Quantitative Determination of Galactolipids from Lycium barbarum L. by SPE Assisted HPLC-ELSD Method and Structural Characterization by ESI-MS/MS

Lipids are important constituents of all living organisms. Galactolipids are a class of acylated membrane lipids with a sugar molecule attached to the third carbon of the glycerol molecule. These compounds are associated primarily with plastid membranes in seed plants [1]. The fruit of Lycium barbarum L. has been widely used in the health food industry because of its possible role in the prevention of chronic disease like age-related macular degeneration. In addition, it may possess antioxidant and antitumor activities, neuroprotective effect, and enhance immunity [2]. An SPE assisted HPLC/ELSD method has been developed for the quantitative determination of galactolipids from Lycium barbarum L. fruits. The separation of six galactolipids and one steroid were achieved by using C-18 column material in HPLC method coupled with an ELS detector. A water/acetonitrile mobile phase, both containing 0.1% acetic acid, was selected for the outlined method. The column temperature was maintained at 25°C. The method was validated for logarithmic linearity, repeatability, limits of detection (LOD) and limits of quantification (LOQ). The LOD and LOQ of galactolipids were found to be in the range from 10–20 µg/mL and 20–50 µg/mL, respectively. The structures of six galactolipids and one steroid were further characterized by ESI-MS/MS method. Ion-trap tandem mass spectrometry coupled with electrospray ionization (ESI) interface method is described for the identification of compounds in L. barbarum. The developed HPLC-ELSD method has been successfully applied for determination of target analytes in different populations of same species. Acknowledgements: This research is funded in part by “Science Based Authentication of Dietary Supplements” Funded by the Food and Drug Administration grant number 2 U01 FD 002071-07. References: [1] Guella G, et al. (2003), Rapid Commun Mass Spectrom, 17: 1982–1994. [2] Inbaraj BS, et al. (2008) J’Pharm Biomed Anal, 47: 812–818.

Fig. 1 HPLC-ELSD chromatograms of standards (A) and extracts of L. barbarum L. (B–C), and typical ESI-MS/MS spectra of analytes (D–F).