Natural and semi-synthetic clerodanes of Croton cajucara and their cytotoxic effects against Ehrlich carcinoma and human K562 leukemia cells

Abstract

The clerodane-type diterpene, trans-dehydrocrotonin (1) the major component of Croton cajucara has shown striking correlation with its therapeutic use in traditional folk medicine. Phytochemical investigations led to the isolation of the metabolites 1, cajucarinolide (6), isocajucarinolide (7), trans-crotonin (2), trans-cajucarin B (3), cis-cajucarin B (4), trans-cajucarin A (5), N-methyltyrosine, vanillic acid and 4-hydroxy-benzoic acid. 6 and 7 were synthesized in good yield by regiospecific oxidation of 1 using singlet-oxygen. All clerodanes were studied for their cytotoxic effects against human K562 leukemia and Ehrlich carcinoma cells. Ehrlich carcinoma assays with IC 50= 166 μM (1), 164 μM (2), 65 μM (6) and 10 μM (7) related to cell growth inhibitory effects were dose dependent. Furthermore, moderate cytotoxic activity against K562 leukemia cells was observed with IC50= 38 μM (3), 33 μM (5), 36 μM (6) and 43 μM (7). The semi-synthetic 2, 6 and 7 showed similar results when compared to the corresponding natural clerodanes. ©2007 Sociedade Brasileira de Química.