Ionic liquid-based ultrasonic-assisted extraction of piperine from white pepper

An ionic liquid-based ultrasonic-assisted extraction (ILUAE) method has been developed for the effective extraction of piperine from white pepper powder. A series of 1-alkyl-3-methylimidazolium ionic liquids differing in composition of alkyl chain and anion were evaluated for extraction efficiency. The results indicate that both the characteristics of anions and cations have remarkable effects on the extraction efficiency. In addition, the ILUAE procedure was also optimized on some ultrasonic parameters, such as ultrasonic power, extraction time and solid–liquid ratio. Compared with the conventional heat-reflux extraction (HRE) and regular UAE, the optimized approach gained the highest extraction efficiency (from 1.950% to 3.577%) within the shortest extraction time (from 2 h to 30 min). Furthermore, the developed method was validated by the recovery, correlation coefficient (R2), and reproducibility (relative standard deviation (RSD), n = 3). Average recoveries of piperine were between 93.5% and 98.7% at spiking levels 0.05, 0.1 and 0.2 mg mL−1 with RSD lower than 5%. The developed method is linear at concentrations within the tested interval, with R2 at 0.9994.