Distribution of Flavan-3-ol Species in Ripe Strawberry Fruit Revealed by Matrix-Assisted Laser Desorption/Ionization-Mass Spectrometry Imaging

• Published in: Molecules (Basel, Switzerland) Switzerland), 2019-12, Vol.25 (1), p.103
• Main Authors: Enomoto, Hirofumi, Takahashi, Senji, Takeda, Shiro, Hatta, Hajime
• Format: Article
• Language: English
• Subjects: Carbon; Catechin; Degree of polymerization; Desorption; Distribution patterns; Epicatechin; flavan-3-ols; Flavonoids; Flavonoids - chemistry; Flavonoids - isolation & purification; Fragaria; Fragaria - chemistry; Fruits; Geographical distribution; Ionization; Ions; Mass spectrometry; mass spectrometry imaging (msi); Mass spectroscopy; matrix-assisted laser desorption/ionization (maldi); Metabolites; Molecular Structure; Negative ions; Plant Extracts - chemistry; Plant Extracts - isolation & purification; Polyphenols; Proanthocyanidins; Procyanidins; propelargonidins; Scientific imaging; Skin; Spatial distribution; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Spectroscopy; Strawberries; strawberry; Tissue Distribution
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules25010103

Flavan-3-ols, which comprise proanthocyanidins and their monomers, are major flavonoids in strawberries, and they have a wide range of biological activities and health benefits. However, their spatial distribution in strawberry fruit remains poorly understood. Therefore, we performed matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI), to visualize flavan-3-ols in ripe strawberry fruit. Peaks matching the / values of flavan-3-ols [M - H] ions were detected in the negative ion mode using 1,5-diaminonaphthalene as matrix. Catechin and/or epicatechin, three B-type procyanidins, and two B-type propelargonidins were identified by MALDI-tandem MS. These flavan-3-ols were mainly distributed in the calyx, in and around the vascular bundles, and in the skin. In-source fragmentation of proanthocyanidins was determined using their standards, suggesting their distribution was mixed ion images of themselves, and fragment ions generated from those had a higher degree of polymerization. B-type procyanidins were predominantly distributed in the vascular bundles than in the skin, whereas B-type propelargonidins were almost equally distributed between the vascular bundles and skin, suggesting that their distribution patterns are different from the type of their flavan-3-ol monomers. Flavan-3-ols, especially B-type procyanidins, may help prevent pathogen infection not only in the skin but also in and around the vascular bundles.