Abstract: In this study the stability of epigallocatechin gallate (EGCG) in a weakly acidic environment alone and in combination with an ultrasonic filed of 0.25 W/cm2 and 135 kHz was quantitatively analysis by high performance liquid chromatography. It was shown that under 20 ℃ and the same pH conditions, ultrasonic treatment caused a decrease of the stability of EGCG, and the loss rate of EGCG was 10.70 %, after 40 min exposure to pH 6.2 with ultrasonic treatment, exhibiting a 5.63-fold increase compared to the absence of ultrasonic. Linear regression indicated that the reaction of EGCG in an ultrasonic field and in a nonultrasonic field followed first-order kinetics. The rate constant was 0.00228 min-1 in the presence of ultrasonic, the activation energy 22861.13 kJ/mol, and the pre-exponential factor 28.30 s-1, which were increased 4.3 times, decreased by 14.0% and increased by 13.5%, respectively.

Key words: epigallocatechin gallate, ultrasonic, stability, chemical dynamics, kinetic model