'-hydroxy-4,4',5',6'-tetramethoxychalcone, have previously been identified in C. odorata leaves. The third was fully characterised spectroscopically and found to be 1,6-dimethyl-4-(1-methylethyl)naphthalene (cadalene), not previously isolated from the Asteraceae. All three compounds were tested for their cytotoxicity and anticancer properties. 2'-Hydroxy-4,4',5',6'-tetramethoxychalcone was found to be both cytotoxic and anticlonogenic at 20 µm in cell lines Cal51, MCF7 and MDAMB-468, and to act synergistically with the Bcl2 inhibitor ABT737 to enhance apoptosis in Cal51 breast cancer cells.