Lipase-catalysed changes in essential oils revealed by comprehensive two-dimensional gas chromatography

Abstract

Candida antarctica lipase A (CALA) was applied for the chemo-selective enzymatic transesterification of terpene and phenyl alcohols in 35 different essential oil samples. Comprehensive two-dimensional gas chromatography with mass spectrometry (GC×GC‒MS) analysis enabled the separation and tentative identification of a cohort of 125 compounds, allowing the instant visualisation of the reaction process changes, amid the complex chemical background of the samples. The results indicate that 42 out of 79 alcohols so-identified were fully or partially esterified within 48 h of reaction, with primary alcohols being the substrates of preference of the enzyme (90–100% conversion), followed by secondary alcohols (mostly ~ 80–100% conversion). No significant conversion of tertiary alcohols and phenols was observed using the tested conditions. Overall, the enzyme’s performance was consistent for primary alcohol substrates identified in multiple samples of different compositions. The observed selectivity, efficiency, robustness, scalability (enzyme/substrate working concentration ratio > 1:160), potential reusability, mild reaction conditions, and other factors make this process a greener and more sustainable alternative for industry applications, particularly for the manufacture of novel flavours and fragrances. Graphical Abstract

Comprehensive Two-Dimensional Gas Chromatography–Mass Spectrometry as a Tool for the Untargeted Study of Hop and Their Metabolites

“…Analysis of selected standards was performed for specific compound identification confirmation. The main classes of volatiles identified and the number of compounds were as follows: alcohols (3), aldehydes (4), esters (47), hydrocarbons (7), ketones (9), monoterpene hydrocarbons (17), oxygenated monoterpenes (12), sesquiterpene hydrocarbons (32), and oxygenated sesquiterpenes (3). The total amount of volatiles is expressed in the last line of the table, demonstrating that there remains a small fraction of unknown compounds, from 3.1% to 12.4% of the total area, which could not be identified using the reported criteria.…”

“…Helium, grade 99.99%, was used as a carrier gas in constant flow (1.0 mL min −1 ). The injector was set in split mode ( 50 The GC×GC-MS method including the solid-state modulator operation was also based on previous research [40,47] and included a DB-5ms UI 1 ), and were connected to the main columns using glass press fit connectors. The GC temperature programme was the same as used in GC-MS analyses, except for the MS source 230 • C, quadrupole 150 • C, threshold 80, 12500 scans (u/s), and 22.8 scan/s.…”

“…The GC temperature programme was the same as used in GC-MS analyses, except for the MS source 230 • C, quadrupole 150 • C, threshold 80, 12500 scans (u/s), and 22.8 scan/s. The solid-state modulator configuration was adapted from the literature [47] and included the same temperature program of the GC oven for the modulator entry oven and a 20 • C offset above the GC oven for the exit oven. The trap temperature program was −50 • C (8 min) and 2 • C min −1 to −20 • C (37 min).…”