Lentisone, a new phytotoxic anthraquinone produced by Ascochyta lentis, the causal agent of ascochyta blight in Lens culinaris

An aggressive isolate of Ascochyta lentis obtained from lentil (Lens culinaris L.) produced various metabolites in vitro. The metabolites were isolated from the culture filtrates and characterized by spectroscopic, chemical, and optical methods. A new phytotoxic anthraquinone, named lentisone, was isolated and characterized as (1S,2S,3S)-1,2,3,8-tetrahydroxy-1,2,3,4- tetrahydro-6-methylanthraquinone together with the well-known pachybasin (1-hydroxy-3-methylanthraquinone), tyrosol, and pseurotin A. Lentisone, tyrosol, and pseurotin A were phytotoxic to lentil, with lentisone the most toxic of all. The toxicity of these compounds is light-dependent. Finally, lentisone was also found to be phytotoxic to chickpea, pea, and faba bean, with toxicity in the latter higher than in any other tested legume, including lentil.