Simultaneous determination of phenolic acids and flavonoids in Lycium barbarum Linnaeus by HPLC–DAD–ESI-MS

A high-performance liquid chromatography–diode array detection–mass spectrometry method with electrospray ionization mode (HPLC–DAD–ESI-MS) was developed for simultaneous determination of phenolic acids and flavonoids in fruits of Lycium barbarum Linnaeus, a widely used traditional Chinese herb possessing vital biological activity. Both phenolic acids and flavonoids were extracted with 50% ethanol and purified using a polymeric solid phase extraction cartridge followed by HPLC–DAD–ESI-MS analysis. By employing a Vydac C18 column, a total of 52 phenolic acids and flavonoids were separated within 70 min using a gradient mobile phase of 0.5% (v/v) formic acid in water and acetonitrile–water (94:6, v/v) with flow rate at 1 mL/min, column temperature at 30 °C and detection wavelength at 280 nm. Of 52 compounds, 15 phenolic acids and flavonoids were positively identified based on both absorption and mass spectra, with the remaining 37 tentatively identified by comparison of absorption spectra with reported values in the literature. Internal standards 3-hydroxybenzoic acid and hesperidin were used for quantitation of phenolic acids and flavonoids, respectively. Among the 15 positively identified compounds, quercetin-rhamno-di-hexoside was present in largest mass fraction (438.6 μg/g), followed by quercetin-3-O-rutinoside (281.3 μg/g), dicaffeoylquinic acid isomers (250.1 μg/g), chlorogenic acid (237.0 μg/g), quercetin-di-(rhamnohexoside) (117.5 μg/g), quercetin-di-(rhamno)-hexoside (116.8 μg/g), kaempferol-3-O-rutinoside (97.7 μg/g), isorhamnetin-3-O-rutinoside (72.1 μg/g), p-coumaric acid (64.0 μg/g), caffeic acid (23.7 μg/g) and vanillic acid (22.8 μg/g).