Abstract
The present study investigated the effects of tannase and ultrasound treatment on the bioactive compounds and antioxidant activity of green tea extract. The single-factor experiments and the response surface methodology were conducted to study the effects of parameters on antioxidant activity of green tea extract. The highest antioxidant activity was found under the optimal condition with the buffer solution pH value of 4.62, ultrasonic temperature of 44.12 °C, ultrasonic time of 12.17 min, tannase concentration of 1 mg/mL, and ultrasonic power of 360 W. Furthermore, phenolic profiles of the extracts were identified and quantified by high-performance liquid chromatography. Overall, it was found that tannase led to an increase in gallic acid and a decrease in epigallocatechin gallate, and ultrasounds could also enhance the efficiency of enzymatic reaction.
Highlights
Reactive oxygen species (ROS) are produced in the human body, and excessive ROS could cause oxidative stress in organisms and promote the development of some chronic diseases [1,2]
It showed that tannase had an optimal pH value of 5.0, and the result is similar to a study reported by Costa et al, which illustrated that the free tannase was active and stable at pH 5.0 [55]
It was mainly related to the protonation and deprotonation of amino acids at the active site, and the alternation in conformation induced by the ionization from other amino acids [56]
Summary
Reactive oxygen species (ROS) are produced in the human body, and excessive ROS could cause oxidative stress in organisms and promote the development of some chronic diseases [1,2]. The natural antioxidants from plants play an important role in human health. They have been demonstrated to have free radical scavenging activity and protect against oxidative stress [3]. The natural antioxidants could be used for the prevention and management of several diseases, but it has caused some argument. The antioxidant is usually considered to inhibit the onset of cancers [10]. One of the most important uses of natural antioxidants is as the food additives in the food industry [15]
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