Differing mechanisms of simple nitrile formation on glucosinolate degradation in Lepidium sativum and Nasturtium officinale seeds

Williams, David J., Critchley, Christa, Pun, Sharon, Chaliha, Mridusmita and O'Hare, Timothy J. (2009) Differing mechanisms of simple nitrile formation on glucosinolate degradation in Lepidium sativum and Nasturtium officinale seeds. Phytochemistry, 70 11-12: 1401-1409. doi:10.1016/j.phytochem.2009.07.035


Author Williams, David J.
Critchley, Christa
Pun, Sharon
Chaliha, Mridusmita
O'Hare, Timothy J.
Title Differing mechanisms of simple nitrile formation on glucosinolate degradation in Lepidium sativum and Nasturtium officinale seeds
Formatted title
Differing mechanisms of simple nitrile formation on glucosinolate degradation in Lepidium sativum and Nasturtium officinale seeds
Journal name Phytochemistry   Check publisher's open access policy
ISSN 0031-9422
1873-3700
Publication date 2009-07
Sub-type Article (original research)
DOI 10.1016/j.phytochem.2009.07.035
Volume 70
Issue 11-12
Start page 1401
End page 1409
Total pages 9
Place of publication Oxford , United Kingdom
Publisher Pergamon
Collection year 2010
Language eng
Subject C1
820215 Vegetables
060101 Analytical Biochemistry
Formatted abstract
Glucosinolates are sulphur-containing glycosides found in brassicaceous plants that can be hydrolysed enzymatically by plant myrosinase or non-enzymatically to form primarily isothiocyanates and/or simple nitriles. From a human health perspective, isothiocyanates are quite important because they are major inducers of carcinogen-detoxifying enzymes. Two of the most potent inducers are benzyl isothiocyanate (BITC) present in garden cress (Lepidium sativum), and phenylethyl isothiocyanate (PEITC) present in watercress (Nasturtium officinale). Previous studies on these salad crops have indicated that significant amounts of simple nitriles are produced at the expense of the isothiocyanates. These studies also suggested that nitrile formation may occur by different pathways: (1) under the control of specifier protein in garden cress and (2) by an unspecified, non-enzymatic path in watercress. In an effort to understand more about the mechanisms involved in simple nitrile formation in these species, we analysed their seeds for specifier protein and myrosinase activities, endogenous iron content and glucosinolate degradation products after addition of different iron species, specific chelators and various heat treatments. We confirmed that simple nitrile formation was predominantly under specifier protein control (thiocyanate-forming protein) in garden cress seeds. Limited thermal degradation of the major glucosinolate, glucotropaeolin (benzyl glucosinolate), occurred when seed material was heated to >120 °C. In the watercress seeds, however, we show for the first time that gluconasturtiin (phenylethyl glucosinolate) undergoes a non-enzymatic, iron-dependent degradation to a simple nitrile. On heating the seeds to 120 °C or greater, thermal degradation of this heat-labile glucosinolate increased simple nitrile levels many fold.
Keyword Glucotropaeolin
Gluconasturtiin
Garden cress
Lepidium sativum
Watercress
Nasturtium officinale
Enzymatic and non-enzymatic simple nitrile formation
Thiocyanate-forming protein
Epithiospecifier protein
Myrosinase
Total and ferrous iron
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: 2010 Higher Education Research Data Collection
School of Biological Sciences Publications
 
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Created: Mon, 30 Nov 2009, 12:21:40 EST by Hayley Ware on behalf of School of Biological Sciences