Fungal Endophytes and the Chemistry of Lolium Toxins

The origin of the toxins appeared to become clear around the turn of the twentieth century when microscopists identified the presence of a mutualistic fungal mycelium located immediately outside the aleurone layer of the darnel grain (Freeman 1904). After various taxonomic revisions, the fungus is now named Neotyphodium occultans (Moon et al. 2000). N. occultans appears to be an asexually propagated congener of the Epichloe'spp. that form endophytic associations with many grasses. Significantly, Neotyphodium and Epichloe' are genera within the fungal family Clavicipitaceae, which includes the ergot organism Claviceps purpurea (Kuldau et al. 1997).

Hofmeister (1892) was the first to isolate alkaloids from darnel. He called a novel compound purified from grain extracts 'temuline' (it is now named nor-loline). Subsequently, temuline was shown to be just one representative of a family of structurally related alkaloids from Lolium spp. known collectively as the lolines and chemically classified as saturated pyrrolizidines (Fig. 9a). It is well established

R R1

Loline CH3 H Norloline H H N-methylloline CH3 CH3 N-formylloline CH3 CHO N-formylnorloline H CHO N-acetylloline CH3 CHCH3 N-acetylnorloline H CHCH3

Ergot alkaloids 0

r/"lP

Dihydroergocornine CH(CH3)2 Dihydroergocristine CH2C6H5 Dihydro-a-ergocryptine CH2CH(CH3)2 Dihydro-p-ergocryptine CH(CH3)CH2CH3

Lolitrem B

h3c ch3

h3C>Cf~CH3

ch3

TVch3oh h3c NHY^nh^c 0^y0H

0y^OH

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