Controlled biosynthesis of neoviridogriseins, new homologues of viridogrisein. IV. In vitro synergism between neoviridogrisein II and the antibiotics of the mikamycin A group.

Neoviridogrisein II is a homologue of viridogrisein in which the hydroxyproline residue is replaced by proline. Neoviridogrisein II proved to be more active than the parent antibiotic against Gram-positive bacteria and Mycoplasma species. When neoviridogrisein II or viridogrisein was combined with griseoviridin, a non-peptidyl macrocyclic lactone, synergism was observed: maximum synergistic effect was observed for a combination ratio that depended on the test bacterium used. Neoviridogrisein II also exerted synergism when combined with mikamycin A and A-2315A.