Determination Of The Flavone Glycosides In Chinese Tea Varieties

Tea is abundant of flavones. Major flavones are quercetin, kaempferol, myricetin and apigenin, which are usually found in tea bound to sugars as O-glycosides, such as quercetin3-O-glucoside, quercetin3-O-galactoside, kaempferol3-O-rutinoside, quercetin3-O-rhamnoside, vitexin3-O-rhamnoside. Flavones are believed to be important for the astringent taste and color of tea, the analysis of flavonols are recommended as a measure of tea quality.In this study, A standardized profiling method based on high performance liquid chromatography combined with mass spectrometric detection (MS) was established to identify and quantify the flavones and flavone glycosides in different tea vareties. This method was involved to analyze the contents of flavones and flavone glycosides in different tea vareties and the tea leaves in different tea growth period. The results showed that:1. LC-MS analysis method:mobile phase A (acetonitrile:acetic acid:water,3:0.5:96.5, v:v:v), and mobile phase B (acetonitrile:acetic acid:water,30:0.5:69.5, v: v:v); gradient elution:the phase B from20%linear increased to60%within30min, linear increased to65%within10min, and linear increased to67.5%within another10min, then increased to80%within25min; flow rate of1mL/min; injection volume was20μl; detection wavelength was360nm; column temperature was at25℃. MS conditions for the ionization mode:API-ES; polarity:positive and negative; mass range:100-1000m/z; fragmentor:100V; dying gas flow:12-13L/min; nebulizer pressure:50-60psig; dying gas temperature:350℃; capillary voltage:3500V. Combined with dual-wavelength detection technology, the analysis and separation of tea catechins (280nm) and flavones and flavone glycosides (360nm) were good, without disturbing each other.2. In tea leaves for different growth periods, the contents of three flavonol aglycones, quercetin, myricetin and kaempferol, were very low, and some were not detected. The contents of flavone glycosides were widely distributed. The major flavone glycosides were quercetin glycosides, accounting for about half of the total flavone glycosides. The contents of myricetin glycosides, apigenin glycosides and quercetin glycosides gradually increased with the increasing of shoots maturity. However, the change of the contents of kaempferol glycosides was different. It increased first, and then declined. The contents of total flavone glycosides and flavonoids gradually increased with the increasing of shoots maturity, and the proportion of the total flavonol glycosides in flavonoids was60%-85%.3. The contents of three flavonol aglycones, quercetin, myricetin and kaempferol were also very low in18different tea varieties. The contents of flavone glycosides were widely distributed. The major flavone glycosides were quercetin glycosides, accounting for about half of the total flavone glycosides, and the next were kaempferol glycosides. The total content of flavone glycosides was highest in the tea variety of Shubei up to7.41mg/g, and lowest in the tea variety of Wuniuzao with only6.03mg/g in9tea varieties for green tea manufacture. Among4tea varietiea for black tea manufacture, the total content of flavone glycosides was highest in the tea variety of Zhenong25up to9.53mg/g, and lowest in the tea variety of Zhenghedabaicha with only7.46mg/g. Among5tea varieties for oolong tea manufacture, the total content of flavone glycosides was highest in the tea variety of Fenghuangshuixian up to9.20mg/g, and lowest in the tea variety of Fujianshuixian with only3.88mg/g. The results clearly showed that the total contents of flavone glycosides in9tea varieties for black and oolong tea manufacture were higher than9tea varieties for green tea manufacture, and the proportion of the total flavonol glycosides in flavonoids was70%-90%.