LL-E19085alpha

A new family of antibacterial antibiotics has been isolated from Micromonospora citrea. The compounds, designated citreamicins alpha, beta, gamma, zeta and eta are of the polycyclic xanthone structure type. Their isolation, characterization and structure determination are presented.

In vitro antibacterial activity of 429 clinical isolates of gram-positive cocci was tested against citreamicin-alpha (LL-E 19085-alpha) by the agar dilution method. The microorganisms consisted of 313 isolates of staphylococci and 116 strains of streptococci. In vitro activity of citreamicin-alpha was compared with ampicillin, augmentin, cephalothin, erythromycin and vancomycin. MICs of citreamicin-alpha for staphylococci ranged between 0.12-4.0 micrograms/ml and 0.03-0.12 micrograms/ml for Streptococcus pyogenes. Enterococci, however, were relatively more resistant, requiring 2.0 micrograms/ml of this drug to inhibit 64% of the 62 isolates tested. In vitro activity of this antibacterial agent was far superior to that of ampicillin, augmentin, cephalothin and erythromycin, but equal to or slightly inferior to that of vancomycin.

When the citreamicin-producing organism Micromonospora citrea NRRL 189351 was incubated in the presence of the methylation inhibitors sinefungin or aminopterin, biosynthesis of the zeta component was stimulated approximately 20 to 200-fold above the level normally produced. Inhibition of a second methylation reaction, which is superficially very similar to the first, was not detected. Other known methylation inhibitors failed to yield any change in the natural pattern of citreamicins produced. This approach is an excellent route for preparing citreamicin zeta, which can be used as a substrate for semi-synthesis or for further biosynthetic studies.