Time-of-flight accurate mass spectrometry identification of quinoline alkaloids in honey

Abstract

Time-of-flight accurate mass spectrometry (TOF-MS), following a previous chromatographic (gas or liquid chromatography) separation step, is applied to the identification and structural elucidation of quinoline-like alkaloids in honey. Both electron ionization (EI) MS and positive electrospray (ESI+) MS spectra afforded the molecular ions (M(.+) and M+H(+), respectively) of target compounds with mass errors below 5 mDa. Scan EI-MS and product ion scan ESI-MS/MS spectra permitted confirmation of the existence of a quinoline ring in the structures of the candidate compounds. Also, the observed fragmentation patterns were useful to discriminate between quinoline derivatives having the same empirical formula but different functionalities, such as aldoximes and amides. In the particular case of phenylquinolines, ESI-MS/MS spectra provided valuable clues regarding the position of the phenyl moiety attached to the quinoline ring. The aforementioned spectral information, combined with retention times matching, led to the identification of quinoline and five quinoline derivatives, substituted at carbon number 4, in honey samples. An isomer of phenyquinoline was also noticed; however, its exact structure could not be established. Liquid-liquid microextraction and gas chromatography (GC) TOF-MS were applied to the screening of the aforementioned compounds in a total of 62 honeys. Species displaying higher occurrence frequencies were 4-quinolinecarbonitrile, 4-quinolinecarboxaldehyde, 4-quinolinealdoxime, and the phenylquinoline isomer. The Pearson test revealed strong correlations among the first three compounds.

Time resolved growth of (N)-polycyclic aromatic hydrocarbons in engine deposits uncovered with OrbiSIMS depth profiling

“…S20 †). 44 Alkylated quinolines secondary ions were identified in all samples up to C 43 H 76 N + (−0.5 ppm). MS/MS of C 11 H 12 N + and C 10 H 10 N + both showed alkyl and CHN losses (Fig.…”

Odorant receptors for floral- and plant-derived volatiles in the yellow fever mosquito, Aedes aegypti (Diptera: Culicidae)

“…Indoles are relatively ubiquitous in natural settings and are present in potential nectar sources [ 81 , 82 ]. AaegOR71 responded to 4-quinoline carboxaldehyde, a compound identified in honey samples and endophytic bacteria, via gas chromatography [ 79 , 80 ]. However, indoles are emitted naturally from many sources, including flowers, vertebrate hosts, and oviposition sites of microbiotic origin, suggesting they influence multiple behaviors across species [ 81 , 82 ].…”

Odorant receptors for floral- and plant-derived volatiles in the yellow fever mosquito,Aedes aegypti(Diptera: Culicidae)

“…Indoles are relatively ubiquitous in natural settings and are present in potential nectar sources. AaegOR71 responded to 4-quinoline carboxaldehyde, a compound identified in honey samples and endophytic bacteria via gas chromatography [69][70]. However, indoles are emitted naturally from many sources, including flowers, vertebrate hosts, and oviposition sites of microbiotic origin, suggesting they influence multiple behaviors across species [71][72].…”

“…Indoles are relatively ubiquitous in natural settings and are present in potential nectar sources. AaegOR1 responds to 4-quinoline carboxaldehyde, which has been found in honey samples and endophytic bacteria via gas chromatography [55][56][57]. However, indole and its related compounds have many other sources and influence behaviors across species [58], so it is uncertain if these ORs are directly related to floral odor sensing.…”

“…AaegOR10 responds to 3-methylindole (skatole), which is found in animal feces and produces behavioral responses in other Dipteran species [60][61][62][63]. 4ethylphenol, the primary ligand of AaegOR13, is a volatile constituent in wine and animal waste and has been linked to oviposition in Culex pipiens [64][65][66]. While there is little evidence about natural sources of 2,3-dimethylindole, the AaegOR55 ligand it is closely related structurally to 3-methylindole.…”