Identification of structurally diverse alkaloids in Talguenea quinquinervia (gill. Et hook) by liquid chromatography/electrospray ionisation tandem mass spectroscopy and insecticidal activity

Abstract

Introduction Talguenea quinquinervia has been used in folk medicine and to dye wool, and the main constituents are alkaloids and triterpenes. Identification of these type of compounds in this specie is a necessary step to understand the biological properties. Objective To evaluate the relationship between the chemical composition of root from T. quinquinervia and its insecticidal properties using liquid chromatography electrospray ionisation tandem mass spectrometry (LC‐ESI‐MS/MS). Methods Alkaloids were extracted using Soxhlet extraction with methanol. Total extract was partitioned at pH 2 and 12 to enrich alkaloid constituents and to remove interferences. The separation of alkaloids in the Talguenea extract was performed on a C18 column using gradient elution and their tandem mass spectra were obtained by quadrupole time‐of‐flight tandem mass spectrometry (QTOF‐MS/MS) to perform accurate mass measurements of fragment ions for the alkaloid constituents. Results Several types of alkaloids were separated and identified by LC‐ESI‐MS/MS. The structural assignment of individual alkaloids was performed based on convergence of MS/MS spectral data, pH partitioning behaviour, LC retention behaviour, and accurate mass measurements. The pH partition of the extract provided structural information about unknown alkaloids extracted from T. quinquinervia. A total of 20 compounds were identified and tentatively characterised, and of these 15 alkaloids were reported for the first time in the investigated T. quinquinervia. Conclusion The chemical profiling of alkaloids in T. quinquinervia with different origins was performed for the first time and provided diagnostic ions for diverse alkaloids in T. quinquinervia. Insecticidal activity observed can be explain by the presence of alkaloid and pentacyclic triterpenes on the fractions assayed.

Identification of Sassafras albidum alkaloids by high‐performance thin‐layer chromatography tandem mass spectrometry and mapping by desorption electrospray ionization mass spectrometry imaging

“…albidum 6 . Coclaurine, N ‐methyl coclaurine, and armepavine showed similar fragmentation pattern described in previous works and are described here for the first time in the genus Sassafras 21,30,31 . Coclaurine and N‐ methyl coclaurine are important intermediates in the biosynthesis pathway of reticuline 33,34 .…”

“…Seven benzylisoquinoline alkaloids were observed in the root extract; they showed fragmentation patterns with key ions ( a – e ) generated in the MS 2 and MS 3 (Figure 4). These ions, previously described in literature, help to identify the substitutions in two essential parts of benzylisoquinoline alkaloids, the benzyl and isoquinoline moiety 30,31 . Similar to aporphine alkaloids with secondary and tertiary nitrogen, benzylisoquinolines display the loss of 17 and 31 Da representing the cleavage of the amino group as [M + H‐NH 3 ] + and [M + H‐NH 2 CH 3 ] + respectively, generating ion a 30,31 .…”

“…These ions, previously described in literature, help to identify the substitutions in two essential parts of benzylisoquinoline alkaloids, the benzyl and isoquinoline moiety 30,31 . Similar to aporphine alkaloids with secondary and tertiary nitrogen, benzylisoquinolines display the loss of 17 and 31 Da representing the cleavage of the amino group as [M + H‐NH 3 ] + and [M + H‐NH 2 CH 3 ] + respectively, generating ion a 30,31 . Compounds 1 (norcinnamolaurine), 2 (coclaurine), and 3 (cinnamolaurine) were characterized by the presence of secondary nitrogen, while Compounds 4 ( N ‐methylcoclaurine), 5 ( N ‐methylisococlaurine), and 11 (reticuline) were characterized with the presence of tertiary nitrogen.…”

“…DESI‐MS n analysis was performed in all alkaloids separated offline by HPTLC, and the structural characterization was investigated based on the fragmentation pattern of these compounds and comparison with literature data. Both isoquinoline and aporphine alkaloids have known fragmentation pathways that help to characterize its main substituents and its structure 29–32 . A total of 12 alkaloids were identified, five aporphine and seven benzylisoquinoline.…”

Rapid structural characterisation of benzylisoquinoline and aporphine alkaloids from Ocotea spixiana acaricide extract by HPTLC‐DESI‐MSn

“…The type‐ c ion is the key ion of MS 3 fragmentation of ion a , occurring as a rearrangement after the loss of the benzyl groups. Alkaloids 1 , 2 and 4 showed type c ion with m/z 175 suggesting the presence of vicinal OCH 3 and OH groups on the ring A 32 …”