An Efficient Method for the Isolation of Peramine, an Insect Feeding Deterrent Produced by the Fungus Acremonium Lolii

Abstract

Peramine 111, a novel fungal metabolite isolated from perennial ryegrass (Loliumperenne L.) infected with the fungal endophyte Acremonium lolii Latch, Christensen, Samuels (Fungi Imperfecti) (1,2), is a highly active feeding deterrent to the Argentine stem weevil (Listronotus bonariensis Kuschel) and is implicated in the resistance of endophyte-infected ryegrasses and fescues to this insect pest. The original isolation of peramine from herbage (1) required final purification as the diacetyl derivative (2) and was deemed impractical for producing sufficient underivatized material for further biological testing. We now report an improved procedure for the isolation of peramine from seed which uses ion exchange and reversed-phase chromatography to take advantage of the strongly basic guanidino group and the lipophilic pyrrolopyrazine moieties present in peramine. This procedure has yielded for the first time pure crystalline peramine for which spectroscopic data is now reported. This data supports the 3-(3'-guanidinopropyl)-2methylpyrrolo-1 1,2-a]pyrazin- 1(2H)-one structure originally proposed for peramine from the nmr analysis of the diacetyl derivative (2). TIC analysis of A. lolii infected seeds and seedlings indicated the presence of