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Open AccessArticle

Localization of Flavan-3-ol Species in Peanut Testa by Mass Spectrometry Imaging

1
Department of Biosciences, Faculty of Science and Engineering, Teikyo University, Utsunomiya 320-8551, Japan
2
Division of Integrated Science and Engineering, Graduate School of Science and Engineering, Teikyo University, Utsunomiya 320-8551, Japan
3
Advanced Instrumental Analysis Center, Teikyo University, Utsunomiya 320-8551, Japan
4
Application Department Daltonics Division, Bruker Japan K.K., Yokohama 221-0022, Japan
*
Author to whom correspondence should be addressed.
Academic Editors: Teresa Escribano-Bailón and Ignacio García-Estévez
Molecules 2020, 25(10), 2373; https://doi.org/10.3390/molecules25102373
Received: 30 April 2020 / Revised: 16 May 2020 / Accepted: 20 May 2020 / Published: 20 May 2020
(This article belongs to the Special Issue Tannin Analysis, Chemistry, and Functions)
Flavan-3-ols, procyanidins and their monomers are major flavonoids present in peanuts that show a wide range of biological properties and health benefits, based on their potent antioxidant activity. Procyanidin oligomers, especially A-type, are reportedly abundant in peanut skin; however, their localization in the raw peanut testa remains poorly understood. Therefore, we performed matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) to investigate the localization of flavan-3-ols in peanut testa. 1,5-Diaminonaphthalene was coated onto the peanut section by matrix vapor deposition/recrystallization, and MALDI-MSI measurements were performed in the negative-ion mode. Peaks matching the m/z values of flavan-3-ol [M − H] ions were observed in the mass spectrum extracted from the outer epidermis of the peanut testa, using the region of interest function. Catechin and/or epicatechin, five A-type, and one B-type procyanidins were assigned by the fragment ions generated by retro-Diels-Alder, heterocyclic ring fission, and quinone methide reactions detected in MALDI-tandem MS spectra. These flavan-3-ols were localized in the outer epidermis of the peanut testa. This information will contribute to improving the extraction and purification efficiencies of flavan-3-ols from peanut testa. As flavan-3-ols display anti-microbial activity, it is speculated that flavan-3-ols present in the outer epidermis of peanut testa act to prevent pathogen infection. View Full-Text
Keywords: peanut testa; procyanidins; flavan-3-ols; mass spectrometry imaging (MSI); matrix assisted laser desorption/ionization (MALDI); matrix vapor deposition/recrystallization peanut testa; procyanidins; flavan-3-ols; mass spectrometry imaging (MSI); matrix assisted laser desorption/ionization (MALDI); matrix vapor deposition/recrystallization
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Enomoto, H.; Nirasawa, T. Localization of Flavan-3-ol Species in Peanut Testa by Mass Spectrometry Imaging. Molecules 2020, 25, 2373.

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