Abstract
Integerrimine (ITR), a pyrrolizidine alkaloid from Senecio brasiliensis, was tested for genotoxicity using the wing somatic mutation and recombination test (SMART) in Drosophila melanogaster. The compound was administered by chronic feeding (48 hours) of 3-day-old larvae. Two different crosses involving the markers flare (flr) and multiple wing hairs (mwh) were used, that is, the standard (ST) cross and the high bioactivation (HB) cross, which has a high cytochrome P450-dependent bioactivation capacity. In both crosses, the wings of two types of progeny were analyzed, that is, inversion-free marker heterozygotes and balancer heterozygotes carrying multiple inversions. ITR was found to be equally potent in inducing spots in a dose-related manner in the marker heterozygotes of both crosses. This indicates that the bioactivation capacity present in larvae of the ST cross is sufficient to reveal the genotoxic activity of ITR. In the balancer heterozygotes of both crosses, where all recombinational events are eliminated due to the inversions, the frequencies of induced spots were considerably reduced which documents the recombinagenic activity of ITR. Linear regression analysis of the dose response relationships for both genotypes shows that 85% to 90% of the wing spots are due to mitotic recombination.
