Isolation of Lolicine A, Lolicine B, Lolitriol, and Lolitrem N from Lolium perenne Infected with Neotyphodium lolii and Evidence for the Natural Occurrence of 31-Epilolitrem N and 31-Epilolitrem F.
Lolicines A (1a) and B (2a), late-eluting lolitrem-like compounds, were identified in extracts of perennial ryegrass (Lolium perenne) seed that was infected with the endophytic fungus Neotyphodium lolii. The lolicines were isolated as their 11-O-propionates (1b and 2b) and their structures determined by mass spectrometry and one- and two-dimensional NMR spectroscopy. The structures of lolicines A and B were similar to those of paspaline (5a) and paspaline B (5b), compounds known to be biosynthetic precursors of several groups of more complex indole-diterpenoids, suggesting that the lolicines might be biosynthetic precursors of the lolitrem group of indole-diterpenoid neurotoxins. During purification of 1b and 2b, a third compound, lolitrem N (4c), was isolated as its propionate (4d) and identified as 35-epilolitriol. A further late-eluting compound was isolated as its acetate from the same fraction as the lolicines. This compound was found to be identical with lolitriol 10-O-acetate (4b) prepared from lolitrem B (3a). This finding confirms lolitriol (4a) as a natural constituent of endophyte-infected perennial ryegrass, and is consistent with the proposal that lolitriol is a biosynthetic precursor of lolitrems A (9), B (3a), and E (10). Detailed examination of the (1)H NMR spectra of 4b revealed the presence of 31-epilolitrem N 10-O-acetate (4f) as a naturally occurring contaminant, indicating that 31-epilolitrem N (4e) is a metabolite of endophyte-infected ryegrass. Analysis of the NMR spectra of 3a led to a reassignment of the C-19-C-21 resonances of the lolitrems, and identified 31-epilolitrem F (3c) as a natural constituent of L. perenne.
Munday-Finch
SC
New Zealand Pastoral Agriculture Research Institute Ltd., Ruakura Agricultural Research Centre, Private Bag 3123, Hamilton, New Zealand, and Chemistry Department, The University of Waikato, Private Bag 3105, Hamilton, New Zealand.
Wilkins
AL
Miles
CO