Working with Streptomyces sp. MA406-A-1, effects of addition of various amino acids on the production of formycin were examined. In replacement culture, it was confirmed that lysine, aspartate or glutamate stimulates the production of formycin and carbon molecules in these amino acids incorporated efficiently into formycin. It is estimated that biosynthesis of formycin in this organism is closely related to lysine metabolism but not to biosynthesis of purine nucleosides. Formycin was originally isolated as an antitumor antibiotic from the culture filtrates of Nocardia interforma1) and identified as 7-amino-3-/3-D-ribofuranosyl-lH-pyrazolo-[4, 3d] pyrimi-dine2-7). This antibiotic, having been also found in cultured broth of Streptomyces lavendulae8) or S. gummaensis9), is one of microbial products which contain an unusual C-riboside linkage in their molecules. The other natural C-riboside products of microorganisms are formycin B2'8.10) oxoformycin B11,12), pseudouridine13-15), showdomycin16-18) pyrazomycin19-22) and minimy-cin23,24). Formycin, formycin B and oxoformycin B are pyrazolopyrimidine nucleosides and structural analogs of adenosine, inosine and xanthosine, respectively. Formycin has been found

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A carcinostatic principle was isolated from the fig homogenate and identified as benzaldehyde .1•`3) Dur ing the purification process, the active principle was

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