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Molecules 2018, 23(2), 179; https://doi.org/10.3390/molecules23020179

Antioxidant and Cytoprotective Effects of Tibetan Tea and Its Phenolic Components

1,2,†
,
1,2,†,* , 3,4
,
1
,
1
,
1,2
,
1,2
and
3,4,*
1
School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006, China
2
Innovative Research & Development Laboratory of TCM, Guangzhou University of Chinese Medicine, Guangzhou 510006, China; Guangzhou 510006, China
3
School of Basic Medical Science, Guangzhou University of Chinese Medicine, Guangzhou 510006, China
4
The Research Center of Basic Integrative Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006, China
These authors contributed equally to this work.
*
Authors to whom correspondence should be addressed.
Received: 6 December 2017 / Revised: 22 January 2018 / Accepted: 23 January 2018 / Published: 24 January 2018
(This article belongs to the Special Issue Catechin in Human Health and Disease)
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Abstract

Tibetan tea (Kangzhuan) is an essential beverage of the Tibetan people. In this study, a lyophilized aqueous extract of Tibetan tea (LATT) was prepared and analyzed by HPLC. The results suggested that there were at least five phenolic components, including gallic acid, and four catechins (i.e., (+)-catechin, (−)-catechin gallate (CG), (−)-epicatechin gallate (ECG), and (−)-epigallocatechin gallate). Gallic acid, the four catechins, and LATT were then comparatively investigated by four antioxidant assays: ferric reducing antioxidant power, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide radical (PTIO•) scavenging, 1,1-diphenyl-2-picryl-hydrazl radical scavenging, and 2,2′-azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid) radical scavenging assays. In these assays, LATT, along with the five phenolic components, increased their antioxidant effects in a concentration-dependent manner; however, the half maximal scavenging concentrations of ECG were always lower than those of CG. Gallic acid and the four catechins were also suggested to chelate Fe2+ based on UV-visible spectral analysis. Ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC−ESI−Q−TOF−MS/MS) analysis suggested that, when mixed with PTIO•, the five phenolic components could yield two types of radical adduct formation (RAF) products (i.e., tea phenolic dimers and tea phenolic-PTIO• adducts). In a flow cytometry assay, (+)-catechin and LATT was observed to have a cytoprotective effect towards oxidative-stressed bone marrow-derived mesenchymal stem cells. Based on this evidence, we concluded that LATT possesses antioxidative or cytoprotective properties. These effects may mainly be attributed to the presence of phenolic components, including gallic acid and the four catechins. These phenolic components may undergo electron transfer, H+-transfer, and Fe2+-chelating pathways to exhibit antioxidative or cytoprotective effects. In these effects, two diastereoisomeric CG and ECG showed differences to which a steric effect from the 2-carbon may contribute. Phenolic component decay may cause RAF in the antioxidant process. View Full-Text
Keywords: Kangzhuan; cytoprotection; catechins; steric effect; antioxidant mechanisms Kangzhuan; cytoprotection; catechins; steric effect; antioxidant mechanisms
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Xie, H.; Li, X.; Ren, Z.; Qiu, W.; Chen, J.; Jiang, Q.; Chen, B.; Chen, D. Antioxidant and Cytoprotective Effects of Tibetan Tea and Its Phenolic Components. Molecules 2018, 23, 179.

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