Liquid Chromatography Electrospray Ionization Tandem Mass Spectrometric Determination of Quassin and Neoquassin in Fruits and Vegetables

Abstract

Quassia amara wood chips are used by organic farmers as a valid alternative to synthetic insecticides. The powder of Q. amara contains high levels of quassin, neoquassin and picrasinoside B. In this study we developed a liquid chromatography mass spectrometry method for the rapid and accurate quantification of the insecticide quassinoids on fruits and vegetables. Quassinoids were extracted from fruits and vegetables with acetonitrile and separated on a Zorbax Column Eclipse XDB C8 by isocratic elution with a mobile phase consisting of water and methanol with 0.1% of formic acid. Using a high-performance liquid chromatograph coupled with an electrospray ionization tandem mass spectrometer (HPLC/ESI-MS/MS), quassinoids were selectively and simultaneously detected monitoring the multiple reaction (MRM) transitions of proton adduct precursor ions: m/z 389.5 --> 222.9 for quassin, 391.5 --> 372.9 for neoquassin and 576.1 --> 394.5 for picrasinoside B. For all quassinoids calibration was linear over a working range of 1 and 100 microg/kg with r > 0.991. Limit of determination (LOD) and limit of quantification (LOQ) for both quassinoids were 0.5 and 1 microg/kg respectively while for picrasinoside B they were 5 and 10 microg/kg. Quassinoid recoveries ranged from 85.3% to 105.3% with coefficients of variation between 2.5% and 12.8% for fruit and vegetables. The presence of interfering compounds in the fruit and vegetable extract was evaluated and found to be minimal. Due to the linear behavior it was concluded that the multiple reaction transitions of precursor ions can be used for analytical purposes, i.e. for identification and quantification of quassin, neoquassin, and picrasinoside B in fruit and vegetable extracts at trace levels.

Development and Validation of Liquid Chromatography Combined with Tandem Mass Spectrometry Methods for the Quantitation of Simalikalactone E in Extracts of Quassia amara L. and in Mouse Blood

“…Sarais et al . () detected quassin and neoquassin contained in the wood of Quassia amara , with a limit of detection (LOD) and LOQ of 0.5 and 1 µg/kg respectively for both compounds, by MRM transitions of their respective proton adduct precursor ions by HPLC–ESI/QTOF (quadrupole time‐of‐flight) MS/MS. The [M + H] + ions of quassin and neoquassin can also be detected with a matrix‐assisted laser desorption ionisation (MALDI) source (Mishra et al ., ).…”

“…Compared with the results herein, those described by Sarais et al . () displayed a lower limit of quantitation, while those reported by Pohlit et al . () have a wider linearity range and can be used for the analysis of more concentrated samples.…”

“…Sarais et al . () quantified quassin, neoquassin and picrasinoside B by LC–ESI/triple quadrupole/MS/MS with a linearity range from 1 to 100 µg/kg and LOQ of 1 µg/kg. Pohlit et al .…”

“…More recently, Pohlit et al (2009) quantitated the quassinoids isobrucein B and neosergeolide in Picrolemma sprucei infusions using triple quadrupole HPLC with electrospray ionisation (ESI) MS/MS and multiple reaction monitoring (MRM), with limits of quantitation (LOQ) of 0.25 and 0.5 mg/L respectively. Sarais et al (2010) detected quassin and neoquassin contained in the wood of Quassia amara, with a limit of detection (LOD) and LOQ of 0.5 and 1 μg/kg respectively for both compounds, by MRM transitions of their respective proton adduct precursor ions by HPLC-ESI/QTOF (quadrupole time-of-flight) MS/MS. The [M + H] + ions of quassin and neoquassin can also be detected with a matrix-assisted laser desorption ionisation (MALDI) source (Mishra et al, 2010).…”

Pesticides of Botanical Origin: a Promising Tool in Plant Protection

“…Besides limonoids, also the quassinoids and saponins fall in the PSMs'category of triterpenoids, being though much less studied (Table 2). Quassinoids, the bitter principles of the Simaroubaceae family (Quassia amara, Cassia camara and Picrasma exelca), are a group of structurally complex and highly oxygenated degraded triterpenes (Sarais et al, 2010). They are divided into five groups according to their basic skeleton, C-18, C-19, C-20, C-22 and C-25.…”