Abstract: Ultrasound technology was applied to extract phenolic components from Guanxi pomelo peels. Effects of ultrasonic treatment parameters including ultrasonic treatment time, ultrasonic treatment temperature and ultrasonic treatment power on the content and antioxidant capacity of phenolic acids were explored. Totally 7 phenolic acids were determined by HPLC-PDA. Folin-Ciocalteu method and ferric reducing antioxidant power (FRAP) assay were adopted to evaluate the antioxidant capacity of the extracts obtained by ultrasonic treatment. The results showed that sinapic acid content was the highest in Guanxi pomelo peels, and the contents of seven phenolic acids were increased with the increase of treatment time and temperature. However, the contents of phenolic acids exhibited a decrease after ultrasonic treatment at 40 ℃ for 60 min. Ultrasonic treatment power revealed a positive effect on the contents of phenolic acids. Furthermore, ultrasonic treatment parameters had significantly effect on the content of total phenolic acids. A linear relationship was observed between Trolox-equivalent antioxidant capacity (TEAC) value and the content of total phenolic acids after ultrasonic treatments with correlation coefficients of 0.8832 at 30 ℃, 0.8874 at 40 ℃ (the length of treatment time varied from 10, 20, 30, 45 to 60 min at both temperature levels), and 0.9397 at four ultrasonic power levels, respectively. Therefore, the antioxidant activity of Guanxi pomelo peel extract was correlated with the content of total phenolic acids, and obviously improved by ultrasonic treatment.

Key words: ultrasonic treatment, Guanxi pomelo peels, phenolic acids, antioxidant capacity