Abstract

In this paper, characterizations of pure major catechins and method for determination of total catechins in green tea leaves have been reported using UV-visible spectrometer. Most research activities have been focused on chromatographic methods, however spectrophotometirc method is preferred because of its rapidity, high accuracy, and reproducibility. The optical transition properties of Epigallocatechin Gallate (EGCG) and Epicatechin Gallate (ECG) in water, methanol, ethanol, acetonitrile and Epigallocatechin (EGC) and Epicatechin (EC) in water were measured. The results show that, EGCG has highest molar decadic absorption coefficient in methanol than in the other solvents. ECG has the highest absorption cross-section, transitional dipole moment, and oscillator strength of all the catechins in water. On the other hand, EGC has the least optical transition properties of all the catechins in water. Limits of detection (LOD) were comprised in the range 3.1×10^-2gmL^-1 to and reproducibilities with RSD lower than 2%. After characterization of the electron transition, a method was developed for UV-Visible determination of total catechins. Using the developed method, the content of total catechins in Ethiopian and Sri Lanka green tea leaves at room temperature was determined. The result of the experiment indicates that, Ethiopian green tea leaves has the greater total catechins (17±0.01%) than Sri Lanka green tea leaves (7.17±0.12%).

Key words: Tea leaves, catechins, extraction, UV-visible spectrometer, optical transition properties.