Studies on Antibiotics from Helminthosporium sp. Fungi. VII Siccanin, a New Antifungal Antibiotic Produced by Helminthosporium Siccans

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The investigation of the antimicrobial activity of filtrates of cultures of organisms pathogenic to plants has shown, as previously reported¹⁾, that the fungi belonging to Helminthosporium are the most promising source of new antibiotics. Of this group of fungi, it was reported that six species, Ophiobolus miyabeanus, Helminthosporium turcicum, Ophiobolus heterostrophus, Helminthosporium leersii, Helminthosporium panici-miliacei and Helminthosporium zizaniae, produced ophiobolin,^2,3,4) that under certain cultural conditions Helminthosporium zizaniae yielded zizanin,⁵⁾ a new antibiotic different from ophiobolin, and that pyrenophorin,⁶⁾ a new antibiotic, was produced by Pyrenophora avenae.

This report concerns the study of the effective substance obtained from the BH-34 strain of Helminthosporium siccans. Extraction of the culture filtrate of the BH-34 strain yielded an antibiotic substance in crystalline form which differed from ophiobolin, zizanin and pyrenophorin. Inasmuch as no antibiotic substance produced by Helminthosporium siccans has yet been reported and as its physical and chemical properties as well as its antimicrobial spectrum demonstrate it to be a new antibiotic. This effective substance was named siccanin.

The production, physical and chemical properties and spectrum of antimicrobial activity of this substance are described herein.