Wortmannin, an antibiotic produced by Penicillium wortmanni

Wortmannin is an antibiotic isolated from a culture of Penicillium wortmanni Klöcker. It is not antibacterial. In its antifungal properties it is remarkably specific; of thirty-eight fungal species examined in spore germination tests, twenty-one were unaffected by 100 μg./ml., whereas five species (Botrytis allii, B. cinerea, B. fabae, Cladosporium herbarum and Rhizopus stolonifer) were inhibited by concentrations between 0·4 and 3·2 μg./ml. Wortmannin is a neutral substance, m.p. 240^° C, very unstable in aqueous solutions of pH 3–8. It causes a characteristic spiral waving of germ-tubes of B. allii, easily distinguishable from that caused by griseofulvin.