Ent-kaurane diterpenoids and other constituents from the stem of Xylopia laevigata (Annonaceae) - Silva, D M; Costa, E V; Nogueira, P CL; Moraes, V RS; Cavalcanti, S CH; Salvador, M J; Ribeiro, L HG; Gadelha, F R; Barison, A; Ferreira, A G (Quim Nova, 2012)