etheroleic-acid and 13-hydroperoxy-9-11-octadecadienoic-acid

Topics: Chromatography, High Pressure Liquid; Cytochrome P-450 Enzyme System; Fatty Acids, Unsaturated; Garlic; Leukotrienes; Linoleic Acids; Lipid Peroxides; Molecular Structure; Oxidoreductases; Plant Proteins; Plants, Medicinal; Substrate Specificity

The microsomal fraction of homogenate of garlic (Allium sativum L.) bulbs contains a divinyl ether synthase which catalyzes conversion of (9Z,11E,13S)-13-hydroperoxy-9, 11-octadecadienoic acid and (9Z,11E,13S,15Z)-13-hydroperoxy-9,11,15-octadecatri eno ic acid into (9Z,11E,1'E,)-12-(1'-hexenyloxy)-9,11-dodecadienoic acid (etherolenic acid) and (9Z,11E,1'E,3'Z)-12-(1',3'-hexadienyloxy)-9,11-dode cadienoic acid (etherolenic acid), respectively. Two isomers of etherolenic acid were isolated. As shown by NMR spectrometry, the double bond configurations of these compounds were (9E,11E,1'E) and (9Z,11Z,1'E). Experiments with linoleic acid (13R,S)-hydroperoxide demonstrated that the S enantiomer was a much better substrate for the divinyl ether synthase compared to the R enantiomer. Incubation of (9Z,11E,13S)-[18O2]hydroperoxy-9,11-octadecadienoic acid led to the formation of etherolenic acid which retained 18O in the ether oxygen. An intermediary role of an epoxyallylic cation in etherolenic acid biosynthesis is postulated.

Topics: Chromatography, High Pressure Liquid; Cytochrome P-450 Enzyme System; Fatty Acids, Unsaturated; Garlic; Isomerism; Leukotrienes; Linoleic Acids; Lipid Peroxides; Magnetic Resonance Spectroscopy; Microsomes; Oxidoreductases; Plant Proteins; Plants, Medicinal; Substrate Specificity

Incubations of [1-14C]linoleic acid or [1-14C]-(9Z,11E, 13S)-13-hydropero xy-9,11-octadecadienoic acid (13-HPOD) with juice of garlic bulbs lead to the formation of one predominant labelled product, viz., the novel divinyl ether (9Z,11E, 1'E)-12-(1'-hexenyloxy)-9,11-dodecadienoic acid ('etheroleic acid'). With lesser efficiency [1-14C]alpha-linolenic acid or [1-14C](9Z,11E, 13S,15Z)-13-hydroperoxy-9,11,15-octadecatrienoic acid (13-HPOT) are converted in this way into (9Z,11E,1'E,1'E,3'Z)-12-(1',3'-hexadienyloxy)-9,11- dodecadienoic acid ('etherolenic acid'). Thus, garlic bulbs possess the activity of a new 13-hydroperoxide-specific divinyl ether synthase.

Topics: alpha-Linolenic Acid; Chromatography, High Pressure Liquid; Fatty Acids, Unsaturated; Garlic; Linoleic Acid; Linoleic Acids; Linolenic Acids; Lipid Peroxides; Lipoxygenase; Magnetic Resonance Spectroscopy; Plants, Medicinal