Study on Ultrasonic-Assisted Extraction of Star Anise Oleoresin from the Fruits of Illicium verum and Preliminary Investigation of Its Antimicrobial Activity

Abstract

Ultrasonic-assisted extraction of oleoresin from the fruit of Illicium verum was explored. Effects of many parameters on the yield of oleoresin were investigated by single factor experiment and orthogonal experiment design was also carried out to optimize the extraction conditions. Antimicrobial activity was determined by disc diffusion method. Results showed that the optimum extraction conditions were as follows: ratio of material to solvent was 6:60 (g/mL, ethyl acetate as a solvent), ultrasonic time was 30 min, 60–80 mesh powder granularity, ultrasonic power was 264 W and ultrasonic temperature was 30 °C. Under these conditions, the yield could reach 23.89% and the content of trans-anethole in the oleoresin was 90.91% by GC-MS analysis. Oleoresin exhibited a good inhibitory effect against Escherichia coli and Bacillus subtilis and antimicrobial activity positively correlated with the concentrations. Besides, the antimicrobial activity of unpurified oleoresin was stronger than purified oleoresin and it was not recommended for star anise oleoresin with purification treatment in terms of antimicrobial activity. In conclusion, star anise oleoresin extracted by ultrasonic-assisted method was feasible and the oleoresin can be developed as a natural source of antimicrobial agent in many areas.