99932-94-2Relevant articles and documents
The Biosynthesis of Calendic Acid, Octadeca-(8E,10E,12Z)-trienoic Acid, by Developing Marigold Seeds: Origins of (E,E,Z) and (Z,E,Z) conjugated Triene Acids in Higher Plants
Crombie, Leslie,Holloway, Stephen J.
, p. 2425 - 2434 (2007/10/02)
Using an homogenate of marigold seeds, gathered 15 days after flower-drop, linoleic acid and oleic acid were incorporated into calendic acid with little randomisation of the label. Linolenic acid was not incorporated.Despite requiring 12,13-dehydrogenation to form linoleic acid, the putative precursor, oleic acid was better incorporated than administered linoleic acid.Stearic acid, requiring both 12,13- and 9,10-dehydrogenation, was a poor precursor.The results of a series of doublelabelling experiments support and supplement these conclusions. Octadec-9-enoic acid was synthesised and employed in a mass-spectral experiment to show that conversion into calendic acid involves loss of two deuterium and two hydrogen atoms (deuterium at C-16 and C-17 was introduced for loading purposes only, in order to increase the sensitivity of the experiment).Taken with -labelling work, the experiment indicates that during conversion of linoleic acid into calendic acid, there is no loss of the labelled hydrogens at C-9, -10, -12, or -13, but loss of hydrogen from each of C-8 and C-11. (9S)-Hydroxyoctadeca-(10E,12Z)-dienoic acid (α-dimorphecolic acid) was isolated and converted into (R/S)-hydroxy- and hydroperoxy-octadeca-(10E,12Z)-dienoic acids.Neither labelled specimen was converted into calendic acid by marigold seed homogenate.Abstraction of a hydrogen atom from C-11 of linoleic acid is viewed as giving an (E)-allylic radical which, as in lipoxygenase reactions, can be trapped by oxygen at C-9, thus providing a source of α-dimorphecolic acid, a minor component of marigold seed oil.However, this hydroxyacid is apparently a terminus rather than an intermediate for calendic acid.Formation of the latter seems best accounted for by formal loss of a hydrogen atom from C-8 of the (E)-allylic redical.The general position relating to the formation of (E,E,Z) and (Z,E,Z)-trienes is summarised.
