Metal analogues of mycobactin and exochelin fail to act as effective antimycobacterial agents.

Mycobactins and exochelins from mycobacteria formed complexes with many heavy metals in the absence of iron. Although many of these complexes affected the growth of M. tuberculosis and M. avium in laboratory culture medium and in serum the complexes were not stable enough in the presence of iron, which displaced the metal ion, to be of value as specific antimycobacterial agents.