Determination of Theaflavins Including Methylated Theaflavins in Black Tea Leaves by Solid-Phase Extraction and HPLC Analysis

A quantitative method for four theaflavins and two methylated theaflavin derivatives in black tea leaves was developed by solid-phase extraction and a high-performance liquid chromatographic method with photodiode array detection. The theaflavins in black tea leaves were extracted three times with 4...

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Bibliographic Details
Published in:Journal of agricultural and food chemistry 2007-09, Vol.55 (18), p.7252-7257
Main Authors: Nishimura, Masami, Ishiyama, Kinuko, Watanabe, Akiko, Kawano, Setsuko, Miyase, Toshio, Sano, Mitsuaki
Format: Article
Language:English
Subjects:
Biflavonoids - analysis
Biflavonoids - chemistry
Biological and medical sciences
Camellia sinensis - chemistry
Catechin - analysis
Catechin - chemistry
Chromatography, High Pressure Liquid
Coffee, tea and other stimulative beverage industries
Ethanol
Fermentation
Food industries
Fundamental and applied biological sciences. Psychology
Methylation
Plant Leaves - chemistry
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Summary:A quantitative method for four theaflavins and two methylated theaflavin derivatives in black tea leaves was developed by solid-phase extraction and a high-performance liquid chromatographic method with photodiode array detection. The theaflavins in black tea leaves were extracted three times with 40 vol 50% aqueous ethanol (mg dry tea powder/mL) containing 2% ascorbic acid. The ethanol extracts were diluted 4-fold with distilled water. All diluted extracts were directly applied to the solid-phase C18 cartridge column without concentration. The fraction of theaflavins was obtained by 40% ethanol extraction after rinsing with water followed with 15% ethanol extraction. An aliquot of theaflavins after concentration was injected onto an ODS C18 reversed-phase column, and four theaflavins and two methylated theaflavins were sufficiently separated by a linear gradient system using distilled water and acetonitrile with 0.5% acetic acid. This analytical method is sensitive for the determination of a small amount of methylated theaflavins, since various interfering substances produced during the fermentation process were eliminated in advance by solid-phase extraction. Using this analytical method, we also demonstrated that methylated theaflavins were easily produced during the manufacture of black tea. Keywords: Black tea; methylated theaflavin; solid-phase extraction; HPLC analysis
ISSN:0021-8561
1520-5118
DOI:10.1021/jf070312m