Gunacin

In a screening program for antibiotics which were antagonized by cysteine, a strain, which was characterized as Ustilago sp., was found to produce a new quinone antibiotic, gunacin. The molecular weight M+ = 348.084 determined by mass spectroscopy, corresponds to a molecular formula of C17H16O8. Further spectroscopic data prove that gunacin is a new antibiotic. The antibiotic possesses a good inhibitory effect against mycoplasmas and Gram-positive bacteria including multi-resistant strains. It also possesses a weak activity against Gram-negative bacteria with the exception of Proteus vulgaris, which is more strongly inhibited. The main activity against fungi is found against Trichophyton mentagrophytes. Gunacin shows an inhibition of the DNA synthesis in vivo, is antagonized by mercapto compounds and possesses an acute toxicity of LD50 = 16 mg/kg i.p. and LD50 = 12 mg/kg i.v. in mice. Against HeLa-cell the antibiotic shows an ED50 = 12.11 microgram/ml. Thirty five microgram/ml of gunacin induces 1,063 interferon units.