Abstract: A spectrophotometric method was developed for the quantitative determination of γ-aminobutyric acid (GABA) in mulberry leaf tea. The absorbance of GABA was measured with a microplate reader at 640 nm wavelength, and the linearity of the calibration curve was satisfactory (R2 > 0.99). The average recovery rates of the colorimetric and HPLC methods were 98.46% and 100.10%, with an average relative standard deviation (RSD) of 1.28% and 0.37%, respectively. Both methods could accurately quantitatively determine GABA. Student’s t-test analysis showed that there was no significant difference between the two methods. Mulberry leaves and mulberry leaf tea exhibited no difference in GABA content as determined by colorimetry. The colorimetric method proved to be simple and rapid and was more suitable for large-scale determination of GABA.

Key words: γ-aminobutyric acid, mulberry leaf tea, visible spectrophotometry, high performance liquid chromatography, microplate reader