SIMULTANEOUS EXTRACTION AND ANALYSIS OF FOUR POLYPHENOLS FROM LEAVES OF LYCIUM BARBARUM L.

ABSTRACT Polyphenols are the important active compounds present in the leaves of wild Lycium barbarum L. By liquid chromatography–mass spectrometry, high-performance liquid chromatography and ultraviolet spectra analysis, the main polyphenols in the plant leaves were identified as rutin, chlorogenic acid, quercetin and kaempferol. Microwave-ultrasonic-assisted extraction (M-UAE) and ultrasonic-reflux extraction (URE) of the polyphenols were established in this study. The results showed that M-UAE was suitable for rapid extraction and quantitation of large numbers of samples, while URE was suitable for rapid extraction of massive materials. The simultaneous extraction and analysis of polyphenols from L. barbarum L. leaves by M-UAE were carried out. The effects of several important factors such as microwave pretreatment, ethanol concentration, ultrasonication temperature, the ratio of liquid to solid, and ultrasonication time were optimized. The highest extraction yields of the polyphenols was obtained with ethanol concentration of 70%, microwave preheating to 60C, ultrasonication temperature of 60C, the ratio of liquid to solid of 25 (mL/g), and ultrasonication time of 30 min. The mechanism of M-UAE extraction was investigated and discussed. URE and M-UAE proved to be fast, highly efficient and energy-saving. PRACTICAL APPLICATIONS The four main polyphenols in the leaves of Lycium barbarum were extracted, identified and determined, which presented basis for health protection research on the leaves of L. barbarum. A highly efficient extraction method and apparatus were developed. The ultrasonic-reflux extraction apparatus and microwave-ultrasonic-assisted extraction method both showed great potentials in the extraction of biologically active compounds.