Bildung und Isolierung des Phytotoxins Tentoxin aus Alternaria alternata

A chlorosis‐inducing phytoeffector from culture filtrate of Alternaria alternata (FRIES) KEISSLER, whose mycelium was grown in synthetic media, was isolated with good yields (50 mg/l) and identified as tentoxin. In addition to this compound, purification on Sephadex G‐15 yielded several byproducts with absorbance at 270 nm. This procedure of tentoxin isolation is more effective than traditional ones. The phytotoxin, whose production depends on fermentation‐temperature, can be determined quantitatively in a good agreement by bioassay or spectrophotometry.