The same profile was observed when we assessed the antimutagenicity of C. sylvestris ethanolic extract and of caseargrewiin F against cyclophosphamide, as previously reported by Oliveira et al. (2009). Considering that caseargrewiin F and casearin Cetuximab in vivo X are clerodane diterpenes, these phytochemicals probably contribute to the DNA damage protection observed in ethanolic extract.

Cyclophosphamide also forms adducts with DNA (Mirkes et al., 1984), as do some PAHs in extractable TSP (Umbuzeiro et al., 2008b), which suggests that one possible mechanism of action of C. sylvestris ethanolic extract is the reduction of DNA adduct formation. One of the consequences of DNA adduct formation is the clastogenic effect. When a sample such as C. sylvestris ethanolic extract

is able to decrease the number of micronuclei, it acts against irreparable DNA damage, which is manifested Trichostatin A mouse as chromosome aberrations or aneugenic effects, including clastogenicity ( Scolastici et al., 2008). However, the comet assay detects primary DNA lesions that are reparable ( Scolastici et al., 2008). In the present study, C. sylvestris ethanolic extract and casearin X both reduced the extent of such damage. Given that casearin X, a clerodane diterpene, did not reduce the percentage of micronuclei, another class of compounds must be responsible for this effect of C. sylvestris ethanolic extract. The essential oil of C. sylvestris has also been shown to protect DNA from clastogenic damage, having been found to contain monoterpenes and sesquiterpenes ( Sousa et al., 2007). Oliveira et al. (2009) identified sesquiterpenes

and clerodane diterpenes in the ethanolic extract of C. sylvestris. Of the 15 sesquiterpenes identified in the ethanolic extract, 13 had previously been identified in the essential oil ( Esteves et al., 2005 and Sousa et al., 2007). The protective effect of C. sylvestris ethanolic extract against irreparable DNA damage might be related also to its sesquiterpene Selleckchem HA-1077 content. In the present study, we observed that C. sylvestris ethanolic extract and casearin X have chemopreventive activity against DNA damage induced by TSP emitted from sugarcane burning. Our results suggest that C. sylvestris extract and diterpenes can act by different mechanisms to protect DNA against damage, including repairable and non-repairable damages. This work was supported by grants from the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP, São Paulo Research Foundation; Grant no. 2005/58472-9 to A.M.P and Grant no. 2006/50892-1 to C.M.C.), from the Biota-FAPESP Program (Grant no. 2003/02176-7 to V.S.B.), from the BIOprospecTA Program (Grant no. 2004/07932-7 to D.H.S.S. and A.J.C), and from the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, National Council for Scientific and Technological Development; Grant no. 305615/2006-8 to C.P.S.; scholarship grants to A.R.C. and A.G.S.) The authors declare no conflicts of interest.