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Article

Study of Tetrahydroxylated Anthraquinones—Potential Tool to Assess Degradation of Anthocyanins Rich Food

1
Department of Analytical Chemistry, Faculty of Science, Palacký University, 17. Listopadu 12, 779 00 Olomouc, Czech Republic
2
Department of History, Faculty of Arts, Palacký University, Křížkovského 10, 779 00 Olomouc, Czech Republic
*
Author to whom correspondence should be addressed.
Academic Editor: Igor Jerković
Molecules 2021, 26(1), 2; https://doi.org/10.3390/molecules26010002
Received: 8 December 2020 / Revised: 17 December 2020 / Accepted: 18 December 2020 / Published: 22 December 2020
(This article belongs to the Special Issue Applied Analytical Chemistry)
Degradation of anthocyanins involves scission of the flavonoid skeleton yielding 2,4,6-trihydroxybenzaldehyde (phloroglucinaldehyde, PGA) and a phenolic acid. However, the process is not finished with the formation of PGA, as the consequent condensation of two PGA molecules providing colored hydroxylated anthraquinones was observed for the first time. This process was studied using a combination of preparative column chromatography, nuclear magnetic resonance, liquid chromatography/high resolution tandem mass spectrometry (LC/HRMS2), and quantum calculations using density functional theory. 1,3,5,7-tetrahydroxyanthraquinone (anthrachrysone) and its isomers were found to rise during heating (95 °C) in a buffered PGA model solution (phosphate buffer, pH 7). These compounds were detected in heated red wine after an increase of its pH value. The concentration of the identified anthrachrysone in the red wine reached 0.01 mg·L−1. Presence of those compounds could therefore indicate involvement of certain steps in the processing of plant materials rich in anthocyanins (e.g., utilization of a higher temperature and/or reduction of acidity) or long-term transformation of anthocyanins (potentially, for instance, in archaeological findings such as wine or fruit residues). Additionally, measurement of wine–soil suspensions proved an increase of their pH to the values suitable for anthocyanin cleavage (neutral to slightly alkaline; reached using soil from archaeologically well-known Bull Rock Cave). Although not found in artificially prepared samples (imitations) or authentic materials so far, according to our results the above mentioned conditions are suitable for the formation of tetrahydroxylated anthraquinone derivatives and their monitoring would be beneficial. View Full-Text
Keywords: anthocyanin; degradation; hydroxyanthraquinone; phloroglucinaldehyde; wine anthocyanin; degradation; hydroxyanthraquinone; phloroglucinaldehyde; wine
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MDPI and ACS Style

Kučera, L.; Kurka, O.; Golec, M.; Bednář, P. Study of Tetrahydroxylated Anthraquinones—Potential Tool to Assess Degradation of Anthocyanins Rich Food. Molecules 2021, 26, 2. https://doi.org/10.3390/molecules26010002

AMA Style

Kučera L, Kurka O, Golec M, Bednář P. Study of Tetrahydroxylated Anthraquinones—Potential Tool to Assess Degradation of Anthocyanins Rich Food. Molecules. 2021; 26(1):2. https://doi.org/10.3390/molecules26010002

Chicago/Turabian Style

Kučera, Lukáš, Ondřej Kurka, Martin Golec, and Petr Bednář. 2021. "Study of Tetrahydroxylated Anthraquinones—Potential Tool to Assess Degradation of Anthocyanins Rich Food" Molecules 26, no. 1: 2. https://doi.org/10.3390/molecules26010002

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