Fiscalins: new substance P inhibitors produced by the fungus Neosartorya fischeri. Taxonomy, fermentation, structures, and biological properties.

Three new compounds, named fiscalins A, B, and C, were found in culture broth produced by a Neosartorya fischeri. These compounds inhibit the binding of radiolabeled substance P ligand to the human neurokinin (NK-1) receptor, with Ki values of 57, 174, and 68 microM, respectively. Detailed spectroscopic and amino acid analyses led to the elucidation of structures for the three fiscalins. The structures contain an indolyl moiety linked to an athranilic acid derived tricyclic system. The absolute configuration of fiscalin A was determined by X-ray crystallography and chiral amino acid analysis. The presence of fiscalins was detected directly in crude cellular extracts using LC-MS methods.