As a negative control, other cuttings were treated for 8 h with Hoagland’s solution alone and, as a vehicle control, with Hoagland’s solution (4 h), as well as with Tween 20 (20%,

4 h). After each treatment, the cuttings were allowed to recover for 24 h in Hoagland’s solution; the young inflorescences were collected and fixed in a solution of acetic acid/ethanol (1:3). At least 10 cuttings were scored, and only preparations showing early tetrads were counted. The number of micronuclei in 300 tetrads per slide was counted at a magnification of × 400, and the results are expressed as the percentage GABA inhibition of micronuclei. Six-week-old Balb/c male mice were maintained in a temperature- and humidity-controlled environment (22 ± 2 °C; 55 ± 10% humidity), on a 12/12 h light/dark cycle. Before the experiments, the animals were acclimatized for 1 week, during which

time they had free access to a commercial diet (Purina®) and water. The study was approved by the Animal Research Ethics Committee of the São Paulo State University, College of Pharmaceutical Sciences (res. CEP/FCF/CAr no. 01/2006) Mice were randomly assigned to 9 groups of 8 animals each. Group 1 (negative control) mice received only drinking water (0.6 ml/day by gavage) for 2 weeks before treatment with 0.9% saline solution by i.p. injection. Group 2 (positive control) mice also received only drinking water for 2 weeks but were treated on day 15 with i.p. injections of TSP at 3.75 mg/kg body see more weight (BW). Group 3 mice received 0.6 ml Tween 20 (20%) or Tween 80 (6%) by gavage, for 2 weeks, and were treated CAL-101 clinical trial on day 15 with TSP (3.75 mg/kg BW, i.p. The mice in groups 4–9 were treated by gavage (0.6 ml/day) with solutions of ethanolic extract of C. sylvestris (3.9, 7.5, and 15.0 mg/kg BW; groups 4, 5, and 6, respectively) and casearin X (0.3, 0.6, and 1.2 mg/kg BW; groups 7, 8, and 9, respectively) for 2 weeks, all receiving i.p. injections of TSP (3.75 mg/kg BW) on day 15. Mouse bone marrow was collected 24 h after TSP injection. The micronucleus test was carried out as described by Schmid (1975). All slides

were stained with May–Grunwald Giemsa and coded to avoid observer bias. For each experimental result, 1000 polychromatic erythrocytes (PCEs, immature erythrocytes) were scored in order to determine the percentage of micronucleated PCEs. To assess cytotoxicity, the ratio of PCEs to normochromatic erythrocytes (NCEs, mature erythrocytes) was determined in 200 cells. For the comet assay of mouse blood cells, the experimental design was the same as was that for the micronucleus test in mouse bone marrow. Peripheral blood was collected in heparinized capillary vials and kept on ice until use. In brief, 20 μl of blood was homogenized with low-melting-point agarose, spread on a microscope slide pre-coated with normal-melting-point agarose, and coverslipped.