Adrian H. B. Deas

Epoxyoctadecanoic acids in plant cutins and suberins

Abstract Three C 18 epoxy acids occur in plant cutins and suberins. 9,10-Epoxy-18-hydroxyoctadecanoic acid is a common constituent of both cutins and suberins whilst 9,10-epoxy-18-hydroxyoctadec-12-enoic acid is also present in some cutins. 9,10-Epoxyoctadecane-1,18-dioic acid occurs more commonly in suberins. Epoxy acids may comprise up to 60% of the total monomers obtained from some polymers. The epoxy compounds are readily converted into their corresponding alkoxyhydrin alkyl esters on depolymerization of cutin or suberin by alcoholysis. The chromatographic and MS properties of the alkoxyhydrin derivatives enable them to be readily distinguished from other cutin and suberin hydroxyfatty acids and to be used for the qualitative and quantitative determination of epoxy acids in the polymers.

Occurrence of positional isomers of dihydroxyhexadecanoic acid in plant cutins and suberins

Abstract Positional isomers of dihydroxyhexadecanoic acid have been found in cutin and suberin hydrolysates and identified using combined gas chromatography—mass spectrometry of their TMS derivatives. The acid is usually a mixture of the 10,16-, 9,16-, 8,16- and 7,16-isomers which are eluted as a single peak using packed GLC columns. The major isomers are commonly 10,16- and 9,16- with the other isomers occurring in smaller quantities. The implications of the results in the biosynthesis of cutin and suberin are discussed.

The enantiomeric composition of triadimenol produced during metabolism of triadimefon by fungi: III. Relationship with sensitivity to triadimefon

Abstract Fifteen species of fungi, grown in shake culture in a liquid nutrient medium containing a 50:50 mixture of the 1 R and 1 S enantiomers of triadimefon, reduced triadimefon to triadimenol, the extent of reduction varying from 95% according to species. Each produced its own characteristic pattern of two or more of the four possible enantiomers of triadimenol and the stereoselectivity and stereospecificity of the reduction is discussed. The sensitivity of each fungus to individual enantiomers and a mixture of enantiomers of triadimefon and of triadimenol was assessed. Three broadly defined groups of fungi were found: (i) sensitive to both triadimefon and tridimenol, (ii) insensitive to both, and (iii) insensitive to triadimefon but moderately sensitive to triadimenol. In many cases it was possible to predict, at least semiquantitatively, the sensitivity of an organism to triadimefon from a knowledge of its characteristic metabolism to triadimenol and its sensitivity to the individual triadimenol enantiomers. No evidence for synergism or antagonism was found.

Composition of cutin from coffee leaves

Abstract The constituents of the cutin of coffee leaves have been identified using TLC, GLC and GLC-MS. Dihydroxyhexadecanoic acids comprise more than 60% of the total acids. Other compounds identified include C 16 -C 34 monobasic acids, C 14 and C 15 monohydroxymonobasic acids, 16-hydroxyhexadecanoic acid and monohydroxyhexadecane-1,16-dioic acids. All acids having a secondary hydroxyl group exhibit positional isomerism with the group predominantly at both 9- and 10-positions. No major differences occur in the composition of cutin from young and mature leaves or from the adaxial and abaxial surfaces.

Identification of 16-hydroxyoxohexadecanoic acid monomers in plant cutins☆

Abstract The structure of a new hydroxyketo fatty acid which occurs as a major monomer of Citrus limon fruit cutin has been determined by IR, NMR and MS. The monomer was shown to be a mixture of positional isomers of 16-hydroxyoxohexadecanoic acid with the 10-oxo isomer predominating. Substantial amounts of the 9-oxo isomer were present together with smaller quantities of the 8- and 7-isomers. The same compounds were also found to be important constituents of the fruit cutins of Physalis peruviana and Ribes nigrum .