The authors thank to FAPERGS/CNPq (Programa PRONEX–process no. 10/0012-7) for financial support, CNPq (A.V.Z.—process no. 135999/2008-1; M.M.S. and M.G.R.V.) and CAPES (A.J.) for their scholarships. We thank Janaina A. Barbará for her careful experimental work. We also thank Refinaria Alberto Pasqualini—REFAP S.A. for the donation of AVK