Determination of Combretastatin A-4 in Combretum leprosum

Species of Combretum are known to contain powerful anticancer compounds. Combretastatins, a group of stilbenes with anti-tubulin and hence antimitotic activity have been isolated from Combretum caffrum Eckl. et Zeyh. [1]. Since Combretastatin A-4 is one of the active substances, we developed a method based on LC-ESI-MS/MS for screening of this compound within Brazilian Combretaceae family plants. The selected plant for this study Combretum leprosum was collected in Ceará State, Brazil. Leaves, stems and flowers were extracted with the following solvents: methylene dichloride, tetrahydrofuran, and acetone. Extracts were submitted to a clean-up step using silica cartridges. The extracts were analyzed using C-18 column, gradient elution, electrospray interface and full scan mode. The compound eluted in 16min and M/Z 317.2g mol^–1 was attributed to Combretastatin A-4 since the standard showed a similar retention time and M/Z. Tetrahydrofuran was the most efficient solvent for extraction. Combretastatin A-4 was detected in all parts of the plant, but the major concentration was found in the leaves. LC-ESI-MS/MS has become an important tool for screening of biologically active substances in plants. References [1] Pettit GR, et al. (1989) Experientia 45: 209.