A systematic search for solasodine, an important starting material for the partial synthesis of steroidal hormones as well as other potentially bioactive constituents of various Solanum species of Brazil has been undertaken. Thus, the fruits of S. paludosum, S. asperum, S. sessiliflorum and Solanum sp. were found to contain significant amounts of solasodine. The root bark of S. paludosum which showed curare like activity yielded tomatidenol and another yet unidentified alkaloid responsible for the biological activity. The fruits of S. asperum yielded a new spirosolane alkaloid, solaparnaine. The stem bark of S. pseudo-quina showed convulsive and excitatory activity from which (25S)-isosolafloridine was identified as the active principle. In addition, the latter alkaloid was also found to show antimicrobial activity.