Identification of hydroxymethylpyrazines using mass spectrometry

Abstract

Pyrazines are well-known natural products that are present in bacterial odours and food flavouring agents and are used as insect pheromones. Recently, a number of hydroxymethylpyrazines have been identified as thynnine wasp pheromones and orchid semiochemicals that are essential for pollination in sexually deceptive plants. These compounds are present in low amounts in complex blends, making GC-MS (including high-resolution techniques) the method of choice for their structure elucidation. We report the EI mass spectra for 14 representative compounds and have found that based on characteristic fragmentations, it is possible to distinguish between different positional isomers of hydroxymethylpyrazines. The presence or absence of either [M - 17] , [M - 18] or [M - 19] fragment species provides characteristic information to allow the distinction between the different isomers. Considering the importance of pyrazines as a group of bioactive natural products, and the recent findings of biological activity for hydroxymethylpyrazines, our results presented here will aid the identification of these compounds in other biological systems. Copyright © 2015 John Wiley & Sons, Ltd.

A Specific Blend of Drakolide and Hydroxymethylpyrazines: An Unusual Pollinator Sexual Attractant Used by the Endangered Orchid Drakaea micrantha

“…The most abundant EAD‐active compound 1, has also previously been reported as EAD‐active to the Catocheillus wasp that pollinates some populations of D. livida . The homologue 2 (in lower abundance than 1 in D. micrantha ) is identified here for the first time as a natural product, having already been synthesized as part of a mass spectrometry study . Compounds 1 and 2 , although EAD‐active, did not elicit strong attraction of the Zeleboria pollinator in preliminary field tests (SI, Figure S1).…”

“…Key tools facilitating the identification of the compounds included gas chromatography‐electroantennography (GC‐EAD), where insect antennae were employed as the detector, and semi‐preparative gas chromatography. GC‐EAD repeatedly detected two compounds (Figure ), identified as hydroxymethylpyrazines 1 and 2 by synthesis, GC‐MS and co‐injection on two GC columns. The most abundant EAD‐active compound 1, has also previously been reported as EAD‐active to the Catocheillus wasp that pollinates some populations of D. livida .…”

Quantum chemical electron impact mass spectrum prediction for de novo structure elucidation: Assessment against experimental reference data and comparison to competitive fragmentation modeling

“…Mass spectrometry (MS) is of major importance for identifying the presence of small quantities of a compound in a mixture, particularly because it is several orders of magnitude more sensitive than equivalent structure determination methods . Indeed, MS is often the only feasible identification method in contexts like the identification of semiochemicals, where abundances of critical compounds may be in the ng range.…”

A Specific Blend of Drakolide and Hydroxymethylpyrazines: An Unusual Pollinator Sexual Attractant Used by the Endangered Orchid Drakaea micrantha

“…4mm 20 mm), and the only member of the genus pollinated by a Zeleboria thynnine wasp.W ed emonstrate that pollination of D. micrantha requires as pecific blend of 2-hydroxymethyl-3,5,6-trimethylpyrazine (1), 2-hydroxymethyl-3,5dimethyl-6-ethylpyrazine (2)a nd the unique b-hydroxylactone 4-hydroxy-3-methyl-6S-(pentan-2S-yl)-5,6-dihydro-2Hpyran-2-one (3c,h ere termed drakolide). Key tools facilitating the identification of the compounds included gas chromatography-electroantennography (GC-EAD), where insect antennae were employed as the detector,a nd semi-preparative gas chromatography.G C-EAD repeatedly detected two compounds ( Figure 1), identified as hydroxymethylpyrazines 1 and 2 by synthesis, [6] GC-MS [7] and co-injection on two GC columns.T he most abundant EAD-active compound 1, has also previously been reported as EAD-active to the Catocheillus wasp that pollinates some populations of D. livida. [1b] Thehomologue 2 (in lower abundance than 1 in D. micrantha) is identified here for the first time as anatural product, having already been synthesized as part of am ass spectrometry study.…”

“…[1b] Thehomologue 2 (in lower abundance than 1 in D. micrantha) is identified here for the first time as anatural product, having already been synthesized as part of am ass spectrometry study. [7] Compounds 1 and 2,a lthough EAD-active,d id not elicit strong attraction of the Zeleboria pollinator in preliminary field tests (SI, Figure S1). Therefore,tofind the missing component(s) of the semiochemical blend not detected by GC-EAD,b ioassay-guided semi-preparative GC of floral extracts was conducted.…”