The somatic mutation and recombination test (SMART) in wing cells of Drosophila melanogaster was used to test the mutagenic and recombinogenic activities of five aporphinoid alkaloids isolated from Ocotea acutifolia: thalicminine (1), (+)-dicentrine (2), (+)-ocoteine (3), (+)-6S-ocoteine N-oxide (4), and (+)-leucoxine (5). Third-stage larvae derived from the standard cross with wing cell markers mwh and/or flr(3) were treated chronically. The frequencies of mutant spots observed in marked heterozygous descendants revealed significant dose-dependent genotoxicity for alkaloids 1-4; compounds 1 and 2 were the most active. Alkaloids 1-4 also induced mitotic recombination. The presence of a methoxyl group at C-3 (as in compound 3) lowers its genotoxic effect relative to that of unsubstituted analogue 2, and the introduction of an N-oxide functionality (3 vs. 4) further reduces genotoxicity. The very planar conformation of oxo-aporphine alkaloid 1 may account for its higher genotoxicity vs. its less-planar analogues 3 and 4. As previously reported for (+)-dicentrine (2), alkaloids 1, 3, and 4 may also be DNA intercalating agents, interfering with the catalytic activity of topoisomerases.

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