Systematic characterization of flavonoids from Siraitia grosvenorii leaf extract using an integrated strategy of high-speed counter-current chromatography combined with ultra high performance liquid chromatography and electrospray ionization quadrupole time-of-flight mass spectrometry.

The chemical constituents of the Siraitia grosvenorii leaf extract were studied. Firstly, high-speed counter-current chromatography was applied to the one-step separation of four compounds from S. grosvenorii leaf extract with the solvent system composed of 0.01% acetic acid water/n-butanol/n-hexane/methanol (5:3:1:1, v/v/v/v). In this work, 270 mg of crude sample yielded four compounds, a new kaempferol O-glycoside derivative, kaempferol 3-O-α-L-[4-O-(4-carboxy-3-hydroxy-3-methylbutanoyl)]-rhamnopyranoside-7-O-α-L-rhamnopyranoside, named kaempferitrin A (2.1 mg, 90%), and three known compounds, grosvenorine (3.4 mg, 93%), kaempferitrin (14.4 mg, 99%) and afzelin (4 mg, 98%), and the structures of these compounds were identified by NMR spectroscopy and mass spectrometry. Then, ultra high performance liquid chromatography with electrospray ionization quadrupole time-of-flight mass spectrometry was used to illustrate the dominant flavonoids in S. grosvenorii leaf extract. 34 flavonoids including 19 kaempferol O-glycosides, 4 quercetin O-glycosides, 6 flavanone derivatives, and 5 polymethoxyflavones, were accurately or tentatively identified by carefully comparing their retention times, UV data, precise masses, the typical fragments of the standards and literature data. Most of these compounds were reported for the first time. This study establishes a foundation for the further development and utilization of S. grosvenorii leaves in future.