Enantiodifferentiation of 3-sec-butyl-2-methoxypyrazine in different species using multidimensional and comprehensive two-dimensional gas chromatographic approaches

Abstract

With respect to the current hypothesis that natural amino acids may serve as starting material for the biosynthesis of alkyl-methoxypyrazines, the enantiomeric distribution of the potent aroma compound 3-sec-butyl-2-methoxypyrazine (SBMP) was determined in various species using heart-cut multidimensional gas chromatography (H/C MDGC) or comprehensive two-dimensional gas chromatography (GC × GC). Complementary to an earlier described separation on octakis-(6-O-methyl-2,3-di-O-pentyl)-γ-cyclodextrin used as chiral stationary phase, we found a reversal of the elution order of SBMP enantiomers on heptakis-(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin, providing further confirmation options for that type of analysis. Optimization of the enantioseparation of SBMP in a single-oven H/C enantio-MDGC system involved the use of a dual-jet cryo modulator for trapping of analytes transferred from the achiral (1)D column to the chiral (2)D column before starting the (2)D enantioseparation with an independent temperature ramp. For the enantiodifferentiation by enantio-GC × GC, the modulation period had to be significantly shortened to avoid loss of chiral resolution gained in (1)D. H/C MDGC with mass spectrometric detection (MS) using selected ion monitoring (SIM) was sufficient for parts per billion level analysis, whereas H/C MDGC-MS/MS or GC × GC time-of-flight (TOF) MS were necessary for parts per trillion level analysis. In various vegetables, lady beetles and Vitis vinifera species analyzed, only (S)-SBMP was detected, supporting the hypothesis of natural amino acids serving as starting material for the biosynthesis of alkyl-methoxypyrazines.

Quantification of cork off-flavor compounds in natural cork stoppers and wine by multidimensional gas chromatography mass spectrometry

“…Analysis of MDMP, IPMP, IBMP, MIB, TCA and GSM was done with the H/C enantioMDGC-MS-MS system basically described previously [26]. A TraceGC ultra (ThermoFisher Scientific) was equipped with a Deans' switching device (SGE Analytical Science, Victoria, Australia) for H/C and a dual-jet modulator (ThermoFisher Scientific) using liquid CO 2 for cryo-trapping of the transferred fraction.…”

Compositional changes of the floral scent volatile emissions from Asian skunk cabbage (Symplocarpus renifolius, Araceae) over flowering sex phases

“…Although IPMP was a minor component (mean ± SD, 0.018 ± 0.02%) in female‐phase volatiles (Table ), its GC–MS/O peak was accompanied by a relatively intense odour (Table ). IPMP has a very low odour threshold (0.002 ppb in water) for humans; it is widely distributed in plants, including pea shells, bell peppers and beetroots . IPMP is found in volatiles emitted from female‐phase inflorescences of some Araceae species, such as Philodendron acutatum and four Xanthosoma spp …”

GC‐MS aroma characterization of vegetable matrices: Focus on 3‐alkyl‐2‐methoxypyrazines

“…3‐Isopropyl‐2‐methoxypyrazine possesses a strong vegetable‐like odor and has been detected particularly in green peas and cucumber . In dilute aqueous solution (from 0.1 to 10 ppb), its odor notes resemble those of freshly shelled green peas, pea shells, while in other cases was defined similar to that of raw potatoes …”

“…3‐Isobutyl‐2‐methoxypyrazine was found to be the most important and characterizing aroma in bell peppers, while it has been reported to be the major contributor in the aroma of unripe berries . On the other side, s BMP dominates in vegetables, such as beetroot or carrot …”

“…Differently from grapes, musts, and wines, vegetable MP quantitative data are very scarce . Early studies on MPs in vegetables reported that IPMP and s BMP are among the most potent aroma compounds in green peas, and, being the highest level of methoxypyrazines found in pericarp tissue, mainly in peas shells .…”