Characterization of procyanidin B2 oxidation products in an apple juice model solution and confirmation of their presence in apple juice by high-performance liquid chromatography coupled to electrospray ion trap mass spectrometry

• Published in: Journal of mass spectrometry. 2011-11, Vol.46 (11), p.1186-1197
• Main Authors: Poupard, Pascal, Sanoner, Philippe, Baron, Alain, Renard, Catherine M. G. C., Guyot, Sylvain
• Format: Article
• Language: English
• Subjects: Alcoholic beverages and cider; Apples; Beverages - analysis; Biflavonoids - analysis; Biflavonoids - chemistry; Biological and medical sciences; Caffeoylquinic acid; Catechin - analysis; Catechin - chemistry; Chromatography, High Pressure Liquid - methods; Cider; condensed tannins; Fermented food industries; Food industries; Fruit - chemistry; Fruit and vegetable industries; Fundamental and applied biological sciences. Psychology; Juices; Life Sciences; Malus - chemistry; Mass spectrometry; Mathematical models; Models, Molecular; Non alcoholic beverage industries and mineral waters; Oxidation; Oxidation-Reduction; polyphenol oxidase; Proanthocyanidins - analysis; Proanthocyanidins - chemistry; procyanidin A2; Procyanidins; Quinic Acid - analogs & derivatives; Quinic Acid - chemistry; Spectrometry, Mass, Electrospray Ionization; Tandem Mass Spectrometry - methods
• ISSN: 1076-5174; 1096-9888; 1096-9888
• DOI: 10.1002/jms.2007

Procyanidins (i.e. condensed tannins) are polyphenols commonly found in fruits. During juice and cider making, apple polyphenol oxidase catalyzes the oxidation of caffeoylquinic acid (CQA) into its corresponding o‐quinone which further reacts with procyanidins and other polyphenols, leading to the formation of numerous oxidation products. However, the structure and the reaction pathways of these neoformed phenolic compounds are still largely unknown. Experiments were carried out on a model system to gain insights into the chemical processes occurring during the initial steps of fruit processing. Procyanidin B2 was oxidized by caffeoylquinic acid o‐quinone (CQAoq) in an apple juice model solution. The reaction products were monitored using high performance liquid chromatography (HPLC) coupled to ultraviolet (UV)‐visible and electrospray tandem mass spectrometry (ESI‐MS/MS) in the negative mode. Oxidative conversion of procyanidin B2 ([M‐H]− at m/z 577) into procyanidin A2 at m/z 575 was unambiguously confirmed. In addition, several classes of products were characterized by their deprotonated molecules ([M‐H]−) and their MS/MS fragmentation patterns: hetero‐dimers (m/z 929) and homo‐dimers (m/z 1153 and 705) resulting from dimerization involving procyanidin and CQA molecules; intramolecular addition products at m/z 575, 573, 927, 1151 and 703. Interestingly, no extensive polymerization was observed. Analysis of a cider apple juice enabled comparison with the results obtained on a biosynthetic model solution. However, procyanidin A2 did not accumulate but seemed to be an intermediate in the formation of an end‐product at m/z 573 for which two structural hypotheses are given. These structural modifications of native polyphenols as a consequence of oxidation probably have an impact on the organoleptic and nutritional properties of apple juices and other apple‐derived foods. Copyright © 2011 John Wiley & Sons, Ltd.