abstract
An UHPLC method for the determination of flavonol glycosides (FOG) from green and oolong tea vs. black
tea has been developed for the first time. Sample clean-up method by means of polyamide column
chromatography was optimized with multiple-step elution. Using UHPLC and HPLC with gradient elution
and photodiode array detection, eighteen FOG compounds were determined with the aid of electrospray
tandem mass spectrometry. These FOG compounds were qualified on both UHPLC and HPLC, and this
UHPLC method successfully separated rutin (quercetin-3-O-rutinoside) and K-grg (kaempferol-3-O-glucorhamnoglucoside)
while conventional HPLC method did not. The total amounts of FOG compounds in
the tea samples were 2.32–5.67 g/kg dry weight (calculated as aglycones), and there is no significant
difference for the total FOG content among green tea, oolong tea and black tea. However, kaempferol glycosides
are more abundant in green teas, while oolong tea has more quercetin and myricetin glycosides.
In black tea quercetin glycosides were most abundant.