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Antioxidant phenolic compounds from Pu-erh tea.

Hai Ming Zhang¹, Cheng Fang Wang, Sheng Min Shen

¹State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, Beijing 100875, China.

Molecules (Basel, Switzerland)

|November 29, 2012

Summary

Eight phenolic compounds from Pu-erh tea were identified and their antioxidant potential assessed. Quercetin and kaempferol showed the highest DPPH scavenging activity, while gallic acid demonstrated superior ABTS radical scavenging ability.

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Area of Science:

Food Chemistry
Natural Product Chemistry
Pharmacognosy

Background:

Pu-erh tea is a fermented tea with a rich history of traditional use.
The complex chemical composition of Pu-erh tea suggests potential health benefits, particularly related to antioxidant properties.
Understanding the specific compounds responsible for these activities is crucial for quality control and therapeutic applications.

Purpose of the Study:

To isolate and identify key phenolic compounds from Pu-erh tea water extract.
To evaluate the in vitro antioxidant activities of the isolated compounds using DPPH and ABTS radical scavenging assays.
To determine the contribution of these phenolic compounds to the overall antioxidant capacity of Pu-erh tea.

Main Methods:

Isolation of compounds using chromatographic techniques.
Structure elucidation of isolated compounds utilizing Nuclear Magnetic Resonance (NMR) and Mass Spectrometry (MS).
In vitro antioxidant activity assessment via DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-9-sulfonic acid)) radical scavenging assays with microplate methods.

Main Results:

Eight phenolic compounds were successfully isolated and identified: gallic acid, (+)-catechin, (−)-epicatechin, (−)-epicatechin-3-O-gallate, (−)-epigallocatechin-3-O-gallate, (−)-epiafzelechin-3-O-gallate, kaempferol, and quercetin.
Quercetin (8) and kaempferol (7) exhibited the highest DPPH radical scavenging capacity.
Gallic acid (1) demonstrated the strongest ABTS radical scavenging activity, followed by (+)-catechin (2).

Conclusions:

The isolated phenolic compounds significantly contribute to the antioxidant activity of Pu-erh tea.
Specific compounds like quercetin, kaempferol, and gallic acid are key players in Pu-erh tea's free radical scavenging properties.
This study provides valuable insights into the phytochemical profile and antioxidant potential of Pu-erh tea, supporting its health-promoting attributes.