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Your search keyword '"Joyce, Nigel I."' showing total 21 results
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21 results on '"Joyce, Nigel I."'

14. Glycosides of the Neurotoxin Tutin in Toxic Honeys Are from Coriaria arboreaPhloem Sap, Not Insect Metabolism

Author

Watkins, Oliver C., Joyce, Nigel I., Gould, Nick, and Perry, Nigel B.

Abstract

Some honeys contain the neurotoxin tutin (1) plus hyenanchin (2), 2-(β-d-glucopyranosyl)tutin (3), and 2-[6′-(α-d-glucopyranosyl)-β-d-glucopyranosyl]tutin (4). These honeys are made by bees collecting honeydew from passionvine hoppers feeding on the sap of tutu plants (Coriariaspp.). We report a LC-MS study showing that all these picrotoxanes are of plant, not insect, origin. Hyenanchin was barely detectable and the diglucoside was not detectable in C. arborealeaves, but tutu phloem sap contained all four compounds at concentrations up to the highest found in honeydew. It is proposed that the diglucoside may function as a transport form of tutin, analogous to sucrose transport in phloem.

Published
2018
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21. Sesquiterpene lactones in Arnica montana: helenalin and dihydrohelenalin chemotypes in Spain.

Author

Perry NB, Burgess EJ, Rodríguez Guitián MA, Romero Franco R, López Mosquera E, Smallfield BM, Joyce NI, and Littlejohn RP

Subjects
Chromatography, Liquid methods, Flowers, Isomerism, Sesquiterpenes, Guaiane, Spain, Arnica chemistry, Lactones isolation & purification, Phenols isolation & purification, Plant Extracts chemistry, Sesquiterpenes isolation & purification
Abstract

An analytical RPLC method for sesquiterpene lactones in Arnica montana has been extended to include quantitative analyses of dihydrohelenalin esters. LC-ESI-MS-MS distinguished the isomeric helenalin and dihydrohelenalin esters. The dihydrohelenalin esters have lower response factors for UV detection than do helenalin esters, which must be taken into account for quantitative analyses. Analyses of flowers from 16 different wild populations of A. montana in Spain showed differing proportions of helenalin and dihydrohelenalin esters. For the first time a chemotype with high levels of helenalin esters (total helenalins 5.2-10.3 mg/g dry weight) is reported in Spanish A. montana. These samples were from heath lands at high altitude (1330-1460 m), whereas samples from meadows and peat bogs at lower altitudes were the expected chemotype with high levels of dihydrohelenalin esters (total dihydrohelenalins 10.9-18.2 mg/g). The phenolic compounds, both flavonoid glycosides and caffeoylquinic acids, in Spanish A. montana are reported for the first time. The levels of several of these compounds differed significantly between samples from heath lands and samples from peat bogs or meadows, with the heath land samples being most similar to central European A. montana in their phenolic composition., (Copyright Georg Thieme Verlag KG Stuttgart. New York.)

Published
2009
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