Identification of new flavonoid compounds in dandelion Taraxacum mongolicum Hand.-Mazz. and evaluation of their antioxidant activities

Abstract Due to the interest in the potential pharmacological application of dandelion, the chemical constituents and activities of Taraxacum mongolicum Hand.-Mazz were studied. Box-Behnken response surface methodology was employed to optimize the protocol for extraction of flavonoids from dandelion. The molecular structures of different flavonoid compounds were acquired and analyzed by liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) spectroscopy. Seven flavonoid compounds were isolated and purified, namely, hesperetin−5'-O-β-rhamnoglucoside (I), quercetin (II), hesperetin−7-glucuronide (III), kaempferol−3-glucoside (IV), baicalein (V), hyperseroside (VI) and rutin (VII), among which the flavonoid compounds II, III, V, VI were extracted for the first time from dandelion, whereas the compound I : hesperetin−5'-O-β-rhamnoglucoside, was identified as a new type of flavonoid that had never reported in the literature. The antioxidant activities of the extracted flavonoids were examined, and the determination of structure-related antioxidant activity could be interpreted based on DFT calculations. As such, we have not only illustrated the rich flavonoid contents in Taraxacum mongolicum Hand.-Mazz, but also revealed new types of flavonoids in dandelion in terms of structure and antioxidant properties.