Analysis of Abscisic Acid in Tea Leaves and Changes in the Contents of Abscisic Acid during the 1st and 2nd Crop Seasons

Abstract

A method for the analysis of abscisic acid (ABA) in tea leaves was investigated by gas chromatography-mass spectrometry. The procedure based on Yoshida et al. was adopted, as follows. The fresh leaves were extracted with methanol and filtrated. After removal of methanol in vacuo, the residue was dissolved in water and adjusted to pH 3, then extracted with chloroform. The residue obtained after evaporation of chloroform was passed through the Sep-pack silica column. After the addition of ethyl stearate as an internal standard, the ABA fraction was methylated with diazomethan and chromatographed. Separation of compounds was achieved employing a temperature programme on a 1.5m×3mm I.D. 1% XE60 column. ABA-Me was detected by selective ion monitoring of m/z 261 (MH-H₂O) in CIMS (iso-buthan). Because selective ion monitoring of the base peak of ABA-Me in EIMS were not sufficient to detect ABA in tea leaves.
Using the method as described above, the ABA content of tea leaves sampled from three positions on the stem during the 1st and 2nd crop season. In the case of 1st crop season, the ABA content of new leaves was higher than that of old leaves until early June. However, the former was equivalent to the latter after middle June due to decrease in the former. The ABA contents of overwintered leaves from two different positions on the stem did not showed significant difference. In the case of 2nd crop season, the change in the content of ABA in new leaves was approximately similar to that in old leaves