Chemical and biological characterisation of tolaasins A-E: new lipodepsipeptides produced by Pseudomonas tolaasii.

Pseudomonas tolaasii, the causal agent of brown blotch disease of Agaricus bisporusand of the yellowing of Pleurotus ostreatus, produces in culture an extracellular toxin, called tolaasin I, which has been shown to have an important role in the development of disease symptoms. The toxin, previously characterized as a lipodepsipeptide with a long and hydrophobic peptide chain, was isolated from the culture filtrates together with tolaasin II, a minor component structurally related to tolaasin I. This paper reports the preliminary structural elucidation data (based on NMR studies and MS spectra) and biological activity of four minor analogues, named tolaasins A, B, D and E, as well as the complete characterization of the tolaasin C.