Catechin Photolysis Suppression by Aluminum Chloride under Alkaline Conditions and Assessment with Liquid Chromatography-Mass Spectrometry

Meei-Ju Yang; Shwu-Yuan Lee; Chieh-I Liu; Shih-Hsuan Chen; Iou-Zen Chen; Tsung-Chen Su; Jeu-Ming P Yuann; Chien-Wei Cheng; Shiuh-Tsuen Huang; Ji-Yuan Liang

doi:10.3390/molecules25245985

Catechin Photolysis Suppression by Aluminum Chloride under Alkaline Conditions and Assessment with Liquid Chromatography-Mass Spectrometry

Molecules. 2020 Dec 17;25(24):5985. doi: 10.3390/molecules25245985.

Authors

Affiliations

¹ Tea Research and Extension Station, Taoyuan 32654, Taiwan.
² Department of Tourism and Leisure, Hsing-Wu University, New Taipei City 24452, Taiwan.
³ Department of Biotechnology, Ming-Chuan University, Gui-Shan 33343, Taiwan.
⁴ Department of Horticulture and Landscape Architecture, National Taiwan University, Taipei 10617, Taiwan.
⁵ Department of Science Education and Application, National Taichung University of Education, Taichung 40306, Taiwan.
⁶ Department of Soil and Environmental Sciences, National Chung Hsing University, Taichung 40200, Taiwan.

Abstract

Tea is rich in catechins and aluminum. In this study, the process of catechin photolysis was applied as a model for examining the effects of aluminum chloride (AlCl₃) on the structural changes of catechin and the alteration of aluminum complexes under blue light irradiation (BLI) at pH 8 using liquid chromatography and mass spectrometry techniques. Additionally, the effects of anions on catechin upon the addition of AlCl₃ and treatment with BLI were also studied. In this study, when 1 mM catechin was treated with BLI, a superoxide anion radical (O2•-) was generated in an air-saturated aqueous solution, in addition to forming a dimeric catechin (proanthocyanidin) via a photon-induced redox reaction. The relative percentage of catechin was found to be 59.0 and 95.7 for catechin treated with BLI and catechin upon the addition of 1 mM AlCl₃ treated with BLI, respectively. It suggested that catechin treated with BLI could be suppressed by AlCl₃, while AlCl₃ did not form a complex with catechin in the photolytic system. However, under the same conditions, it was also found that the addition of AlCl₃ inhibited the photolytic formation of O2•-, and reduced the generation of proanthocyanidin, suggesting that the disconnection of proanthocyanidin was achieved by AlCl₃ acting as a catalyst under treatment with BLI. The influence of 1 mM fluoride (F-) and 1 mM oxalate (C2O42-) ions on the photolysis of 1 mM catechin upon the addition of 1 mM AlCl₃ and treatment with BLI was found to be insignificant, implying that, during the photolysis of catechin, the Al species were either neutral or negatively charged and the aluminum species did not form a complex with anions in the photolytic system. Therefore, aluminum, which is an amphoteric species, has an inherent potential to stabilize the photolysis of catechin in an alkaline conditions, while suppressing the O2•- and proanthocyanidin generation via aluminum ion catalysis in the catechin/Al system under treatment with BLI.

Keywords: aluminum chloride; blue light; catechin; proanthocyanidin; superoxide anion radical.

MeSH terms

Aluminum / chemistry
Aluminum Chloride / chemistry*
Catechin / chemistry*
Chromatography, Liquid
Light
Mass Spectrometry
Photolysis*
Plants / chemistry
Proanthocyanidins / chemistry*
Superoxides / chemistry*
Tea / chemistry

Substances

Proanthocyanidins
Tea
Superoxides
proanthocyanidin
Aluminum Chloride
Catechin
Aluminum