[Isolation and preparation of flavonoids from the leaves of Nelumbo nucifera Gaertn by preparative reversed-phase high performance liquid chromatography].

It has been confirmed that flavonoids in the leaves of Nelumbo nucifera Gaertn (lotus leaves) have many pharmacological activities. Currently, total flavones in the leaves of Nelumbo nucifera Gaertn have been studied extensively, however, only a few researches were able to investigate the individual components in it. At first, crude extract was obtained from lotus leaves by reflux extraction using 60% ethanol for three times. Then, the concentrated crude extract was separated on a D-101 column (eluted with 70% ethanol) and a polyamide column (step gradient 15% to 90% ethanol). The Fr-1 fraction was obtained from the eluate of 45% ethanol and was subjected to a preparative reversed-phase high performance liquid chromatograph (RP-HPLC) for the isolation of target components. The preparation of the individual flavonoids was carried out on an RP-HPLC with a Symmetry Prep C18 column, and the mobile phase was water-acetonitrile at a flow rate of 5.0 mL/min. Three compounds were identified with ultra violet absorbance (UV), infrared (IR), nuclear magnetic resonance (NMR) and mass spectrometry (MS). They were hyperin, isoquercetin and astragalin. To our knowledge that astragalin was the first time successfully isolated from this plant. The purity of the three compounds was all over 97%.