Grahamimycins: antibiotics from Cytospora sp. Ehrenb. W.F.P.L. 13A.

Aerobic fermentation of cultures of Cytospora sp. Ehrenb. W.F.P.L. 13A produces a group of novel, broad-spectrum, dilactone, macrocyclic antibiotics. These compounds, named grahamimycins, were isolated from the culture medium by extraction with organic solvents and separated by chromatography. Three active components have been obtained in crystalline form and have been designated grahamimycins A, A1, and B. The most active of these, grahamimycin A, exhibited activity against 36 species of bacteria, 8 species of blue-green algae (cyanobacteria), and 2 species of green algae, and antifungal activity against 5 fungi. Studies on the growth of the Cytospora with respect to formation of antibiotic activity, and the isolation, characterization, and structure elucidation of the grahamimycins are described. These studies indicate that the grahamimycins are distinct from other known antibiotics and represent a new class of antibiotic structures.