In vivo growth-inhibition of sarcoma 180 by piplartine and piperine, two alkaloid amides from Piper - Bezerra, D P; Castro, F O; Alves, A PNN; Pessoa, C; Moraes, M O; Silveira, E R; Lima, M AS; Elmiro, F JM; Costa-Lotufo, L V (Braz J Med Biol Res, 2006)