The present invention relates to novel active compounds named Citrullimycines, which are obtainable by cultivation of Streptomyces sp. ST 101396 (DSM 13309), and to their pharmaceutically acceptable salts and derivatives. The present invention further relates to a process for the production of the Citrullimycines, to the microorganism Streptomycetes sp. ST 101396 (DSM 13309), to the use of the Citrullimycines and their pharmaceutically acceptable salts and derivatives as pharmaceuticals, for example as inhibitors of the neurotensin receptor, and to pharmaceutical compositions comprising Citrullimycines or a pharmaceutically acceptable salt or derivative thereof.