New Alkaloids from Phalaris Spp.: A Cause for Concern?

Abstract

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.

Diastereoselective Michael Additions of N-Boc-2-(tert-butyldimethylsiloxy)pyrrole to 2-(Arylsulfinyl)-1,4-benzoquinones

“…These lactam skeletons are present in several therapeutic agents and some natural products exhibiting interesting biological properties . The interest in these compounds is related to their use as substrates for inter or intramolecular conjugated additions, leading to pyrrolo[3,2- b ]benzofurans, which are present in compounds such as BODIPY dyes and the alkaloid phalarine . Several examples of TBSOP as a nucleophile have been reported and illustrate the successful addition to carbonyl-related compounds such as aldehydes, imines, and heteroatom-stabilized carbenium ions.…”