Extraction of bioactive alkaloids from Melocactus zehntneri using supercritical fluid - Brandão, G. H. A; Rigo, G; Roque, Alan de Araújo; Souza, A. C. D; Scopel, Marina; Nascimento, Cláudio Augusto Oller do; Tasca, T; Pereira, C G; Giordani, Raquel Brandt (The Journal of Supercritical Fluids, 2017)