As described in the first report¹⁾ of this series, a Streptomyces S-2-210 resembling Str. aureus was found to produce antibiotics that seemed to belong to quinoxaline antibiotics. From culture of the strain, a mixture of antibiotics was easily crystallized, and the main component named as triostin C was isolated by column chromatography. Two other minor components named as triostins A and B were detected on paperchromatogram, but they have not been isolated yet.

It seemed that triostins A, B and C were quite closely related to one another. They also had many similar properties to those of other quinoxaline antibiotics, but they differed from others in some properties. The crystal preparation of a mixture of triostins A, B and C obtained on the way of isolating triostin C is designated as “triostin complex” in this paper.

This paper deals with the isolation procedures, the physical and chemical properties, and the biological properties of triostin C.