Aerothionin, a bromotyrosine derivative with antimycobacterial activity from the marine sponge Aplysina gerardogreeni (Demospongia)

Aerothionin and calafianin, two bromotyrosine derivatives isolated from the marine sponge Aplysina gerardogreeni, were evaluated against multidrug-resistant clinical isolates of M. tuberculosis. Antimycobacterial activity of these compounds were tested by the modified microplate Alamar Blue assay against four monoresistant variants of M. tuberculosis H37Rv (rifampin, isoniazid, ethambutol and streptomycin resistant), but only aerothionin was active against all the monoresistant variants of M. tuberculosis H37 Rv at 12.5 μg/mL. Because of this activity, aerothionin was also tested against eight Mycobacterium tuberculosis clinical isolates with different drug-resistance patterns, and nine nontuberculosis mycobacteria species. It was active against all the drug resistant clinical isolates, regardless of their resistance patterns, with minimum inhibitory concentrations from 6.5 to 25 μg/mL. Three out of nine nontuberculosis mycobacteria were inhibited by aerothionin: M. kansasii (50 μg/mL), M. scrofulaceum (100 μg/mL) and M. avium (100 μg/mL).