Antiproliferative activity of methanol extracts of four species of Croton on different human cell lines - Savietto, Jóice P; Furlan, Cláudia Maria; Motta, Lucimar B; Salatino, Maria Luiza Faria; Carvalho, João E; Ruiz, Ana Lúcia T. G; Salatino, Antonio; Santos, Deborah Yara Alves Cursino dos (Revista Brasileira de Farmacognosia=Brazilian Journal of Pharmacognosy, 2013)