Rationalising the retro-Diels-Alder fragmentation pattern of viscutins using electrospray interface-tandem mass spectrometry coupled to theoretical modelling

Babra Moyo; Yolanda Novokoza; Nikita Tawanda Tavengwa; Nikolai Kuhnert; Kevin Lobb; Ntakadzeni Edwin Madala

doi:10.1002/rcm.9592

Rationalising the retro-Diels-Alder fragmentation pattern of viscutins using electrospray interface-tandem mass spectrometry coupled to theoretical modelling

Rapid Commun Mass Spectrom. 2023 Aug 15;37(15):e9592. doi: 10.1002/rcm.9592.

Authors

Babra Moyo^{1

2}, Yolanda Novokoza^{3

4}, Nikita Tawanda Tavengwa⁵, Nikolai Kuhnert⁶, Kevin Lobb^{3

4}, Ntakadzeni Edwin Madala^{1

7}

Affiliations

¹ Department of Biochemistry and Microbiology, Faculty of Science, Engineering and Agriculture, University of Venda, Thohoyandou, South Africa.
² Department of Food Science and Technology, Faculty of Science, Engineering and Agriculture, University of Venda, Thohoyandou, South Africa.
³ Department of Chemistry, Rhodes University, Makhanda, South Africa.
⁴ Research Unit in BioInformatics (RUBi), Rhodes University, Makhanda, South Africa.
⁵ Department of Chemistry, Faculty of Science, Engineering and Agriculture, University of Venda, Thohoyandou, South Africa.
⁶ Department of Life Sciences and Chemistry, Jacobs University Bremen, Bremen, Germany.
⁷ Stellenbosch Institute for Advanced Study, Stellenbosch University, Stellenbosch, South Africa.

PMID: 37408087
DOI: 10.1002/rcm.9592

Abstract

Rationale: Although mass spectrometry (MS) is a powerful tool in structural elucidation of unknown flavonoids based on their unique fragmentation patterns, proposing the correct fragmentation mechanism is still a challenge from tandem mass spectrometry data only. In recent years, computational tools such as molecular networking and MS2LDA have played a major role in the identification of structurally related compounds through an in-depth survey of their fragmentation patterns.

Methods: Therefore, in this study, three viscutin molecules in Viscum combreticola Engl. crude extracts were characterised using ultra-high-performance liquid chromatography-quadrupole-time-of-flight tandem mass spectrometry and MS2LDA, a computational tool. Ion-trap mass spectrometry and density functional theoretical modelling were used as confirmatory tools to rationalise the unique fragmentation patterns observed for these molecules.

Results: Here, MS2LDA revealed the presence of a unique Mass2Motif in all the three viscutin molecules at m/z 137, which was confirmed to be a ^1,3 A^- RDA (retro-Diels-Alder) fragmentation product using liquid chromatography-ion-trap mass spectrometry and density functional theoretical modelling. Moreover, MS2LDA proved to be useful in differentiating this spectral feature that was specific to viscutin molecules in the presence of other isobaric ions at m/z 137 occurring in compounds in other molecular families.

Conclusion: Therefore, the results of the current study showed that computational tools such as MS2LDA are essential in uncovering some gas-phase fragmentation reactions of molecules in MS and that theoretical modelling is a powerful tool in rationalising these reactions in metabolite identification.

Abstract

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