Chapter 10
New Alkaloids from Phalaris Spp.: A Cause for Concern?
Downloaded by NORTH CAROLINA STATE UNIV on September 23, 2012 | http://pubs.acs.org Publication Date: December 20, 1999 | doi: 10.1021/bk-2000-0745.ch010
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Neil Anderton , Peter A. Cockrum , Steven M . Colegate , John A. Edgar , and Kirsty Flower 2
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Plant Toxins Unit, CSIRO Division of Animal Health, Private Bag 24, Geelong, Victoria 3220, Australia Kybybolite Research Centre, P.O. Box 2, Kybybolite, South Australia 5262, Australia 2
Phalaris spp. grasses are useful pasture components but have been associated with neurological and sudden death intoxication syndromes. Despite agronomic development of Phalaris spp. to produce "low -toxicity" cultivars, outbreaks of intoxication have continued to occur. These outbreaks could result from a combination of poorly understood environmental or animal factors exacerbating the effect of the low concentration of known toxic alkaloids. Alternatively, previously unrecognised alkaloids could have intrinsic toxicity. Recent investigations have revealed the presence of the cardioactive N -methyltyramine in P. aquatica cultivars, and alkaloids of unknown toxicity i.e., the oxindoles coerulescine and horsfiline, and the furanobisindole phalarine, in P. coerulescens cultivars. The structures of coerulescine and phalarine were determined using NMR spectroscopy and mass spectrometry.
The grass Phalaris aquatica (syn. P. tuberosa) has been introduced into Australia from its native Mediterranean habitat. Selected for its drought tolerance, the winter growing perennial also withstands waterlogging and is especially adaptable to heavier soils in areas of 400-650 mm annual rainfall. However, use of the grass as a pasture component has been complicated by the seed-shedding characteristics of the early imports and an associated toxicity. The seed-shedding problems were able to be addressed once a cultivar was isolated that displayed a high seed retention. Development of this cultivar allowed the simple and economic harvesting of seed for commercial distribution (7, 2). Thus, P. aquatica has become firmly established in the southern, temperate areas of Australia. Corresponding author. 140
©2000 American Chemical Society
In Natural and Selected Synthetic Toxins; Tu, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1999.
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Toxicity was first associated with P. aquatica by McDonald (3) who reported a muscular incoordination or "staggers" syndrome in sheep and cattle grazing Phalaris pastures. Cattle and sheep seemed to be more susceptible to fresh new growth of the plant whilst horses seemed unaffected by the Phalaris toxins despite extended grazing on pastures that caused adverse effects in cattle and sheep. Subsequently considerable effort has been directed at developing "non-toxic" cultivars of Phalaris (/, 2, 4)
Downloaded by NORTH CAROLINA STATE UNIV on September 23, 2012 | http://pubs.acs.org Publication Date: December 20, 1999 | doi: 10.1021/bk-2000-0745.ch010
Clinical Effects of Phalaris Intoxication Early field reports of Phalaris intoxication described a sudden death, cardiac effect and a neurological staggers syndrome in sheep and cattle (3, 5). An initial differentiation of Phalaris spp. intoxication into peracute, acute and chronic syndromes (
