Discovery of Three New Phytotoxins from the Fungus Aspergillus nidulans by Pathway Inactivation

Abstract

Fungi are a source of novel phytotoxic compounds to be explored in the search for effective and environmentally safe herbicides. The genetic inactivation of the biosynthetic pathway of the new phytotoxin cichorine has led to the isolation of three novel phytotoxins from the fungus Aspergillus nidulans: 8-methoxycichorine (4), 8-epi-methoxycichorine (5), and N-(4’-carboxybutyl) cichorine (6). The structure of the new compounds was clearly determined by a combination of nuclear magnetic resonance (NMR) analysis and high-resolution electrospray ionization (HRESIMS). The phytotoxic bioassay was studied on leaves from Zea mays and Medicago polymorpha L. at the concentration of 5 × 10−3 M by using a moist chamber technique. Novel phytotoxins 8-methoxycichorine (4), 8-epi-methoxycichorine (5), and N-(4’-carboxybutyl) cichorine (6) exhibited a better phytotoxic effect than cichorine.