Enhanced Coverage and Sensitivity of Imprint DESI Mass Spectrometry Imaging for Plant Leaf Metabolites by Post-photoionization

Plant metabolites exhibit a variety of different chemical properties, physiological activities, and biological functions. However, untargeted imaging of highly diverse metabolic profiles is still a great challenge. Here, metabolites in plant leaves were imaged via imprint, followed by desorption electrospray ionization/post-photoionization (imprint DESI/PI) mass spectrometry imaging. In contrast to the traditional imprint DESI method, quite a few metabolites, such as terpenoids, flavonoids, glycosides, alkylphenols, amino acids, phenolic acids, tannins, and lipids, in fresh sage leaves, ginkgo leaves, and tea leaves were well detected and imaged by imprint DESI/PI. More than 80 metabolites were additionally identified, and more than 1 order of magnitude higher signal intensities were obtained for most metabolites in the negative ion mode. By virtue of the significant improvement of coverage and sensitivity of PI, the catechin biosynthesis network in fresh tea leaves could be clearly illustrated, indicating the potential applicability of imprint DESI/PI in exploring the sites and pathways of plant metabolic conversion.

Unveiling Dynamic Changes of Chemical Constituents in Raw and Processed Fuzi With Different Steaming Time Points Using Desorption Electrospray Ionization Mass Spectrometry Imaging Combined With Metabolomics

Fuzi is a famous toxic traditional herbal medicine, which has long been used for the treatment of various diseases in China and many other Asian countries because of its extraordinary pharmacological activities and high toxicity. Different processing methods to attenuate the toxicity of Fuzi are important for its safe clinical use. In this study, desorption electrospray ionization mass spectrometry imaging (DESI-MSI) with a metabolomics-combined multivariate statistical analysis approach was applied to investigate a series of Aconitum alkaloids and explore potential metabolic markers to understand the differences between raw and processed Fuzi with different steaming time points. Moreover, the selected metabolic markers were visualized by DESI-MSI, and six index alkaloids’ contents were determined through HPLC. The results indicated visible differences among raw and processed Fuzi with different steaming times, and 4.0 h is the proper time for toxicity attenuation and efficacy reservation. A total of 42 metabolic markers were identified to discriminate raw Fuzi and those steamed for 4.0 and 8.0 h, which were clearly visualized in DESI-MSI. The transformation from diester-diterpenoid alkaloids to monoester-diterpenoid alkaloids and then to non-esterified diterpene alkaloids through hydrolysis is the major toxicity attenuation process during steaming. DESI-MSI combined with metabolomics provides an efficient method to visualize the changeable rules and screen the metabolic markers of Aconitum alkaloids during steaming. The wide application of this technique could help identify markers and reveal the possible chemical transition mechanism in the “Paozhi” processes of Fuzi. It also provides an efficient and easy way to quality control and ensures the safety of Fuzi and other toxic traditional Chinese medicine.

Assessing direct analysis in real-time mass spectrometry for the identification and serotyping of Legionella pneumophila

AIMS

The efficacy of ambient mass spectrometry to identify and serotype Legionella pneumophila was assessed. To this aim, isolated waterborne colonies were submitted to a rapid extraction method and analysed by direct analysis in real-time mass spectrometry (DART-HRMS).

METHODS AND RESULTS

The DART-HRMS profiles, coupled with partial least squares discriminant analysis (PLS-DA), were first evaluated for their ability to differentiate Legionella spp. from other bacteria. The resultant classification model achieved an accuracy of 98.1% on validation. Capitalising on these encouraging results, DART-HRMS profiling was explored as an alternative approach for the identification of L. pneumophila sg. 1, L. pneumophila sg. 2-15 and L. non-pneumophila; therefore, a different PLS-DA classifier was built. When tested on a validation set, this second classifier reached an overall accuracy of 95.93%. It identified the harmful L. pneumophila sg. 1 with an impressive specificity (100%) and slightly lower sensitivity (91.7%), and similar performances were reached in the classification of L. pneumophila sg. 2-15 and L. non-pneumophila.

CONCLUSIONS

The results of this study show the DART-HMRS method has good accuracy, and it is an effective method for Legionella serogroup profiling.

SIGNIFICANCE AND IMPACT OF THE STUDY

These preliminary findings could open a new avenue for the rapid identification and quick epidemiologic tracing of L. pneumophila, with a consequent improvement to risk assessment.

Rapid and sensitive detection of trace malachite green and its metabolite in aquatic products using molecularly imprinted polymer-coated wooden-tip electrospray ionization mass spectrometry

In this study, a molecularly imprinted polymer-coated wooden-tip (MIPCWT) electrospray ionization mass spectrometry (ESI-MS) method was developed for rapid and sensitive detection of trace malachite green (MG) and its metabolite in aquatic products.