High-Throughput Detection of an Alkaloidal Plant Metabolome in Plant Extracts Using LC-ESI-QTOF-MS

Abstract

Plant alkaloids represent a diverse group of nitrogen-containing natural products. These compounds are considered valuable in drug discovery and development. High-throughput identification of such plant secondary metabolites in complex plant extracts is essential for drug discovery, lead optimization, and understanding the biological pathway. The present study aims to rapidly identify different classes of alkaloids in plant extracts through the liquid chromatography with electrospray ionization-tandem mass spectrometry (LC−ESI-MS/MS) approach using 161 isolated and purified alkaloids. These are biologically important unique alkaloids belonging to different sub-classes such as isoquinoline, quinoline, indole, tropane, pyridine, piperidine, quinolizidine, aporphine, steroidal, and terpenoid. The majority of these are not available commercially and are known to manifest valuable biological activities. Four pools of a maximum of 50 phytostandards each were prepared, based on their log P value to minimize co-elution for rapid and cost-effective analyses. MS/MS spectra were acquired in the positive ionization mode by using their [M + H] + and/or [M + Na] + with both the average collisional energy (25.5−62 eV) and individual collisional energies (10, 20, 30, and 40 eV). Accurate mass, high-resolution mass spectrometry (HR-MS) data, MS/MS data, and retention times were curated for each compound. The developed LC−MS/MS method was successfully used to interrogate and fast dereplicate alkaloids in 13 medicinal plant extracts and a herbal formulation. A total of 56 alkaloids were identified based on the reference standard retention times (RTs), HR-MS spectra, and/or MS/MS spectra. The MS data have been submitted to the MetaboLights online database (MTBLS2914). The mass spectrometric and chromatographic data will be useful for the discovery of new congeners and the study of biological pathways of alkaloids in the plant kingdom.

Development of an HPLC-MS/MS Method for the Determination of Alkaloids in Lupins

“…More recently, other methods were developed by reversed-phase liquid chromatography interfaced with electrospray ionization coupled with high-resolution MS (RPLC-ESI-HRMS), mainly using a quadrupole-time of flight (Q-TOF) or Orbitrap MS instruments. The latter provides high selectivity and sensitivity for the untargeted screening of phytotoxins, including some QAs such us lupinine, sparteine, and cytisine and indole alkaloids such as gramine, in environmental samples, lupins, feed, and plant extracts [ 20 , 21 , 22 , 23 ].…”

Study on chemical constituents and fingerprints of Phellodendron amurense Rupr. based on ultra‐performance liquid chromatography–quadrupole–time‐of‐flight–mass spectrometry

“…The parent ion peaks of compounds 28, 32, 33, and 62 were m/z 342.1705, m/z 342.1705, m/z 326.1391, and m/z 356.1863, respectively; their secondary characteristic fragment ions were m/z 297.1123, m/z 265.0861, m/z 295.0916, or m/z 311.1278 [17, 18], which can be used to identify aporphine alkaloids. Taking compound 28 as an example, it is a quaternary amine producing parent ion [M] + , and the (CH 3 ) 2 NH substituent was lost easily, producing the characteristic fragment ions at m/z 297.1123, and then CH 3 OH group was lost, resulting in characteristic fragment ions at m/z 265.0861.…”

“…These characteristic ions can be used to rapidly identify protoberberine alkaloids. [17,18], which can be used to identify aporphine alkaloids. Taking compound 28 as an example, it is a quaternary amine producing parent ion [M] + , and the (CH 3 ) 2 NH substituent was lost easily, producing the characteristic fragment ions at m/z 297.1123, and then CH 3 OH group was lost, resulting in characteristic fragment ions at m/z 265.0861.…”

Microorganisms in Plant Growth and Development: Roles in Abiotic Stress Tolerance and Secondary Metabolites Secretion

“…Alkaloids are nitrogen-containing SM with a family of more than 12,000 compounds with low molecular weights [105]. The biosynthesis of alkaloids was more observed when plants are exposed to high-temperature conditions and begins with reactions involving amino acids such as tryptophan, tyrosine, ornithine, and phenylalanine [106]. The family of alkaloids includes purine alkaloids, pyridine alkaloids, tropane alkaloids, benzylisoquinoline alkaloids, and terpenoid indole alkaloids, which account for about 3000 compounds [107].…”