Showing papers by "Stephen T. Lee published in 2005"

Solid-phase extraction and HPLC-MS profiling of pyrrolizidine alkaloids and their N-oxides: a case study of Echium plantagineum.

Abstract: Pyrrolizidine alkaloids and their N-oxides can be extracted from the dried methanolic extracts of plant material using dilute aqueous acid. The subsequent integration of solid-phase extraction (with a strong cation exchanger) of the alkaloids and N-oxides from the aqueous acid solution, together with analysis using HPLC-ESI/MS, provides a method for the simultaneous profiling of the pyrrolizidine alkaloids and their N-oxides in plant samples and the collection of useful structural data as an aid in their identification. The N-oxide character of the analytes may be confirmed by treating analytical samples with a redox resin and observing the formation of the corresponding parent pyrrolizidine alkaloids. The present case study of Echium plantagineum highlighted a higher ratio of N-oxides to the parent tertiary bases than has been previously reported. Furthermore, a higher proportion of acetylated pyrrolizidine-N-oxides was observed in the flower heads relative to the leaves. Six pyrrolizidine alkaloids or pyrrolizidine-N-oxides, not previously reported from E. plantagineum, were tentatively identified on the basis of MS and biogenetic considerations. Three of these, 3'-O-acetylintermedine/lycopsamine, leptanthine-N-oxide and 9-O-angelylretronecine-N-oxide, have been reported elsewhere, whilst three others, 3'-O-acetylechiumine-N-oxide, echimiplatine-N-oxide and echiuplatine-N-oxide, appear unreported from any other source.

Locoweed (Oxytropis sericea)-induced lesions in mule deer (Odocoileius hemionus).

Abstract: Locoweed poisoning has been reported in wildlife, but it is unknown whether mule deer (Odocoileius hemionus)are susceptible. In areas that are heavily infested with locoweed, deer and elk (Cervus elaphus nelsoni)have developed a spongiform encephalopathy, chronic wasting disease (CWD). Although these are distinct diseases, no good comparisons are available. The purpose of this study was to induce and describe chronic locoweed poisoning in deer and compare it with the lesions of CWD. Two groups of four mule deer were fed either a complete pelleted ration or a similar ration containing 15% locoweed (Oxytropis sericea). Poisoned deer lost weight and developed a scruffy, dull coat. They developed reluctance to move, and movement produced subtle intention tremors. Poisoned deer had extensive vacuolation of visceral tissues, which was most severe in the exocrine pancreas. Thyroid follicular epithelium, renal tubular epithelium, and macrophages in many tissues were mildly vacuolated. The exposed deer also had mi...

Ammodendrine and N-methylammodendrine enantiomers: isolation, optical rotation, and toxicity.

Abstract: Ammodendrine (1) was found to occur as a mixture of enantiomers in two different collections of plants identified as Lupinus formosus. The ammodendrine fraction was reacted in a peptide coupling reaction with 9-fluorenylmethoxycarbonyl-l-alanine (Fmoc-l-Ala-OH) to give diastereomers, which were separated by preparative HPLC. The pure d- and l-ammodendrine enantiomers were then obtained by Edman degradation. Optical rotation measurements revealed that the d- and l-enantiomers had optical rotations of [α]24D +5.4° and −5.7°, respectively. d- and l-N-methylammodendrine enantiomers were synthesized from the corresponding ammodendrine enantiomers, and their optical rotations established as [α]23D +62.4° and −59.0°, respectively. A mouse bioassay was used to determine the difference in toxicity between these two pairs of naturally occurring enantiomers. The LD50 of (+)-d-ammodendrine in mice was determined to be 94.1 ± 7 mg/kg and that of (−)-l-ammodendrine as 115.0 ± 7 mg/kg. The LD50 of (+)-d-N-methylammoden...