Structures of trienomycins A, B and C, novel cytocidal ansamycin antibiotics

The structures of novel antibiotics, trienomycins A, B and C produced by Streptomyces sp. No. 83-16, have been determined on the basis of their spectroscopical and chemical properties. Trienomycins are unique ansamycin antibiotics with a triene and an 1,3,5-trisubstituted benzene moieties in the molecule. The antibiotics possess potent cytocidal activity against HeLa S3 cells at concentrations of 0.005 (trienomycin A), 0.1 (trienomycin C) and 0.2 micrograms/ml (trienomycin B) (IC50 value), respectively. However, trienomycins showed no antimicrobial activity against the bacteria, fungi and yeasts examined with the exception of weak activity versus Piricularia oryzae at a concentration of 1,000 micrograms/ml.