Chemical constituents of Papulaspora immersa, an endophyte from smallanthus sonchifolius (Asteraceae), and their cytotoxic activity - Gallo, Margareth Borges Coutinho; Cavalcanti, Bruno Coêlho; Barros, Francisco Washington Araújo; Moraes, Manoel Odorico de; Costa-Lotufo, Letícia Veras; Pessoa, Claudia; Bastos, Jairo Kenupp; Pupo, Mônica Tallarico (Chemistry & Biodiversity, 2010)